Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 211144 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 744 AM EDT TUE OCT 21 2014 .SYNOPSIS... LOW PRESSURE EVOLVING FROM THE LOWER GREAT LAKES INTO THE MID- ATLANTIC AND NORTHEAST STATES WILL CONTINUE TO BRING COOL AND UNSETTLED WEATHER TO THE REGION THROUGH MID-WEEK. SLOWLY IMPROVING CONDITIONS ARE EXPECTED BY THE END OF THE WEEK WITH MILDER WEATHER BY EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/... WATER VAPOR IMAGERY SHOWED A PAIR OF SHORTWAVE IMPULSES AT 09Z: 1) DIGGING SWD THROUGH SRN ONTARIO (HELPING TO EVENTUALLY CARVE OUT AND CLOSE OFF UPPER LOW) AND 2) ROTATING EWD THRU CENTRAL PENNSYLVANIA. THE PA IMPULSE WILL CONTINUE SHIFT EWD THRU THE MORNING AND MAINTAIN SHOWER ACTIVITY PRIMARILY OVER THE NORTHWESTERN AND NORTH-CENTRAL ALLEGHENIES...WHICH SHOULD BECOME ENHANCED BY POST FRONTAL NW/UPSLOPE FLOW. LATEST HRRR CONFIRMS THIS WHILE KEEPING MOST AREAS S/E OF THE I-99 CORRIDOR MAINLY DRY THRU MID-LATE MORNING. ALL GUIDANCE SHOWS THE UPPER LEVEL ENERGY BECOMING BETTER ORGANIZED AND EVENTUALLY CLOSING OFF OVER PA BY THIS EVE/00Z. MEANWHILE...SFC LOW CURRENTLY CENTERED OVER BUFFALO NY WILL TRANSFER ITS ENERGY TO COASTAL DEVELOPMENT NEAR OR JUST OFFSHORE NJ AND THE DELMARVA. THE LATEST RAP SFC PRES FALLS ARE STARTING TO SHOW THIS WITH -3 TO -4MB FALLS. DIFFERENCES START TO EMERGE IN THE MODELS WITH THE SFC LOW TRACK/POSITION BY 22/12Z WITH THE GFS/GEFS MEMBERS BEING WEST OF THE ECMWF/CMC ENSEMBLE MEMBERS. RELATIVELY COOL AIR ALOFT ACCOMPANYING THE EVOLVING UPPER LEVEL LOW WITH MID-LVL LAPSE RATES IN THE 6.5-7.0 C/KM RANGE...AND LG SCALE LIFT GENERATED BY VORT MAXIMA PIVOTING OVER THE REGION SHOULD PROMOTE INCREASED COVERAGE OF SHOWER ACTIVITY BY THE AFTERNOON. HRRR SHOWS BULK OF SHOWERS OVER WRN PA THROUGH 18Z WITH DEVELOPING SHOWERS OVER CENTRAL AND ERN SECTIONS LATER IN THE AFTERNOON. THE MODEL GUIDANCE PROGS WEAK INSTABILITY /CAPES GENERALLY AOB 300 J/KG/ ACROSS THE SOUTH CENTRAL AND SERN ZONES WHICH...WHEN COUPLED WITH THE STEEP MID-LVL LAPSE RATES...MAY PROVE SUFFICIENT FOR A FEW ISOLATED/EMBEDDED LOW-TOPPED TSTMS TO FORM WITHIN A BROADER AREA OF SCT TO NMRS SHOWERS. MAIN CHANGE TO DAY 1 MAX/MIN TEMPS WAS TO RAISE OVERNIGHT LOWS GIVEN PLENTY OF CLOUD COVER AND 5-10KT SUSTAINED N-NW WINDS. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... MODEL AND ENSEMBLE GUIDANCE SHOWS THE CLOSED UPPER LOW PIVOTING AND WRAPPING NWWD THROUGH 12Z THURS WITH SFC LOW BECOMING NEARLY STACKED ABOUT 100-200 MILES SSE OF LONG ISLAND. THERE CONTINUES TO BE SOME PLACEMENT ISSUES WITH THE SFC LOW WITH THE 00Z GFS/GEFS AND 21Z SREF ALL REASONABLY WELL CLUSTERED. THE PREVIOUS TWO RUNS OF THE ECMWF ARE SOUTH OF THIS CONSENSUS WITH THE 00Z NAM/CMC TO THE EAST. A SUPERBLEND OF OP/ENS/WPC QPF SHOWS THE HIGHEST POPS OVER THE ERN 1/3 OF THE CWA EARLY WED NEAR POSSIBLE ZONE OF WRAP- AROUND PCPN...BEFORE TRENDING LOWER WED NGT INTO THURS. IT WILL FEEL RATHER RAW WITH PLENTY OF CLOUDS AND A CHILLY/GUSTY NLY WIND. A 50/50 BLEND OF CONSENSUS AND BIAS CORRECTED CONSENSUS GUIDANCE YIELDED SLIGHTLY LOWER DAYTIME HIGHS AND WARMER OVERNIGHT LOWS. THIS MAKES SENSE GIVEN THE OVERALL SYNOPTIC PATTERN. && .LONG TERM /THURSDAY THROUGH MONDAY/... THE PERIOD WILL START WITH THE NEW ENGLAND COASTAL STORM LIFTING SLOWLY NEWD ALONG THE NORTHEAST COAST TOWARD THE CANADIAN MARITIMES THU INTO SAT. THIS LOW WILL KEEP THE CHANCE OF CHILLY WRAP-AROUND RAINS IN THE FCST FOR DAY 3 POSSIBLY INTO DAY 4 DEPENDING ON HOW FAST THE STORM LIFTS OUT. THE KEY HERE LKLY LIES UPSTREAM WITH STRONG SHORTWAVE CURRENTLY MOVING INTO NRN CA. THIS ENERGY IS EXPECTED TO SPLIT OVER THE CENTRAL U.S. WITH NRN STREAM ENERGY PROJECTED TO DIG SEWD THROUGH THE APPALACHIANS AND MOVE OFF THE EAST COAST BY SAT NGT. THE 00Z NON NCEP DATA WANTS TO HANG ONTO THE NW FLOW BEHIND THE DEPARTING STORM A LITTLE LONGER THAN THE GFS/GEFS WHICH SHOW SFC HIGH PRES BUILDING INTO THE AREA ON SUNDAY. THIS SEEMS DUE TO MORE PRONOUNCED SHORTWAVE ENERGY DIGGING SEWD ACRS SOUTH-CENTRAL CANADA INTO THE NORTHEAST STATES DOWN THE FRONT-SIDE OF A SUBTROPCIAL RIDGE MIGRATING EWD FROM AZ/NM INTO TX. WITH THE FLOW ALOFT FCST TO TREND TOWARD LESS AMPLIFICATION AND SLIGHTLY MORE PROGRESSIVE IN TIME WITH A BROAD BELT OF WESTERLIES EXTENDING FROM THE PACIFIC COAST INTO THE NATIONS MIDSECTION...THE DOWNSTREAM PATTERN SHOULD EVENTUALLY UNDERGO SOME RECONFIGURATION. THIS SHOULD SEND HEIGHTS RISING WHICH WOULD SUPPORT MILDER TEMP TREND INTO EARLY NEXT WEEK. THAT BEING SAID...WITH THE PATTERN RECONFIGURATION TIED TO SMALLER SCALE DISTURBANCES WHICH TEND TO BE RATHER NOISY AT THESE RANGES...THE EVOLUTION OF THE CHANGE IN FLOW IS LIKELY TO BE HANDLED DIFFERENTLY IN UPCOMING MODEL AND ENSEMBLE CYCLES. THE TAKEHOME MESSAGE: WEATHER CONDITIONS LKLY TRENDING DRIER AND MILDER FROM THE WEEKEND INTO EARLY NEXT WEEK. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... NO MAJOR CHANGES TO 12Z TAF PACKAGE. LOW PRESSURE OVER WESTERN LAKE ONTARIO EARLY THIS MORNING WILL KEEP SOME SHOWERS ACROSS THE WESTERN PORTION OF CENTRAL PA THIS MORNING. MOST OF THE HEAVIER SHOWERS ACROSS THE SUSQUEHANNA VALLEY HAVE MOVED EAST OF THE AREA. THE MAIN PROBLEM WILL BE LOW CIGS IN SPOTS...MAINLY ACROSS THE FAR WEST. VISIBILITIES IN MOST LOCATIONS ARE STILL GOOD. BY LATER THIS MORNING INTO THIS AFTERNOON...SHOWERS WILL BE MORE SCATTERED IN NATURE...AND MUCH OF THE AREA EAST OF THE WESTERN MOUNTAINS WILL BE VFR. AS THE LOW REFORMS OFF THE EAST COAST LATER TODAY...LOWER CIGS AND SHOWERS WILL SPREAD EASTWARD LATE. THE AIRMASS WILL BE QUITE COLD ALOFT TODAY...THUS ISOLATED THUNDERSTORMS WILL BE POSSIBLE. NOT LOOKING AT REAL STRONG WINDS TODAY. HOWEVER...AS THE LOW REFORMS OFF THE EAST COAST TONIGHT...WINDS WILL PICK UP SOME. THE SFC AND UPPER LEVEL LOW WILL KEEP CLOUDY...BREEZY...AND AT TIMES WET CONDITIONS ACROSS THE AREA INTO THU. EXPECT SOME IMPROVEMENT ON FRIDAY...AS THE SYSTEM SLOWLY WORKS EASTWARD. OUTLOOK... WED-FRI...LOW CIGS POSS W MTNS...MAINLY AT NIGHT/EARLY AM. SAT...NO SIG WX EXPECTED. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...STEINBUGL NEAR TERM...STEINBUGL SHORT TERM...STEINBUGL LONG TERM...STEINBUGL AVIATION...FITZGERALD/MARTIN

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