Area Forecast Discussion
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000 FXUS61 KPBZ 311612 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1212 PM EDT SUN AUG 31 2014 .SYNOPSIS... STEADY RAIN SHOWERS AND A FEW RUMBLES OF THUNDER TODAY AS HUMID CONDITIONS REMAIN. SCATTERED RAIN CHANCES FOR LABOR DAY...BUT OVERALL DRIER CONDITIONS EXPECTED. && .NEAR TERM /THROUGH MONDAY/... CURRENT RADAR IMAGERY SHOWS A LARGE SWATH OF LIGHT TO MODERATE RAIN SHOWERS SPLAYED ACROSS THE AREA FROM SW TO NE. OVERALL RAIN RATES HAVE REMAINED AT 0.5" PER HOUR OR LESS...BUT SEVERAL HOURS OF THIS HAS LED TO SOME RATHER HIGH 6HR TOTALS. HIGHEST AMOUNTS SINCE MIDNIGHT FOLLOW A RELATIVELY NARROW CORRIDOR FROM MONROE COUNTY IN OH NORTHEAST THROUGH ALLEGHENY COUNTY TO NRN INDIANA COUNTY IN PA. RAIN TOTALS OF 1" ARE COMMON WITH SEVERAL LOCATIONS RECEIVING UP TO 2". WHILE THIS NORMALLY WOULDNT PRODUCE MANY WATER PROBLEMS AFTER NEARLY A WEEK OF DRY WEATHER...POOR DRAINAGE IN URBAN ENVIRONMENTS MAKE IT DIFFICULT FOR 2" OF WATER TO PROPERLY RUNOFF. AS A RESULT...HAVE HAD TO ISSUE A FLOOD ADVISORY FOR ALLEGHENY COUNTY THROUGH EARLY AFTERNOON. BACK EDGE OF THE RAIN QUICKLY ERODING THROUGH NERN OH AND NW PA AS THE H5 MOISTURE DRIES UP. NEAR TERM MODELS CONTINUE TO SHOW CONVECTION FIRING OVER NCNTRL OH...BUT COPIOUS AMOUNTS OF CLOUD COVER SHOULD PRECLUDE ANY FURTHER BUILDUP OF INSTABILITY. EXPECTING SOME ADDITIONAL SHOWERS ALONG OUR WRN FLANK...BUT THUNDER CHANCES ARE LOOKING INCREASINGLY LESS LIKELY. EVEN REGARDLESS OF THE ACTUAL STRENGTH OF ANY SHOWERS OR THUNDERSTORMS THIS EVENING...THEY WILL TAP INTO AN AIRMASS WITH PW VALUES AROUND 2" AND WET BULB ZERO HEIGHTS NEAR 13KFT. SHOWERS OF ANY FORM TODAY/TONIGHT WILL BE EFFICIENT RAIN PRODUCERS. ANOTHER MID-LEVEL WAVE CURRENTLY TRACKING TROUGH TN/KY IS POISED TO ARRIVE THIS EVENING...BUT THE CURRENT TRAJECTORY WOULD FAVOR SHOWERS SPREADING ACROSS OUR SOUTH AND SOUTHEAST. WHILE THIS AREA HAD BEEN THE BIGGEST CONCERN COMING INTO THE EVENT...WITH FFG VALUES AROUND 1.5" IN 3HR...IT HAS SEEN VERY LITTLE RAINFALL THROUGH THE DAY. BECAUSE OF THE RELATIVELY TAME RAIN RATES MORE OF A STRATIFORM RAIN EVENT...AND WITH MOST OF TONIGHTS RAIN EXPECTED TO FALL OVER OUR SERN COUNTIES THAT HAVE HAVE REMAINED RELATIVELY UNSCATHED...HAVE DECIDED TO HOLD OFF ON HOISTING ANY FLASH FLOOD WATCH. TAX && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... WARM AND HUMID MONDAY IN SOUTHWEST FLOW ALOFT...BUT NO REAL KICKER FOR CONVECTION SO CHANCE POPS MAINTAINED WITH MAINLY DIFFERENTIAL HEATING ACTING ON LOW LEVEL INSTABILITY. FAIRLY STRONG COLD FRONT AND UPPER THROUGH WILL BRING LIKELY POPS BACK TO THE FORECAST TUESDAY. HIGH PRESSURE WILL GIVE A DRY AND SEASONAL FORECAST FOR WEDNESDAY WITH SOMEWHAT LESS HUMIDITY. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... HIGH PRESSURE WILL REMAIN ALONG THE EAST COAST THROUGH THURSDAY NIGHT...ALLOWING CONDITIONS TO REMAIN DRY. WHILE THE 00Z GFS KEEPS AN APPROACHING COLD FRONT TO THE NORTHWEST ON FRIDAY...ECMWF AND SEVERAL ENSEMBLES SHOW THE FRONT APPROACHING MORE QUICKLY...AND HAVE SPED UP TIMING IN FORECAST. WHILE PRECIPITATION COVERAGE WILL WANE OVERNIGHT...COVERAGE SHOULD INCREASE AGAIN ON SATURDAY WITH FAIRLY DECENT MODEL TIMING THIS FAR OUT. IN ADVANCE OF THE COLD FRONT...TEMPERATURES WILL BE ABOUT FIVE DEGREES ABOVE NORMAL. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/... WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS WILL ADVANCE INTO THE REGION FROM THE SOUTHWEST. THIS WILL BRING MVFR RESTRICTIONS TO ALL SITES...AND IFR CONDITIONS CANNOT BE RULED OUT. ALTHOUGH AN ISOLATED THUNDERSTORM IS POSSIBLE DURING THE MORNING HOURS...BEST CHANCE FOR ANY THUNDERSTORMS WOULD BE DURING PEAK HEATING THIS AFTERNOON. RAIN WILL BEGIN TO DIMINISH FROM NORTHWEST TO SOUTHEAST THIS EVENING...BUT CONDITIONS ARE STILL EXPECTED TO REMAIN LOW MVFR. OUTLOOK.../SUNDAY NIGHT THROUGH THURSDAY/... RESTRICTIONS ARE POSSIBLE AGAIN WITH A COLD FRONT ON TUESDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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