Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 230649
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
249 AM EDT WED JUL 23 2014

.SYNOPSIS...
A COLD FRONT WILL PUSH SOUTHEAST ACROSS THE COMMONWEALTH LATE
TODAY AND TONIGHT. A REFRESHING...COOLER AND LESS HUMID AIRMASS
WILL OVERSPREAD THE COMMONWEALTH FOR THE END OF THE WEEK INTO THE
WEEKEND.

&&

.NEAR TERM /UNTIL 8 AM THIS MORNING/...
WEAK RIDGING OVER THE REGION AT THE SURFACE AND ALOFT...COMBINED
WITH VERY WARM MID LEVEL TEMPS OF 9-11C WILL KEEP CONDITIONS
MAINLY CLEAR BUT MUGGY FOR THE REST OF THE OVERNIGHT HOURS.

CURRENT DEWPOINTS IN THE MID TO UPPER 60S ARE A FEW DEG SHY OF THE
EXPECTED MIN TEMPS AROUND SUNRISE.

PATCHY LOW CLOUDS AND FOG WILL LIKELY FORM OVER THE NEXT FEW
HOURS...BUT SHOULDN/T BE AS EXTENSIVE AS EARLY TUESDAY.

A BKN LINE OF SHRA/TSRA SLIDING SE ACROSS THE PENNSINSULA OF SRN
ONTARIO IS SHOWN TO WEAKEN AS IT CROSSES LAKE ERIE SHORTLY BEFORE
DAYBREAK AND ENCOUNTERS THE VERY STRONG MID-LEVEL CAP ACROSS NWRN
PENN.

&&

.SHORT TERM /8 AM THIS MORNING THROUGH 6 PM TODAY/...
A DRY START TO THE DAY WILL GIVE WAY TO INCREASING CHANCES FOR
SHOWERS AND THUNDERSTORMS AS FORCING INCREASES ASSOCIATED WITH THE
APPROACHING COLD FRONT. WE ARE NOT OUTLOOKED FOR SEVERE AT THIS
TIME BUT THE AIRMASS CHANGE WILL BE FAIRLY STARK FOR MID JULY AND
FORECAST CAPES IN EXCESS OF 1200J SUGGEST SPC MIGHT EXPAND THEIR
SLIGHT RISK WITH LATER UPDATES. EITHER WAY IT LOOKS LIKE AN
UNSETTLED AND WET DAY AS THE FRONT TRAVERSES THE REGION.

THANKS TO A WARMING LOW LEVEL WSW DOWNSLOPE FLOW AHEAD OF THE
CFRONT...HIGH TEMPS WED WILL BE THE WARMEST OF THE WEEK...RANGING
FROM THE LOWER 80S ACROSS THE HIGHEST TERRAIN OF THE NORTH AND
WEST...TO THE MID AND UPPER 80S IN THE CENTRAL VALLEY...AND LOWER
90S IN THE GREATER YORK/HARRISBURG AREA.

&&

.LONG TERM /TONIGHT THROUGH TUESDAY/...
OVERALL SCENARIO REMAINS UNCHANGED IN THE LONG TERM PERIOD AS A
LARGE UPPER RIDGE BUILDING OVER THE FOUR CORNERS REGION IS
FORECAST TO EXPAND NORTH AND EAST INTO THE ROCKIES AND PLAINS
DURING THE PERIOD. DOWNSTREAM...THIS WILL LEAD TO LONG WAVE
TROFFING OVER THE EASTERN THIRD OF THE COUNTRY. UPPER LOW TO THE
EAST OF HUDSON BAY WILL BE STRENGTHENED AT TIMES BY SHORTWAVE
ENERGY IN THE STRONGER JET STREAM FLOW ACROSS CANADA. SOUTHWARD
EXTENSION OF THIS LOW/TROF WILL AT TIMES DURING THE PERIOD
STRENGTHENING THE TROFFING ACROSS THE NORTHEASTERN U.S./OUR
REGION. THE TREND OF MEDIUM RANGE MODEL GUIDANCE IS FOR
STRONGER/DEEPER TROFFING DOWNSTREAM ACROSS THE EASTERN
U.S...DEVELOPING AN ALMOST FULL LATITUDE TROF EXTENDING FROM THE
EASTERN CANADA LOW SWD TO FLORIDA. THIS WILL LIKELY SERVE TO
EXPAND AND PROLONG THE CHANCES FOR PCPN THIS WEEKEND.

GUIDANCE FORECASTS CONTINUE TO BRING A FRONT AND INCREASED
CHANGES FOR PRECIPITATION TOWARD PA IN THE WEDNESDAY/THURSDAY TIME
FRAME AND SHOW A SECOND...POTENTIALLY STRONGER SYSTEM LATE NEXT
WEEKEND. THE TREND OF STRONGER TROUGHING MENTIONED ABOVE HAS LEAD
TO SLOWER ARRIVAL AND DEPARTURE OF THE FRONTAL SYSTEM IN THE DAILY
PROGS. THE ECMWF IN LATEST RUN HAS SLOWED UP THE PROGRESSION OF
THIS UPPER LEVEL LOW...WHERE THE GFS OPERATIONAL AND ENSEMBLES
HAVE SPED UP ITS PROGRESSION THROUGH THE GREAT LAKES REGION. A
WARM FRONT WILL BE ON THE DOORSTEP OF PA SUNDAY...AS THE EC
CONTINUES TO SLOW ITS PROGRESSION SO EXPECT THE WARM FRONT TO MOVE
IN CLOSER TO MIDDAY SUNDAY. HAVE THUS ADJUSTED POPS/TIME.

ASSOCIATED COLD FRONT DOES NOT CROSS THE STATE TIL MONDAY...WHERE
SURPRISINGLY AT THIS POINT...THE EC AND GFS COME CLOSELY IN PHASE.
THIS LARGE UPPER LEVEL LOW COULD BECOME QUASI STATIONARY OVER
SOUTHERN CANADA...GREAT LAKES REGION WHICH COULD LEAD TO A
POTENTIAL PROLONGED PERIOD OF SHOWERS AND THUNDERSTORM THROUGH THE
MIDDLE OF NEXT WEEK.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
23/06Z...CUT BACK ON FOG THIS MORNING GIVEN OBS TRENDS AND LGT
S-SW GRADIENT SFC WIND IN ADVANCE OF COLD FRONT SEWD ACRS LWR MI
TWD THE ERN LKS. LINE OF STORMS IN ADVANCE OF COLD FRONT MOVG ACRS
LK ERIE ARE FCST BY COSPA/HRRR/SPC 4KM WRF TO WEAKEN OR DISSIPATE
AS THEY REACH NW PA AROUND DAYBREAK.

AFTER SOMEWHAT OF A LULL IN CONVECTION DURING THE MID TO LATE
MORNING...EXPECT SCT TO NMRS SHWRS AND TSTMS TO DEVELOP FROM THIS
AFTN INTO THE EVE ALONG AND AHEAD OF THE COLD FRONT..AS IT SHIFTS
SEWD ACRS THE AIRSPACE. CVRG SHOULD BE GREATEST OVER THE CNTRL AND
ERN PRTNS OF THE AIRSPACE WITH SOME STG TO LCLY SVR STORMS
POSSIBLE. PREVAILING CONDS WILL VFR WITH BRIEF MVFR-IFR VIS
REDUCTIONS IN TSRA IMPACTS. WND SHIFT FROM SW TO NW BY TONIGHT
WITH MAIN PCPN ACTIVITY BCMG CONFINED TO SERN AREAS INTO THU.
POST-FRONTAL MVFR SEEMS PROBABLE OVER WRN SXNS TNGT.

OUTLOOK...

THU...SCT TSTM IMPACTS PSBL SERN AIRFIELDS AS COLD FRONT SLOWS
ALONG THE MID-ATLC COAST.
FRI...PATCHY MORNING FOG...OTHERWISE VFR/NO SIG WX.
SAT...PATCHY MORNING FOG...OTHERWISE VFR. ISOLD PM TSTM PSBL.
SUN...TSTM IMPACTS LKLY AS WARM FRONT LIFTS NWD ACRS AIRSPACE.

 &&

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

&&

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

&&

$$
SYNOPSIS...LA CORTE/LAMBERT
NEAR TERM...DEVOIR/LAMBERT
SHORT TERM...LA CORTE
LONG TERM...LAMBERT/CERU
AVIATION...STEINBUGL



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