Area Forecast Discussion
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000 FXUS61 KPBZ 292051 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 451 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/...
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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
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&& .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... 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 /SATURDAY 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 /21Z TUESDAY THROUGH SUNDAY/... VFR STRATOCUMULUS WILL CONTINUE THROUGH THE AFTERNOON INTO THE EVENING HOURS WITH SKIES GENERALLY OVERCAST...BUT COULD STILL SEE AN ISOLATED MVFR CEILING DURING THE AFTERNOON HOURS. CLOUDS SHOULD SCATTER OUT SOMEWHAT OVERNIGHT...WITH THE POTENTIAL FOR SOME MVFR FOG AT ZZV WITH LIGHT WINDS EXPECTED. CLOUDS WILL BUILD IN ONCE AGAIN ON WEDNESDAY...WITH SCATTERED SHOWERS DEVELOPING ACROSS THE REGION. NOT ENOUGH CONFIDENCE TO INCLUDE PREVAILING SHOWERS AT THIS TIME...AND HAVE JUST INCLUDED VCSH FOR NOW. THERE WILL ONLY BE A SLIGHT CHANCE OF THUNDER...SO THAT WAS NOT INCLUDED IN THE FORECAST EITHER. 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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