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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