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Area Forecast Discussion
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000
FXUS61 KCTP 212004
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
404 PM EDT SUN SEP 21 2014

.SYNOPSIS...
A COLD FRONT WILL PUSH EAST ACROSS THE STATE LATE THIS AFTERNOON
AND THIS EVENING...ACCOMPANIED BY SHOWERS AND ISOLATED
THUNDERSTORMS. A POTENT UPPER AIR DISTURBANCE AND UNSEASONABLY
COLD AIR ALOFT WILL DROP SOUTHEAST FROM LAKE ERIE THIS EVENING
BRINGING NUMEROUS SHOWERS...MAINLY TO THE NORTHWEST MOUNTAINS
OVERNIGHT. A LARGE AREA OF HIGH PRESSURE WILL BUILD OUT OF
CENTRAL CANADA AND PROVIDE GENERALLY FAIR AND COOL WEATHER FOR
MOST IF NOT ALL OF THIS WEEK.

&&

.NEAR TERM /UNTIL 10 PM THIS EVENING/...
A FEW AREAS OF SHOWERS WILL ACCOMPANY A PREFRONTAL TROUGH AND
COLD FRONTAL PASSAGE ACROSS THE CWA LATE THIS AFTERNOON AND THIS
EVENING.

BEST LARGE SCALE FORCING /ASSOCIATED WITH THE RIGHT ENTRANCE
REGION OF A SWRLY 100 KT 300 MB JET/ WILL BE ACROSS CENTRAL AND
NRN PENN THROUGH 22Z. THAT/S WHERE THE GREATEST CONCENTRATION OF
SHOWERS WILL OCCUR WITH BASIN AVG QPF OF 2-3 TENTHS OF AN INCH
LIKELY. ALTHOUGH LESS RAINFALL IS EXPECTED ON AVERAGE ACROSS
SOUTHERN PENN /INCLUDING THE LOWER SUSQ VALLEY/ A FEW GUSTY...
LOW-TOPPED TSRA ARE POSSIBLE IN ANY LOCATION AS POCKETS
SUNSHINE...TEMPS IN THE 70S TO LOWER 80S SE...AND DEWPOINTS IN
THE L-M 60S WILL CREATE SFC BASED CAPES OF 1000-1500 J/KG AND
PINPOINT RAINFALL AMOUNT AOA 0.25 INCH.

IN THE WAKE OF THE CFROPA...A DRY SLOT LASTING 2-4 HOURS ACROSS
THE NW MTNS /AND LONGER ELSEWHERE/ PUSHES IN LATE THIS
AFTERNOON/EARLY EVENING. THIS WILL BE FOLLOWED BY A POTENT UPPER
VORT MAX AND THE LEADING EDGE OF QUITE COLD 850 MB AIR /DROPPING
TO SLIGHTLY BELOW ZERO ACROSS THE NORTH ON MONDAY/. MORE ON THE
IMPACT OF THIS COLDER AIR ALOFT IN THE SHORT TERM SECTION BELOW.

&&

.SHORT TERM /10 PM THIS EVENING THROUGH 6 AM MONDAY/...
WHILE SKIES GO SCATTERED-BKN LATER THIS EVENING WITH A FEW
SPRINKLES POSSIBLE EAST OF THE ALLEGHENIES...NUMEROUS UPSLOPE AND
LAKE EFFECT RAIN SHOWERS WILL IMPACT THE NW MTNS AND LAUREL
HIGHLANDS BEGINNING LATER THIS EVENING. DELTA-T DIFF BETWEEN THE
LAKE TEMPS OF AROUND 20C AND THE MUCH COLDER AIR ALOFT WILL BE
AROUND 20C /AND WELL-BEYOND THE THRESHOLD FOR LAKE EFFECT PRECIP/.

A GUSTY WEST-NORTHWEST GRADIENT WIND WILL FOLLOW THE FRONT THIS
EVENING. WIND GUSTS OF 25-30 MPH ARE LIKELY ACROSS THE WEST
TONIGHT. WINDS SHOULD BE A TAD LIGHTER FOR MUCH OF THE NIGHT ACROSS
THE EASTERN HALF OF THE CWA AS BOUNDARY LAYER DECOUPLES WITHIN
THE CLEAR SLOT PRIOR TO THE DEEP COLD AIR ADVECTION.

LOW TEMPS TONIGHT WILL VARY FORM THE MID TO UPPER 40S ACROSS THE
NORTHERN AND WRN MTNS...TO THE LOWER AND MID 50S IN THE CENTRAL
AND SOUTHERN PORTIONS OF THE STATE.

&&

.LONG TERM /MONDAY THROUGH SUNDAY/...

TYPICAL POST-FRONTAL SET-UP TOMORROW AS THE RESIDUAL AND LAKE
MOISTURE ASCENDING THE MTNS COUPLED WITH THE COLD AIR MOVING IN
ALOFT WILL GENERATE INSTABILITY AND SHOULD CAUSE SCT SHRA FOR THE
NWRN THIRD OF THE AREA...AND OVER THE LAURELS...THROUGH THE
MORNING HOURS MONDAY. 8H TEMPS DIP TO JUST ABOVE ZERO MONDAY
MORNING AND STAY IN THE SINGLE DIGITS. THIS WILL KEEP MAX
TEMPERATURES WELL BELOW NORMAL AND MAY BE LIMITED TO THE M50S IN
THE MTNS AND IN THE LOW TO MID 60S THROUGH MOST OF CENTRAL
PA...AND IN THE UPPER 60S IN THE SOUTHERN PIEDMONT.

THE DEEP UPPER LEVEL TROUGH WILL MOVE EASTWARD MONDAY NIGHT...AND
THE LARGE SFC SYSTEM OFF THE COAST WILL CONTINUE ITS NORTHEASTWARD
TREK. HIGH PRESSURE WILL BUILD IN USHERING IN A LONG TERM PERIOD
OF DRY AND FAIR WEATHER. IS BEGINNING AND IT SORT OF PARKS ITSELF
OVER NEW YORK AND NEW ENGLAND WITH +2 TO +3 SIGMA ABOVE NORMAL
MSLP ANOMALIES BY WEDNESDAY-THURSDAY. THE MODELS SEEM TO BE IN
FAIR AGREEMENT SHOWING A BLOCKING 500 HPA ANTICYCLONE TO THE
NORTHWEST AS A MASSIVE 500 HPA POSITIVE HEIGHT ANOMALY OF +2 TO +3
SIGMA DEVELOPS OVER CENTRAL CANADA BY THURSDAY AND INTO FRIDAY.

THE MODELS AND ENSEMBLE MEANS DO WELL FORECASTING ANTICYCLONES SO
THERE SEEMS TO BE MORE OF A CONSENSUS ON THE FAIR WEATHER FORECAST
NEXT WEEK. EXPECT DIURNAL VALLEY FOG AND LOW CLOUDS LIKELY TO
AFFECT THE REGION EACH MORNING ONCE THE BIG HIGH TAKES HOLD....AND
CONTINUING DAILY INTO NEXT WEEKEND. THAT MASSIVE HIGH SHOULD
CONTINUE THE DRY FAIR WEATHER THROUGH NEXT WEEKEND. 

&&

.AVIATION /19Z SUNDAY THROUGH FRIDAY/...
LOCALIZED MVFR AND VSBYS WILL ACCOMPANY FAST-MOVING SHOWERS AND
PERHAPS A FEW BRIEF TSRA ALONG AND AHEAD OF A COLD FRONT LATE THIS
AFTERNOON AND EARLY THIS EVENING. 

OTHERWISE...CONDITIONS WILL BE MAINLY VFR THROUGH 00Z.

A POTENT UPPER LEVEL DISTURBANCE AND ASSOCIATED POOL OF
UNSEASONABLY COLD AIR ALOFT WILL PUSH SOUTHEAST ACROSS THE REGION
OVERNIGHT. NUMEROUS...LAKE EFFECT AND UPSLOPE SHOWERS WILL IMPACT
THE NORTHERN AND WRN MTNS OF PENN WITH IFR CIGS /AND PERIODS OF
MVFR VSBYS/ IN THE 00Z-15Z MONDAY PERIOD OCCURRING FROM KBFD...TO
KFIG AND KJST.

ELSEWHERE ACROSS THE CENTRAL RIDGE AND VALLEY REGION OF THE STATE...
PERIODS OF BKN STRATO CU WILL BE IN THE LOW- END VFR TO UPPER END
MVFR CATEGORY.

VFR CONDITIONS SHOULD PREVAIL INTO MID/LATE WEEK WITH THE
EXCEPTION OF SOME PATCHY MORNING FOG.

OUTLOOK...
MON...AM LOW CIGS WITH SCATTERED SHOWERS POSSIBLE ACROSS THE NRN
AND WRN MTNS. 
TUE...AM FOG POSS W MTNS. 
WED...AM FOG POSS...MAINLY NORTHERN PA. 
THU AND FRI...PATCHY AM FOG POSSIBLE.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...GRUMM/CERU
AVIATION...LAMBERT



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