Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Feb 08 2024 00:53:10 FOUS30 KWBC 080053 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 752 PM EST Wed Feb 07 2024 Day 1 Valid 01Z Thu Feb 08 2024 - 12Z Thu Feb 08 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FROM THE CENTRAL CALIFORNIA COAST INTO SOUTHERN CALIFORNIA... 0100 UTC Update -- Removed the Marginal Risk area over northern portions of the Central CA Coast based on the observational trends, i.e. the eastward progression of the surface front/axis of widespread pre-frontal precipitation. Based on the latest trends and (radar and satellite especially), along with the recent HREF guidance, continue to expect a brief period (2-3 hours) with spotty/isolated max hourly rainfall rates of 0.4-0.5 inch. The 18Z HREF probabilities of 0.50+ inch/hr rates peak between 50-70% down through LA Metro through 0800Z, then drop to 40% or less thereafter farther south through SD Metro. Meanwhile, HREF probabilities of 1.00+ inches within a 3 hour period top out at just 15-20%. Thus despite the current wet soils from the most recent AR (NASA SPoRT top meter soil moisture percentiles at 98+ percent), the quick progression of the pre-frontal precipitation axis, limited deep layer instability (MUCAPEs 100 J/Kg or less), and thus restricted short-term rainfall rates will at most maintain the isolated/localized flash flood threat overnight. Hurley Day 2 Valid 12Z Thu Feb 08 2024 - 12Z Fri Feb 09 2024 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR CENTRAL ARIZONA ... 21Z update... The overall setup of this event and specifics have not significantly changed from the previous issuance. The Marginal Risk area that is in place over central Arizona continues to highlight the locations with an elevated threat for rapid runoff and flooding concerns, therefore no adjustments were made at this time. Campbell Trailing shortwave trough will pivot out of California with increased large scale forcing in-of central and western AZ by Thursday morning. Convective risks will be lower compared to the recent setup, however enough lingering moisture and ascent focused over the Mogollon Rim will initiate another round of moderate precip over the aforementioned area. A textbook area of mid-level difluence is depicted within all major guidance with the heaviest precip centered along the western Mogollon Rim to the west of Prescott, eventually across the central terrain to the north of Phoenix. Snow levels will be down to 5000ft MSL by Thursday thanks to the lower heights brought on by the mean trough that will encompass most of the country east of the Mississippi, so the main concern will lie within the lowlands and locations prone to flooding due to complexity of the terrain. Antecedent conditions will be primed due to the preceding 36 hrs of rainfall, so despite precip totals generally hovering between 0.75-1.25" for the event, that could very well be enough for some localized flooding concerns in those valley locations within the southern portions of the Mogollon Rim. This is a low-end MRGL, but the complexity of the terrain coupled with additional rainfall over an area with historically low FFG's will allow for the threat and the maintenance of the Marginal Risk area.=20=20 Kleebauer Day 3 Valid 12Z Fri Feb 09 2024 - 12Z Sat Feb 10 2024 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Campbell Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!7go7xH3H2CqOMkuVSXCs7METryEc2Mllmb06hJv2GQJx= fRbQFK05E5lyo7d7Iz5n4699vf583WbY3sIvSW4qbfs7FiU$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!7go7xH3H2CqOMkuVSXCs7METryEc2Mllmb06hJv2GQJx= fRbQFK05E5lyo7d7Iz5n4699vf583WbY3sIvSW4q2EElHsw$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!7go7xH3H2CqOMkuVSXCs7METryEc2Mllmb06hJv2GQJx= fRbQFK05E5lyo7d7Iz5n4699vf583WbY3sIvSW4qEwTx35U$=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) .