Subj : HVYRAIN: Excessive Rainfall Discussion To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Dec 23 2022 08:37:26 FOUS30 KWBC 230837 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 336 AM EST Fri Dec 23 2022 Day 1 Valid 12Z Fri Dec 23 2022 - 12Z Sat Dec 24 2022 ....A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS FOR PORTIONS OF NEW ENGLAND... The threat of excessive rainfall continues over parts of interior New England to the coast of Maine today as a plume of moisture, supported by onshore flow and a strong low level jet, enters the region. A deep upper-level low will continue pushing it's surface reflection and powerful attendant cold front through the Ohio Valley and East Coast today. A coastal low and attendant quasi-stationary front will lift north this afternoon, advecting with it a plume of anomalous moisture into portions of the Northeast. The merging of the two systems will allow for the enhancement of precipitation, especially over the terrain of New Hampshire and Maine where 50kt+ low level jet winds will support rain rates of around 0.5in/hr. Precipitation should start as snow early this morning before quickly transitioning into a steady rainfall today and wrapping up as snow tonight. The slight risk from yesterday's issuance was adjusted by cutting back the southern tip into northern New Hampshire to account for heightened FFGs and the latest 00z guidance suite, which suggest a more northerly solution with the axis of greatest QPF. There are concerns of melting snow causing additional flash flooding concerns. The heaviest rainfall should come to an end by this evening. Kebede Day 2 Valid 12Z Sat Dec 24 2022 - 12Z Sun Dec 25 2022 ....A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE PACIFIC NORTHWEST... The arrival of an East Pacific front will advect a relatively weak plume of moisture into the Pacific Northwest on Saturday. Rain rates of around a quarter of an inch with higher values over the Olympics may support some isolated flash flooding risk. Thus, the highest qpf is likely to accumulate over the terrain, particularly the Olympic Mountains where between 2-3 inches and locally higher amounts are possible. Kebede Day 3 Valid 12Z Sun Dec 25 2022 - 12Z Mon Dec 26 2022 ....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF THE PACIFIC NORTHWEST... A new, more powerful low pressure system will enter the Gulf of Alaska on Sunday, sending a potent cold front directly into the Pacific Northwest. This cold front will be the focus for additional heavy rainfall over portions of the coastal Pacific Northwest, much like Saturday. Thus the heaviest precipitation is expected to occur over the higher elevations, especially the Olympic Mountains where the greatest chance for isolated flash flooding may occur. This marginal risk will extend south into northwestern Oregon where up to a quarter inch rates are possible. Kebede Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/94epoints.txt__;!!DZ3fjg!-6eDNA9gj5OJoszxl1NMVcnfl60T5oqM2VLfKjFLRM0j= wPGCxTzLChnTNCb8oHVPhuL36DYQRE_xJQmP9usZnQw9ACc$=20 Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/98epoints.txt__;!!DZ3fjg!-6eDNA9gj5OJoszxl1NMVcnfl60T5oqM2VLfKjFLRM0j= wPGCxTzLChnTNCb8oHVPhuL36DYQRE_xJQmP9usZwosh8vI$=20 Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go= v/qpf/99epoints.txt__;!!DZ3fjg!-6eDNA9gj5OJoszxl1NMVcnfl60T5oqM2VLfKjFLRM0j= wPGCxTzLChnTNCb8oHVPhuL36DYQRE_xJQmP9usZThLkUwg$=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) .