- 
HVYRAIN: Excessive Rainfa
From  Dumas Walker@21:1/175 to  All on Sat Feb  8 09:04:00 2025
 
 
 
FOUS30 KWBC 080733
 QPFERD
 
 Excessive Rainfall Discussion
 NWS Weather Prediction Center College Park MD
 233 AM EST Sat Feb 8 2025
 
 Day 1
 Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025
 
 ...West Virginia...
 
 Strong N-S quasi-zonal mid and upper level flow will be perturbed
 a bit during Day 1 (12Z Sat-12Z Sun) as a 150+ kt upper level jet
 streak traverses the Upper Midwest and Ohio Valley, while a flat
 500 mb vort lobe pushes across the Lower Great Lakes. Broad-scale
 exit region forcing associated with the upper jet axis will surge
 southwesterly low-level inflow ahead of the surface frontal wave,
 with 850 mb moisture flux anomalies peaking between 4-5 standard
 deviations above normal later this afternoon into Sat night, while
 TPW values peak around 1". Robust synoptic-scale support and low-
 level moisture transport will be offset somewhat by the weak
 elevated instability, with MUCAPEs generally less than 500 J/Kg.
 Nevertheless, even though not advertised on the latest (00Z Sat)
 HREF, the aforementioned dynamic and thermodynamic ingredients will
 be sufficient for spotty hourly rain rates of 0.5"+ and 3-hourly
 rates of 1.0"+, with localized event totals between 1.5-2.0"+.
 
 Current 3-hr flash flood guidance values remain quite low (1" or
 less) across the outlook area, which includes much of WV. Despite
 the lack of instability, the low FFG values could be exceeded over
 isolated areas with 2 consecutive hours of 0.5"+/hr rainfall rates.
 Since the soils in these areas are saturated, and the terrain is
 rugged, we have maintained the Marginal Risk area for much of WV
 (outside of its northern or eastern Panhandles).
 
 Hurley/Roth
 
 
 Day 2 Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025
 
 The probability of rainfall exceeding flash flood guidance is less
 than 5 percent.
 
 Hurley
 
 
 Day 3
 Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025
 
 The probability of rainfall exceeding flash flood guidance is less
 than 5 percent.
 
 Hurley
 
 $$
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- 
From  Dumas Walker@21:1/175 to  All on Sun Feb  9 08:58:00 2025
 
 
 
FOUS30 KWBC 090808
 QPFERD
 
 Excessive Rainfall Discussion
 NWS Weather Prediction Center College Park MD
 308 AM EST Sun Feb 9 2025
 
 Day 1
 Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025
 
 The probability of rainfall exceeding flash flood guidance is less
 than 5 percent.
 
 Hurley
 
 
 Day 2
 Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025
 
 The probability of rainfall exceeding flash flood guidance is less
 than 5 percent.
 
 Hurley
 
 
 Day 3
 Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025
 
 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
 THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY...
 
 ...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
 Strong NW-SE upper level jet streak will dive southeast into CA
 late on Day 3 (Tue night) -- on the western periphery of the
 longwave trough towards the base. As this occurs, the broad western
 U.S. trough will amplify, thereby enhancing the deep-layer ascent
 and southwesterly flow/moisture transport within a maturing Warm
 Conveyor Belt (WCB) downstream across the Mid South-Lower MS Valley
 and TN Valley. 850-700 mb moisture flux anomalies increase to 2-3
 standard deviations above normal Tue-Tue night, while TPW values
 climb to 1.5-1.75" (around +2 standard deviation above normal). The strengthening dynamical and thermodynamical support will make for
 efficient rainfall rates despite the lack of deep-layer
 instability. Much of the guidance, non-CAM at this point being a
 Day 3 forecast, depicts a widespread swath of 1.5-2.5" of rain
 within the outlook areas, with more stripes of >3" within the
 Slight Risk area. Storm motions nearly parallel to the WSW-ENE
 oriented surface boundary will boost the potential for training,
 and even though currently the non-CAM guidance is advertising
 meager deep-layer elevated instability (MUCAPEs generally 250-500
 J/Kg), believe these values will be amplified somewhat as the event
 gets within the high-res CAM windows, again given the dynamic and
 thermodynamic response to the broad-scale upper trough amplification.
 
 2.00"+/3hr rainfall rates are anticipated where the cells do
 train, again most likely within the Slight Risk area, which could
 lead to localized-scattered instances of flash flooding.
 
 Hurley
 
 $$
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- 
From  Dumas Walker@21:1/175 to  All on Mon Feb 10 09:13:00 2025
 
 
 
FOUS30 KWBC 100829
 QPFERD
 
 Excessive Rainfall Discussion
 NWS Weather Prediction Center College Park MD
 329 AM EST Mon Feb 10 2025
 
 Day 1
 Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025
 
 The probability of rainfall exceeding flash flood guidance is less
 than 5 percent.
 
 Beginning Monday afternoon, an increase of convergence on the nose
 of 850mb flow extending from Texas into Tennessee will support an
 increase in light to moderate rain and a few rumbles of thunder
 from eastern Oklahoma through Kentucky/Tennessee. Rain rates are
 expected to be modest (around 0.25-0.5 inch/3-hour period),
 although some of this rainfall will eventually reach areas of
 southeastern Kentucky where soils are moist and sensitive from
 antecedent rainfall. The relatively short duration of light to
 moderate rainfall in this area precludes an introduction of
 Marginal/5% risk probabilities, although one may be needed in later
 outlook updates if a longer duration of rainfall (greater than 3-6
 hours) becomes apparent across southeastern Kentucky.
 
 Cook
 
 
 Day 2
 Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025
 
 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
 THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY...
 
 ...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
 Increasing coverage of showers and thunderstorms along and ahead of
 a well defined cold front trailing a developing area of low
 pressure taking shape over the Tennessee Valley will lead to an
 increasing threat of excessive rainfall Wednesday into early
 Thursday from easter Texas and parts of Arkansas and Louisiana
 into the west aspect of the Appalachians of Tennessee and southeast
 Kentucky. At the synoptic scale, a broad trough over the western
 U.S. will amplify, thereby enhancing the deep-layer ascent and
 southwesterly flow/moisture transport over this part of the country
 due to a increasing low level flow. 850-700 mb moisture flux
 anomalies still look to increase to 2-3 standard deviations above
 normal Tuesday/Tuesday night while Precipitable Water values climb
 to 1.5-1.75" (around +2 standard deviation above normal). The
 strengthening dynamical and thermodynamical support will make for
 efficient rainfall rates despite the lack of deep- layer
 instability and the exit region of a 125 to 150 kt upper level jet
 should aid deep layer vertical ascent. Much of the guidance
 generally depicts a widespread swath of 1.5-3" of rain within the
 outlook areas, with the most aggressive model being the ECMWF with
 maximum values exceeding 4 inches. Storm motions nearly parallel
 to the WSW-ENE oriented surface boundary will boost the potential
 for training despite meager deep- layer elevated instability
 (MUCAPEs generally 250-500 J/Kg). With 2.00"+/3hr rainfall rates
 still being anticipated where the cells do train, again most
 likely within the Slight Risk area, which could lead to localized-
 scattered instances of flash flooding.
 
 Bann
 
 
 Day 3
 Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025
 
 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
 TENNESSEE VALLEY INTO THE MID-SOUTH,,,
 
 ...Tennessee Valley into the Mid-South...
 The threat of excessive rainfall will continue on Wednesday and
 early Thursday ahead of the same system which brought the
 excessive rainfall potential on Tuesday into early Wednesday as a
 cold front makes its way eastward. Broad scale ascent will continue
 to aided by the southern entrance region of a 135 to 155 kt upper
 level jet...while moisture convergence is maximized along a well
 defined surface cold front which intercepts a plume of moisture
 being pulled northward by a 40 to 50 knot low level jet. There is
 still spread in the guidance about placement of where the heaviest
 rainfall will occur but amounts generally in the 1 to 3 inch
 range...with locally higher amount where any enhanced rainfall
 rates set up due to banding/training. Given antecedent
 conditions...feel that a Slight risk should suffice.
 
 ...California Coast...
 The plume of moisture from the Pacific Ocean towards the end of Day
 2 will start to bring rain to the coastal areas during the Day 3 period...beginning in northern and central portions of California
 on Wednesday that propagates southward during Wednesday night and
 Thursday. Present indications are that the heaviest amounts remain
 off shore...but a general uptick in amounts was noted over the past
 24 hours in this area.
 
 Bann
 
 $$
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- 
From  Dumas Walker@21:1/175 to  All on Tue Feb 11 09:53:00 2025
 
 
 
FOUS30 KWBC 110836
 QPFERD
 
 Excessive Rainfall Discussion
 NWS Weather Prediction Center College Park MD
 336 AM EST Tue Feb 11 2025
 
 Day 1
 Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025
 
 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
 THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY...
 
 Few changes needed to the old Day 2 ERO as it propagates into the
 Day1 period. Main focus for heavy rainfall and the potential for
 excessive rainfall will be along and ahead of a cold front
 associated with a developing synoptic scale low pressure system
 within a broad/fairly flat flow pattern. Inclusion of more CAM
 guidance supports the idea of higher intensity rainfall extending
 as far west as eastern Texas...a tendency we often see convection
 get organized farther southwest than expected in events like this,
 and there is growing QPF signal in the 12z ECMWF, UKMET and Gem Reg
 over this area. The Slight risk area extended northeastward where
 there is a bit of instability that develops later in the period but
 looks to be lacking initially. At expect the flash flood risk to
 pick up more over this area as we head into day 2.
 
 Bann
 
 
 Day 2
 Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025
 
 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PARTS OF THE
 TENNESSEE VALLEY INTO THE MID-SOUTH...
 
 ...Tennessee Valley into the Mid-South...
 
 The prolonged heavy rainfall event will continue om Wednesday into
 Wednesday night over the Southeast. The extended duration of this
 event will lead to storm total rainfall into the 3-5" range, with
 locally higher totals possible. As stronger forcing ejects eastward
 on Wednesday, an increase in the low level jet should aid in both
 increasing moisture convergence and advecting instability
 northward. The best overlap of ingredients that has the potential
 for excessive rainfall looks to be over parts of AL/GA into far
 southwest Tennessee. This is approximately the same area as the
 previous Day 3 outlook...and given no major shifts in the synoptic
 pattern saw little reason to make too many changes.
 
 ...California Coast...
 The plume of moisture from the Pacific Ocean towards the end of Day
 2 will start to bring rain to the coastal areas during the Day 3 period...beginning in northern and central portions of California
 on Wednesday that propagates southward on Wednesday night and
 early Thursday. Present indications are that the axis of the
 Atmospheric River and the associated heaviest amounts remain off
 shore or right along the coastal terrain...but a general uptick in
 amounts was noted over the past 24 hours in this area.
 
 Bann
 
 
 Day 3
 Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025
 
 ..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL PARTS OF THE
 SOUTHERN CALIFORNIA COAST...
 
 There is a Moderate Risk of excessive rainfall over portions of the
 Southern California coast embedded within a broader Slight risk of
 excessive rainfall covering much of the central and southern
 California coast. An atmospheric river is expected to skirt the
 coast as it makes its way south and east. The primary concern is
 for damaging flooding and debris flow from the numerous fresh burn
 scars in the region given the 24-hour QPF in the 1.5 to 3.5 inch
 range...with potentially localized higher amounts. In
 addition...the area is highly urbanized and an environment in which
 much of the rainfall will turn immediately to runoff. Farther
 north...the Slight risk was extended into portions of the
 Sacramento Valley and San Joaquin Valley...where QPF is not
 expected to be as great but the conditions have been wetter and
 soils are more saturated than soils farther south.
 
 Bann
 
 $$
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- 
From  Dumas Walker@21:1/175 to  All on Wed Feb 12 08:36:00 2025
 
 
 
FOUS30 KWBC 120741
 QPFERD
 
 Excessive Rainfall Discussion
 NWS Weather Prediction Center College Park MD
 241 AM EST Wed Feb 12 2025
 
 Day 1
 Valid 12Z Wed Feb 12 2025 - 12Z Thu Feb 13 2025
 
 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS MUCH OF THE
 DEEP SOUTH AND COASTAL AREAS OF CALIFORNIA...
 
 Large Marginal and Slight Risk areas extend from Louisiana to the
 central Appalachians and portions of Virginia. The Marginal and
 Slight Risk areas cover multiple regimes for excessive rainfall potential:
 
 1) Long-duration, moderate to heavy rainfall along an axis
 extending from east Texas (beginning at 12Z) east-northeastward
 into northern Georgia and the southern Appalachians. Much of this
 axis has experienced appreciable antecedent rainfall amounts (in
 the 2-3 inch range on February 11) and models are consistent in
 depicting at least one more round of heavy rain across that same
 axis as a thunderstorm complex organizes and moves east-
 northeastward from in Texas later this morning. Another 1-3 inches
 of is expected (heaviest from western in to central Mississippi).
 Given the wet soils from prior rainfall, several instances of
 flash flooding are expected from central Louisiana through the
 southern Appalachians and northern Georgia.
 
 2) Somewhat lighter rainfall should occur across portions of
 Virginia and West Virginia through the day. Not only are soils
 water-logged and streamflows above average across these areas, but
 recent snow/ice could melt under persistent warm advection and
 temperatures slowly rising above freezing through the forecast
 period. Light to moderate rainfall could enhance excessive
 runoff/ponding especially in sensitive areas and low spots.
 
 3) CAMs are in very loose agreement in depiction of east-west
 oriented outflow boundary left behind by convective complex(es)
 across portions of southern MS/AL through early afternoon. Strong south-southwesterly 850mb flow and abundant moisture should result
 in reignition of deep convection focused along boundaries for much
 of the afternoon and early evening. The orientation of these
 boundaries should focus convective development and may allow for
 training and intense rainfall rates at times. This is supported in
 particular by the 00Z HRRR, which depicts 5-9 inch rain amounts
 across southern Alabama through 12Z Thursday. Uncertainty in the
 specific placement of boundaries/heavy rainfall corridors and dry
 antecedent conditions are factors that preclude a higher risk,
 although some higher-end flash flood potential exists in this
 scenario - especially if complexes can materialize over more
 populated areas of LA/MS/AL/GA.
 
 Cook
 
 
 Day 2
 Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025
 
 ..THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL PARTS OF THE
 SOUTHERN CALIFORNIA COAST...
 
 ...California...
 The peak of the atmospheric river is expected during this period
 with the initial focus on coastal central California at the start
 of the period, then the best IVT shifts southward through the
 period, reaching southern California by the end of the period
 Thursday night. IVT values from the GFS peak at around 600-700
 kg/m/s initially along the central coast then settle around 400-500
 kg/m/s as the AR reaches SoCal. The greatest QPF amounts will be
 confined to the coastal terrain areas as well as for the Sierra.
 Total amounts for the 24-hour period look to be between 1-3" with
 the favored terrain areas and peaks topping out between 4- 6"+.
 
 The primary concern is the potential for damaging and potentially life-threatening burn scar flash flooding and debris flows,
 particularly for southern California where the Moderate Risk (Level
 3/4) is in place. Even outside the burn scar regions, the intense
 rain rates and rainfall totals over the highly urbanized area could
 bring scattered to numerous instances of flash flooding. Elsewhere,
 a broad Slight Risk (Level 2/4) exists for much of the coastal
 ranges as well as the Central Valley and lower elevations of the Sierra Nevada.
 
 A Moderate Risk of excessive rainfall continues from yesterday's Day
 3 ERO across portions of the Southern California coast, and for the
 new Day 2 ERO was expanded slightly on the northwest side to
 encompass the Lake Burn Scar (2024), while also eastward to include
 the southwest San Bernardino Mountains, including the Line Burn Scar
 (also 2024). Again, the primary concern is for damaging flooding and
 debris flow from the numerous fresh burn scars in the region given
 the 24-hour QPF in the 1.5 to 3.5 inch range (with localized higher
 amounts). In addition, the area is highly urbanized and an
 environment in which much of the rainfall will turn immediately to runoff.
 
 Farther inland, given the QPF trends and snow levels, the Slight
 Risk was extended into eastern portions of the San Joaquin Valley
 and southern Sierra/adjacent foothills. This expansion includes the
 Borel burn scar (2024).
 
 ...Florida Panhandle and Southern Georgia...
 Lingering heavy rainfall will continue Thursday across portions of
 the Florida Panhandle and southern Georgia, ahead of the approaching
 cold front. Rainfall amounts look to be generally in the 1-3"
 range, with some potential for localized rain rates sufficiently
 high enough to cause some urban/localized flooding concerns.
 
 Hurley/Taylor
 
 
 Day 3
 Valid 12Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025
 
 ...Southern California...
 IVT plume weakens while pushing southward across SoCal to begin
 the Day 3 Period. While the bulk of the event (Slight-Moderate
 excessive rainfall risk) is expected on Day 2 or through Thursday
 night, will maintain a Marginal Risk into the early part of Day 3
 (Friday morning), especially if the southward AR progression slows down a bit.
 
 ...Mid South...
 Amplifying longwave trough across the Southwest-4 Corners Region
 Fri-Fri night will lead to backing mid/upper layer flow and
 deepening WAA/moistening downstream within a maturing Warm Conveyor
 Belt (WCB). Thermodynamic profiles will respond appreciably as a
 result, especially late in the period (Fri night) as the low- level
 flow backs SSW and increases (to 50+ kts at 850 mb). This leads to
 robust low-level moisture transport late Friday night into early
 Saturday morning, with 850-700 mb moisture flux anomalies ramping
 up to 4-5 standard deviations above normal per the ensembles. There
 will also be a corresponding uptick in elevated instability as
 well, to the tune of 500-1000 J/Kg towards 12Z Sat. While the main
 event will be on Saturday (see Day 4 ERO), will maintain the
 Marginal Risk inherited from yesterday's Day 4 ERO given the
 anticipation of the ingredients ramping up fairly quickly Friday
 night, which given the probabilistic QPF along with the latest CSU UFVS-verified ERO first-guess fields, could lead to localized
 runoff issues across portions of the Mid South. by the pre-dawn hours Saturday.
 
 Hurley
 $$
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- 
From  Dumas Walker@21:1/175 to  All on Thu Feb 13 08:45:00 2025
 
 
 
FOUS30 KWBC 130812
 QPFERD
 
 Excessive Rainfall Discussion
 NWS Weather Prediction Center College Park MD
 312 AM EST Thu Feb 13 2025
 
 Day 1
 Valid 12Z Thu Feb 13 2025 - 12Z Fri Feb 14 2025
 
 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
 OF SOUTHERN CALIFORNIA...
 
 ...California...
 Overall, not much change to the previous forecast, with the
 unfolding atmospheric river expected to peak near the start of the
 period.  A long warm front currently extending along the coast is
 expected to press inland this morning, with IVTs climbing to around
 700-800 kg/m/s near the upstream cold front as it approaches the
 coast later this morning. The strongest moisture flux is expected
 to center near SF Bay at the start of the period, before steadily
 shifting south along the coast today. Models continue to show IVTs
 decreasing as the axis moves south, dropping to around 400-500
 kg/m/s as the AR reaches Southern California later this afternoon
 into the evening. Guidance has remained fairly consistent,
 indicating precipitation amounts of 4-6 inches along the central to
 southern coastal ranges and the Sierra Nevada, falling mostly as
 rain below 6000 ft.
 
 A Moderate Risk (level 3/4) remains in place across portions
 Southern California, from Santa Barbara County southeastward into
 the San Gabriel and San Bernadino mountains, where damaging and
 potentially life-threatening burn scar flash flooding and debris
 flows remain a primary concern. Even outside of the burn scar areas,
 intense rain rates over complex terrain and urban areas may produce
 scattered to numerous instances of flash flooding. Elsewhere, a
 broad Slight Risk (Level 2/4) exists for much of the remaining
 coastal ranges as well as parts of the Central Valley and the lower
 elevations of the Sierra Nevada.
 
 ...Florida Panhandle and Southern Georgia...
 
 Lingering heavy rainfall will continue this morning across
 portions of the Florida Panhandle and southern Georgia ahead of an
 approaching cold front. HREF neighborhood probabilities indicate
 that additional rainfall amounts of 1-2 inches are likely within
 the highlighted area, with some potential for localized rain rates
 high enough to cause some urban/localized flooding concerns.
 
 Pereira
 
 
 Day 2
 Valid 12Z Fri Feb 14 2025 - 12Z Sat Feb 15 2025
 
 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
 THE MID-SOUTH...
 
 ...Mid-South...
 
 Although most of the convective activity, and thus heavy rainfall
 threat, in the region should be concentrated in the Day 3 period
 (after 12Z Saturday), model guidance does indicate that convection
 is likely to begin blossoming late Friday Night. Conditions will
 become increasingly favorable after 06Z Saturday with a strong 55-65
 knot low-level jet expanding east from the Plains, and significant
 northward moisture transport leading to rapid moistening of the
 boundary layer. MUCAPE values of around 500-1000 j/kg should support
 organized convection with the potential for rainfall rates in excess
 of 1 inch per hour at times. Although there is a lack of a
 significant front or boundary to help organize a band of convection,
 the strength of the LLJ may support backbuilding within a broad zone
 of developing convective clusters. This may be enough for some brief
 training and a ramp-up in flash flood potential prior to 12Z
 Saturday. The 00Z runs of the NAM Nest and FV3 show more widespread
 convection than other models; if this trend persists as additional
 hi-res guidance becomes available, an expansion of the Marginal Risk
 and/or the addition of a Slight Risk area may become warranted with time.
 
 ...Southern California...
 
 The Marginal Risk was removed for southern California given a more
 limited QPF signal on the latest guidance, and hi-res models in
 excellent agreement on a lack of organized convection. The bulk of
 the threat should be in the Day 1 period.
 
 Lamers
 
 
 Day 3
 Valid 12Z Sat Feb 15 2025 - 12Z Sun Feb 16 2025
 
 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
 THE TENNESSEE AND OHIO VALLEYS AND THE CENTRAL APPALACHIANS...
 
 ...Ohio and Tennessee Valleys...
 
 Confidence remains high in significant rainfall-related impacts on
 Saturday and Saturday Night with model guidance in excellent
 agreement depicting a swath of 3-6 inches of rainfall in the 24-hour
 period across the region. Although models vary slightly with the
 placement, they almost unanimously depict a corridor of heavy rain
 about 750mi long centered somewhere in TN/KY. This same region has
 generally seen above average precipitation in recent weeks, with the
 14-day precip in much of KY, N TN, WV, and W VA at least double the
 normal values. The confluence of these factors should make the
 region especially vulnerable to flooding from the predicted
 rainfall. For additional context on the current hydrologic picture
 across the region, refer to the National Hydrologic Discussion from
 the National Water Center at water.noaa.gov.
 
 Convection may be ongoing at the beginning of the forecast period
 and should become increasingly focused along a developing warm front
 to the east of a surface low that will be emerging out of the Plains
 on Saturday. The front will be positioned on the nose of very strong
 SW, or even WSW, inflow, which should favor backbuilding and
 training and a corridor of very heavy rainfall. The environment will
 be atypical of mid-February with PWATs reaching around 1.5 inches
 and MUCAPE of 500-1000 j/kg. For example, the Nashville sounding
 archive exists back to 1948 and they've only ever reached 1000 j/kg
 MUCAPE once in February, and 1.5 inch PWATs a few times. The
 environment will support rainfall rates in excess of 1 inch per
 hour, and given the potential for training and backbuilding, these
 rates may be sustained for several hours in some locations. These
 would be the areas of greatest concern for flash flooding -- not
 only in terms of likelihood but severity -- particularly if the
 higher rain rates are sustained over urban areas or vulnerable
 terrain for extended periods of time.
 
 The inherited Moderate Risk was mostly maintained as-is with a
 slight expansion to the southwest in the vicinity of Memphis, TN;
 and a more significant expansion eastward into S WV and W VA. The WV-
 VA border region just received some significant snowfall, and model
 guidance indicates a fairly high probability of warm, moist air (dew
 points in excess of 45 degrees) accompanying the rainfall into this
 area, which may lead to a combination of runoff from rain and snow melt.
 
 It's worth noting a couple additional things. First, the amount of
 rain forecast from E KY into S WV and W VA in particular is quite
 unusual for the heart of the winter season. Calendar day precip
 records across that area for January and February are generally in
 the 2-3 inch range, and NBM probabilities indicate it is likely (60+
 percent chance) we will see these types of 24-hour rainfall totals
 in those areas. Second, this relatively rare winter rain event would
 be delivered to an area that has been quite wet recently, and in
 some areas has snow on the ground. And third, the high-end scenarios
 in much of the Moderate Risk area would be significant by historical
 standards. The NBM 90th percentile from N TN into S/E KY and S WV is
 on par with the top several wettest days (for any season!) in the
 station records in the area. This corridor is where the greatest
 concern for severe impacts exists, and it's possible an upgrade to
 High Risk may be needed for portions of the area in subsequent updates.
 
 Lamers
 $$
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