Area Forecast Discussion
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000 FXUS61 KPBZ 252302 AAA AFDPBZ AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PITTSBURGH PA 602 PM EST WED FEB 25 2015 .SYNOPSIS... LIGHT SNOW SHOWERS THURSDAY WILL GIVE WAY TO DRY AND FRIGID CONDITIONS FRIDAY. && .NEAR TERM /THROUGH THURSDAY/... 6 PM UPDATE...JUST SOME MINOR MODIFICATIONS TO OVERNIGHT PERIOD. HAVE INCREASED CLOUD COVER AS BROAD CIRRUS SHIELD OVERSPREADS THE REGION. OVERNIGHT TEMPS WILL BE TRICKY THANKS TO THE COMBINATION OF CLOUD COVER AND WARMER AIR ALOFT NUDGING IN OVER THE SOUTH. IN SPITE OF ALL OF THIS...A LIGHT NORTHERLY WIND WILL CONTINUE ACROSS THE ENTIRE REGION INTO THURSDAY MORNING. THIS FLOW WILL REINFORCE THE DRY AIR MASS NEAR THE SURFACE AND MAKE THE OVERNIGHT TEMP FORECAST DIFFICULT. A THERMAL GRADIENT AT THE SURFACE SHOWS UP NICELY ON THE LATEST OBS WITH TEMPS ACROSS THE NORTH IN THE TEENS WHILE TEMPS ACROSS THE SOUTH ARE IN THE LOW TO MID 30S. THIS SETUP WILL CONTINUE OVERNIGHT WITH MUCH COLDER TEMPS TO THE NORTH. RAISED TEMPS JUST A BIT FROM PREVIOUS FORECAST AS THE INCREASE IN CLOUD COVER WILL PREVENT OPTIMAL RADIATIONAL COOLING. PREVIOUS DISCUSSION... COLD ADVECTION AT 850MB TONIGHT WHILE WINDS ALOFT BECOME SOUTHWESTERLY AND MID LEVEL MOISTURE INCREASES. NORTHERN STREAM SYSTEM APPROACHES FROM THE WEST...WHILE A UPPER LEVEL DISTURBANCE MOVES NORTHEAST TO THE MID ATLANTIC STATES. THIS PUTS THE BULK OF THE REGION IN BETWEEN SYSTEMS WITH LIMITED DEEP MOISTURE. LIGHT SNOW SHOWERS WILL SPREAD TOWARD THE RIDGES BEFORE DAYBREAK FROM THE SOUTHERN SYSTEM...WHILE SNOW SHOWERS WITH NORTHERN STREAM WAVE WILL MOVE IN FROM THE WEST. AN INCH OR SO FOR THE HIGHER RIDGES AND LESS THAN AN INCH NEAR THE I-80 CORRIDOR. TEMPERATURES WILL BE A BIT TRICKY WITH CLOUD COVER FIGHTING THE COLD ADVECTION OVERNIGHT...SINGLE DIGITS FAR NORTH TO UPPER TEENS FAR SOUTH. TEMPERATURES WILL STRUGGLE INTO THE TEENS AND 20S THURSDAY. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/... SNOW SHOWERS WILL BE DIMINISHING WEST TO EAST THURSDAY EVENING WITH 850MB TEMPS RANGING FROM -18 TO -20C BY 12Z FRIDAY BASED ON THE NAM. THIS WILL PUSH TEMPERATURES INTO THE SINGLE DIGITS WITH BELOW ZERO READING ACROSS THE NORTH. ARCTIC HIGH WILL BUILD OVER REGION FOR FRIDAY THROUGH SATURDAY KEEPING TEMPERATURE 25 TO 30 DEGREES BELOW AVERAGE. CLEAR SKIES FRIDAY NIGHT WITH CALM WINDS OVER SNOW WILL ALLOW FOR TEMPERATURES WELL BELOW ZERO FRIDAY NIGHT. SURFACE RIDGE AXIS BEGINS TO PUSH EAST SATURDAY AFTERNOON ALLOWING TEMPERATURES TO RECOVER INTO THE 20S WITH NEAR 30 FOR THE MASON DIXON LINE. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... MINIMAL CHANGES TO THE EXTENDED WERE MADE MAINLY FOR COORDINATION WITH SURROUNDING OFFICES. MARCH BEGINS WITH SFC HIGH PRESSURE BEING SHUNTED TO OUR EAST AS A LONGWAVE TROF DIGS IN ALONG THE PACIFIC COAST. THIS WILL AT LEAST TEMPORARILY BRING A CHANGE TO THE UPPER LEVEL FLOW TO A MORE ZONAL REGIME. A WEST TO EAST BOUNDARY WILL SERVE AS A LOOSE FOCUS FOR PRECIPITATION OVERSPREADING THE REGION BY LATE WEEKEND. TEMPERATURES SUNDAY SHOULD MOVE TOWARD THE SEASONAL AVERAGE...WHICH WILL PROVIDE A MIX OF PRECIPITATION TYPES. GIVEN THE RECENT COLD TEMPERATURES...SFC TEMPERATURES MAY RESULT IN FREEZING RAIN BEING INCLUDED IN FUTURE UPDATES. AT THE MOMENT...INCLUSION OF A FEW HOURS OF FREEZING RAIN IS A BIT TOO FINE SCALE AND THUS CONFIDENCE IS NOT HIGH ENOUGH. LONG RANGE GUIDANCE VARIES A BIT HEADING INTO NEXT WEEK...BUT SIGNS POINT TO ANOTHER STORM SYSTEM FROM THE SOUTHERN STREAM MOVING EAST MID WEEK WITH ANOTHER ROUND OF MIXED PRECIPITATION. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... PREVAILING VFR CONDITIONS ARE EXPECTED ACROSS THE TAF SITES THROUGH THE REMAINDER OF THE AFTERNOON. SOME MVFR STRATOCUMULUS ASSOCIATED WITH THE SAGGING COLD FRONT MAY OCCASIONAL IMPACT KFKL AND KDUJ FOR THE NEXT HOUR OR SO BUT IMPROVEMENT TO VFR IS EXPECTED AND FORECAST. HIGH CLOUDS WILL BEGIN TO SPREAD NORTHWARD IN ADVANCE OF THE LOW PRESSURE SYSTEM MOVING ACROSS THE SOUTHERN STATES OVERNIGHT INTO TUESDAY. WHILE THE HEAVIEST PRECIPITATION WITH THIS SYSTEM WILL STAY SOUTH...A DIGGING UPPER TROUGH OVER THE GREAT LAKES WILL PULL SOME MOISTURE IN FROM THIS SYSTEM. THIS SHOULD BRING A PERIOD OF MVFR CIGS AND VSBYS IN SNOW ACROSS MOST OF THE TAF SITES TOMORROW MORNING...WITH PERIODIC IFR VISIBILITY POSSIBLE. FOR NOW...OPTED TO TREND TO MVFR CONDITIONS BY TOMORROW MORNING...LEAVING PREVAILING IFR OUT. WNW WIND THIS AFTERNOON WILL SHIFT TO THE E-NE OVERNIGHT. WIND GUSTS WILL DIMINISH UNTIL TOMORROW AFTERNOON. OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/... RESTRICTIONS MAY LINGER INTO FRIDAY BEFORE HIGH PRESSURE BRINGS VFR CONDITIONS FOR MUCH OF THE WEEKEND. RESTRICTION POSSIBILITIES WILL RETURN LATE SUNDAY/MONDAY WITH AN APPROACHING COLD FRONT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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