Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 171825 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 225 PM EDT THU APR 17 2014 .SYNOPSIS... A RIDGE OF HIGH PRESSURE WILL EXTEND FROM THE CANADIAN MARITIMES...SOUTHWEST TO THE MID ATLANTIC COAST...KEEPING FAIR AND DRY WEATHER ACROSS MOST OF THE REGION THROUGH FRIDAY. A WEAK COLD FRONT WILL MOVE EAST FROM THE GREAT LAKES REGION AND BRUSH NORTHERN AND WESTERN PENNSYLVANIA WITH SOME CLOUDS AND PERHAPS A FEW RAIN SHOWERS LATE FRIDAY AND FRIDAY NIGHT. ANOTHER AREA OF HIGH PRESSURE WILL BUILD EAST INTO THE COMMONWEALTH FOR THE WEEKEND SUPPLY ANOTHER FEW DAYS OF PLEASANT MID SPRING WEATHER. TEMPERATURES WILL MODERATE FURTHER THIS WEEKEND AND RISE ABOVE NORMAL BY EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... VARIABLE AMOUNTS OF MAINLY THIN CIRRUS WILL OCCUR ACROSS CENTRAL AND NWRN PENN FOR THE REST OF TODAY...ACCOMPANIED BY A SOUTHEASTERLY WIND OF 10-12KTS WITH GUSTS OF 15-20KTS IN MANY LOCATIONS. ALTHOUGH WINDS ARE SIMILAR TO YESTERDAY /ALBEIT FROM THE OPPOSITE DIRECTION/ MOTHER NATURE IS LESS DECEIVING WITH RESPECT TO TEMPS...WHICH ARE 8-10F WARMER IN ALL LOCATIONS COMPARED TO THIS SAME TIME WEDNESDAY. SOME LLVL MARINE MOISTURE /THE BULK OF IT WHICH IS STILL LURKING ALONG...AND OFF THE SOUTHERN NJ AND DELMARVA COAST/ IS CONTINUING TOO ADVECT NW AND ACROSS THE LOWER SUSQ VALLEY. THE EXTENT OF THESE SHALLOW...SCT-BKN STRATO CLOUDS SHOULD CONTINUE TO INCREASE AND COVER MOST OF THE REGION ALONG AND TO THE SE OF I-81 BY DUSK. TEMPS REMAIN ON TRACK TO REACH MID TO LATE AFTERNOON HIGHS IN THE LOW TO MID 50S. AS THE RELATIVELY SHALLOW VERTICAL MIXING SUBSIDES THIS EVENING...WE SHOULD SEE THE STRATO CU DECK ACROSS THE LOWER SUSQ VALLEY AND ADJACENT SERN AND ECENT PA SOLIDIFY INTO A MORE UNIFORM BKN- OVC CLOUD LAYER AND ADVANCE INTO THE CENTRAL RIDGE AND VALLEY REGION AS THE MEAN SFC-850 MB FLOW REMAINS FROM THE SOUTHEAST. ELSEWHERE...PERIODS OF CIRRUS WILL OCCUR. THE CLOUDS /AND HIGHER DEWPOINTS /IN THE 20S/ WILL HELP TO CURB THE TEMP DROP TONIGHT...AND MINS EARLY FRIDAY WILL BE SEVERAL DEG F OR MORE HIGHER THAN EARLY THIS THURSDAY MORNING. THE UNCERTAINTY OF THE AMOUNT OF CLOUD COVER TONIGHT AND EARLY FRIDAY...COMBINED WITH THE INCREASING SFC DEWPOINTS...AND LIGHT SE WINDS HAS DIRECTED US TOWARD TRANSITIONING FROM A FREEZE WATCH TO A FROST ADVISORY...WITH MIN TEMPS IN THE 32-35 RANGE IN MOST LOCATIONS. SOME OF THE TYPICALLY COLDER RURAL VALLEYS COULD SEE DAYBREAK TEMPS IN THE UPPER 20S /ESP IF A PERIOD OF CLEARING OCCURS/. TEMPS ACROSS THE CENTRAL AND NW ZONES WILL BE JUST A TAD LOWER THAN THOSE LOWER SUSQ COUNTIES COVERED BY THE FROST ADVISORY. && .SHORT TERM /FRIDAY/... THE MEAN BLYR FLOW VEERS A BIT MORE TO THE SSE OR SOUTH DURING THE DAY FRIDAY...WHICH WILL HELP AN ILL-DEFINED WARM FRONT LIFT NORTH ACROSS THE REGION AND INTO NEW YORK STATE. A BROAD...NEARLY NORTH-SOUTH AXIS OF LLVL MOISTURE CONVERGENCE AND HIGHER DEWPOINTS WILL HELP TO CREATE MORE IN THE WAY OF STRATO CU...THAN THE NEARLY NON-EXISTENT AMOUNTS THAT WE/VE SEEN IN THE UNUSUALLY COLD...AND BONE-DRY AIRMASS THE PAST FEW DAYS. OTHERWISE...THE LLVL RIDGE AXIS STAYS IN PLACE ALONG THE MID ATLANTIC PIEDMONT AND HELPS TO DEFLECT A WEAK NORTHERN STREAM SYSTEM TO OUR NORTH. A SIGNIFICANTLY STRONGER SRN STREAM STORM WILL ALSO BE HELD AT BAY WELL TO THE SOUTH OF THE AREA. A FEW LIGHT SHOWERS MAY GRAZE THE NWRN COS LATE FRIDAY...OR FRIDAY NIGHT. && .LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/... DRY WEATHER SHOULD CONTINUE FOR THE REST OF THE WEEKEND AS ANOTHER RIDGE OF HIGH PRESSURE BUILD EAST FROM THE OHIO VALLEY AND UPPER GREAT LAKES REGION. LOOKING INTO THE MEDIUM RANGE...WHILE FCST CONFIDENCE IN THE PCPN PATTERN IS AVG AT BEST THE GUIDANCE FAVORS A MAINLY DRY FCST SUN- MON BEFORE RAIN CHANCES RETURN BY TUESDAY. THE UNCERTAINTY IS ASSOCD WITH A LOW AMPLITUDE PACIFIC SHORTWAVE TROUGH EJECTING EASTWARD FROM THE NORTHERN ROCKIES. THE GENERALLY WEAK NATURE OF THE PACIFIC ENERGY CROSSING THE NORTHERN-TIER CONUS ALONG WITH A SOMEWHAT UNUSUAL BUT RATHER EXPLICIT NORTH-SOUTH SPLIT IN THE 500MB FLOW BOTH CONTRIBUTE TO LOW CONFIDENCE IN THE FCST. THE SPLIT FLOW ALOFT APPEARS TO BE SHORT-LIVED AS THE LW PATTERN IS FCST TO REAMPLIFY BY THE MIDDLE OF NEXT WEEK...WITH STRONG HEIGHT FALLS/SPRING CUT-OFF LOW PROGGED TO MIGRATE FROM THE WEST COAST INTO THE GREAT BASIN...SUPPORTING SLIGHTLY ABOVE-AVG 500MB RIDGING SPREADING EWD FROM THE PLAINS TO THE MIDWEST AND EVENTUALLY INTO THE NORTHEAST TOWARD THE END OF NEXT WEEK. A CANADIAN SHORTWAVE CROSSING NORTHERN NEW ENGLAND MAY DELAY THE HEIGHT RISES IN THE EAST AND SEND A BACK-DOOR COLD FRONT INTO THE MID-ATLC AROUND DAY 8. OVERALL...EXPECT TEMPERATURES TO MODERATE FROM BELOW NORMAL TO NEAR OR SLIGHTLY ABOVE LATE APRIL NORMALS BY NEXT WEDNESDAY. OPPORTUNITIES FOR RAIN NOW APPEAR TO BE FOCUSED IN THE FRI NGT SATURDAY MORNING AND TUESDAY TIME-FRAMES. SO MOST OF THE EASTER WEEKEND LOOKS LIKE IT WILL BE MAINLY DRY IN CENTRAL PA. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... VFR CONDITIONS WILL CONTINUE THROUGH THIS EVENING. A LAYER OF SHALLOW/BKN MVFR-LOW END VFR STRATOCU WILL BE SLIDING IN FROM THE SE /DURING THE MID TO LATE AFTERNOON ACROSS THE LOWER SUSQ VALLEY AIRFIELD/...AND REACHING THE CENTRAL MTNS LATE TONIGHT/EARLY FRIDAY MORNING. MAINLY SUNNY SKIES WILL CONTINUE WITH SOUTHEAST TO SOUTH-SOUTHEAST WINDS AVERAGING TO 8-12 KTS WITH OCCASIONAL GUSTS AROUND 20 KTS. THE WIND WILL SUBSIDE DURING THE EARLY EVENING. CHANCE FOR LIGHT RAIN TO IMPACT MAINLY NW LATE FRIDAY AFTERNOON OR FRIDAY NIGHT WITH LOW PROB OF RESTRICTIONS. VFR ELSEWHERE. OUTLOOK... FRI...GENERALLY VFR. AREAS OF MVFR CIGS POSS ACROSS CENTRAL AND SE PA EARLY. FRI NIGHT-SAT...REDUCED CIGS/VSBYS POSS WITH CHANCE OF LIGHT RAIN SHOWERS /MAINLY NW HALF/. SUN-MON...NO SIG WX. TUE...A FEW...TO SEVERAL-HOUR PERIOD OF MVFR CIGS WITH BRIEF MVFR VSBYS IN SHOWERS ACCOMPANYING A COLD FRONTAL PASSAGE. && .CTP WATCHES/WARNINGS/ADVISORIES... FROST ADVISORY FROM 2 AM TO 8 AM EDT FRIDAY FOR PAZ057-059- 063>066. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...LAMBERT LONG TERM...LAMBERT/STEINBUGL AVIATION...LAMBERT

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