Area Forecast Discussion
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000 FXUS61 KPBZ 271121 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 721 AM EDT SAT JUN 27 2015 .SYNOPSIS... UNSEASONABLY DEEP LOW PRESSURE WILL MOVE THROUGH THE REGION TODAY...WITH MUCH COLDER AND WINDY CONDITIONS TO END THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... RAIN WILL HAVE OVERSPREAD THE ENTIRE AREA EARLY THIS MORNING... WITH THE SURFACE LOW OVER NORTH-CENTRAL OHIO. OVERALL SURFACE LOW PROGRESSION AND DEEPENING IS FORECAST TO SLOW AS THE SYSTEM STACKS AND OCCLUDES OVER NORTH-CENTRAL OHIO BY LATE IN THE DAY. TAIL END OF RAIN SHIELD WILL THUS PROGRESS NORTHEASTWARD WITH THE MID LEVEL DRY SLOT THROUGH THE MORNING HOURS. THE TIMING OF THAT FEATURE WITH WARM FRONT POSITIONING AND PROLONGED MOISTURE CONVERGENCE NORTH AND EAST OF THE MID LEVEL LOW WILL DETERMINE WHERE THE HEAVIEST RAINFALL OCCURS. AT MOMENT...AREAS NORTH AND EAST OF PITTSBURGH ARE PROJECTED FOR THE HIGHER TOTALS. THERE IS AN INTERESTING COMPONENT TO THE AFTERNOON/EVENING FORECAST. GIVEN THE STRENGTH AND CUTOFF NATURE OF THIS SYSTEM...DEEP LAYER SPEED AND DIRECTIONAL SHEAR WILL BE HIGH...WHILE BOUNDARY LAYER VALUES ESCALATE IN VICINITY OF THE AFOREMENTIONED WARM FRONT. SHOULD SUFFICIENT DESTABILIZATION OCCUR...THEN THE POTENTIAL FOR SEVERE WEATHER WILL ESCALATE. DESTABILIZATION WILL BE VERY DEPENDENT ON HOW MUCH OF THE THICK CLOUD COVER WILL BE WORN AWAY WITH THE RATHER IMPRESSIVE DRY SLOT. WITH STRONG WARM AIR ADVECTION ALOFT IN THE PERIPHERY OF THE DRIER AIR...A BREAK IN THE CLOUD COVER WOULD ALLOW FOR RAPID ATMOSPHERIC MIXING AND A QUICK RISE IN SURFACE TEMPERATURES. THIS WOULD INCREASE THE ATMOSPHERIC BUOYANCY NEAR THE SURFACE ALLOWING FOR THE POTENTIAL FOR MORE SURFACE BASED CONVECTION RATHER THEN ELEVATED. WITH SUCH A HIGH SHEAR ENVIRONMENT...ANY CONVECTION THAT DOES FORM SHOULD BE ABLE TO SUSTAIN UPDRAFTS CREATING THE RISK FOR MORE POTENT CONVECTION. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... SHOWERS AND COOLER TEMPERATURES CAN BE EXPECTED TONIGHT AND THROUGH MUCH OF SUNDAY. SYSTEM FINALLY EXITS EARLY MONDAY AND THERE WILL BE A SHORT REPRIEVE IN THE ACTIVE WEATHER. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... MODEL GUIDANCE FAVORS INCREASED RIDGING IN THE WEST WITH DOWNSTREAM DEEPENING TROUGHING ACROSS THE GREAT LAKES. THIS WILL LIKELY KEEP THINGS FAIRLY ACTIVE AND WET OVER THE CWA...WITH TEMPERATURES LIKELY TO REMAIN BELOW NORMAL. MONDAY NIGHT INTO TUESDAY SEES THE BEST SHOT AT WIDESPREAD RAIN SHOWERS ACROSS THE AREA. && .AVIATION /11Z SATURDAY THROUGH WEDNESDAY/...
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SHOWERS WILL CONTINUE THROUGH THE MORNING AS A WARM FRONT LIFTS NORTH OVER THE AREA. RESTRICTIONS ARE LIKELY THROUGH THE MORNING WITH IFR CONDITIONS DURING PERIODS OF HEAVIER RAIN...THROUGH NOON TODAY. CIG RESTRICTIONS LOOK MORE LIKELY TO PERSIST THROUGH THE DAY AT FKL AND DUJ LOOK AS THEY SIT UNDER THE UPPER LOW TRACK...WHILE LOCATIONS SOUTH SHOULD SEE A BREAK IN THE PRECIPITATION BY EARLY AFTERNOON AND IMPROVE TO VFR AS MODELS SHOW A DECENT DRY SLOT MOVING IN. IF THERE ARE BREAKS IN THE CLOUDS TO ALLOW ADDITIONAL SURFACE HEATING...THESE LOCATIONS MAY SEE THUNDERSTORMS DEVELOP DURING THE AFTERNOON...WITH SOME POTENTIALLY BECOMING SEVERE. .OUTLOOK.../SATURDAY NIGHT THROUGH WEDNESDAY/... RESTRICTIONS ARE LIKELY THROUGH THE REST OF THE WEEKEND WITH PASSAGE OF A STRONG LOW PRESSURE SYSTEM. AN APPROACHING COLD FRONT MAY CAUSE POSSIBLE RESTRICTIONS WITH RAIN MONDAY AND TUESDAY.
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&& .HYDROLOGY... A RAPIDLY DEEPENING SYSTEM WILL DROP HEAVY RAIN ONTO THE AREA FRIDAY NIGHT INTO SATURDAY. AT THIS TIME...MOST OF THE AREA SEEMS LIKELY TO RECEIVE 1 TO 1.75 INCHES THROUGH THE PERIOD...HOWEVER SOME AREAS NORTH OF I-80 MAY SEE IN EXCESS OF 2 INCHES. LOCALIZED URBAN AND SMALL STREAM FLOODING WILL BE THE MOST LIKELY PROBLEM...HOWEVER AS THE TRACK OF THE SYSTEM IS PINNED DOWN MORE CLOSELY...AND EXACT BASINS WHICH WILL RECEIVE THE MOST RAINFALL ARE DETERMINED...A MORE ADEQUATE DETERMINATION OF THE RISK OF RIVER FLOODING CAN BE MADE. && .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...FLOOD WATCH UNTIL 5 PM EDT THIS AFTERNOON FOR MDZ001. OH...FLOOD WATCH UNTIL 5 PM EDT THIS AFTERNOON FOR OHZ039>041- 048>050-057>059-068-069. PA...FLOOD WATCH UNTIL 5 PM EDT THIS AFTERNOON FOR PAZ014-020>023- 029-031-073>076. FLOOD WATCH THROUGH LATE TONIGHT FOR PAZ007>009-013-015-016. WV...FLOOD WATCH UNTIL 5 PM EDT THIS AFTERNOON FOR WVZ001>004-012- 021>023-041.
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