Area Forecast Discussion
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000 FXUS61 KPBZ 150526 AAC AFDPBZ AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PITTSBURGH PA 126 AM EDT TUE APR 15 2014 .SYNOPSIS... A STRONG COLD FRONT WILL CROSS THE REGION EARLY THIS MORNING BRINGING MUCH COLDER AIR AND RAIN AND SNOW SHOWERS. WELL BELOW AVERAGE TEMPERATURES ARE EXPECTED THROUGH WEDNESDAY. && .NEAR TERM /THROUGH TODAY/... MAJOR CHANGES FOR OVERNIGHT PERIOD IS ADJUSTMENT TO THE POPS... TRYING TO GET A HANDLE ON TEMPS AND PRECIP TYPE. NONE OF THE MODELS ARE HANDLING HOW FAST THE SHALLOW COLD AIR LAYER IS MOVING EASTWARD AND IN TURN THE SPEED OF A CHANGE OVER TO SNOW. USING CRITICAL THICKNESSES AND CURRENT OBS TO THE WEST...WILL ATTEMPT TO FIND A GOOD THICKNESS VALUE TO RELY ON FOR A CHANGE OVER TIME. RAIN SHOWER ACTIVITY WILL MOVE THROUGH THE AREA AHEAD OF THE FRONT...IN CORRELATION WITH THE NEXT UPPER LEVEL WAVE. MODEL SOLUTIONS OF FRONTS FORWARD SPEED HAS INCREASED WITH FROPA AT PIT EXPECTED BETWEEN 08-09Z. TIMING EVERYTHING...CHANGE OVER...SURFACE TEMPS... PRECIPITATION IS A REAL CHALLENGE. LOOKING AT WHAT HAS ALREADY OCCURRED TO THE WEST...A DROP IN TEMPS OF 15 TO 20 DEGREES LOOKS REASONABLE IN ABOUT 2 TO 3 HOURS. COMPLICATING THIS TIMING IS THE SURFACE WAVE THAT IS CURRENTLY MOVING NORTHEASTWARD ALONG THE BOUNDARY. THIS WAVE HAS BEEN ABLE TO SOMEWHAT SLOW THE EASTWARD PROGRESSION OF THE COLD AIR. HOWEVER...IF CURRENT MODEL DEPICTIONS ARE CORRECT...THIS WAVE WILL QUICKLY PICK UP SPEED AND STREAK NORTHEASTWARD AS DAWN APPROACHES. THIS MAY DECREASE THE TIME REQUIRED FOR THESE LARGE SURFACE TEMP DROPS. COLD FRONT WILL BE EAST OF MY AREA BY 12Z AND STRONG CAA WILL BE UNDERWAY ACROSS THE ENTIRE REGION. PRECIP COVERAGE WILL BE TRICKY WITH THE LOSS OF UPPER LEVEL SUPPORT AND DUE TO THE LOW-LEVEL JET SHIFTING EASTWARD. AGAIN LOOKING AT WHAT IS OCCURRING WESTWARD... RAIN SHOWERS SHOULD CHANGE OVER TO SNOW SHOWERS THIS MORNING. ATMOSPHERE SHOULD BE COLD ENOUGH TO SUPPORT SNOW ACROSS THE ENTIRE REGION BY LATE MORNING. THERE WILL LIKELY BE A PERIOD OF SNOW SHOWERS BEHIND THE FRONT FOR ALL LOCATIONS THIS MORNING FOR THE WESTERN HALF AND CONTINUING INTO THE AFTERNOON FOR THE EAST. COULD SEE SOME WHITENING OF GRASSY AREAS...BUT A WARM GROUND WILL HAMPER THIS. TEMPS TODAY WILL BE A CHALLENGE TO SAY THE LEAST. SNOW SHOWERS FROM THE FRONT SHOULD WRAP UP THIS AFTERNOON IN THE FAR EAST. HOWEVER...EXPECT MORE SNOW SHOWERS TO DEVELOP LATER THIS AFTERNOON WITH NORTHWEST WINDS AND STRONG CAA. CURRENT THINKING IS THAT THE NORTH AND RIDGES ARE AT GREATEST RISK TO SEE AND EXTENDED PERIOD OF SNOW SHOWERS...ALTHOUGH MIXING HEIGHTS OVER THE RIDGES GIVE ME PAUSE AS THEY DECREASE QUICKLY AS EVENING APPROACHES. && .SHORT TERM /TONIGHT THROUGH THURSDAY/... COLD AIR WILL REMAIN IN PLACE INTO EARLY WEDNESDAY MORNING. ANY SNOW SHOWER ACTIVITY SHOULD DECREASE LATE THIS EVENING AS INVERSIONS DROP...SUBSIDENCE INCREASE AND WINDS ALOFT SHIFT TO A MORE NORTHERLY DIRECTION. THE COLDEST AIR BEGINS TO RETREAT NORTHWARD AS DAWN APPROACHES WEDNESDAY. WAA AND SURFACE HIGH WILL PROVIDE A DRY WEDNESDAY WITH SUNSHINE... HOWEVER TEMPS WILL REMAIN BELOW NORMAL. WARMING TREND CONTINUES ON THURSDAY. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... A RETURN TO SPRING FOR THE LONG TERM...WITH THE RISK FOR SHOWERS FRIDAY NIGHT/SAT. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... CONDITION DETERIORATION AND A WIND VEER TO THE NW CAN BE EXPECTED AS A COLD FRONT SWEEPS ACRS THE UPR OH VALLEY REGION THIS MRNG. WITH THE WIND VEER WL COME A RAPID INFLUX OF COLD AIR WHICH WL CHANGE ANY RAIN SHWRS TO SNOW. COLD ADVCTN OFF THE LAKES WL MAINTAIN SNOW SHWR...AND MVFR STRATOCU UNTIL EARLY WED MRNG. .OUTLOOK.../WEDNESDAY THROUGH SATURDAY/... NXT CHC FOR GENERAL RESTRICITIONS IS EXPECTED WITH A WEEKEND LOW PRES ADVN AND PASSAGE. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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