Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Feb 09 2024 20:17:48 FOUS30 KWBC 092017 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 312 PM EST Fri Feb 09 2024 Day 1 Valid 16Z Fri Feb 09 2024 - 12Z Sat Feb 10 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 2 Valid 12Z Sat Feb 10 2024 - 12Z Sun Feb 11 2024 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE GULF COAST STATES TO THE SOUTHEAST U.S... 21Z update... The latest runs of hi-res guidance are showing thunderstorms tracking across central-eastern Texas over multiple hours with rainfall rates exceeding 0.50-1.00 inch/hr. Therefore the Marginal Risk area was expanded westward to cover the potential for excessive rainfall and local flash flooding concerns. The overall axis of QPF has remained similar to the previous forecast although there have been some increases. As such the Marginal Risk area was also extended further northeast across eastern Kentucky, western Virginia and into far southern West Virginia. The Slight Risk area was adjusted a little further into eastern Texas and north/northeast to the tri-border of Kentucky, Tennessee and Virginia. Campbell Increasing large scale ascent across portions of the South and Southeast U.S. ahead of a vigorous upper trough will set the stage for increasing chances of heavy to possibly excessive rainfall from the the Gulf Coast region into parts of the Southeast U.S.. The latest guidance continue to depict an elongated axis of QPF, with areal averages of 1 to 3 inches, to form along the slow-moving/stalled surface front stretched across the Lower Mississippi Valley, South- and Southeast-US...with models favoring an axis from northern Louisiana, southern Arkansas and northern Mississippi. A few models suggested maximums of 3-4+ inches to focus over these locations. Given the latest trends for a west-east increase of areal coverage along the front, the northern periphery of the previously issued Slight Risk area was nudged just a bit farther northward. Beyond that...few changes were made. Bann Day 3 Valid 12Z Sun Feb 11 2024 - 12Z Mon Feb 12 2024 ....THERE IS A MARGINAL RISK AREA OVER PORTIONS OF THE SOUTHEAST U.S. ON SUNDAY... 21Z update... Guidance continue to depict an areal footprint of QPF across the Gulf states and into the Southeast during this period. The latest WPC forecast did have a decrease in QPF across portions Mississippi while increasing across east-central Georgia and western South Carolina. There is still an elevated threat for excessive rainfall and local instances of flash flooding however the Marginal Risk as a whole was shifted eastward by a couple tiers of counties. Campbell There may a lingering threat for excessive rainfall early in the Day 3 period as the upper level dynamics begins to accelerate eastward. Then the on-shore flow of Gulf moisture becomes re-established later in the day as the vigorous short wave ejecting out of the southern Rockies makes its way north and eastward and results in the flow aloft to become increasingly difluent. While there is some overlap with a northwest to southeast stripe in Alabama where 14-day rainfall amounts of a couple inches was observed...the axis of heaviest rain should generally be over areas that have had little or no rainfall recently so a Marginal risk area should be sufficient...especially given that WPC deterministic rainfall amounts are generally at or below 2 inches, Bann Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!5FGnigqeUnKzyB4tc0vY4Ae2U-sb4TCYk95TJPE2vCXH= ij1sSqTXmExlnJM5tyOIabn9ux315xrRqQZfI9684yM1HkU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!5FGnigqeUnKzyB4tc0vY4Ae2U-sb4TCYk95TJPE2vCXH= ij1sSqTXmExlnJM5tyOIabn9ux315xrRqQZfI968GEre5RI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!5FGnigqeUnKzyB4tc0vY4Ae2U-sb4TCYk95TJPE2vCXH= ij1sSqTXmExlnJM5tyOIabn9ux315xrRqQZfI968wQepY1c$=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) .