Area Forecast Discussion
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000 FXUS61 KPBZ 292354 AAB AFDPBZ AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PITTSBURGH PA 754 PM EDT TUE JUL 29 2014 .SYNOPSIS... TEMPERATURES WILL MODERATE TOWARD NORMAL BY LATE WEEK WITH THE BEST CHANCE FOR SHOWERS ON WEDNESDAY. && .NEAR TERM /THROUGH WEDNESDAY/... 8PM UPDATE...ONLY MINOR CHANGES TO OVERNIGHT. ADJUSTED CLOUD COVER AND NUDGED TEMPS CLOSER TO LATEST GUIDANCE. PREVIOUS DISCUSSION... NORTHWESTERLY COLD ADVECTION WILL BEGIN TO WANE THIS EVENING AS LOW LEVEL FLOW SHOULD SWITCH AROUND TO THE WEST OR SOUTHWEST AHEAD OF THE NEXT INCOMING SYSTEM. THE BOUNDARY ASSOCIATED WITH THIS SYSTEM CURRENTLY RUNS FROM ROUGHLY DETROIT TO FORT WAYNE...WITH AT LEAST SOME NOMINAL SCATTERING OUT OF THE STRATOCUMULUS AHEAD OF IT. THIS SHOULD YIELD SOME BREAKS IN THE CLOUDS FOR AN HOUR OR TWO BEFORE THE WIND SHIFTS BACK TO THE NORTHWEST AND COLD ADVECTION STRATOCUMULUS AGAIN FILLS BACK IN. SOME SHOWER ACTIVITY IS NOTED ALONG THE BOUNDARY...AND GIVEN INSTABILITY PARAMETERS WITH SAID LIFTING MECHANISM...A SHOWER OR TWO CANNOT BE RULED OUT OVERNIGHT AS THE BOUNDARY PASSES. REGARDLESS...YET ANOTHER COLD NIGHT IS IN STORE FOR THE REGION. A MID-LEVEL WAVE LOOKS TO TRANSLATE SOUTHWARD THROUGH THE AREA ON WEDNESDAY...WITH STEEPENING MID-LEVEL LAPSE RATES AND VERY LOW WET BULB ZERO HEIGHTS DOWN TOWARD 7 KFT. WITH PRECIPITATION COOLING AND STEEP LAPSE RATES AND FAIRLY LOW DEWPOINTS BELOW THIS LEVEL...SOME GRAUPEL IS NOT OUT OF THE QUESTION. HOWEVER...CAPE VALUES BELOW 200 J/KG AND VERY SLIM POSITIVE AREA IN THE CHARGE SEPARATION LAYER MAKE THUNDER A TOUGH THING TO CALL FOR. AS SUCH...POPS WERE RAISED QUITE A BIT FROM THE PREVIOUS FORECAST...WHILE THUNDER WAS REMOVED FROM THE FORECAST. HIGHS WERE SUMMARILY REDUCED TO ACCOUNT FOR SIGNIFICANT PRECIPITATION COOLING. FRIES && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... SHORTWAVE EXITS WEDNESDAY NIGHT WITH SHOWERS ENDING. UPPER LEVEL TROUGH THEN BEGIN TO LIFT OUT AS CLOSED LOW BEGINS TO SHIFT WEST WITH HEIGHTS RISING OFF THE EAST COAST. TEMPERATURES WILL GRADUALLY WARM THROUGH THE PERIOD AND APPROACH SEASONAL AVERAGES FRIDAY. SHOWERS CHANCES WILL LINGER MAINLY TOWARD I-80 THURSDAY AFTERNOON CLOSER TO LAKE MOISTURE AND COLDER TEMPERATURES ALOFT. ON FRIDAY FLOW ALOFT WILL BEGIN TO SHIFT TO THE SOUTHWEST ALLOWING DEEPER MOISTURE TO ADVECT NORTH. MODELS DIFFER ON HOW FAST AND WHERE THIS WILL OCCUR...BUT WOULD EXPECT BETTER MOISTURE TO BEGIN TO MOVE UP ALONG THE RIDGES BEFORE INCREASING FARTHER WEST TOWARD OHIO. FOR NOW CHANCE POPS MOST LOCATIONS FRIDAY. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... ALTHOUGH THE MEAN TROUGH MAINTAINS THROUGH THE WEEKEND...H500 HEIGHTS WILL HAVE RECOVERED TO THE POINT THAT ALLOWS SEASONABLE TEMPERATURES. DEW POINT WILL REMAIN COMFORTABLE WITHOUT ANY SIGNIFICANT MOISTURE INFLUX FROM THE SOUTH. A SHORTWAVE MAY PROVIDE DECENT SHRA/TSRA COVERAGE SATURDAY AFTERNOON/EVENING...WHILE SUNDAY WILL SEE A RETURN OF MORE SPARSE PRECIPITATION BEHIND THIS DISTURBANCE. THERE ARE HINTS THAT THE TROUGH MAY TRY TO LIFT OUT EARLY NEXT WEEK...AT LEAST TEMPORARILY. THIS MAY LEAD TO LITTLE OR NO AFTERNOON PRECIP BY TUESDAY...AS WELL AS CONTINUED SEASONABLE WARMTH. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... STRATOCU LAYER WILL QUICKLY DECREASE DURING THE EARLY PART OF THE FORECAST PERIOD. HOWEVER...ANOTHER AREA OF CLOUDS WILL SWING THROUGH FROM THE NORTHWEST WITH THE NEXT UPPER LEVEL WAVE. WILL KEEP IN A VFR FORECAST FOR THE NIGHT AND FOR MOST PORTS ON WEDNESDAY. THE EXCEPTION WILL BE AT FKL AND DUJ WHERE MVFR CIGS WITH SHOWERS ARE POSSIBLE WITH THE PASSAGE OF A WEAK SURFACE BOUNDARY WEDNESDAY AFTERNOON. OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/... NO WDSPRD RSTRNS EXPD. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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