Area Forecast Discussion
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742 FXUS61 KPBZ 201817 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 217 PM EDT WED MAY 20 2015 .SYNOPSIS...
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COOL TEMPERATURES WILL REMAIN THROUGH LATE WEEK. A WEAK DISTURBANCE WILL BRING A CHANCE OF SHOWERS MAINLY FROM PITTSBURGH SOUTH TONIGHT.
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&& .NEAR TERM /THROUGH THURSDAY/...
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STRATOCUMULUS REMAINS ENTRENCHED OVER MUCH OF THE FORECAST AREA THIS AFTERNOON. ALONG WITH STRONG COLD ADVECTION...THIS HAS ATTRIBUTED TO TEMPERATURES STRUGGLING TO REACH THE MID 50`S OVER...WITH MOST LOCATIONS NORTH AND EAST OF PIT UNABLE TO REACH 50 AS OF YET. THUS...TEMPERATURES THROUGH THE REST OF THE AFTERNOON WERE ADJUSTED DOWNWARD. WHILE CLOUDS SEEM TO BE THINNING JUST A BIT...IT SHOULD BE QUICKLY FILLED IN BY HIGH-MID DECK FROM THE NEXT APPROACHING SYSTEM BASED ON LATEST SATELLITE DATA. TONIGHT...A LOW PRESSURE SYSTEM MOVING FROM THE PLAINS TO THE CAROLINAS WILL BRING THE CHANCE FOR RAIN SHOWERS AS THE 850HPA LOW CROSSES OVERHEAD. OMEGA FROM THE RIGHT ENTRANCE REGION OF AN UPPER LEVEL JET AND ISENTROPIC LIFT SUPPORTS SOME QPF PER THE LATEST MODEL GUIDANCE. ALL OF THE MODELS WERE SLOW TO CATCH ONTO THIS SYSTEM BUT WITH THE LATEST MODEL RUNS...FELT COMFORTABLE ENOUGH TO ADD LIKELY POPS TO AT LEAST THE RIDGE ZONES. THERE REMAINS THE CONCERN THAT DRY AIR AT THE SURFACE WILL LEAD TO RAIN EVAPORATING BEFORE REACHING THE SURFACE SO POPS BEYOND THE HIGHER TERRAIN WERE KEPT IN THE CHANCE CATEGORY. SYSTEM WILL BE EAST OF THE RIDGES BY MIDDAY BUT LINGERING CLOUD COVER WILL ONCE AGAIN MAKE IT DIFFICULT FOR HIGH TEMPERATURES. GENERALLY STAYED CLOSE TO MAV GUIDANCE...WHICH IS 5 TO 10 DEGREES BELOW NORMAL.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
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UPPER LEVEL TROUGH WILL DEEPEN ON FRIDAY AS IT DROPS A MOISTURE STARVED COLD FRONT ACROSS THE REGION. THIS WILL REINFORCE THE COLD AIR OVER THE AREA...WITH HIGH TEMPERATURES LIKELY REALIZED EARLY. ADDED ONLY SLIGHT CHANCE POPS WITH THE FRONT AS IT REACHES THE RIDGES FRIDAY AFTERNOON BUT OTHERWISE DONT THINK THERE WILL BE MUCH MOISTURE TO SUPPORT POPS ELSEWHERE AT THIS TIME. BEHIND THE FRONT FRIDAY NIGHT SURFACE HIGH PRESSURE WILL CENTER OVER MUCH OF THE GREAT LAKES. WITH CALM WIND AND CLEAR SKIES...STRONG RADIATIONAL COOLING MAY SUPPORT SOME LOW TEMPERATURES IN THE MID 30`S...PER THE LATEST MOS GUIDANCE. IN ADDITION...FROST MAY BE POSSIBLE FROM POINTS NORTH OF PITTSBURGH AND IN THE RIDGES. FOR NOW...HEDGED TOWARD THESE COOLER VALUES BUT OPTED TO STAY CLOSER TO MET AND MEX VALUES WHICH ARE STILL 10 DEGREES BELOW NORMAL. TEMPERATURES SHOULD BEGIN TO REBOUND BY SATURDAY...WITH PLENTY OF SUNSHINE AS HIGH PRESSURE SHIFTS TOWARD THE EAST.
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&& .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... UPPER RIDGING OVER THE SOUTHEAST CONUS IS EXPECTED TO SET UP INTO EARLY NEXT WEEK...AS ADVANCING SHORTWAVES ON THE NORTHERN PERIPHERY OF THE RIDGE BRINGING SHOWER AND THUNDERSTORM CHANCES LATE SUNDAY INTO EARLY NEXT WEEK. MAINTAINED NO HIGHER THAN CHANCE POPS WITH NORTHERN EXTENT OF THE INFLUENCE OF THE RIDGE AND PLACEMENT OF A SURFACE BOUNDARY REMAINING IN QUESTION. USED WPC BASED ENSEMBLE MEAN GUIDANCE WITH DOWNWARD TWEAKS TO POPS TO HELP SMOOTH OUT INDIVIDUAL MODEL DIFFERENCES. SEASONALLY WARM TEMPERATURES ARE EXPECTED. && .AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
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AFTERNOON HEATING AND MIXING IS FINALLY MAKING SOME IN-ROADS ON THE STRATO-CU DECK THAT LINGERED THROUGH MIDDAY. ANY CIG-BASED RESTRICTIONS THAT PERSIST THIS AFTERNOON WILL QUICKLY IMPROVE THROUGH THE EARLY EVENING. HIGH CLOUDS TONIGHT WILL FILL BACK IN...BUT VFR IS EXPECTED. LATE TONIGHT AN UPPER-LEVEL SHORTWAVE TROF WILL APPROACH...GRADUALLY THICKENING THE CLOUD DECK. MODELS HAVE SHOWN SOME DIFFICULTY DEPICTING THE PROGRESSION OF THIS DISTURBANCE...AND ARE NOW SHOWING A LOT MORE MOISTURE AVAILABLE. THIS MEANS THAT RESTRICTIONS ARE POSSIBLE...MAINLY SOUTH AND EAST OF PITTSBURGH. ELSEWHERE...VFR CONDITIONS ARE EXPECTED THROUGH THE BALANCE OF THE TAF PERIOD. TAX .OUTLOOK.../THURSDAY THROUGH SUNDAY/... RESTRICTIONS ARE POSSIBLE WITH A LATE SUNDAY WARM FRONT.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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