Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 271009 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 609 AM EDT WED AUG 27 2014 .SYNOPSIS... A COLD FRONT WILL MOVE ACROSS THE REGION TODAY AND PROVIDE A FOCUS FOR THUNDERSTORMS. HIGH PRESSURE WILL ARRIVE BEHIND THE FRONT AND BRING DRY WEATHER TO THE AREA THROUGH THE END OF THE WEEK. ABOVE NORMAL TEMPERATURES AND INCREASINGLY HUMID CONDITIONS ARE FORECAST OVER THE LABOR DAY HOLIDAY WEEKEND AND INTO THE FIRST WEEK OF SEPTEMBER. && .NEAR TERM /THROUGH TONIGHT/... PATCHY FOG IN THE RIVER/STREAM VALLEYS OF SCENTRL/SERN PA WILL ERODE SHORTLY AFTER SUNRISE WITH LCL VISBYS IMPROVING BY 14Z. CLOUDS ARE INCREASING OVER THE NW MTNS IN ADVANCE OF SFC COLD FRONT SHIFTING SEWD FROM THE LAKE ERIE SHORELINE. A LOW AMPLITUDE UPPER TROUGH OVER THE GREAT LAKES REGION THIS MORNING WILL TRANSLATE EWD INTO THE NORTHEAST STATES TONIGHT AND MOVE OFFSHORE DURING THE D2 PERIOD. AT THE SFC...A COLD FRONT ANALYZED FROM THE ST. LAWRENCE VLY SWWD BACK ACRS THE LWR LKS WILL PUSH SEWD ACRS CENTRAL PA THIS AFTN BEFORE SHIFTING SOUTH OF THE MASON DIXON LINE AFTER 00Z. THE GLOBAL MODELS ARE WELL CLUSTERED WITH THE UPPER TROUGH AND ASSOCIATED COLD FRONT CROSSING THE NORTHEAST...WITH A NON-NAM CONSENSUS SOLUTION PREFERRED BY WPC AS IT APPEARS TO BE STRONGER ALOFT AND A TAD SLOWER WITH THE ADVANCE OF THE SFC FRONT. THE MAIN FCST CONCERN IN THE NEAR TERM IS THE POTENTIAL FOR STRONG TO LOCALLY SVR STORMS THIS AFTN. MODELS ADVECT RICH BLYR MSTR EWD FROM THE OH VLY INTO CENTRAL PA IN ADVANCE OF THE SFC COLD FRONT...WITH 60-65F DEWPOINTS PROGGED BY THE CONSENSUS GUIDANCE. THE NAM IS LKLY TOO MOIST WITH LOW 70S DEWPOINTS. STRONG HEATING AND DESTABILIZATION WILL LEAD TO MU CAPES IN EXCESS OF 1000 J/KG ALONG A NARROW CORRIDOR PRECEDING THE COLD FRONT. THE LOW-MID LVL BACKGROUND WIND FIELDS WILL NOT BE PARTICULARLY STRONG...AND THE BEST DEEP SHEAR LAGS THE FRONT. HOWEVER...A FEW CELLS CAPABLE OF PRODUCING SMALL TO MARGINALLY SEVERE HAIL AND LOCALLY STRONG TO DMGG WIND GUSTS WILL BE POSSIBLE GIVEN COMBO OF "SUFFICIENT" SHEAR AND DECENT INSTABILITY. THE D1 SPC OUTLOOK PLACES THE ERN ZONES IN THE CATEGORICAL SEE TEXT WITH 5% SVR PROBS BUT COULD SEE AN ISOLD SVR STORM FURTHER WEST ACROSS S-CENTRAL PA TO THE LAUREL HIGHLANDS. CONVECTIVE ACTIVITY SHOULD WEAKEN QUICKLY WITH THE LOSS OF DAYTIME HEATING AND EVENTUALLY DISSIPATE/SHIFT S-SEWD AFTER MIDNIGHT. AFTERNOON TEMPS WILL APPROACH 90F FROM THE SCNTRL RIDGE/VALLEY REGION INTO THE LWR SUSQ VLY...WITH UPPER 70S TO LOW 80S COMMON IN THE NW/NCNTRL HIGH TERRAIN. && .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/... HIGH PRESSURE AND MUCH DRIER AIR WITH LOW/COMFORTABLE HUMIDITY WILL OVERSPREAD THE AREA ON THURSDAY. ENS DATA SHOWS TEMPS ALOFT SLIGHTLY BLW NORMAL OVER NRN/NERN PA WHICH SHOULD PROMOTE AFTN CU/SC CLOUDS. TEMPS RANGE FROM AROUND 70F IN THE NW TO 80F IN THE SE. THU NGT LOOKS SEASONABLY COOL WITH VALLEY FOG PROBABLE UNDER SFC RIDGE WITH M/CLR SKIES AND NEARLY CALM WINDS. WAA CLOUDS MAY IMPACT MIN TEMP FCST BUT FOR NOW SEE NO REASON TO DEVIATE FROM CONSENSUS GUIDANCE. && .LONG TERM /FRIDAY THROUGH TUESDAY/... MEDIUM RANGE FLOW PATTERN ACRS THE CONUS WILL FEATURE TROUGHING IN THE WEST AND FAIRLY HIGH HEIGHTS FCST TO PREVAIL OVER THE EAST (FOR A CHANGE) SUPPORTED BY SUBTROPICAL RIDGE ANCHORED OVER THE SOUTHEAST. HIGH PRESSURE CENTERED OVER UPSTATE NY AT THE START OF THE PERIOD WILL MOVE OFF THE NRN NEW ENGLAND COAST ON SATURDAY AS TODAYS FRONTAL BOUNDARY PIVOTS BACK NWD AS A WARM FRONT...IN RESPONSE TO SHORTWAVE/SFC WAVE FCST TO TRACK NEWD FROM THE ERN PLAINS/MS VLY. OVER THE PAST 12-24 HOURS THE LATEST GUIDANCE HAS TRENDED NWD WITH SFC LOW TRACKS THRU THE GREAT LAKES AROUND D4/SUN AND WITH LEADING FRONTAL BOUNDARY WHICH IS NOW PROGGED BY WPC TO STAY NORTH OF PA. A MORE DEFINED COLD FRONT SHOULD APPROACH THE AREA BY THE MIDDLE OF NEXT WEEK. A RATHER MOIST RETURN FLOW AROUND SOUTHEAST RIDGE AND AHEAD MID LVL SHORTWV TRACKING NEWD FROM THE ERN PLAINS/MS VLY ALONG WITH INTERACTION WITH ASSOCIATED SFC WAVE/WAVY LEADING FRONTAL ZONE SHOULD SPELL AN INCREASING PROBABILITY/OPPORTUNITY FOR RAIN INTO THE WEEKEND. HOWEVER CONFIDENCE IN PCPN DETAILS (I.E. POPS) IS MEDIUM AT BEST DUE TO MODEL SPREAD/DEPENDENCE ON SMALLER SCALE FEATURES. THE FCST MAY BE PERCEIVED AS SOMEWHAT PESSIMISTIC WITH NEARLY DAILY CHC FOR SHWRS/TSTMS HOWEVER PCPN WILL CERTAINLY NOT BE CONTINUOUS WITH PERIODS OF DRY WX MIXED IN BTWN GENERALLY SCT AND LARGELY DISORGANIZED/WEAKLY FORCED PCPN. THERE IS HIGHER CONFIDENCE IN A WARMING TREND WITH MAX TEMPS 5-10F ABOVE NORMAL OVER THE WEEKEND AND INTO THE FIRST WEEK OF SEPT. && .AVIATION /10Z WEDNESDAY THROUGH SUNDAY/... LEADING EDGE OF STRATO CU AND LOW-END ALTO CU ASSOCIATED WITH AN AXIS OF MUCH HIGHER PWAT AIR /NEAR 1.75 INCHES FROM NERN OHIO TO SWRN NEW YORK/ WERE DRIFTING ACROSS THE NORTHERN AND WESTERN MOUNTAINS OF PENN AT DAYBREAK...WHILE SKIES WERE CLEAR ACROSS THE SOUTHERN HALF OF THE STATE. LIGHT AND VARIABLE...TO LIGHT SOUTHWESTERLY WIND WAS NOTED AT ALL AIRFIELDS. SFC COLD FRONT WAS SLIDING JUST SE OF THE I-90 CORRIDOR FROM KCLE TO KERI AND KROC ATTM. CLOUD BASES AT KBFD AND KJST SHOULD DIP INTO THE MVFR RANGE AT TIMES LATER THIS MORNING AND EARLY THIS AFTERNOON /WITH SOME OCNL IFR POSSIBLE AT BRADFORD BETWEEN 11-14Z/. THE COLD FRONT WILL DRIFT SLOWLY SE AND CROSS CENTRAL PA AIRFIELDS DURING THE LATE AFTERNOON HOURS...BEFORE REACHING THE LOWER SUSQUEHANNA VALLEY /KMDT AND KLNS/ LATER THIS EVENING. INSTABILITY AND MOISTURE WILL BE QUITE HIGH AHEAD OF THE COLD FRONT...SO INCLUDED VCTS FOR ABOUT A 4-HOUR PERIOD PRECEDING THE FRONTAL PASSAGE. BRIEF MVFR CONDITIONS ARE POSSIBLE IN THE THUNDERSTORMS. MAINLY VFR IS EXPECTED TONIGHT INTO THURSDAY IN THE WAKE OF THE CFROPA. A 6-10 HOUR PERIOD OF NW WINDS AVERAGE 8-10 KTS...WITH GUSTS IN THE MID-UPPER TEENS IS EXPECTED LATE TODAY AND TONIGHT IN THE MDTLY TIGHT LLVL PRESSURE GRADIENT FOLLOWING THE COLD FRONT. OUTLOOK... THU-FRI...LATE NIGHT-EARLY MORNING RESTRICTIONS IN FOG POSSIBLE...OTHERWISE VFR. SAT-SUN...MAINLY VFR. CHC OF AFTERNOON SHOWERS/ISOLD TSTMS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...STEINBUGL NEAR TERM...STEINBUGL SHORT TERM...STEINBUGL LONG TERM...STEINBUGL AVIATION...LAMBERT

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