Subj : HVYRAIN: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Nov 23 2022 00:40:51 FOUS30 KWBC 230040 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 739 PM EST Tue Nov 22 2022 Day 1 Valid 01Z Wed Nov 23 2022 - 12Z Wed Nov 23 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ALONG THE EAST CENTRAL COAST OF FLORIDA... ....Central East Coast to Southern Florida... RADAR and VWP suite denote a weak inflection at 850mb along just east of S Brevard/Indian River county with weak trof extending south-southwest across the southern Peninsula. Instability remains sufficient south of the frontal boundary in the near-term, but forcing continues to weaken along with with diurnal wind flow shifting off-shore. It is possible a few weak, nearly stationary thunderstorms could develop along this weak trof over land, but the potential/coverage for excessive rainfall is likely to widely isolated including the urban centers along the I-95 corridor. As such, will drop the Marginal Risk of Excessive Rainfall, though the risk remains non-zero, especially over the next few hours. Gallina Day 2 Valid 12Z Wed Nov 23 2022 - 12Z Thu Nov 24 2022 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Wegman Day 3 Valid 12Z Thu Nov 24 2022 - 12Z Fri Nov 25 2022 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EAST TEXAS INTO THE LOWER MISSISSIPPI VALLEY... ....2030Z Update... The models remain in good agreement on an area of heavy rain developing on Thanksgiving Day into Thursday night across a swath of the country from east TX through northern MS. A nearly stationary frontal boundary situated under a 130 kt southwesterly jet will draw plentiful Gulf moisture northward into the Slight Risk area, where the front will act as a focal point for convection that is likely to either train over the same areas or result in multiple rounds of heavy rain over the area. While there remains some uncertainty on where the heaviest rainfall will set up, it appears likely that with PWATS of 1.5 to 1.75", which are over 2 standard deviations above normal, and a steady supply of additional Gulf moisture over these same areas should overcome antecedent dry conditions and result in localized flash flooding. Further, there will be a bit of rainfall Wednesday night over northern areas that may help to saturate the soils. Instability will be greatest across western areas in east TX, where the heaviest rainfall rates will be, but then those storms will quickly move northeastward across the rest of the Slight Risk area. In coordination with the FWD/Dallas-Fort Worth, TX and HGX/Houston, TX forecast offices, a Slight Risk was introduced with this update. Wegman ....Previous Discussion... Model guidance has come into better agreement with the developing closed low over the Southern Plains Thursday into Friday. There continues to be some timing differences with the GFS and ECMWF slightly more progressive than the NAM, CMC and UKMET. Despite these timing differences, there is model consensus for an expanding area of heavy precipitation late day 2 continuing into day 3 from northeast Texas, eastward into the Lower Mississippi as strengthening southerly low level flow off the western Gulf late day 2 will raise PW values to 1.5-1.75"+ (2+ standard deviations above the mean) from eastern Texas, eastward into the Lower Mississippi Valley. Much of this region has had below average precip totals over the past several weeks, save for upper coastal TX into southwest coastal LA. This is resulting in stream flows below average across much of this region. For this reason, only a marginal risk area is denoted day 3. This may be upgraded to a slight risk in subsequent outlooks if model consensus for the heaviest axis remains consistent. There will be potential for training of cells in a general south southwest to north northeasterly direction across the marginal risk area, supporting potential for totals in the 3-5"+ range where training occurs. Oravec Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_ym0ioPJNJJxoVXvNaq0vk5xKPdcl0GyF6mqjzrn6GPQ= CIDnTVUVvaRc8KPhtA1I2IRQMVDm_04MvqZoMHvfl8zTGOM$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_ym0ioPJNJJxoVXvNaq0vk5xKPdcl0GyF6mqjzrn6GPQ= CIDnTVUVvaRc8KPhtA1I2IRQMVDm_04MvqZoMHvfminekqU$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_ym0ioPJNJJxoVXvNaq0vk5xKPdcl0GyF6mqjzrn6GPQ= CIDnTVUVvaRc8KPhtA1I2IRQMVDm_04MvqZoMHvfb-nd84o$=20 $$ =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .