Area Forecast Discussion
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000 FXUS61 KPBZ 240510 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 110 AM EDT FRI APR 24 2015 .SYNOPSIS... DRY AND COOL WEATHER CAN BE EXPECTED TODAY AS HIGH PRESSURE SLIDES ACROSS THE REGION...BUT THE REPRIEVE WILL BE BRIEF AS LOW PRESSURE IS FORECAST TO GENERATE RAIN ON SATURDAY. && .NEAR TERM /THROUGH TODAY/... RESIDUAL FLURRIES AND CLOUDS WILL DIMINISH THROUGHTHE PREDAWN HOURS AS SUBSIDENCE INCREASES UNDER BUILDING HIGH PRESSURE. MAINLY SUNNY SKIES ARE EXPECTED TODAY AS BACKING WIND...DRY ADVECTION AND THE SUBSIDENCE INVERSION SHOULD SUPPORT ONLY SOME HIGH BASED CU OR STATOCU. NEVERTHELESS...THE COLD AIRMASS WILL BE SLOW TO RECOVER AND HIGHS WERE PROJECTED ABOUT 10 TO 15 DEGREES UNDER THE AVERAGES USING THE LATEST GFS NUMBERS. && .SHORT TERM /TONIGHT THROUGH MONDAY/... PRECIPITATION IS EXPECTED TO SPREAD NORTHEASTWARD SATURDAY AS WARM...MOIST ADVECTION INCREASES AHEAD OF LOW PRESSURE ADVANCING OUT OF THE MIDWEST. MODELS ARE IN GENERAL AGREEMENT THAT THE CENTER OF THE APPROACHING SHORTWAVE TROUGH WILL PASS JUST SOUTH OF THE FORECAST AREA SATURDAY NIGHT. SUCH A TRACK WOULD KEEP THE FORECAST AREA ALONG OR JUST NORTH OF THE ASSOCIATED WARM FRONT...AND IN PRIME TERRITORY FOR A BAND OF LIGHT TO MODERATE RAIN OWING TO DEFORMATION AND ISENTROPIC LIFT. AT ANY RATE...THE SYSTEM IS PROGGED TO MOVE RAPIDLY OVER THE ATLANTIC ON SUNDAY...SPELLING AN END TO PRECIPITATION. NO CHANGES WERE MADE TO SATURDAY POPS WHICH CONTINUE TO FEATURE CHANCE NUMBERS OVER THE I 80 CORRIDOR AND CATEGORICALS OVER I 70 GIVEN THE AFOREMENTIONED TRACK...ALTHOUGH ADJUSTMENTS WERE MADE FOR FASTER EXITING AS PER THE LATEST TIMING TRENDS. SUNDAY IS THUS EXPECTED TO BE A DAY OF IMPROVEMENT AS SURFACE HIGH PRESSURE BUILDS UNDER NORTHERLY FLOW ALOFT. A FAIRLY STRONG...BUT MOISTURE DEFICIENT SHORTWAVE IS FORECAST TO PASS THROUGH THE WESTERN FLANK OF UPPER LOW PRESSURE EARLY ON MONDAY...SLIGHT TO CHANCE POPS NUMBERS WERE MAINTAINED MAINLY OVER THE EASTERN HALF OF THE COUNTY WARNING FOR PASSAGE OF THIS FEATURE...WHICH MAY INCLUDE SOME SNOW SHOWERS OR FLURRIES. TEMPERATURES PRIOR TO THE RAIN WILL BETRICKY TONIGHT. INITIAL CONDITIONS OF DRY AIR...LIGHT WIND AND CLEAR SKY WILL BE FAVORABLE FOR RADIATIONAL COOLING...BUT CIRROSTRATUS IS EXPECTED TO BECOME INCREASINGLY ABUNDANT AFTER MIDNIGHT AND WILL LIKELY LIMIT THE IMMEDIATE PREDAWN DROP. THE COLD TEMP FORECAST WAS THUS CONSTRUCTED FOR AN EARLY LOW READING...WITH STABILIZATION OR A SLOW RISE WITH THE APPROACH OF DAWN. THE REST OF THE PERIOD WILL FEATURE SUB AVERAGE READINGS GIVEN THE PRESENCE OF THE NORTHEASTERN U.S. LOW. EXPECT TEMPERATURES ABOUT 5 TO 10 DEGREES BELOW NORMAL FOR THE START OF THE NEW WEEK. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... THE UPPER-LEVEL LOW WILL SIT AND SPIN OVER NEW ENGLAND SUNDAY NIGHT INTO MONDAY NIGHT. MOISTURE WILL SPILL INTO WESTERN PENNSYLVANIA BY MONDAY MORNING...AND A SHORTWAVE TROUGH PIVOTING AROUND THE UPPER LOW WILL BRING AT LEAST A SLIGHT CHANCE OF PRECIPITATION FOR PENNSYLVANIA COUNTIES MONDAY INTO MONDAY NIGHT. CANNOT RULE OUT A FEW SNOWFLAKES MIXING IN RIGHT AROUND SUNRISE FOR FOREST...CLARION...AND JEFFERSON COUNTIES BOTH MONDAY AND TUESDAY MORNINGS. BY THE TIME THE UPPER LOW MOVES OFFSHORE TUESDAY...A SURFACE LOW WILL BEGIN DEVELOPING ALONG THE GULF COAST AND MOVE TO THE NORTHEAST. THE ECMWF KEEPS THE LOW WELL EAST OF THE REGION WITH NO RAIN LOCALLY...BUT THE GFS...UKMET AND THE NAEFS KEEP THE LOW CLOSER TO THE COAST AND SPREAD RAIN INTO THE REGION. HAVE BUMPED UP POPS WEDNESDAY...ALTHOUGH FUTURE MODEL RUNS WILL BE NEEDED TO DETERMINE THE EXACT TRACK OF THE LOW. WITH SOME SORT OF NORTHERLY FLOW EXPECTED THROUGH THE EXTENDED FORECAST AND MUCH CLOUD COVER WITH THE TWO MAIN SYSTEMS... TEMPERATURES WILL CONTINUE TO BE BELOW NORMAL BUT WILL RISE CLOSER TO CLIMATOLOGICAL VALUES BY THE END OF THE PERIOD. THE EASTERN CONUS TROUGH AND RESULTING NORTHWESTERLY WIND WILL CONTINUE TO HOLD TEMPERATURES UNDER THE AVERAGES. HAVE TRENDED TOWARDS WPC NUMBERS...WHICH KEEP AT LEAST SOME CHANCE OF PRECIPITATION IN THE FORECAST. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... VFR CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD WITH DECREASING CLOUD COVERAGE AND WINDS BECOMING GUSTY AGAIN BY MID MORNING. .OUTLOOK.../FRIDAY THROUGH TUESDAY/... RESTRICTIONS WILL BE POSSIBLE SATURDAY AFTERNOON THROUGH SUNDAY AFTERNOON AS LOW PRESSURE TRACKS ACROSS THE OHIO VALLEY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$ 15

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