Area Forecast Discussion
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000 FXUS61 KPBZ 291517 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1117 AM EDT SAT AUG 29 2015 .SYNOPSIS... AFTER A WARM AND DRY SATURDAY...RAIN CHANCES RETURN LATE TONIGHT AND SUNDAY WITH PASSAGE OF A WEAK COLD FRONT. && .NEAR TERM /THROUGH TONIGHT/... HIGH PRESSURE CENTERED OVER EASTERN PA IS EXPECTED TO BRING DRY AND WARM WEATHER TODAY. CLOUDS ARE EXPECTED TO INCREASE BY EVENING WITH THE APPROACH OF A WEAK SHORTWAVE. THIS WAVE WILL ALSO BRING SLIGHT CHANCES FOR SHOWERS AND STORMS AS IT APPROACHES. THE PBZ MORNING SOUNDING SUPPORTS HIGHS A LITTLE ABOVE SEASONAL LEVELS TODAY...WITH LOWS AROUND 5 DEGREES ABOVE AVERAGE TONIGHT. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... FRONT WILL SETTLE INTO THE FORECAST AREA ON SUNDAY. HOWEVER...WITH MIDLEVEL SUPPORT WEAKENING AND PULLING OFF TO THE EAST...AND SURFACE HIGH PRESSURE IN CONTROL...THE FRONT WILL STRETCH OUT AND LARGELY DISSIPATE. ENOUGH MOISTURE AND INSTABILITY WILL REMAIN FOR SCATTERED SHOWERS AND STORMS. COVERAGE WILL BE INFLUENCED BY DIURNAL FACTORS...WITH A PEAK DURING THE AFTERNOON HOURS. GOING TO KEEP POPS IN THE CHANCE RANGE DUE TO LACK OF LARGE-SCALE FORCING...WITH VALUES DROPPING TO SLIGHT CHANCE SUNDAY NIGHT. PRECIP TOTALS WILL LIKELY REMAIN UNDER A QUARTER INCH IN GENERAL...AND WILL NOT DO MUCH TO ALLEVIATE THE OVERALL DRY ANTECEDENT CONDITIONS. ON MONDAY...A DRIER AND MORE STABLE AIRMASS WILL TRY TO SINK INTO THE CWA...BUT WILL BE HINDERED BY WEAK MIDLEVEL ENERGY MOVING NORTHWARDS ACROSS THE CENTRAL APPALACHIANS. DO NOT THINK THAT THIS FAIRLY DIFFUSE VORTICITY WILL MAKE IT TO THE PITTSBURGH AREA...BUT THERE WILL BE ENOUGH SUPPORT FOR SOME ISOLATED SHRA/TSRA MAINLY SOUTH OF I-80. SO WILL MAINTAIN A SLIGHT CHANCE POP DURING THE DAY. LOSS OF HEATING PLUS STRETCHING/WEAKENING OF VORT ENERGY WILL ALLOW PRECIPITATION TO CEASE BY SUNSET. DRIER AIR MAKES A LITTLE MORE HEADWAY SOUTH ON TUESDAY...AND THINK ISOLATED DIURNAL CONVECTION WILL BE LIMITED TO SOUTH OF PIT. BLENDED MOSGUIDE WITH GOING FORECAST TO DERIVE TEMPERATURES. NOT MUCH CHANGE TO VALUES...WITH ABOVE NORMAL TEMPERATURES THROUGHOUT. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... H500 RIDGING PATTERN TAKES HOLD THROUGH THE EXTENDED PERIOD...WITH NO ORGANIZED WEATHER SYSTEMS FORESEEN THROUGH SATURDAY. APPEARS TO BE JUST ENOUGH MOISTURE FOR ISOLATED DIURNAL CONVECTION INTO FRIDAY AT LEAST...AND ELECTED TO ADD SLIGHT CHANCE POPS EACH DAY. HOWEVER...THE STRENGTH OF MID- LEVEL CAPPING WILL NEED TO BE EVALUATED AS TIME GOES ON TO DETERMINE THE DAILY PRECIP CHANCES...WITH FRIDAY AND SATURDAY PARTICULARLY NOTEWORTHY DRY CANDIDATES. MORE CERTAIN IS THE LIKELIHOOD OF CONTINUED ABOVE NORMAL TEMPERATURES...AND HPC GUIDANCE WAS USED IN COMBINATION WITH THE PREVIOUS FORECAST FOR THE VALUES. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... A WEAK FRONT WILL APPROACH THIS AFTERNOON WITH A WEST TO EAST INCREASE IN MID CLOUDS TOWARD 00Z. ONLY ISOLATED LIGHT SHOWERS EXPECTED AS FRONT DISSIPATES ACROSS REGION LATER TONIGHT...NOT ENOUGH FOR ANY MENTION AT ANY PORT. WINDS WILL BE LIGHT MAINLY FROM THE WEST. OUTLOOK...SUNDAY THROUGH WEDNESDAY... BRIEF RESTRICTIONS POSSIBLE IN SCATTERED SHOWERS SUNDAY. GENERAL VFR EXCEPT FOR POSSIBLE PATCHY MORNING FOG THE REMAINDER OF THE WEEK. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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