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   FOUS30 KWBC 191944   
   QPFERD   
      
   Excessive Rainfall Discussion   
   NWS Weather Prediction Center College Park MD   
   244 PM EST Wed Nov 19 2025   
      
   Day 1   
   Valid 16Z Wed Nov 19 2025 - 12Z Thu Nov 20 2025   
      
   ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF   
   SOUTH-CENTRAL TEXAS, INCLUDING PORTIONS OF THE HILL COUNTRY...   
      
   ...Special 1915z Update...   
      
   A targeted Moderate Risk was introduce in collaboration with the   
   San Antonio and San Angelo local offices, generally encompassing   
   Del Rio and points east-northeast(including much of Val Verde,   
   Kinney, Edwards, and Real Counties). This is where 5" exceedance   
   probs are maximized (12z HREF indicating probabilities near 20%   
   through 12z with experimental 06z REFS indicating probs as high as   
   60%). Given the sensitivity of the Hill Country with the potential   
   for 3"+/hr rainfall rates developing rapidly late tonight, it was   
   decided to introduce the Moderate Risk for the Day 1 period (with   
   greater confidence in realizing 5"+ localized totals just beyond   
   the Day 1 period ending at 12z Thursday). An updated Day 2 outlook   
   will also reflect this upgrade shortly (as the bulk of the realized   
   impacts of the Moderate Risk are anticipated to occur around or   
   just beyond 12z Thu).   
      
   Churchill   
      
      
   ...16z Update...   
      
   Minimal adjustments to the ERO areas with this update, as the   
   inherited Slight Risk area is still positioned well within the   
   consensus of the 12z CAMs 3"+ QPF signal (40-70% odds per latest   
   40-km neighborhood 3" exceedance HREF probabilities). While this is   
   also the higher confidence corridor for localized 5"+ amounts (per   
   both the 12z HREF PMM and 10-20% probs for 5" exceedance), there   
   are indications of a secondary training corridor by some of the   
   CAMs (mainly the ARW and ARW2) across portions of North TX into the   
   ArkLaTex (20-30% and 5-15% for 3" and 5" exceedance, respectively).   
   While this area remains more of a conditional flash flood threat   
   (dependent on west-to-east training convection along the quasi-   
   stationary boundary with weak forcing), the Marginal Risk was   
   expanded more into the ArkLaTex to account for the latest QPF   
   spread in the 12z guidance (with the bulk of the QPF still expected   
   late in the period for both regions).   
      
   Maintained the Marginal Risk elsewhere (Southwest U.S.) where   
   longer duration rainfall (with instability being the main limiting   
   factor for convection and higher rainfall rates) could result in   
   localized flood impacts for sensitive areas.   
      
   Churchill   
      
   ...Previous Discussion...   
      
   A large mid/upper trough over the southwestern U.S. will take on a   
   negative tilt while moving slowly eastward toward the southern   
   Rockies through 12Z Thursday. As this occurs, abundant Gulf   
   moisture will be drawn northwestward across much of central and   
   southeastern Texas. Low-level trajectories indicating upslope into   
   higher terrain of northern Mexican provinces and areas of 1000-1500   
   J/kg SBCAPE are supportive of scattered thunderstorms developing   
   over northern Coahuila and the general vicinity of Del Rio/Eagle   
   Pass. CAMs depict a concerning signal for training in this region   
   as cells both 1) migrate northeastward beneath southwesterly   
   steering flow aloft while 2) redeveloping upstream closer to higher   
   terrain. A narrow corridor of 1-3 inch rainfall totals could   
   develop in these areas. Ultimately, local convective evolution will   
   determine the degree of training and length of heavier rain rates   
   in this area. Slight Risk and attendant probabilities are   
   maintained for this forecast as there is some lingering uncertainty   
   regarding specific location of this axis of heavier rain. However,   
   PW values approaching 1.5 and slow right-moving motions with any   
   cells that can acquire mature cold pools/updraft rotation may   
   force a locally significant flash flood threat occurring during the   
   overnight and early morning Thursday. Convective/rainfall trends   
   will be monitored for any enhanced training that would necessitate   
   a Moderate Risk upgrade.   
      
   Farther northeast, models depict deep convection in a more   
   scattered fashion toward Dallas/Fort Worth and into northeast Texas   
   (and perhaps western Arkansas). While thermodynamic profiles will   
   gradually become more supportive of heavy rainfall, weak forcing   
   (with the mid/upper wave well west of the region), weak/non-   
   existent low-level convergence, and subtle ridging aloft just east   
   of the region casts some doubt on convective coverage and   
   resultant flash flood risk. A Marginal Risk remains in place for   
   locally training storms, although this risk appears to be quite   
   conditional.   
      
   Across Arizona and New Mexico, deep southerly flow aloft will allow   
   for scattered shower and thunderstorm activity to drift northward   
   through much of the day. An uptick in convective coverage is   
   expected during peak heating hours, with isolated/localized flash   
   flood potential existing across any low-lying, sensitive, and/or   
   urban areas. Heavy rainfall (exceeding 1 inch) is expected to occur   
   on a relatively localized basis. Later in the forecast period   
   (between 00Z-12Z Thursday), models depict potential for heavier   
   rainfall to develop in a few locales across southern New Mexico   
   near several active burn scars. Isolated flash flooding could   
   occur near these burn scars.   
      
   Cook   
      
      
   Day 2   
   Valid 12Z Thu Nov 20 2025 - 12Z Fri Nov 21 2025   
      
   ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF   
   SOUTH-CENTRAL TEXAS, INCLUDING PORTIONS OF THE HILL COUNTRY...   
      
   ...20z Update...   
      
   A couple of significant changes to the outlook areas for this   
   update.   
      
   This first is to introduce a targeted Moderate Risk upgrade for=20   
   the same areas as detailed for Day 1. This is due to increasing=20   
   likelihood for localized 5"+ storm totals beyond the 12z Thursday=20   
   Day 1/2 cut- off, which may result in numerous instances of flash=20   
   flooding in a relatively small area (with higher confidence overall   
   in locally significant flash flooding as opposed to the total=20   
   areal coverage). While 6-hr FFG exceedance probs from the HREF are=20   
   below 20% through the end of Day 1, they increase meaningfully to=20   
   near 60% going into Day 2 (through 18z Thu).=20   
      
   The second significant change was to split up the larger Slight   
   Risk area into two distinct areas, 1) South-Central TX and 2)   
   eastern OK into northern AR and southern MO. This reflects the   
   consensus of the latest CAM guidance which suggests a large gap in   
   convection across North TX during the period (with questions still   
   lingering regarding the eastward extent of both the South-Central   
   TX and Ozarks clusters of convection into the later half of Day 2).=20   
      
   Churchill=20   
      
   ..Previous Discussions..   
      
   ...Southern Plains...   
      
   The environment continues to becomes more supportive of storms   
   capable of producing heavy to potentially excessive rainfall as the   
   flow aloft backs over portions of Texas and Oklahoma and becomes   
   increasingly diffluent as an upper trough approaches the region. At   
   lower levels...an airmass with precipitable water values gets   
   drawn northward an converges along a surface front over parts of   
   Texas and Oklahoma. Excessive rainfall is possible by means of   
   intense rainfall rates by individual storms in regions with the   
   highest amount of instability (presumably ahead of the approaching   
   cold front) and by training of cells/multiple rounds of convection   
   (more of a factor where synoptic scale forcing and mesoscale   
   forcing act in tandem farther north). The axis of highest   
   precipitable water values... 1.5-1.75"... sets up over the eastern   
   half of Texas into southeastern-most Oklahoma and into Arkansas.   
   Those values are well above average for mid-November. Localized   
   rainfall amounts up to 2.5" in an hour with additional local totals   
   of 5" possible within this set up which would result in scattered   
   instances of flash flooding.   
      
   ...California...   
      
   Maintained a Marginal Risk area from continuity for portions of   
   coastal Southern California as the next area of low pressure over   
   the eastern North Pacific drops southward off the California coast   
   and brings another round of rainfall Thursday into early Friday.   
   Rainfall amounts at this point look to be pretty modest but the   
   rain will be falling on areas where antecedent conditions have   
   been wet for the better part of 5 or 6 days. That may result in   
   additional localized flooding on Thursday or Thursday night.   
      
   Bann   
      
      
   Day 3   
   Valid 12Z Fri Nov 21 2025 - 12Z Sat Nov 22 2025   
      
   ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF   
   THE OHIO VALLEY AND PORTIONS OF THE SOUTHWEST US...   
      
   20Z Update: Limited changes necessary from the previous forecast due=20   
   to general run-to-run continuity. Heaviest rainfall still trending=20   
   closer to the southern Peninsular Range with an extension of=20   
   convection back over the southeast CA deserts and southwest AZ for=20   
   the MRGL over the west. Moderate to locally heavy rain possible for=20   
   the Ohio Valley. Steady forward propagation of broad QPF shield=20   
   should limit the necessity for more than the current MRGL risk. Will=20   
   assess the southern portion of the risk area closely in the coming=20   
   days as this region, extending into the Southeast CONUS will be most=20   
   coincident with a purely convective regime as instability is=20   
   prevalent within a broad, but modest theta_E depiction. This area=20   
   would promote higher rate potential, but could be a case where=20   
   forcing is not enough to activate the better thermodynamic=20   
   environment. For now, maintain relatively continuity of the MRGL=20   
   with some minor adjustments overall.=20=20   
      
   Kleebauer   
      
   ..Previous Discussions..   
      
   ...Ohio Valley...   
      
   Rain will be spreading northward and eastward from the Plains on   
   Day 2 into the Ohio Valley on Friday and Friday night in   
   association with the surface low coming out of the mid-Mississippi   
   Valley. Between above normal levels of moisture being transported   
   into the region from the south and flow aloft becoming confluent...   
   there is still the possibility for isolated downpours that lead to   
   spotty problems from run-off despite the set up becoming less   
   favorable with time.   
      
   ...Southwest US...   
      
   A mid- and upper-level trough with an embedded closed low will   
   continue to drop southward on Friday...with an embedded closed low   
   expected near the US border with Mexico by 00Z on Saturday. Showers   
   and embedded thunderstorms should be developing in the highly   
   diffluent flow to the east of the trough where precipitable water   
   values approaching an inch rotate into southern California and   
   western Arizona. Opted to remain at a Marginal threshold given the   
   timing of the best upper support but a Slight may still be needed.   
      
   Bann   
      
      
   Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/94epoints.txt__;!!DZ3fjg!4d5j5wVsMKW1-KyosgZyD43l88P3PsWnUMRt1zgclFC0=   
   _AsbDUaSGUAJFJxmJ-pM0j1uNnB10XXj4TmSmTfL4AY6Yfg$=20   
   Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/98epoints.txt__;!!DZ3fjg!4d5j5wVsMKW1-KyosgZyD43l88P3PsWnUMRt1zgclFC0=   
   _AsbDUaSGUAJFJxmJ-pM0j1uNnB10XXj4TmSmTfLo4HehAk$=20   
   Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=   
   v/qpf/99epoints.txt__;!!DZ3fjg!4d5j5wVsMKW1-KyosgZyD43l88P3PsWnUMRt1zgclFC0=   
   _AsbDUaSGUAJFJxmJ-pM0j1uNnB10XXj4TmSmTfLT3ccbKE$=20   
      
   =3D =3D =3D   
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