Area Forecast Discussion
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000 FXUS61 KPBZ 250200 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1000 PM EDT FRI APR 24 2015 .SYNOPSIS...
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DRY AND COOL CONDITIONS EXPECTED OVERNIGHT...FOLLOWED BY A CHANCE OF RAIN LATE SATURDAY AFTERNOON THROUGH SUNDAY MORNING AS A WEAK DISTURBANCE PASSES TO THE SOUTH. TEMPERATURES WILL REMAIN BELOW NORMAL INTO NEXT WEEK.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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TEMPERATURES WILL FALL QUICKLY OVER THE NEXT COUPLE HOURS WITH THE MAJORITY OF THE FORECAST AREA STILL UNDER CLEAR SKIES AND LIGHT SURFACE WINDS IN PLACE NOW THAT NIGHTTIME INVERSIONS HAVE SET UP. LATEST SATELLITE IMAGERY SHOWS INCREASED CLOUD COVERAGE ASSOCIATED WITH THE NEXT DISTURBANCE JUST EAST OF THE FORECAST AREA...BUT EASTWARD PROGRESS HAS BEEN RELATIVELY SLOW AND MID- LEVEL CLOUD COVERAGE IS STILL BACK TO INDIANA. THE CURRENT FORECAST IS BASED ON THE EXPECTATION THAT CLOUD COVERAGE WILL REMAIN LIMITED THROUGH MUCH OF THE NIGHT...BUT IF ANY MEANINGFUL CLOUD COVERAGE MOVES IN EARLIER THAN EXPECTED...THE CURRENT FORECAST MIGHT BE A LITTLE TOO LOW. ADJUSTMENTS WILL BE MADE IF NECESSARY. WHILE THE SURFACE REFLECTION OF THE NEXT SYSTEM THAT WILL PLAGUE THE AREA WILL LIKELY REMAIN WELL BACK IN THE MID-MISSISSIPPI VALLEY BY SATURDAY AFTERNOON...A WARM FRONT WILL LIKELY EXTEND WELL TO ITS EAST INTO THE CENTRAL APPALACHIANS. DIFFERENTIAL THETA-E ADVECTION AS WELL AS PVA WILL STREAM NORTH OF THIS FRONT OVER GENERALLY THE SOUTHWESTERN HALF OF THE CWA BY SATURDAY AFTERNOON. THIS WILL RESULT IN RAIN INCREASING FROM THE SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. HOWEVER...DUE TO ABUNDANT DRY AIR IN PLACE UPON ITS ARRIVAL...SEVERAL HOURS OF VIRGA ARE LIKELY BEFORE THE RAIN ACTUALLY HITS THE GROUND. BECAUSE OF THIS...PRECIPITATION OUTBREAK IN THE FORECAST MORE CLOSELY ALIGNS WITH THE SLOWER-DEVELOPING AND HIGHER LOW LEVEL RESOLVING NAM. ASSUMING THIS VERIFIES...RAIN MAY HOLD OFF IN PITTSBURGH ITSELF FOR THE MAJORITY OF THE DAY ON SATURDAY. EVEN STILL...A CONTINUATION OF BELOW NORMAL TEMPERATURES WILL BE LIKELY. FRIES
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
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WHILE THE SURFACE REFLECTION OF THE NEXT SYSTEM THAT WILL PLAGUE THE AREA WILL LIKELY REMAIN WELL BACK IN THE MID-MISSISSIPPI VALLEY BY SATURDAY AFTERNOON...A WARM FRONT WILL LIKELY EXTEND WELL TO ITS EAST INTO THE CENTRAL APPALACHIANS. DIFFERENTIAL THETA-E ADVECTION AS WELL AS PVA WILL STREAM NORTH OF THIS FRONT OVER GENERALLY THE SOUTHWESTERN HALF OF THE CWA BY SATURDAY AFTERNOON. THIS WILL RESULT IN RAIN INCREASING FROM THE SOUTHWEST TO NORTHEAST THROUGH THE AFTERNOON. HOWEVER...DUE TO ABUNDANT DRY AIR IN PLACE UPON ITS ARRIVAL...SEVERAL HOURS OF VIRGA ARE LIKELY BEFORE THE RAIN ACTUALLY HITS THE GROUND. BECAUSE OF THIS...PRECIPITATION OUTBREAK IN THE FORECAST MORE CLOSELY ALIGNS WITH THE SLOWER-DEVELOPING AND HIGHER LOW LEVEL RESOLVING NAM. ASSUMING THIS VERIFIES...RAIN MAY HOLD OFF IN PITTSBURGH ITSELF FOR THE MAJORITY OF THE DAY ON SATURDAY. EVEN STILL...A CONTINUATION OF BELOW NORMAL TEMPERATURES WILL BE LIKELY. FRIES MODELS CONTINUE TO HAVE A SURFACE LOW MOVE JUST SOUTH OF THE FORECAST AREA OVER KY/WV SATURDAY NIGHT. WHILE THERE MAY INITIALLY BE CONCERNS FOR DRY AIR AT THE SURFACE...AS MENTIONED ABOVE...THIS SHOULD BE OVERCOME BY NIGHTFALL WITH THE FOCUS OF PRECIPITATION REMAINING ALONG A STALLED WARM FRONT OVER THE REGION. ISENTROPIC LIFT WILL PROVIDE FOR LIGHT TO MODERATE RAINFALL...ALBEIT FOR A BRIEF PERIOD...AS THE SYSTEM SHIFTS TO THE EAST BY SUNDAY MORNING. POPS WERE KEPT CATEGORICAL BUT SHIFTED A BIT FURTHER WEST AT THE START OF THE NIGHT...ESPECIALLY OVER POINTS SOUTH AND WEST OF PITTSBURGH AS THE MODELS SUGGEST A MORE NW-SE LOW TRACK AND PRECIP AXIS. DRY AIR WILL ENCROACH RATHER QUICKLY BY SUNDAY MORNING WITH BUILDING HIGH PRESSURE...CUTTING OFF THE CHANCE FOR PRECIPITATION SAVE FOR THE RIDGES. NORTHERLY FLOW ALOFT SHOULD LIMIT CLOUD COVERAGE BEYOND SOME DIURNAL CU SUNDAY AFTERNOON. ANOTHER SHORTWAVE IS FORECAST TO DROP SOUTHWARD OUT OF THE EASTERN GREAT LAKES LATE SUNDAY NIGHT/MONDAY PROVIDING FOR A REINFORCING SHOT OF COLD AIR. WHILE THERE WILL BE LITTLE MOISTURE PRESENT WITH THIS FEATURE...A RETURN OF NW FLOW WILL PROMOTE THE CHANCE FOR RAIN SHOWERS...AND A BRIEF PERIOD OF SNOW SHOWERS..FOR POINTS NORTH AND IN THE THE RIDGES. TEMPERATURE THROUGHOUT THE ENTIRE PERIOD WERE PRODUCED USING A COMBINATION OF THE NAM AND GFS MOS...WHICH WAS CLOSE TO 5 TO 10 DEGREES BELOW SEASONAL AVERAGES.
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&& .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... UPPER LEVEL LOW OVER NEW ENGLAND SHOULD BEGIN TO MOVE OFFSHORE TUESDAY...WHICH SHOULD ALLOW FOR AT LEAST SOME PARTIAL CLEARING TO OCCUR OVER THE REGION. THE CLEARING WOULD LIKELY BE SHORT LIVED...AS MODELS PROJECT A SURFACE LOW WILL DEVELOP ALONG THE GULF COAST AND MOVE TO THE NORTHEAST. STILL LOTS OF UNCERTAINTY WITH THE TRACK OF THIS LOW...AND RECENT MODEL TRENDS HAVE SUGGESTED THE LOW MAY STAY FARTHER TO THE SOUTHEAST. WILL TREND THE FORECAST IN THIS DIRECTION...REDUCING BUT NOT ELIMINATING SHOWERS WEDNESDAY AND THURSDAY. ALTHOUGH TEMPERATURES ARE STILL EXPECTED TO BE A FEW DEGREES BELOW NORMAL THROUGH THE EXTENDED FORECAST...THE MORE SOUTHERLY TREND OF THE MID WEEK SURFACE LOW SHOULD ALLOW FOR MORE SUNSHINE LOCALLY...AND HAVE BROUGHT TEMPS UP A FEW DEGREES TO COMPENSATE. PRECIPITATION IN THE FORECAST. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... VFR CONDITIONS ARE EXPECTED THROUGH EARLY SATURDAY AFTERNOON AS HIGH PRESSURE SLOWLY EXITS. MID LEVEL CLOUDS SHOULD INCREASE LATE TONIGHT IN WARM ADVECTION AHEAD OF APPROACHING LOW PRESSURE. THE LOW IS EXPECTED TO BRING SHOWERS MAINLY SOUTH OF I 80 BY MID TO LATE AFTERNOON AS IT TRACKS ACROSS THE OHIO VALLEY...WITH EVENTUAL MVFR CONDITIONS SOUTH OF PIT. .OUTLOOK.../SATURDAY NIGHT THROUGH WEDNESDAY/... RESTRICTIONS ARE LIKELY TO CONINUE SOUTH OF PIT SATURDAY NIGHT WITH THE LOW PRESSURE. RESTRICITIONS ARE POSSIBLE MONDAY WITH AN UPPER TROUGH. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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