Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jan 12 2024 22:07:39 AWUS01 KWNH 122207 FFGMPD PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-130400- Mesoscale Precipitation Discussion 0012 NWS Weather Prediction Center College Park MD 506 PM EST Fri Jan 12 2024 Areas affected...northern Mid-Atlantic region Concerning...Heavy rainfall...Flash flooding possible Valid 122200Z - 130400Z SUMMARY...Areas of moderate to heavy rain are expected to translate northward through the Mid-Atlantic region late this evening and early tonight. Occasional hourly totals over 0.5 inches will be possible and 1 to 1.5 inches in 3 hours where training occurs. Given wet antecedent conditions due to recent above average rainfall, localized excess runoff/flooding will be possible. DISCUSSION...2130Z radar imagery showed pockets of moderate to heavy rainfall occurring from the western Carolinas into portions of southern VA near the Blue Ridge Mountains. CIRA LPW imagery showed strong low to mid-level moisture transport was occurring from the south ahead of an occluded cyclone analyzed over the TN Valley and Southeast at 21Z, with 925-850 mb mean layer winds ranging from 40-60 kt across the Mid-Atlantic states, supporting a rapid increase in total precipitable water. As an example, the PWAT value at Columbia, SC increased from 0.3 to 1.0 inches over the past 6 hours according to GPS data. The RAP has been consistent with the axis of strong moisture transport along the East Coast late this evening, supported by strengthening 925-850 mb winds peaking in the 70-80 kt range from eastern VA into the Delmarva Peninsula by 05Z, increasing PWAT values to near 1 inch along the I-81 corridor and up to 1.3 inches along the I-95 corridor from RMN to PHL. An SW to NE axis of low level convergence is likely to set up along the leading edge of the stronger low level winds, near or just west of the I-50 corridor from DCA to PHL, which will be parallel to deeper layer steering flow. Additional forcing due to upslope flow into the Blue Ridge and central Appalachians is expected to support locally higher rainfall rates as well. MUCAPE will increase up to a couple hundred J/kg according to the past few cycles of the RAP in the vicinity of the I-95 corridor, which while weak, may still support some hourly rainfall totals over 0.5 inches and 3 hour totals of 1 to 1.5 inches due to training/repeating areas of heavy rain. Given very wet antecedent conditions due to recent heavy rainfall and many areas streams/rivers running above normal, excess runoff from heavy rain may lead to a few areas of isolated flooding, perhaps focused best across low lying and urban locations that experience poor drainage. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5tvYiUUlmCvKwFZpwIRF63x69Z4TNKjhli762Rn5jwQRCn98j4ExVDUyP3YD9QUfGhZq= Z5HtSBjBShAufx-VipDSnlk$ for graphic product... ATTN...WFO...AKQ...BGM...CTP...LWX...PBZ...PHI...RLX...RNK... ATTN...RFC...MARFC...OHRFC...SERFC...NWC... LAT...LON 41287682 40837574 40037521 39347605 38777680=20 37627810 37317921 37318007 37958053 39367964=20 40487878 41187805=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) .