Area Forecast Discussion
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000 FXUS61 KPBZ 311319 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 919 AM EDT THU JUL 31 2014 .SYNOPSIS... TEMPERATURES WILL REMAIN NEAR NORMAL WITH DAILY CHANCES FOR SHOWERS AND THUNDERSTORMS FRIDAY THROUGH SUNDAY. DRY AND MILD CONDITIONS TO RETURN BY THE BEGINNING OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... MORNING UPDATE MADE TO ADD SCATTERED SHOWERS TO THE ZONES OVER WESTMORELAND AND INDIANA AS AN UPPER LEVEL SHORTWAVE DEPARTS. NO OTHER CHANGES NEEDED. PREVIOUS DISCUSSION FOLLOWS... AS THE TROF AXIS SHIFTS EAST OF THE AREA TODAY THE OVERALL CHANCE FOR PRECIPITATION WANES. 00Z NAM/GFS CONTINUE TO SHOW SOME RESIDUAL DEEP MOISTURE LASTING THROUGH THE EARLY AFTERNOON HOURS...MAINLY ACROSS OUR NRN TIER OF COUNTIES. WITH THE COLD POOL ALOFT STILL IN PLAY...LOW TO MID LEVEL LAPSE RATES WILL ONCE AGAIN GENERATE MOSTLY CLOUD COVER...BUT SOME ISOLATED SHOWERS COULD DEVELOP. HI-RES WRF MODEL RUNS ALSO SUPPORTIVE OF SHOWERS DEVELOPING NEAR OR NORTH OF I-80 AGAIN TODAY. 00Z NAM HAS THE NEXT SYSTEM BEGINNING TO PULL MOISTURE NORTHWARD FROM THE ATLANTIC OFF THE SE COAST TONIGHT. THIS WILL ADVECT HIGH CLOUDS INTO THE AREA BUT WITH THE LLVL FLOW PRIMARILY OUT OF THE SE...DOWNSLOPING WILL KEEP THE MAJORITY OF OUR AREA DRY THROUGH EARLY FRIDAY. ATTM TIMING DIFFERENCES EXIST AMONG MODELS FOR THE ONSET OF PRECIPITATION SPREADING SOUTH TO NORTH FRIDAY. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... FLOW ALOFT WILL BECOME MORE SOUTHWESTERLY AS THE UPPER TROUGH BEGINS TO FILL AND LIFT TO THE NORTHEAST. THIS WILL ALLOW FOR INCREASED MOISTURE ADVECTION INTO THE FORECAST AREA WITH PWATS JUST SHY OF 1.5" BY SATURDAY AFTERNOON. THERE WILL BE A SLIGHT CHANCE OF THUNDERSTORM DEVELOPMENT BY LATE FRIDAY MORNING MAINLY OVER THE RIDGES...BUT COVERAGE WILL INCREASE TO INCLUDE ALL ZONES DURING THE AFTERNOON AS A SHORTWAVE TROUGH TRANSITIONS OVER THE AREA LATE FRIDAY AFTERNOON THROUGH SATURDAY MORNING. THUNDERSTORM CHANCES WILL CONTINUE THROUGH SATURDAY AS MODELS INDICATE ENOUGH INSTABILITY AND MODEL PROGS SHOW THE AREA UNDER A FAVORABLE REGION OF THE UPPER JET...WITH EASTERN ZONES HAVING THE BEST SHOT OF SEEING ANY DEVELOPMENT. WITHOUT ANY APPARENT TRIGGER ATTM...ITS POSSIBLE CLOUD COVERAGE MAY KEEP THINGS TOO STABLE FOR STORMS TO TRIGGER SO MAY NEED TO ADJUST POPS IN THE COMING DAYS AS FORECAST CONFIDENCE REGARDING THIS INCREASES. MORE OF THE SAME ON SUNDAY AS THERE IS MINIMAL CHANGE IN THE OVERALL SETUP...HOWEVER THERE IS SOME DISAGREEMENT AMONG OPERATIONAL MODELS WHETHER OR NOT A SECOND SHORTWAVE WILL CROSS THE REGION...WHICH WILL WOULD BE THE DIFFERENCE BETWEEN SCATTERED COVERAGE AREAWIDE OR MINIMAL COVERAGE WITH A FOCUS OVER THE RIDGES. TEMPERATURES WILL BE AT TO SLIGHTLY BELOW SEASONAL AVERAGE THROUGH THE WEEKEND. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... MAINLY DRY AND MILD CONDITIONS CAN BE EXPECTED THROUGH THE FIRST HALF OF THE WEEK AS THE LONGWAVE PATTERN BECOMES MORE ZONAL AND DRY WEST/NORTHWEST FLOW SETS UP ACROSS THE REGION. OPERATIONAL MODELS VARY GREATLY ON THE IDEA OF SHOWERS/THUNDERSTORMS RETURNING BY MIDWEEK SO HAVE INCLUDED A SLIGHT CHANCE ON WEDNESDAY...INCREASING ON THURSDAY BASED ON ENSEMBLE GUIDANCE. && .AVIATION /13Z THURSDAY THROUGH MONDAY/... SOME IFR STRATUS AND FOG WILL LIFT BY 14Z. FROM KBVI TO KDUJ. BROAD UPPER LEVEL TROF SWINGS THROUGH THE TODAY WITH ENOUGH MOISTURE AVAILABLE TO GENERATE SOME ISOLATED SHOWERS MAINLY NORTH OF KPIT INTO EARLY AFTERNOON. NEXT RESTRICTIONS COULD COME OVERNIGHT TONIGHT INTO FRI AS THE HIGH CLOUDS FROM THE NEXT SYSTEM COULD BE SLOW TO ARRIVE. ADDITIONAL LIGHT FOG DEVELOPMENT IS EXPECTED. OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/... A LOW PRESSURE SYSTEM OVER THE WEEKEND COULD BRING ADDITIONAL RESTRICTIONS. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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