Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu May 25 2023 07:44:10 FOUS30 KWBC 250744 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 343 AM EDT Thu May 25 2023 Day 1 Valid 12Z Thu May 25 2023 - 12Z Fri May 26 2023 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF CENTRAL AND SOUTH FLORIDA, A LARGE PORTION OF THE PLAINS, NORTHERN ROCKIES, AND INTERMOUNTAIN WEST... ....Great Basin-Northern Rockies-High Plains... Amplifying longwave upper trough will allow for an expansive area of large scale forcing (upper difluence) eastward into the High Plains. In addition, the guidance continues to depict an elongated Warm Conveyor Belt (WCB) east of the upper trough, extending from northern Mexico through the Plains and into south-central Canada. Deterministic and probabilistic QPF from the models again support a localized or isolated flash flood threat possible anywhere within the broad risk area. We did give consideration for a Slight risk upgrade over portions of western KS into the OK/TX panhandle and adjacent portions of CO and NM. The HREF exceedance probabilities are a bit more elevated over these areas (though not in consecutive 3-hourly periods), and this is generally aligned with the area depicted as a Slight risk in the CSU ML output. However, the current pattern and continued spread in model QPF output do not convey the look of a more organized flash flood risk at this point, especially in the wake of the most recent MCS/MCV track and surface boundary locations from the convection Wednesday night. So while we could eventually need a Slight risk upgrade, feel the day shift will have an upper hand in honing in on the timing and location of any upgrade with the benefit of short-term trends and another cycle of HREF output. For now think the broad Marginal risk still represents the expected isolated flash flood risk best. ....Central and South Florida... Difluence aloft east of the upper level trough, along with continued cyclonic low-mid level flow will once again provide a favorable synoptic scale environment for convection more widespread than what would be typical for late May. This as the 00Z GEFS shows 500 mb height anomalies averaging 3 standard deviations below normal. The thermodynamic profile remains favorable for heavy rainfall as well, as mixed-layer CAPEs between 1000-2000 J/Kg and PWs averaging 1.6 to 1.7 inches are more than sufficient for hourly or sub-hourly rainfall rates of 2+ inches underneath the strongest storms. Thus like the past few days, localized areas of heavy rainfall again appear likely. The 00Z HREF neighborhood and EAS probabilities for Thursday are similar to what the HREF was showing for Wednesday. 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!66kVf9h8_zGrK9_hBzFyNJPCPYKPKrSJZdEfBEUWQ4eG= -sRAMha9PQCxJQ81dJ93yywZxRQ_ahnj6RPuq3VVNe0JMXo$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!66kVf9h8_zGrK9_hBzFyNJPCPYKPKrSJZdEfBEUWQ4eG= -sRAMha9PQCxJQ81dJ93yywZxRQ_ahnj6RPuq3VVlMiga-Q$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!66kVf9h8_zGrK9_hBzFyNJPCPYKPKrSJZdEfBEUWQ4eG= -sRAMha9PQCxJQ81dJ93yywZxRQ_ahnj6RPuq3VV2oxoiTE$=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) .