402 FOUS62 KALR 230039 FFGSJU COUNTY FLASH FLOOD GUIDANCE...PUERTO RICO NATIONAL WEATHER SERVICE SOUTHEAST RIVER FORECAST CENTER...ATLANTA GA 838 PM EDT SAT AUG 22 2026 INCHES OF RAINFALL FOR SPECIFIED DURATIONS REQUIRED TO PRODUCE FLASH FLOODING IN FORECAST ZONES. LOWER AMOUNTS MAY CAUSE FLASH FLOODING IN URBAN OR MOUNTAINOUS AREAS. .B ALR 20260823 Z DH00/DC202608230038 /DUE/PPHCF/PPTCF/PPQCF :IDENTIFIERS ARE 2-LETTER STATE, Z FOR ZONE, 3-DIGIT ZONE NUMBER : :IDENT 1HR 3HR 6HR ZONE NAME :======= ==== ==== ==== ==================== PRZ001 1.9/ 3.6/ 4.9 PRZ002 1.9/ 3.6/ 4.9 PRZ003 1.9/ 3.4/ 4.8 PRZ004 1.9/ 3.4/ 4.8 PRZ005 1.6/ 2.2/ 2.9 PRZ006 1.6/ 2.2/ 2.9 PRZ007 1.6/ 2.2/ 2.9 PRZ008 1.6/ 2.2/ 2.9 PRZ009 1.6/ 2.2/ 2.9 PRZ010 1.6/ 2.2/ 2.9 PRZ011 1.6/ 2.2/ 2.9 PRZ012 2.0/ 3.2/ 4.5 PRZ013 2.0/ 3.2/ 4.5 VIZ001 2.1/ 3.3/ 4.6 VIZ002 2.1/ 3.3/ 4.6 .END $$ S.E.R.F.C. 770-486-0028 or 770-282-2112 Regular Hours 6am-10pm Eastern Time After Hours Please Follow Callback Instructions  811 AWUS01 KWNH 230047 FFGMPD PAZ000-MDZ000-VAZ000-DCZ000-WVZ000-230515- Mesoscale Precipitation Discussion 1114 NWS Weather Prediction Center College Park MD 847 PM EDT Sat Aug 22 2026 Areas affected...central PA into central VA Concerning...Heavy rainfall...Flash flooding possible Valid 230042Z - 230515Z SUMMARY...A threat of flash flooding will continue over the next few hours from portions of central PA into central VA. Hourly rainfall of 1 to 2 inches with peak hourly rainfall of 2 to 3 inches will be possible. DISCUSSION...Mid-level water vapor and GLM imagery from 00Z showed scattered thunderstorms from eastern OH/WV into PA and portions of west-central VA, located out ahead of the base of an amplifying upper trough advancing across the OH Valley, with a couple of leading vorticity maxima at the leading edge. Radar imagery showed a few slow moving and repeating cells over west-central PA and north-central VA (Green, Madison and Culpeper counties) resulting in a broken north-south axis of FLASH Unit Streamflow responses of 200 to 400+ cfs/sq mi and likely a few areas of flash flooding embedded within. Many of these cells are about to be overtaken by eastward propagating boundary from the west, located from near Philipsburg, PA to Cumberland, MD to Waynesboro, VA, advancing between 25-30 kt toward the east. However, the environment out ahead of the advancing line contained 500 to 1500 J/kg MLCAPE (highest to south) and PWs of 1.5 to 1.7 inches via the 00Z LWX sounding and the 00Z SPC mesoanalysis, resulting in localized hourly rainfall of 2 to 3 inches. As the mid to upper-level trough continues to advance east early tonight, thunderstorms will follow suit with movement from west to east over time. Decreasing instability with time for some locations (especially northern and eastern PA) combined with mostly progressive cells should limit the flash flood threat. However, increasing instability over northeastern MD into southeastern PA and the potential for convective development out ahead of the main thunderstorm axis and/or alignment of cells with the mean southwesterly steering flow may result in peak hourly rainfall in excess of 2 inches. Total rainfall of 1 to 3 inches is expected from central PA into central VA, but portions of the northern Mid-Atlantic into eastern PA have received above average rainfall over the past week (200 to 400+ percent of normal). Therefore, locations with above average soil moisture, coupled with any urban locations, will be at higher risk of flash flooding should brief training setup through ~05Z. Otto ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...BGM...CTP...LWX...PHI... ATTN...RFC...RHA...TIR...NWC... LAT...LON 41867775 41867665 41397598 40857568 39927567 39137678 38227790 38357902 39667855 40297843 40987830 41657826