Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Sep 12 2023 07:58:03 FOUS30 KWBC 120757 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 357 AM EDT Tue Sep 12 2023 Day 1 Valid 12Z Tue Sep 12 2023 - 12Z Wed Sep 13 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PARTS OF CENTRAL AND SOUTHERN NEW MEXICO INTO EASTERN ARIZONA... ....Southwest and Four Corners area to the southern High Plains... Active, quasi-zonal southern stream with embedded shortwave energy traversing w-e across the area will continue to support numerous showers and thunderstorms, particularly during the peak heating hours this afternoon. Meanwhile, a subtle (70-90kt) yet persistent upper jet streak along the OK-TX Panhandles into the northern Red River Valley will favor a boost in deep-layer ascent through this evening across east-central AZ into central and southern portions of NM (including the Albuquerque area). This is where we have delineated the Slight Risk in the Day 1 ERO, and while instability will remain marginal given the degree of cloud cover (MUCAPEs generally under 1000 J/Kg), PW and 850-700 moisture flux anomalies will be fairly robust within the Slight Risk area (around 2 standard deviations above normal). The latest (00Z) HREF shows probabilities of QPF exceeding 2.00" peaking between 30-50% within the Slight Risk area during the Day 1 period. Elsewhere, the concentration of heavier rainfall is expected to be more isolated-scattered per the model consensus, and as such the flash flood threat is expected to be more limited/localized (i.e. Marginal Risk). ....Mid Atlantic into the Northeast... Amplifying upper trough over the Upper Midwest-western Great Lakes will pinwheel east into the OH Valley and eastern Great Lakes by Wednesday morning. The bulk of the pre-trough/pre-frontal activity across the Mid Atlantic and Northeast corridor will likely hold off until later this evening/overnight per the latest CAM simulated reflectivity forecasts. The guidance continues to show an uptick in pre-trough/pre-frontal forcing on Wednesday (during the Day 2 ERO period) as shortwave energy entering the trough base leads to a more negative tilt. However, both the deterministic and probabilistic QPF guidance supports a Marginal Risk over a good portion of the northern Mid Atlantic into much of NY west of the Hudson Valley. The latest CAMs still show some spread with the heaviest rainfall, while the relative narrow/limited areal coverage of these heavy rainfall axes support a more isolated (Marginal) flash flood risk. At this point, again with the 00Z guidance in mind, the least amount of spread in the high-res guidance (and highest HREF exceedance probabilities) extend across northeast MD into southeast PA. Within this corridor, the 00Z HREF indicates the highest probabilities of 12hr QPF exceeding 3.00" between 00-12Z Wednesday (40-60%). Hurley Day 2 The Day 2 outlook will be updated by 0830Z. Day 3 The Day 3 outlook will be updated by 0830Z. Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!8G-b5vycAYKTconxGn4MnYwelLd9SfIBXUR_1qAcjUNr= 4k7vpAhwbMqo41SREFSaVbBx0nOJAymmVtNajRpUQn_NCfo$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!8G-b5vycAYKTconxGn4MnYwelLd9SfIBXUR_1qAcjUNr= 4k7vpAhwbMqo41SREFSaVbBx0nOJAymmVtNajRpUwooEKXU$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!8G-b5vycAYKTconxGn4MnYwelLd9SfIBXUR_1qAcjUNr= 4k7vpAhwbMqo41SREFSaVbBx0nOJAymmVtNajRpUTO4LsW0$=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) .