Area Forecast Discussion
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000 FXUS61 KPBZ 271219 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 819 AM EDT MON APR 27 2015 .SYNOPSIS... AN UPPER LEVEL SYSTEM WILL SWING THROUGH THIS AFTERNOON. THIS WILL PROVIDE CLOUDS...SCATTERED RAIN OR SNOW SHOWERS AND COLDER TEMPERATURES. WARMER AIR MOVES BACK IN ON WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... WITH 815AM UPDATE...TWEAKED HOURLY TRENDS FOR CLOUD COVER AND TEMPERATURES. HIGH-RESOLUTION MODELS AND CURRENT FORECAST SEEM TO ALIGN WELL WITH CURRENT RADAR TRENDS...AND NO CHANGES WERE MADE TO THE TIMING OR COVERAGE OF PRECIPITATION TODAY. PREVIOUS DISCUSSION FOLLOWS. IMPRESSIVE SHORTWAVE TROUGH WILL SWING THROUGH THE AREA TODAY... CIRCLING AROUND A LARGE UPPER LOW OFF THE NEW ENGLAND COAST. THIS WAVE WILL THICKEN CLOUDS...INCREASE PRECIPITATION CHANCES AND SPREAD COLDER AIR OVER THE ENTIRE REGION. THE RISK FOR SHOWERS WILL INCREASE AS THE DAY PROGRESSES DUE NOT ONLY TO THE WAVE SWINGING THROUGH...BUT ALSO TO THE RATHER COLD AIR ALOFT. THIS WILL CREATE A SCENARIO IN WHICH THE ATMOSPHERE DESTABILIZES QUICKLY. ADDITIONALLY...WITH THE COLDER AIR ALOFT...RAIN SHOWERS MAY AT TIME MIX WITH SNOW...OR PRECIPITATION MAY FALL AS GRAUPEL. THIS WILL BE ESPECIALLY TRUE OVER THE RIDGES WHERE THERMAL PROFILES BECOME COLD ENOUGH LATE IN THE DAY TO SUPPORT ALL SNOW ON THE HIGHEST PEAKS. TEMPERATURES WILL BE WELL BELOW SEASONABLE LEVELS. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... BUILDING SURFACE HIGH PRESSURE UNDER NORTHERLY FLOW ALOFT WILL RESULT IN A DRY AND SEASONABLY COOL TUESDAY. CLOUDS WILL BE ON THE INCREASE SOUTH TO NORTH WEDNESDAY AS LOW PRESSURE MOVES TOWARD THE MID ATLANTIC STATES. TEMPERATURE THROUGH THE ENTIRE PERIOD A BLEND OF MOS WHICH IS NEAR 5 DEGREES BELOW THE SEASONAL AVERAGES. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... BEST CHANCE FOR SHOWERS APPEARS TO BE LATER WEDNESDAY NIGHT INTO THURSDAY AS SOUTHERN STREAM LOW PRESSURE MOVES OFF THE MID ATLANTIC COAST...FOLLOWED BY A NORTHERN STREAM COLD FRONT. STILL CHANCE POPS THURSDAY AS DOUBT ON HOW MUCH SOUTHERN STREAM MOISTURE WILL BE AVAILABLE. BY FRIDAY AND THROUGH THE WEEKEND...MODEL DISCREPANCIES ON HANDLING UPPER LEVEL LOW OVER EAST COAST MAKE FOR A LOW CONFIDENCE FORECAST. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... VFR CONDITIONS CAN BE EXPECTED UNTIL AN UPPER TROUGH APPROACHES AFTER DAYBREAK. RAIN AND SNOW SHOWERS ARE FORECAST TO DEVELOP FROM THE NORTH AS THE MIXING LAYER DEEPENS UNDER THAT FEATURE. THE VICINITY SHOWER MENTION WILL THUS BE MAINTAINED WITH PREVAILING WORDING OVER PORTS EAST OF PIT. RESTRICTIONS ARE EXPECTED TO BE MVFR...BUT THE INCREASED MIXING LAYER WILL SUPPORT WIND GUSTS AROUND 20 KTS. .OUTLOOK.../TUESDAY THROUGH FRIDAY/... THE NEXT CHANCE FOR GENERAL RESTRICTIONS IS EXPECTED WITH THURSDAY LOW PRESSURE. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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