Area Forecast Discussion
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000 FXUS61 KPBZ 211825 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 225 PM EDT THU AUG 21 2014 .SYNOPSIS... UNSETTLED WEATHER WILL CONTINUE THROUGH THE WEEKEND WITH OCCASIONAL SHOWERS AND THUNDERSTORMS. && .NEAR TERM /THROUGH TONIGHT/... SHOWERS AND THUNDERSTORMS SUPPORTED BY UPPER LEVEL WAVE IS NOW MOVING ACROSS THE UPPER OHIO VALLEY. ADDED LIKELY POPS TO THE NORTH AS UPPER WAVE PASSES THROUGH IN THE AFTERNOON WITH COVERAGE OF CONVECTION EXPECTED TO INCREASE. VISIBLE SATELLITE IMAGERY SHOWS AMPLE CLOUD COVERAGE ACROSS PITTSBURGH AND SOUTH. HENCE...OPTIMAL DAYTIME HEATING WILL NOT OCCUR IN THAT REGION...HOWEVER...INCREASING MOISTURE WILL AID IN INSTABILITY YIELDING SHOWERS AND THUNDERSTORMS. TO THE NORTH...SUFFICIENT HEATING DUE TO LESS CLOUDS HAVE RAMPED UP INSTABILITY. RAP ANALYSIS SHOWS RELATIVELY STRONGER SHEAR IN THIS ZONE AS WELL. THEREFORE...ISOLATED STRONG TO MARGINALLY SEVERE STORMS ARE POSSIBLE THIS AFTERNOON NORTH OF PITTSBURGH. GREATER COVERAGE OF CONVECTION IS EXPECTED TO WANE LATER IN THE EVENING DUE TO LOSS OF HEATING. SOME SHOWERS MAY STILL LINGER ACROSS THE AREA OVERNIGHT DUE TO THE NEARLY STATIONARY SURFACE BOUNDARY. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... AS THE NEXT SHORTWAVE CROSSES THE REGION FROM A WEAKENING AND EXITING UPPER LOW...AXIS OF HEAVY RAINFALL WILL SHIFT EAST ON FRIDAY AS THE BOUNDARY BEGINS TO SLOWLY MOVE. UNCERTAINTY STILL EXISTS FOR ANY FLOODING AS MODELS ARE IN MINOR DISAGREEMENT FOR THE PLACEMENT OF HEAVY RAIN. USED MODEL BLEND OF GFS/NAM FOR POPS AND HPC FOR QPF. UPPER LEVEL RIDGE DEVELOPS THROUGH THE WEEKEND BRINGING SLIGHTLY WARMER THAN NORMAL TEMPERATURES. A FEW SHORTWAVES TOPPING THE RIDGE BRINGS THE CHANCE OF SHOWERS AND THUNDERSTORMS...AT LEAST FOR SATURDAY BUT OVERALL COVERAGE SHOULD BE SMALL. && .LONG TERM /MONDAY THROUGH THURSDAY/... MORE CLARITY EXISTS IN THE EXTENDED FORECAST WITH THE LATEST ROUND OF MODEL GUIDANCE. BY SUN THE SFC LOW FROM THE EARLY WEEKEND DEEPENS OVER THE PIEDMONT OF VA/NC PULLING THE DEEPER MOISTURE SOUTH WITH IT. IN THE MEANTIME...THE UPPER RIDGE CURRENTLY SETTING UP OVER THE SRN MS VALLEY WILL BUILD NORTH FURTHER WITH ITS AXIS SHIFTING EAST THROUGH SUN. THIS WILL WORK TO DEFLECT AN ADVANCING LOW PRESSURE SYSTEM WELL NORTH OF THE GREAT LAKES EARLY NEXT WEEK...RESULTING IN A WARMING AND DRYING TREND. TEMPERATURES SHOULD REMAIN AT OR EVEN JUST ABOVE AVERAGE INTO THE MIDDLE OF NEXT WEEK. TAX && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... STILL LOOKING AT THE BEST PRECIP CHANCES ACROSS NORTHERN WEST VIRGINIA AND SOUTHEAST OHIO THIS AFTERNOON...LESS TO THE NORTH. KEPT PREVAILING SHRA AT ZZV/MGW AND HAVE ONLY VCTS MENTIONED TO THE NORTH. IFR POSSIBLE IN ANY THUNDERSTORM. SHOULD SEE A DECREASE IN COVERAGE WITH LOSS OF HEATING DURING THE EVENING. PUT IN MVFR FOG AT SOME LOCATIONS LATE. WILL NEED TO WATCH EASTERN OHIO LATE TONIGHT FOR POSSIBLE INTRUSION OF MCS. ZZV WOULD HAVE THE BEST CHANCE OF BEING AFFECTED. OUTLOOK.../FRIDAY THROUGH MONDAY/... SEVERAL CROSSING DISTURBANCES WILL CAUSE PERIODIC RESTRICTIONS INTO THE WEEKEND. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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