Area Forecast Discussion
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000 FXUS61 KPBZ 042241 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 641 PM EDT FRI SEP 4 2015 .SYNOPSIS... WARM AND HUMID CONDITIONS WILL CONTINUE THROUGH THE WEEKEND. && .NEAR TERM /THROUGH SATURDAY/... WITH 630PM UPDATE... HAVE INCREASED POPS ACROSS EASTERN HALF OF THE FORECAST AREA THROUGH THE NEXT FEW HOURS AS THUNDERSTORM COVERAGE HAS EXPANDED MORE THAN EXPECTED. WITH NO FLOW VERTICALLY THROUGH THE ATMOSPHERE...DOWNDRAFTS ARE MANAGING TO CREATE SOME GUSTY WINDS AT THE SURFACE AS THUNDERSTORMS COLLAPSE ON THEMSELVES. COVERAGE OF THUNDERSTORMS SHOULD DIMINISH WITH LOSS OF DAYTIME HEATING. PREVIOUS DISCUSSION FOLLOWS. SHORTWAVE/WEAKNESS IN THE UPPER RIDGE WILL MAINTAIN THE CHANCE FOR SHOWERS AND THUNDERSTORMS THROUGH THE EVENING. IN ADDITION...RESIDUAL OUTFLOW BOUNDARIES FROM THIS MORNINGS COMPLEX WILL ALSO BE A CONTRIBUTING FACTOR...AND A FEW STORMS HAVE ALREADY DEVELOPED IN THE HIGHER TERRAIN. WITH NO SHEAR/UPPER LEVEL FLOW...MOST OF THESE STORMS WILL BE RATHER SHORT LIVED. THUS...SLIGHT TO LOW CHANCE POPS WERE MAINTAINED THROUGH THE PERIOD WITH MOST OF THE CONVECTION EXPECTED TO DISSIPATE WITH THE LOSS OF HEATING AT NIGHTFALL. WHILE TEMPERATURES WILL BE CONTINGENT ON CLOUD COVER AND COVERAGE OF STORMS THIS AFTERNOON...GENERALLY STAYED WITH A PERSISTENCE FORECAST WITH TEMPERATURES REMAINING 5 TO 10 DEGREES ABOVE SEASONAL AVERAGES. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... H500 RIDGE WILL REESTABLISH ITSELF OVER THE WEEKEND AND CONTINUE TO KEEP MOST WEATHER SYSTEMS AT BAY. WEAK FLOW OUT OF THE EAST AND SOUTHEAST...AROUND A SURFACE HIGH TO OUR EAST...WILL BRING A SLIGHTLY DRIER AND MORE STABLE AIRMASS ON SATURDAY. WITH PWATS FALLING AND H500 TEMPERATURES RISING...EXPECTING LESS DIURNAL CONVECTIVE COVERAGE. LIMITING POPS TO SLIGHT CHANCE...WITH AREAS NORTH AND EAST OF PIT STAYING DRY. RIDGE REACHES ITS BEST STRENGTH ON SUNDAY WITH H500 HEIGHTS AROUND 590DM. THINK CAPPING WILL BE STRONG ENOUGH TO SUPPRESS CONVECTION AND WILL KEEP THE DRY FORECAST GOING. IF POPS NEED TO BE ADDED EVENTUALLY...IT WOULD BE ALONG THE RIDGES. THE RIDGE STARTS TO WEAKEN ON MONDAY AS A LARGE UPPER LOW ACROSS CANADA MOVES EASTWARD...CAUSING HEIGHTS DOWNSTREAM TO BEGIN TO FALL. STILL...THE LACK OF MOISTURE...CONTINUED CAPPING...AND PERSISTENT SPRAWLING SURFACE HIGH WILL KEEP POPS BELOW 15. ANY SIGNIFICANT PRECIPITATION CHANCE WILL WAIT UNTIL MIDWEEK. TEMPERATURES WERE BASED ON A BLEND OF 12Z BIAS-CORRECTED MOSGUIDE AND PREVIOUS NUMBERS...WITH CONTINUED VALUES OF AROUND 10 DEGREES ABOVE NORMAL. CL && .LONG TERM /TUESDAY THROUGH FRIDAY/... THE STRONG MID/UPPER RIDGE IS PROGGED TO REMAIN THROUGH EARLY NEXT WEEK...WITH CONTINUED WARM AND MUGGY CONDITIONS. RELIEF FROM THE QUITE WARM CONDITIONS MAY COME WITH COLD FRONT LATER WEDNESDAY INTO THURSDAY...AS WELL AS AN INCREASING CHANCE FOR THUNDERSTORMS. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... EXPECT PREVAILING VFR CONDITIONS FOR MUCH OF THE AFTERNOON AND EVENING WITH A SMALL CHANCE OF RESTRICTIONS IN ANY SHOWER OR THUNDERSTORM THAT PASSES DIRECTLY OVER A TAF SITE. WITH LIMITED CONFIDENCE IN ANY ONE SPECIFIC PORT BEING IMPACTED...OPTED TO LEAVE TS MENTION OUT FOR NOW. EXPECT ANOTHER ROUND OF FOG OVERNIGHT WITH PLENTY OF LOW LEVEL MOISTURE AND LITTLE MIXING. IFR FOG WILL BE POSSIBLE IN LOCATIONS THAT RECEIVED RAINFALL DURING THE DAY. OUTLOOK...SATURDAY NIGHT THROUGH WEDNESDAY... GENERAL VFR WITH BRIEF RESTRICTIONS IN EARLY MORNING FOG IS ANTICIPATED EACH DAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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