Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Aug 08 2023 18:37:29 AWUS01 KWNH 081837 FFGMPD MEZ000-MAZ000-NHZ000-VTZ000-NYZ000-090035- Mesoscale Precipitation Discussion 0892 NWS Weather Prediction Center College Park MD 235 PM EDT Tue Aug 08 2023 Areas affected...Northern New England Concerning...Heavy rainfall...Flash flooding possible Valid 081835Z - 090035Z SUMMARY...Areas of flash flooding will be possible this afternoon and into the early evening hours across areas of northern New England from additional rounds of heavy rainfall. DISCUSSION...A rather strong upper-level trough continues to advance northeast early this afternoon up across the St. Lawrence River Valley which is maintaining a corridor of rather strong warm air advection and Atlantic moisture transport up across much of Maine. Surface observations show one area low pressure now moving into southern Quebec, but a triple point low center is seen over southern New Hampshire lifting off to the northeast, and there continues to be a swath of enhanced low-level convergence and a modest nose of instability ahead of this that is working in tandem with larger scale upper-jet dynamics and local orographics for a general south to north axis of heavy rainfall across Maine. In fact, the latest 850/925mb VWP data from GYX and CBW show a persistent 30 to 40+ kt south-southeast fetch coming in off the Gulf of Maine which is helping to drive a nose of 1.75 to 2.0 inch PWs into at least the southern and eastern portions of the state. There is a nose of MUCAPE values of 500 to 750 J/kg nosing up across southern Maine and this coupled with the larger scale forcing may still favor rainfall rates with some of the stronger embedded convective elements that reach over 1 inch/hour. The latest HREF guidance suggests this deeper layer atmospheric river activity helping to drive potentially another 2 to 3 inches of rain locally going through the early evening hours for areas of central and southern Maine, and this may be enough to cause some additional areas of flash flooding given the rainfall totals that have already occurred through midday. Meanwhile, farther back to the west across Vermont and New Hampshire which are closer to the core of the upper-level trough, and closer to the frontal occlusion, there is somewhat stronger instability noted with the aid of somewhat steeper mid-level lapse rates and boundary layer heating via solar insolation. This is resulting in MUCAPE values of 1000 to 1500 J/kg. The latest HREF guidance shows a combination of orographics, frontal convergence and greater instability all favoring an increase in shower and thunderstorm activity here this afternoon with rather slow-moving cells. Additional rainfall amounts here of 1 to 2 inches with isolated heavier amounts will be possible. Given the wet antecedent conditions, additional areas of flash flooding may be possible here as well. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4wftXIfqqghOJB746_p7ulQzkLgulL87b3U9-UTnqGBhc89qg5nXzwd07Uu9JKQMcdp0= kaCNC_Ei0_kyK5TxAnr7M30$ for graphic product... ATTN...WFO...ALY...BOX...BTV...CAR...GYX... ATTN...RFC...NERFC...NWC... LAT...LON 47476803 46876705 45546696 44336802 42787099=20 42967304 44037355 44777315 45527085 47146960=20 =20=20=20=20=20=20=20=20=20=20=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. 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) .