Area Forecast Discussion
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000 FXUS61 KPBZ 060659 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 259 AM EDT WED MAY 6 2015 .SYNOPSIS... SCATTERED SHOWERS TODAY WILL GIVE WAY TO A DRIER MID-WEEK WITH ABOVE AVERAGE TEMPERATURES. && .NEAR TERM /THROUGH THURSDAY/... SHOWER ACTIVITY SEEN ON CURRENT RADAR IMAGERY IS CONFINED TO NORTH OF I-80 AS THE REMNANTS OF THE SURFACE BOUNDARY CONTINUES TO DISSIPATE. MID-LEVEL FLOW IS FROM ABOUT 280 DEGREES...SO CURRENT TRAJECTORY OF SHOWERS SHOULD HOLD THROUGH THE MORNING HOURS...BEFORE DISSIPATING UPON EXITING THE FORECAST AREA. CURRENT IR SATELLITE SHOWING AN EXPANSIVE SECTION OF CLEARING THROUGH THE UPPER OHIO VALLEY. THIS IS A RESULT OF DRIER AIR PUSHING NORTHWARD AS WHAT IS LEFT OF THE BOUNDARY RETREATS NORTH. DRIER AIR WILL MAKE IT DIFFICULT FOR WIDESPREAD FOG TO DEVELOP THIS MORNING...BUT FOG DEVELOPMENT IS EXPECTED IN SOME OF THE MORE SHELTERED AREAS...ESPECIALLY THOSE LOCATIONS THAT RECEIVED RAINFALL IN THE LAST 24HRS. THE LAST OF THE REMAINING DEEP MOISTURE WILL SKIRT THE NORTHEASTERN PERIPHERY OF THE FORECAST AREA WEDNESDAY. CONSIDERABLE WARMING OF THE LOW-LEVELS WILL ENHANCE LOW-LEVEL LAPSE RATES AND FEED INSTABILITY TO THE POINT OF THUNDERSTORM DEVELOPMENT. WITH MOISTURE RETREATING AND ONLY MEAGER FORCING COMING IN THE FORM OF A WEAK MID-LEVEL WAVE...SHOWER AND THUNDERSTORM DEVELOPMENT SHOULD BE LIMITED SPATIALLY. THE AXIS OF THE RIDGE BUILDS IN THROUGH THURSDAY...RESULTING IN A MUCH DRIER FORECAST AND HIGH TEMPERATURES REACHING WELL ABOVE NORMAL. TAX && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
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A RELATIVE MAXIMA IN HEIGHTS WILL BECOME RESIDENT OVER THE AREA BY THE END OF THE WEEK...AS HEIGHTS IN THE INTERMOUNTAIN WEST AND OFF THE SOUTHEAST COAST BOTH DECLINE. THIS SQUEEZES THE AREA INTO A FAIRLY TIGHT CORRIDOR OF RIDGING...YET DUE TO THE SLUGGISHNESS OF ACTIVITY OFF THE SOUTHEAST COAST WITH REGARD TO MOVEMENT...AS WELL AS THE FACT THAT THERE IS LITTLE IMPETUS FOR ACTIVITY IN THE INTERMOUNTAIN WEST TO BE EJECTED EASTWARD...IT WOULD SEEM WE SHOULD REMAIN IN THIS MICRO-RIDGE FOR QUITE A PERIOD. WHILE THE AIR MASS UNDER THE RIDGE WILL BE SOMEWHAT UNSTABLE...OWING TO THE LOW LEVEL MOISTURE WE HAVE ALREADY GAINED THIS WEEK FROM RAINFALL...AND CONTINUE TO WARM AGGRESSIVELY WITH DECENT INSOLATION AND SOUTHWESTERLY POSITIVE THETA-E ADVECTION...A LACK OF FORCING MECHANISMS AND SHEAR SHOULD PRECLUDE MUCH IN THE WAY OF CONVECTIVE DEVELOPMENT THROUGH MUCH OF THE SHORT TERM. SOME SLIGHT CHANCE POPS WERE INCLUDED FOR DIURNAL SHOWERS/STORMS...HOWEVER ACTIVITY SHOULD BE FAIRLY ISOLATED. THE BIG STORY IN THE SHORT TERM WILL BE THE UPWARD RIDE OF THE TEMPERATURE TRAIN. AS CONSENSUS 500 MB HEIGHTS RISE INTO THE MID 580S...AND 850 MB TEMPERATURES SURPASS 16C...IT WOULD SEEM THAT MID 80S LOOK TO BECOME INCREASINGLY LIKELY BY LATE IN THE WEEK. IT WOULD SEEM THE AIR CONDITIONERS MAY GET A PRETTY QUICK START OWING TO DEWPOINTS LIKELY TO BE IN THE LOWER 60S BY THAT TIME AS WELL. FRIES
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&& .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
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RIDGING REMAINS THE LARGE PLAYER IN THE FORECAST RIGHT THROUGH MONDAY. INCREASING MIXING AND SLIGHTLY HIGHER 850 MB TEMPERATURES SHOULD OFFSET SLIGHTLY LOWER HEIGHTS BY MONDAY AS THE THE SYSTEM THAT WILL FINALLY BREAK DOWN THE RIDGE STARTS TO MOVE INTO THE GREAT LAKES. 00Z GUIDANCE HAS INDICATED A FAIRLY MARKED SLOWING OF THE EASTWARD PROGRESSION OF THIS SYSTEM RELATIVE TO EARLIER GUIDANCE...IN LARGE PART DUE TO THE CANADIAN/GFS/GEFS MEMBERS MAINTAINING A DEEPER UPPER REFLECTION OF THE SYSTEM AS IT EMERGES INTO THE UPPER MISSISSIPPI VALLEY. THE ECMWF IS FASTER AND FLATTER WITH THE SYSTEM. POPS IN THE FORECAST AS WELL AS TEMPERATURE EXPECTATIONS WERE ADJUSTED FOR A BIT SLOWER ARRIVAL OF THE SYSTEM LIKELY CENTERED AROUND MONDAY NIGHT. HOWEVER...ONCE THE SYSTEM ARRIVES...THE CONSENSUS IS STRONG THAT DRYING SHOULD BE FAIRLY AGGRESSIVE BEHIND IT. LIKEWISE...MUCH COLDER AIR IS EVIDENT ON THE CONSENSUS IN ITS WAKE. TEMPERATURE EXPECTATIONS WERE ADJUSTED ABRUPTLY DOWNWARD BEYOND TUESDAY TO ACCOUNT FOR THIS. FRIES
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&& .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... BULK OF SHOWER ACTIVITY THIS MORNING SHOULD STAY ALONG THE NORTHERN EDGE OF THE FORECAST AREA. SHOWERS COULD BRING BRIEF VISIBILITY RESTRICTIONS TO FKL/DUJ...BUT A STABILIZING AIRMASS PRECLUDES THE NECESSITY FOR THUNDERSTORM INCLUSION. SHOWERS WILL PUSH EAST OF THE FORECAST AREA JUST AFTER SUNRISE. ELSEWHERE...DRIER AIR ADVANCING FROM THE SOUTH HAS RESULTED IN CLEARING AND PRIMARILY VFR CONDITIONS. DESPITE THE DRIER AIR...SOME FAVORABLE LOCATIONS FOR FOG DEVELOPMENT DO EXIST. FOG SHOULD REMAIN PATCHY THROUGH THE MORNING HOURS AND MAY NOT IMPACT ANY PARTICULAR TERMINAL...BUT CONFIDENCE IN THIS IS NOT HIGH. HAVE INCLUDED TEMPORARY MVFR VISIBILITY RESTRICTIONS FOR MOST LOCATIONS THROUGH 12Z. LATER TODAY...SHOWERS AND THUNDERSTORMS ARE EXPECTED ALONG THE NORTHEAST AND EASTERN PERIPHERY. WHILE SPATIAL COVERAGE IS EXPECTED TO BE LIMITED...DUJ/LBE COULD SEE TEMPORARY RESTRICTIONS LATE THIS AFTERNOON. TAX .OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/... MORNING FOG CANNOT BE RULED OUT THURSDAY OR FRIDAY MORNING. SCATTERED SHOWERS AND POSSIBLE RESTRICTIONS ARE EXPECTED FOR SATURDAY AND SUNDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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