Subj : Heavy Rain/Flood East US To : All From : Mike Powell Date : Fri Jun 06 2025 08:57:00 AWUS01 KWNH 061152 FFGMPD NYZ000-PAZ000-MDZ000-WVZ000-OHZ000-KYZ000-061750- Mesoscale Precipitation Discussion 0378 NWS Weather Prediction Center College Park MD 750 AM EDT Fri Jun 06 2025 Areas affected...Central Appalachians...Northern Mid-Atlantic...Southern NY State Concerning...Heavy rainfall...Flash flooding possible Valid 061150Z - 061750Z SUMMARY...Scattered showers and thunderstorms will generally tend to expand in coverage by midday across the central Appalachians, the northern Mid-Atlantic, and southern NY state. At least isolated areas of flash flooding will be possible given heavy rainfall rates and locally wet antecedent conditions. DISCUSSION...The early morning GOES-E WV suite shows a fairly well-defined shortwave impulse advancing east through the upper OH Valley which will be crossing gradually into the central Appalachians and northern Mid-Atlantic by midday. This energy coupled with a quasi-stationary front and multiple waves of low pressure riding northeast along it is already producing some locally heavy showers and thunderstorms across far eastern OH, the northern WV Panhandle and far western PA. While instability is quite modest with only about 500 to 750 J/kg of MUCAPE in place where the axis of convection is occurring, the diurnal heating cycle by later this morning through midday will facilitate stronger boundary layer instability. This coupled with local orographics and differential heating boundaries, along with a weak upper-level jet streak (associated with the aforementioned shortwave trough) should support a gradual expansion of convective activity that will encompass the central Appalachians and stretch northeastward across the northern Mid-Atlantic and southern NY state. The PW anomalies early this morning are running about 1.5 standard deviations above normal with CIRA-ALPW data showing rather strong concentrations of moisture in the 850/500 mb layer ahead of the shortwave impulse. This coupled with the increasing instability over the next several hours should favor increasingly efficient rainfall rates that by later this morning may reach 1.5+ inches/hour. Cell-motions are forecast to be relatively slow, and with some of the activity capable of briefly training over the same area, some 3-hourly rainfall totals of as much as 2 to 3 inches will be possible. Given the locally wet antecedent conditions that are in place, these heavier rainfall rates/totals may cause at least some isolated ares of flash flooding and this will include some urban flooding impacts as well. Orrison ATTN...WFO...ALY...BGM...BUF...CLE...CTP...ILN...LWX...PBZ... PHI...RLX...RNK... ATTN...RFC...RHA...TAR...TIR...NWC... LAT...LON 43127592 42817468 42037441 41467499 40477713 39197893 37678073 37748220 38738324 39908286 40858186 41888015 42747773 $$ --- SBBSecho 3.20-Linux * Origin: ILink: CCO - capitolcityonline.net (454:3/105) .