Area Forecast Discussion
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000 FXUS61 KPBZ 010139 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 939 PM EDT SAT APR 30 2016 .SYNOPSIS... A COUPLE OF LOW PRESSURE SYSTEMS WILL PROVIDE RAIN OVER THE REGION THROUGH SUNDAY NIGHT. TEMPERATURES ARE EXPECTED TO RISE ABOVE AVERAGE SUNDAY AFTERNOON. && .NEAR TERM /THROUGH SUNDAY/... MADE SLIGHT ADJUSTMENTS TO POPS BASED ON LATEST RADAR TRENDS TO THE LATE EVENING UPDATE. PREVIOUS DISCUSSION FOLLOWS. A SPLIT FLOW PATTERN WITH AN UPPER LEVEL LOW CENTERED OVER THE CENTRAL PLAINS HAS ALLOWED DEEP MOISTURE TO ADVECT OVER THE REGION WITH EMBEDDED UPPER LEVEL SHORTWAVES PROGGED TO CROSS THE FORECAST AREA THROUGH TONIGHT. AT THE SURFACE...A BROAD AREA OF LOW PRESSURE OVER THE MIDWEST IS EXPECTED TO SHIFT OVER THE UPPER OHIO VALLEY BY SUNDAY MORNING. AS A RESULT...A WARM FRONT HAS HELPED FORM STRATIFORM RAIN THIS AFTERNOON AND THUS CATEGORICAL POPS REMAIN IN THE FORECAST UNTIL SUNDAY MORNING WHEN THE CENTER OF LOW PRESSURE EXITS EAST. STRONG UPPER LEVEL FORCING SEEMS LESS FAVORABLE FOR SUNDAY AFTERNOON AS THE UPPER LOW IS PROGGED TO PHASE WITH THE TROUGH ACROSS THE WESTERN GREAT LAKES. HOWEVER...ANOTHER DEVELOPING SURFACE LOW OVER THE OHIO VALLEY IS EXPECTED TO HELP CREATE AREAS OF CONVECTION AS IT CROSSES THE REGION LATE SUNDAY. THE BREAK BETWEEN THE TWO SYSTEMS MAY INCLUDE SOME CLEARING AS INDICATED BY MODELS AND IN TURN INCREASE INSTABILITY. UNCERTAINTY REMAINS IN THE APPROACH OF THE SECONDARY LOW PRESSURE AND BREAKS IN CLOUDS...AND WHILE THE AFOREMENTIONED UPPER LEVEL FORCING REMAINS WEAK...A MARGINAL RISK FOR SEVERE WEATHER IS FORECAST BY SPC. A BLEND OF MODEL DATA WAS USED DUE TO THE UNCERTAINTY WITH THE EVOLUTION OF THE LATE SUNDAY LOW PRESSURE. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... LOW PRESSURE WILL TRACK FROM EASTERN OHIO TO WESTERN NEW YORK SUNDAY NIGHT. HAVE CONTINUED WITH LIKELY POPS DURING THIS TIME PERIOD. WILL NEED TO MONITOR POTENTIAL FOR STRONGER THUNDERSTORMS DURING THIS TIME PERIOD BASED ON POTENTIAL INCREASING INSTABILITY AS TEMPERATURES COOL ALOFT. RAIN WILL RAPIDLY SHIFT EAST MONDAY AS THE LOW CONTINUES ON TO NEW ENGLAND. A DIGGING UPPER LEVEL TROUGH OVER THE NORTHEAST WILL HELP SUPPORT A LOW PRESSURE SYSTEM TO SHIFT OVER THE EAST COAST. POPS ASSOCIATED WITH THIS PASSING SYSTEM ARE CONFINED TO THE ZONES SOUTH AND EAST OF PITTSBURGH WHERE GREATER FORCING IS PROGGED. TEMPERATURES WILL BE AT OR SLIGHTLY BELOW NORMAL. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... LOW PRESSURE WILL TRACK ACROSS CANADA TUESDAY NIGHT AND WEDNESDAY...DRAGGING A COLD FRONT ACROSS THE REGION. ALTHOUGH MODELS ARE IN GOOD AGREEMENT WITH THE LOW TRACK AND TRAILING COLD FRONT...MODEL TIMING OF THE FRONT IS ALL OVER THE PLACE. TUESDAY NIGHT APPEARS TO REMAIN DRY...AND HAVE GONE WITH CHANCE POPS WEDNESDAY INTO WEDNESDAY NIGHT. AN UPPER LEVEL LOW WILL THEN DROP ACROSS THE GREAT LAKES AND REMAIN ACROSS THE EASTERN UNITED STATES THROUGH THE REST OF THE 7 DAY FORECAST. THIS WILL KEEP THE FORECAST COOL WITH SCATTERED SHOWERS AS IMPULSES ROTATE ACROSS THE AREA. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... RAIN WILL CONTINUE TO SPREAD EAST AND REMAIN THROUGH THE OVERNIGHT AS LOW PRESSURE OVER THE CENTRAL PLAINS SLOWLY SHIFTS EAST. LOW LEVELS WILL SATURATE WITH WEAK MIXING AS THE NIGHT PROGRESSES WITH A PERIOD OF IFR BEFORE AND TOWARD MIDNIGHT AND EXTENDING TO MID MORNING SUNDAY. SURFACE LOW WILL TRY PUSH REGION INTO THE WARM SECTOR SUNDAY AFTERNOON WHICH MAY ALLOW FOR MVFR CIGS AS RAIN DIMINISHES FOR A TIME. IF CLOUDS BREAK SUNDAY AFTERNOON INSOLATION MAY ALLOW ENOUGH LOW LEVEL INSTABILITY FOR THUNDERSTORMS...BUT VERY LOW CONFIDENCE IN THAT OCCURRING. SOUTH WINDS OVERNIGHT WILL SHIFT TO SOUTHWEST UNDER 10 KTS SUNDAY. .OUTLOOK /SUNDAY NIGHT THROUGH THURSDAY/... RESTRICTIONS ARE EXPECTED THRU MON AS LOW PRESSURE COMPLETES PASSAGE OVER THE REGION. ANOTHER ROUND OF RESTRICTIONS WILL BE POSSIBLE WEDNESDAY AND WEDNESDAY NIGHT WITH A COLD FRONT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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