Area Forecast Discussion
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000 FXUS61 KPBZ 300437 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1237 AM EDT MON MAR 30 2015 .SYNOPSIS... A WEAK COLD FRONT WILL CROSS THE REGION TONIGHT. LOW PRESSURE IS EXPECTED TO TRACK ACROSS THE AREA TUESDAY. && .NEAR TERM /THROUGH TODAY/... WITH 1230AM UPDATE...TWEAKED HOURLY POPS/TEMPS/WEATHER. MANY LOCATIONS HAD A BRIEF PERIOD OF 30-40 MPH GUSTS AS RAIN BEGAN...BUT WITH NEARLY THE ENTIRE FORECAST AREA NOW EXPERIENCING PRECIPITATION...ADDITIONAL WIND GUSTS SHOULD BE ON THE LIGHTER SIDE. CONTINUE TO SPEED UP DEPARTURE OF OVERALL PRECIPITATION BASED ON RADAR TRENDS. COULD STILL SEE A COUPLE TENTHS OF SNOW ACCUMULATION ACROSS SOME ISOLATED LOCATIONS. AFTER ANY REMAINING SHOWERS EXIT MONDAY MORNING...UPPER TROUGHING ACROSS THE GREAT LAKES COULD ALLOW FOR A RAIN OR SNOW SHOWER NORTH OF I 80...THOUGH LIMITED MOISTURE SHOULD CAP THESE CHANCES. CLOUD COVER SHOULD BEGIN TO DECREASE BY AFTERNOON AS WELL. TEMPS SHOULD BE NEAR SEASONAL LEVELS TONIGHT...AND SEVERAL DEGREES BELOW AVERAGE ON MONDAY. && .SHORT TERM /TONIGHT THROUGH WEDNESDAY/... UNSTABLE NORTHWESTERLY FLOW WILL BRIEFLY TURN WEST-SOUTHWESTERLY BY LATE MONDAY EVENING TO ALLOW FOR THE CWA TO DRY OUT AND AT LEAST PARTIALLY CLEAR OUT. HOWEVER...AN ACTIVE PATTERN LOOKS TO CONTINUE THEREAFTER. RATHER DISTURBING MODEL TRENDS SEEM TO HAVE TAKEN HOLD ON THE 06Z AND 12Z CYCLES TODAY...WITH THE MODELS LARGELY FALLING INTO TWO CAMPS. THE NAM AND CANADIAN FAVOR A MORE NORTHERN TRACK OF A SYSTEM THROUGH THE AREA ON TUESDAY...WHILE THE GFS AND 00Z ECMWF FAVOR A MORE SOUTHERLY TRACK. UNSURPRISINGLY...THE SREF BASICALLY SPLIT THE DIFFERENCE AND ALLOWED FOR A MIDDLE GROUND FORECAST...WHICH WAS LARGELY IN LINE WITH CONTINUITY...SO FORECAST CHANGES REALLY WERE NOT ALL THAT LARGE AS A RESULT. IT DOES SEEM THAT THE GFS WAS SUFFERING FROM SOME GRID SCALE ISSUES...WHILE THE NAM WAS LIKELY SUFFERING FROM ITS HABITUAL OVER DEVELOPMENT ISSUES. THESE PROBLEMS FURTHER LEND CREDENCE TO FAVORING AN ENSEMBLE MEAN APPROACH SUCH AS THE SREF MEAN. A COMPROMISE APPROACH STILL FAVORS RELATIVELY RAPID ENCROACHMENT OF WARM ADVECTION ISENTROPIC ASCENT OVER THE FORECAST AREA LATE MONDAY NIGHT INTO TUESDAY. THIS OCCURS AS A SURFACE LOW CROSSES THE AREA WITH AT LEAST THE SOUTHERN HALF OF THE AREA LIKELY TO ENTER THE WARM SECTOR FOR A PORTION OF THAT TIME AND PROBABLY HALT RAINFALL THERE FOR A TIME. AT THE ONSET...SOME PRECIPITATION TYPE ISSUES MAY BE PRESENT IF THE SOUTHERN SOLUTIONS VERIFY...HOWEVER ANY FROZEN PRECIPITATION SHOULD QUICKLY CHANGE TO RAIN AS WARM ADVECTION QUICKLY LOOKS TO ERODE ANY COLD AIR. THIS IS ESPECIALLY TRUE GIVEN THE LACK OF ANTECEDENT DRY AIR AS THIS SYSTEM ROLLS INTO THE AREA...MINIMIZING THE POTENTIAL FOR WET BULB COOLING AS PRECIPITATION DEVELOPS. A RELATIVELY QUICK DEPARTURE OF THE SYSTEM LOOKS TO OCCUR TUESDAY NIGHT WITH MUCH DRIER AIR FLOODING INTO THE CWA ON WEDNESDAY. SOME TEMPORARY COLD ADVECTION ON WEDNESDAY WILL LIKELY STILL HOLD TEMPERATURES BACK. HOWEVER...DRASTIC PATTERN AMPLIFICATION OF THE PATTERN TO OUR WEST LOOKS TO DEVELOP A STRONG THERMAL RIDGE THAT WILL BE POISED TO PUSH INTO THE AREA LATER IN THE WEEK. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... WHILE THE GFS HAS SLOWED THE ARRIVAL OF A FRONT ON THURSDAY FROM PREVIOUS MODEL RUNS...00Z ECMWF IS EVEN SLOWER THAN THAT. GIVEN THAT THE GFS IS THE MOST OPEN WAVE SOLUTION RELATIVE TO THE CANADIAN...GEFS...AND ECMWF...TIMING SLOWER THAN THE GFS IS LIKELY MORE OPTIMAL FOR THE ARRIVAL OF SHOWERS INTO THE CWA. AS A RESULT...WARM ADVECTION WILL RULE THE ROOST ON THURSDAY...LIKELY ALLOWING FOR THE WARMEST DAY OF THE SEASON TO THIS JUNCTURE. HOWEVER ONCE PRECIPITATION ARRIVES...LOW PRESSURE FORMING ALONG THE COLD FRONT WILL KEEP PRECIPITATION IN THE FORECAST FRIDAY UNTIL IT MOVES INTO NEW ENGLAND SATURDAY. TEMPS WILL DROP AFTER THURSDAY...LEADING BACK TO YET ANOTHER PERIOD OF BELOW NORMAL VALUES. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... A WEAK UPPER LEVEL TROUGH WITH A SURFACE COLD FRONT WILL COMPLETE PASSAGE ACROSS THE UPPER OHIO VALLEY THIS MORNING ACCOMPANIED BY BRIEF WIND GUSTS OF 25 TO 30 KT AND SCATTERED LIGHT RAIN...AND SNOW SHOWERS. CONDITION DETERIORATION TO MVFR IS THUS ANTICIPATED AS THE BOUNDARY LAYER MOISTENS IN THE PREDAWN HOURS WITH IMPROVEMENT AFTER DAYBREAK AS SUBSIDENCE AND DRY ADVECTION INCREASE. .OUTLOOK.../MONDAY NIGHT THROUGH FRIDAY/... RESTRICTIONS ARE LIKELY WITH CROSSING LOW PRESSURE SYSTEMS ON TUESDAY AND THURSDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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