537
FXUS61 KCTP 202336
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
636 PM EST THU FEB 20 2020
SYNOPSIS
AN UPPER LEVEL DISTURBANCE AND COLD FRONT AT THE SURFACE W
WILL MOVE SOUTHEAST ACROSS THE REGION THROUGH EARLY THIS EVENING
BRINGING FLURRIES AND SCATTERED SNOW SHOWERS TO MAINLY THE
NORTHWEST HALF OF THE STATE, WITH JUST SOME SCATTERED FLURRIES
OVER THE SOUTHEAST. A LIGHT COATING OF SNOW IS EXPECTED ACROSS
THE NORTHERN AND WESTERN MOUNTAINS OF THE STATE LATE TODAY AND
TONIGHT.
HIGH PRESSURE OVER THE WESTERN AND NORTHERN US WILL EXPAND TO
COVER THE ENTIRE LOWER 48 ON FRIDAY. COLDER THAN NORMAL
TEMPERATURES TODAY WILL START TO REBOUND ON FRIDAY AND CONTINUE
TO WARM TO 10 TO 15 DEGREES ABOVE NORMAL FOR SATURDAY AND
SUNDAY. THE NEXT CHANCE FOR PRECIPITATION, MAINLY IN THE FORM
OF RAIN, WILL COME MONDAY INTO TUESDAY.
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
SURFACE COLD FRONT WAS NEARLY BISECTING THE STATE FROM SW TO NE
THIS MID AFTERNOON HOUR. AN AREA OF VERY LIGHT SNOW WAS
ASSOCIATED WITH THIS FRONTAL BOUNDARY AND CFA.
THE LOWER LAYER OF CLOUDS, BASED ANYWHERE BETWEEN 2-4 KFT AGL,
WAS FALLING NICELY WITHIN THE FAVORABLE DGZ OF -12 TO -18C AND
ANY OROGRAPHIC LIFT AND NARROW BANDS OF -SHSN WILL BE HIGHLY
EFFICIENT AT PRODUCING AT LEAST FLURRIES, IF NOT SOME BRIEF 2SM
-SHSN WITH A LIGHT COATING TO ONE HALF INCH OF SNOW ACROSS THE
HIGHER TERRAIN OF NORTHERN AND WESTERN PA.
DEEPER DRY AIR, LLVL SUBSIDENCE VIA DOWNSLOPE FLOW AND A LARGER
NEAR SFC T/TD SPREAD ACROSS THE SUSQ VALLEY AND SOUTHERN TIER
COUNTIES SHOULD LIMIT THE PRECIP THERE TO JUST OCNL FLURRIES.
18Z TEMPS IN THE LOW-MID 20S ACROSS THE NORTH, 30S OVER MUCH OF
THE CENTRAL RIDGE AND VALLEY REGION, AND UPPER 30S IN THE SE
WERE A FEW DEG F SHY OF THEIR FCST HIGHS IN MANY LOCATIONS, BUT
SHOULD FALL RIGHT IN LINE OVER THE NEXT HOUR OR SO.
PRECIPITATING NS LAYER WILL DISSIPATE THIS EVENING ACROSS THE SE
HALF OF THE STATE WITH MAINLY BKN VFR TO MVFR CLOUDS STREAMING
SE FROM THE GLAKES ACCOMPANIED BY BRIEF 3-5SM VSBYS IN
-SHSN/FLURRIES ACROSS THE NW MTNS AND LAUREL HIGHLANDS.
LOW TEMPS EARLY FRIDAY WILL BE THE COLDEST OF THIS MODIFIED
OUTBREAK OF ARCTIC AIR, WITH DAYBREAK READINGS RANGING FROM THE
MID AND UPPER SINGLE DIGITS ACROSS THE NORTHERN TIER COUNTIES OF
PA TO THE MID AND UPPER TEENS THROUGHOUT THE CENTRAL AND
SOUTHERN VALLEYS.
WINDS WILL STAY RATHER LIGHT AND FROM THE NW AT 5-10KTS.
SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/
AFTER SOME BKN STRATOCU CLOUDS AND ISOLATED SNOW SHOWERS ACROSS
THE NW MTNS AND LAURELS UNTIL AROUND 14Z FRIDAY, THE REST OF THE
AREA AND REMAINDER OF THE DAY WILL FEATURE PLENTY OF SUNSHINE
UNDER A RIDGE OF HIGH PRESSURE WITH TEMPS A FEW TO SEVERAL DEG
F WARMER THAN TODAY ACRS CENTRAL AND NW PA. IN CONTRAST, THE
LOWER SUSQ VALLEY WILL SEE TEMPS ABOUT 2 OR 3 DEG F LOWER THAN
TODAY.
LONG TERM /SATURDAY THROUGH THURSDAY/
HIGH PRESSURE CENTERED OVER THE SOUTHEAST UNITED STATES WILL
RESULT IN PLENTY OF SUNSHINE AND DRY CONDITIONS THIS WEEKEND.
SATURDAY WILL BE PARTICULARLY DRY ALONG AND JUST EAST/DOWNWIND
OF THE LAUREL HIGHLANDS, WHERE MODEL GUIDANCE SUGGESTS DEWPOINTS
IN THE SINGLE DIGITS TO NEAR 0 AS TEMPERATURES WARM TO THE
UPPER 30S AND LOW 40S. THIS WOULD RESULT IN RELATIVE HUMIDITY
VALUES IN THE UPPER TEENS OR LOW 20S FOR A PERIOD OF TIME
SATURDAY AFTERNOON. AT THE SAME TIME, BLUSTERY WINDS FROM THE
WEST WILL GUST UP TO 20-30 MPH.
TEMPERATURES WILL BE SEVERAL DEGREES WARMER ON SUNDAY, BUT RH
VALUES ARE NOT EXPECTED TO FALL BELOW 30 PERCENT AND WINDS WILL
BE LIGHTER AS THEY TURN TO SOUTHWESTERLY.
AS WE ROUND OUT METEOROLOGICAL WINTER NEXT WEEK, AN UNSETTLED
PATTERN RETURNS WITH A SERIES OF WEATHER SYSTEMS AFFECTING
THE COMMONWEALTH. THE FIRST SYSTEM MOVES FROM THE OHIO VALLEY
NORTHEASTWARD INTO THE GREAT LAKES MONDAY NIGHT, BRINGING
MOSTLY LIGHT RAIN SHOWERS TO THE AREA MON AFTERNOON THROUGH
TUES. MODEL GUIDANCE THEN SUGGESTS A LULL IN PRECIP TUES NIGHT
THROUGH EARLY WED.
ANOTHER ROUND OF PRECIP BREAKS OUT JUST SOUTH OF THE AREA LATE
WEDNESDAY AS A DEEP TROUGH MOVES OUT OF THE MISSISSIPPI VALLEY.
NAEFS AND ECMWF GUIDANCE BOTH SUGGEST A SUB-1000MB LOW MOVING
OVER THE COMMONWEALTH BY WEDNESDAY NIGHT. DETAILS FOR THIS
STORM ARE STILL HIGHLY UNCERTAIN. PRECIP TYPE AND AMOUNT WED
NIGHT-THURSDAY WILL DEPEND LARGELY ON THE TRACK OF THE STORM
AND HOW QUICKLY IT WRAPS UP. BEHIND THAT SYSTEM, STRONG WESTERLY
WINDS AND ARCTIC AIR WILL MOVE INTO THE AREA FOR THE END OF
NEXT WEEK.
AVIATION /00Z FRIDAY THROUGH TUESDAY/
VFR CONDITIONS WILL PERSIST THROUGH THE FORECAST PERIOD WITH
NORTHWEST SFC WINDS MAINLY IN THE 6-10KT RANGE. WINDS WILL
GRADUALLY SHIFT TO WEST-SOUTHWESTERLY BY FRIDAY AFTERNOON WITH
CLEAR SKIES EXPECTED AREAWIDE.
OUTLOOK
THROUGH SUN...MAINLY VFR CONDITIONS ANTICIPATED AS A LARGE AREA
OF CANADIAN HIGH PRESSURE MOVES SOUTHEAST TO THE CENTRAL
APPALACHIANS BY SAT MORNING.
MON AND TUE...INCREASING CLOUDS WITH A CHANCE OF LIGHT RAIN
LATE MONDAY INTO TUESDAY CENTRAL AND SE, AND RAIN OR WET SNOW
OVER THE NW MTNS.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...BANGHOFF/COLBERT
AVIATION...LAMBERT/BANGHOFF
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