Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Nov 10 2022 20:26:37 FOUS30 KWBC 102026 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 325 PM EST Thu Nov 10 2022 Day 1 Valid 2017Z Thu Nov 10 2022 - 12Z Fri Nov 11 2022 ....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS PORTIONS OF THE SOUTHEAST... ....2015 UTC Special ERO Discussion... Updated the Day 1 ERO to remove more of eastern Florida from the Marginal and Slight Risk areas as Nicole continues to pull away from the region,.=20 Bann 16Z Excessive Rainfall Outlook Discussion... Florida Peninsula and Portions of the Southeast U.S... Began removing the eastern Florida peninsula from the Slight Risk area now that the center of Nicole has nearly crossed the width of the peninsula and drier air has been wrapping into the eastern and southern side of the storm. Maintained the Slight Risk in the northern part of the peninsula where deeper moisture continues to feed in from the North Atlantic. Rainfall rates have been pretty modest over an area that tends to be able to handle decent amounts of rainfall...and conditions have been dry for a while.=20 However...still can not rule out some enhanced amounts that leads to excessive rainfall in the inflow band or if there is a prolonged period of rainfall where Nicole pivots and takes on a northward track later.=20 ....Upper Midwest...=20 No changes were made to the inherited Marginal Risk area. The strong low over the Plains and the stationary front over the Marginal Risk area will continue to wring out the 1.25" PWATs and highly anomalous moisture over the area, with RAP guidance suggesting MU CAPE of at least 500 J/kg. The Marginal Risk will primarily focus on the first half of the period, with much of the precipitation both over and changing over to snow by later tonight. =20 Bann Day 2 Valid 12Z Fri Nov 11 2022 - 12Z Sat Nov 12 2022 ....THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR MUCH OF THE APPALACHIANS... 2030 UTC Excessive Rainfall Discussion... Very few changes were needed to the Marginal and Slight Risk areas tied with Nicole in the eastern U.S. as Nicole undergoes its extratropical transition and interacts with a broader scale trough. Inititally, higher rainfall amounts should be along the right-hand side of the system where moisture interacts with the southern end of the Blue Ridge and Allegheny range due to southeasterly flow pushing instability and moisture upslope...followed by increasing coverage of rainfall on the west side of the system in response to an approaching front. Except for some adjustments to account for shadowing by terrain and a subtle shift in the axis of highest QPF...few changes were needed. Bann Western Gulf coast... Precipitable water values are expected to rise to 1.75" while CIN erodes...which allows thunderstorms with heavy rainfall to break out across the region. MU CAPE should be 500-1000 J/kg upstream (to the southwest). here is a brief period Friday afternoon and evening where the low-level inflow/incoming boundary becomes progressive, which explains the spotty heavy rainfall seen on a few pieces of guidance. Hourly rain totals to 2" should be possible closest to the instability pool in southeast TX.=20 However, portions of LA and MS have areas which have received 200% of their seven day average rainfall this past week, increasing sensitivity. Issues should be isolated and mostly within urban areas. Roth/Wegman Day 3 Valid 12Z Sat Nov 12 2022 - 12Z Sun Nov 13 2022 ....THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FOR NORTHERN NEW ENGLAND... 2030 UTC Excessive Rainfall Outlook Discussion... The forecast track and timing of Nicole continues to support a small Marginal Risk area...primarily in the first half of the outlook period. As a result...few changes were needed. Bann ....Previous Excessive Rainfall Outlook Discussion... Heavy rainfall within an area of low- to mid-level frontogenesis around the extratropical evolution of Nicole is expected during the morning and early afternoon hours before the system accelerates out of the area. Precipitable water values rise about 1.5", which is quite anomalous. Hourly rain totals to 1" are possible during this time frame. Spots of northeast NY, northwest VT, and westernmost ME have received 150-300% of their seven day rainfall, and moderate to heavy rain is expected the previous day. Thought it prudent to retain this Marginal Risk area, which was trimmed on its south side due to the accelerating model guidance. Roth Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!9M8qu6R9uE97JnmHK5QhhRaxIJqGT3W9FnDxC-gbWhdp= 1fCvhoiDsK8q0QR8CK4nVKWokRGeHfQiLn1-wLe0wJJV9ZM$=20=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!9M8qu6R9uE97JnmHK5QhhRaxIJqGT3W9FnDxC-gbWhdp= 1fCvhoiDsK8q0QR8CK4nVKWokRGeHfQiLn1-wLe0N1aP7BE$=20=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!9M8qu6R9uE97JnmHK5QhhRaxIJqGT3W9FnDxC-gbWhdp= 1fCvhoiDsK8q0QR8CK4nVKWokRGeHfQiLn1-wLe0O-0HDLI$=20=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. 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