FXUS61 KPBZ 270729
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
229 AM EST FRI NOV 27 2009
.SYNOPSIS...
AN INTENSIFYING EAST COAST STORM WILL BRING BRISK NORTHWEST WINDS
ACROSS THE FORECAST AREA TODAY ALONG WITH SOME LAKE EFFECT SNOW
SHOWERS. HIGH PRESSURE WILL BUILD IN ON SATURDAY...WITH A DRY
WEEKEND EXPECTED.
&&
.NEAR TERM /THROUGH TONIGHT/...
A DEEPING EAST COAST LOW WILL PRODUCE BRISK NORTHWEST WINDS ACROSS
LAKES ERIE AND HURON TODAY INTO TONIGHT. LAKE EFFECT SNOW SHOWERS
CAN BE EXPECTED ACROSS THE FORECAST AREA TODAY THROUGH TONIGHT WITH
SOME ACCUMULATING SNOW POSSIBLE IN THE LAKE EFFECT COUNTIES
CLOSEST TO LAKE ERIE. UPSLOPE FLOW INTO THE MOUNTAIN RIDGES WILL
ALSO BRING THE HEAVIEST SNOW SHOWERS TO THE HIGHER
ELEVATIONS...ESPECIALLY THOUGH THE RIDGES OF TUCKER AND PRESTON
COUNTIES IN WEST VIRGINIA AND GARRETT COUNTY MARYLAND. A WINTER
WEATHER ADVISORY IS IN EFFECT FOR TODAY AND TONIGHT IN THESE THREE
COUNTIES.
SNOW SHOWERS WILL CONTINUE INTO TONIGHT AS THE NORTHWEST FLOW SLOWLY
BEGINS TO WEAKEN. HIGH PRESSURE BUILDING INTO THE DISTRICT TOWARD
DAYBREAK WILL WEAKEN SNOW SHOWER ACTIVITY.
&&
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
SATURDAY...THE FLOW ALOFT WILL BECOME MORE WRLY AND MOISTURE WILL
ADVECT NE OF THE AREA...CUTTING OFF LINGERING SNOW SHOWERS AND
FLURRIES ACROSS THE HIGHER ELEVATIONS AND ALONG AND NORTH OF
INTERSTATE 80 BY NOON. HIGH PRESSURE WILL BUILD IN FROM THE
SOUTH...WITH CLOUD COVERAGE DECREASING FROM THE SOUTHWEST
THROUGHOUT THE DAY. INCREASING SUNSHINE AND WARM ADVECTION
WILL ALLOW FOR TEMPS TO RECOVER TO NORMAL VALUES FOR HIGHS.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
EXPECT THAT A WARM FRONT DEVELOPING AHEAD OF THE LOW PRESSURE
SYSTEM COMING FROM THE PACIFIC NORTHWEST MAY SPREAD SHOWERS ACROSS
THE UPPER OHIO VALLEY SUNDAY NIGHT. HOWEVER THE BULK OF SHOWERS
WILL OCCUR IN BANDS MONDAY...MONDAY NIGHT...AND POSSIBLY TUESDAY
MORNING...WITH THE PASSAGE OF THE COLD FRONT.
A SECOND LOW PRESSURE SYSTEM COMING MOVING THE GULF OF MEXICO TO NEW
ENGLAND LATE WEEK MAY SPREAD SHOWERS AS FAR WEST AS THE UPPER OHIO
VALLEY AS THE UPPER LOW WILL TRACK WEST OF THE APPALACHIAN
MOUNTAINS.
FORECASTED TEMPERATURES USING A BLEND OF HPC GUIDANCE AND GFS MOS.
EXPECT A COOL DOWN TO SLIGHTLY COOLER THAN NORMAL TEMPERATURES FOR
TUESDAY IN THE WAKE OF THE FIRST SYSTEM...THEN NEAR NORMAL
TEMPERATURES WEDNESDAY AND THURSDAY. PRECIPITATION TYPE WITH THE
SECOND SYSTEM MAY BE AN ISSUE AS SURFACE TEMPERATURES WILL BE WITHIN
A COUPLE DEGREES OF THE FREEZING POINT.
&&
.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
EXPECT MVFR CEILINGS TO PREDOMINATE THROUGH THE TAF PERIOD AS COLDER
AIR PUSHES INTO THE UPPER OHIO VALLEY BEHIND A COLD FRONT.
VISIBILITIES WILL LOWER TO MVFR AT TIMES IN SNOW SHOWERS...WITH IFR
RESTRICTIONS IN HEAVIER SNOW SHOWERS ACROSS NORTHWEST PA AND NEAR
THE APPALACHIAN MOUNTAINS.
SURFACE WINDS WILL BE SOUTHWEST NEAR 10 KT...THEN BECOME WEST TO
NORTHWEST AT 15 KT WITH GUSTS TO 25 KT LATER THIS MORNING.
EXPECT COVERAGE OF SNOW SHOWERS TO DECREASE BY LATE TONIGHT AS
CAPPING INVERSION LOWERS. MAINLY VFR CONDITIONS SHOULD PREVAIL UNDER
A SURFACE RIDGE SATURDAY AND EARLY SUNDAY.
NEXT POTENTIAL FOR SUB VFR CONDITIONS ACROSS THE UPPER OHIO VALLEY
WILL BE SUNDAY NIGHT AND MONDAY IN SHOWERS WITH APPROACHING LOW
PRESSURE SYSTEM.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER WEATHER ADVISORY UNTIL 1 AM EST SATURDAY FOR MDZ001.
OH...NONE.
PA...NONE.
WV...WINTER WEATHER ADVISORY UNTIL 1 AM EST SATURDAY FOR WVZ023-041.
&&
$$
