Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 240939 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 539 AM EDT THU JUL 24 2014 .SYNOPSIS... HIGH PRESSURE...AND A REFRESHINGLY COOLER AND LESS HUMID AIRMASS WILL PUSH SOUTHEAST FROM THE GREAT LAKES REGION TODAY AND STAY WITH US RIGHT INTO SATURDAY. A WARM FRONT WILL SLIDE EAST OUT OF THE OHIO VALLEY LATE SATURDAY FOLLOWED BY A WAVY...SLOW MOVING COLD FRONT FOR SUNDAY INTO SUNDAY NIGHT. PERIODS OF SHOWERS AND THUNDERSTORMS WILL AFFECT CENTRAL PENNSYLVANIA AND THE ALLEGHENY PLATEAU SATURDAY NIGHT THROUGH SUNDAY NIGHT. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SURFACE COLD FRONT HAS PUSHED WELL SOUTH OF THE REGION AS OF 08Z. A FEW...WEAK VORT MAXES ALOFT WILL RIDE EAST ACROSS SOUTHERN PENN EARLY TODAY AND COMBINE WITH THE LINGERING HIGH PWAT AIR OF 1.5 TO 1.75 INCHES LOCATED ACROSS THAT REGION TO PRODUCE A FEW LIGHT SHOWERS THIS MORNING...CLOSE TO THE MASON-DIXON LINE. A STRENGTHENING SUBSIDENCE INVERSION WILL HELP TO TRAP PLENTY OF STRATO CU CLOUDS THROUGH AT LEAST THE MORNING HOURS TODAY. A SLOW CLEARING TREND IS EXPECTED LATER THIS AFTERNOON AND EVENING. DAYBREAK TEMPS WILL RANGE FROM THE MID AND UPPER 50S ACROSS THE NRN MTNS...TO THE UPPER 60S THROUGHOUT THE LOWER SUSQUEHANNA RIVER VALLEY. TODAY WILL BE QUITE A NICE DAY FOR MOST OUTDOOR ACTIVITIES AS NOTICEABLY COOLER AND LESS HUMID AIR WILL SPREAD OVER THE REGION. A STUBBORN...AND QUITE STRONG SUBSIDENCE INVERSION WILL TRAP PLENTY OF LLVL MOISTURE AND STRATO CU CLOUDS AT ITS BASE. THE CLOUD LAYER /BETWEEN 3-5 KFT AGL/ SHOULD YIELD SOME BREAKS OF SUNSHINE THROUGHOUT THE DAY /ESPECIALLY DURING THE AFTERNOON ACROSS THE SUSQUEHANNA VALLEY/ AS A SURGE OF DRIER LOW-MID LEVEL AIR MOVES SOUTH ACROSS THAT PART OF THE FCST AREA. CONSENSUS BLEND OF ALL MODEL GUIDANCE INDICATES TEMPS STRUGGLING TO CLIMB OUT OF THE U60S FOR A HIGH IN THE KBFD AREA...WHILE THE CENTRAL ZONES AND LAUREL HIGHLANDS WILL SEE MID TO LATE AFTERNOON MAX TEMPS IN THE MID TO UPPER 70S. HIGHS THROUGHOUT THE LOWER SUSQ REGION WILL BE AROUND 80F /OR ABOUT 6 DEG F BELOW NORMAL/. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... HIGH PRESSURE BUILDING INTO THE STATE FROM THE OHIO VALLEY WILL BRING CLEAR TO PARTLY CLOUDY SKIES TO ALL OF THE REGION TONIGHT. ANOMALOUSLY LOW PWAT AIR OF ONLY AROUND ONE-HALF OF AN INCH /OR LESS/ WILL COMBINE WITH A COOL POOL AT 850 MB...AND LIGHT WIND... TO BRING A VERY CHILLY MID-SUMMER NIGHT. LOW TEMPS AT DAYBREAK FRIDAY WILL VARY FROM AROUND 40F ACROSS THE PERENNIAL COLD SPOTS ACROSS THE NORTH...TO BETWEEN 50 AND 55F THROUGHOUT THE SUSQUEHANNA VALLEY. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... 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 MODERATE TO STRONG 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. A POTENTIALLY STRONGER SYSTEM /STRONGER THAN THE ONE THAT USHERED IN THE COOL AND MUCH LESS HUMID AIRMASS OVERNIGHT WEDNESDAY NIGHT/ WILL AFFECT THE REGION FOR THE SECOND HALF OF THE UPCOMING 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 OUR WESTERN DOORSTEP LATE SATURDAY NIGHT AND 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 /10Z THURSDAY THROUGH MONDAY/...
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FEW SHOWERS TRYING TO MOVE BACK INTO S PA. EXTENSIVE CLOUD COVER HAS CUT BACK THE THREAT OF FOG. 09Z TAFS SENT. EARLIER DISCUSSION BELOW. FOG BEGINNING TO DEVELOP ACROSS THE REGION. IN ADDITION...DECK OF LOWER STRATUS MOVING INTO THE WESTERN MOUNTAINS...WITH TYPICAL UPSLOPE MOIST FLOW BRINGING IN IFR CIGS INTO KJST. EXPECT IFR CONDITIONS OVERNIGHT IN KJST AND KBFD...AND GENERALLY MVFR CONDITIONS ELSEWHERE. HIGH PRESSURE TO PROVIDE GENERALLY VFR CONDITIONS THROUGH SATURDAY...BEFORE SHRA/TSRA MOVE INTO THE WEST LATER SATURDAY...WITH THE RISK OF SHRA/TSRA SUN/MON. OUTLOOK... FRI...PATCHY AM FOG...OTHERWISE VFR. SAT...PATCHY AM FOG...OTHERWISE MAINLY VFR. PM TSRA/MVFR POSS W. SUN...SHRA/TSRA WITH WARM FRONT PASSAGE MON...MORE WIDESPREAD SHRA/TSRA WITH COLD FRONT PASSAGE.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/GARTNER AVIATION...JUNG/MARTIN

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