Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Dec 08 2023 00:25:54 FOUS30 KWBC 080025 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 724 PM EST Thu Dec 07 2023 Day 1 Valid 16Z Thu Dec 07 2023 - 12Z Fri Dec 08 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Cook Day 2 Valid 12Z Fri Dec 08 2023 - 12Z Sat Dec 09 2023 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Putnam Day 3 Valid 12Z Sat Dec 09 2023 - 12Z Sun Dec 10 2023 ....THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF THE PACIFIC NORTHWEST... ....Pacific Northwest... An Atmospheric River will impact the Pacific Northwest Saturday. Rainfall should be less intense and shorter in duration than the prior event this past weekend. However, antecedent conditions have remained wet. IVT values upwards of 500-600 Kg/m/s are forecast along the coast by Saturday evening before beginning to taper off Sunday morning. With flow relatively orthogonal to the coast some heavier rainfall totals are expected along the coastal ranges. Confidence in the location of the heaviest rainfall remains similar to the prior forecast as model guidance QPF has begun to settle on far NW coastal Oregon into Washington after a more aggressive northward shift over the past day. QPF totals currently range between 2-3", with locally higher totals up to 4". Some rainfall may linger into Sunday morning beyond the current day 3 period.=20=20 ....OH/TN Valley into the Southeast... A broad southwest-northeast axis of heavy rainfall is forecast later in the day Saturday through early Sunday from the the Ohio/Tennessee Valleys southwestward into the Mid-South and the Lower Mississippi Valley/central Gulf Coast as Gulf moisture returns northward ahead of an upper-trough/surface cold front pushing eastward. Little modification of the current MRGL risk area was needed as the QPF footprint in updated model guidance remains relatively unchanged. In general, expect organized convection to develop along the cold front in the Ohio/Tennessee Valley where upper flow will be more parallel to the front. While the front should be relatively progressive, storm orientation along the front will allow for at least some training. Further south, somewhat more isolated convection is expected along the front with upper-level flow not quite as parallel to the boundary, along with additional storms possible ahead of the front along the central Gulf Coast. Instability will likely be a bit higher, with MU CAPE from 500-1000 J/Kg, indicating the potential for a bit higher rain rates, though the signal in the guidance currently is not particularly strong on this front. As far as QPF goes, areal average totals from the Mid-South northeast into the Ohio/Tennessee Valleys ranges between about 1-2", with locally higher totals up to 3". However, the latest guidance has trended downward a bit. In addition, confidence in rainfall totals exceeding an inch quickly drops off based on ensemble probabilities. Much of the area also remains in drought. As such, the MRGL risk has been maintained for now. There is certainly a possibility that an embedded SLGT Risk will be needed but likely dependent on an indication in the CAMs as they become available that there will be at least a few more intense downpours.=20=20 Putnam Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!_oYcco81dMniMLP9pNynJcjaw9O1_scy18L2NyN2wslg= cFHAxj2jFb_fi1aElyD1PAVK9UVVxVudTAjh-DwJy9xfNMQ$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!_oYcco81dMniMLP9pNynJcjaw9O1_scy18L2NyN2wslg= cFHAxj2jFb_fi1aElyD1PAVK9UVVxVudTAjh-DwJkmJSkRI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!_oYcco81dMniMLP9pNynJcjaw9O1_scy18L2NyN2wslg= cFHAxj2jFb_fi1aElyD1PAVK9UVVxVudTAjh-DwJm4IVLlY$=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) .