Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 041907 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 307 PM EDT FRI SEP 4 2015 .SYNOPSIS... ABOVE NORMAL TEMPERATURES WILL CONTINUE INTO NEXT WEEK WITH GRADUALLY DECREASING HUMIDITY LEVELS. ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE INTO EARLY THIS EVENING. HIGH PRESSURE WILL ENSURE FAIR AND DRY WEATHER FOR LABOR DAY WEEKEND. && .NEAR TERM /UNTIL 7 PM THIS EVENING/... ISOLATED SHOWERS AND THUNDERSTORMS AGAIN POPPING THIS AFTN AS EXPECTED...MAINLY ACROSS SRN PA. THIS WILL CONTINUE FOR THE NEXT SEVERAL HOURS WITH ANY SLOW MOVING STORMS PRODUCING BRIEF HEAVY DOWNPOURS. GUIDANCE INCLUDING LATEST HRRR IMAGERY SHOWS A CONVERGENCE OF ACTIVITY THROUGH THE LOWER SUSQ VALLEY SOUTH CENTRAL MTNS AS WEAK BACKDOOR COLD FRONT DROPS SOUTH...AND EASTERLY FLOW ON SRN END OF SFC HIGH CONCENTRATES MOISTURE WESTWARD INTO THE REGION. && .SHORT TERM /7 PM THIS EVENING THROUGH 6 PM SATURDAY/... CONVECTION ONGOING AT THE START OF THE PERIOD MAY BE THE LAST OF THE RAIN FOR A FEW DAYS. EXPECT SHRA/TSRA TO WANE THROUGH THE EVENING. THE INTERESTING/CHALLENGING PART OF THIS FORECAST MAY BE THE CLOUD COVER TONIGHT AND SAT MORNING AND RESULTANT MINS/MAXES. THE NAM IS PRETTY AGGRESSIVE IN ADVECTING LOW CRUD/STRATUS IN FROM THE EAST/SOUTHEAST TONIGHT AND PILING IT UP IN THE MOUNTAINS. HOWEVER...THE GFS IS NOT SO BULLISH ON THE LOW LEVEL MOISTURE. IT STILL MAKES LOWER CLOUDS /BELOW 8H/ BUT IS MORE NORTHEASTERLY WITH THE WINDS ON THE SRN PERIPHERY OF THE HIGH. THUS...MORE DRY AIR IS SEEN ADVECTING INTO THE AREA IN THE GFS SOLUTION. THIS ALLOWS THE MARITIME AIR/CLOUDS TO DRY OUT QUICKLY WITH MINIMAL MIXING. THE TROUBLE WITH THE DRIER SOLUTION IS THAT WE HAVE BEEN PRETTY MUGGY AND THE MDL OMEGA FIELDS DO NOT PORTRAY SOME OVERWHELMING DOWN- MOTION. IN FACT...THEY ARE PRETTY NEUTRAL. VERY ISOLATED DIURNAL CONVECTION IS POSSIBLE IN THE FAR WEST/SOUTHWEST ON SAT...BUT THE PWATS WILL BE MUCH LOWER - ONLY RANGING FROM 1 INCH IN THE NE TO 1.25 IN THE WEST. AT THIS POINT...THE MOST PROBABLE SOLUTION IN OUR WEAK FLOW IS THAT THE SFC HIGH STAYS UP OVER NEW ENGLAND AND THE DRY AIR MAKES ONLY SLOW PROGRESS TO MOVE ACROSS THE REGION. WILL KEEP IT MORE CLOUDY AND COOLER IN THE FIRST PART OF THE DAY AND KEEP MAXES SHORT OF GFS-MOS GUIDANCE. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
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A RATHER LARGE AREA OF HIGH PRESSURE AT THE SFC...AND A SLOWLY FLATTENING UPPER RIDGE OVER THE EASTERN U.S...SHOULD MAINTAIN DRY WEATHER SATURDAY NIGHT THROUGH MONDAY. PRECIPITABLE WATER VALUES WILL RANGE FROM BELOW NORMAL AND ONLY AROUND ONE-HALF OF AN INCH ACROSS FAR NERN PENN...TO SLIGHTLY ABOVE NORMAL ALONG THE SE SHORE OF LAKE ERIE SUNDAY SATURDAY NIGHT INTO SUNDAY NIGHT. A FEW SHOWERS OR EVEN A BRIEF TSRA COULD BRUSH OUR FAR NW ZONES DURING THIS INITIAL 24 HOURS OF THE LONG TERM PERIOD...BUT POPS WILL BE LESS THAN 25 PERCENT. AN INITIAL...WEAK...COLD FRONT WILL SLIDE SLOWLY TO THE ESE FROM THE GREAT LAKES/MIDWEST STATES. THIS FEATURE COULD BRING SOME ISOLATED SHRA/TSRA TO OUR NW ZONES BEGINNING TUESDAY AFTERNOON AND EVENING. A SLOWLY AMPLIFYING...BROAD TROUGH FROM THE NRN PLAINS THROUGH THE NE U.S. WEDNESDAY AFTERNOON INTO NEXT WEEKEND WILL PUSH A SECOND...STRONGER CFRONT EAST ACROSS THE COMMONWEALTH WEDNESDAY NIGHT AND THURSDAY. THIS PATTERN TRANSITION WILL BRING A FEW OPPORTUNITIES FOR SHOWERS AND THUNDERSTORMS...ALBEIT MAINLY OF THE SCATTERED AFTERNOON AND EVENING VARIETY. 12Z GEFS AND 12Z EC ARE IN GOOD AGREEMENT ON THE LOCATION OF THIS TROUGH AXIS /FROM LAKE SUPERIOR TO THE MID MISS VALLEY AT 00Z SAT/...THOUGH AS ONE WOULD EXPECT...THE ENSEMBLE MEAN DAMPENS OUT THE AMPLITUDE OF THE TROUGH COMPARED TO THE EC. DETAILS IN THE TIMING OF ANY SPECIFIC SHORTWAVES ROTATING THROUGH THIS AMPLYIFYING TROUGH ARE SIMPLY TOO MUDDY AT THIS TIME RANGE. ONE THING MORE CERTAIN IN THIS MEDIUM RANGE FORECAST IS THE COOLING TEMPS FOR THE LATTER HALF OF THE WEEK AND NEXT WEEKEND...WHEN BOTH MAX AND MIN TEMPS COULD BE UP TO SEVERAL DEG F BELOW NORMAL /ESPECIALLY OVER THE NRN AND WESTERN MTNS OF THE STATE...WHERE MORE CLOUDS AND COOLER TEMPS ALOFT WILL BE FOUND/.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... GENERALLY VFR CONDS EXPECTED THROUGH EARLY EVENING HOURS...SAVE WHERE ISOLATED SHRA/TSRA MAY IMPACT AIRFIELDS...MAINLY ACROSS SOUTHERN PA. A BRIEF VIS REDUCTION IS POSSIBLE IN A FEW SPOTS FROM THESE STORMS...MAINLY THRU 05/01Z. A MOIST SERLY FLOW BEHIND THE COLD FRONT WILL LIKELY PRODUCE SOME LOW CIGS ACROSS THE MTNS OF CENTRAL PA TONIGHT AND EARLY SAT AM. SFC HIGH PRESSURE WILL BUILD INTO THE REGION FOR THE WEEKEND. OUTLOOK... SAT...AM LOW CIGS POSS...MAINLY KBFD/KJST. SUN-TUE...PATCHY AM FOG POSS...MAINLY KBFD/KIPT. WED...COLD FROPA WITH SCT SHRA/TSRA. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO/GARTNER NEAR TERM...GARTNER SHORT TERM...DANGELO/GARTNER LONG TERM...LAMBERT AVIATION...GARTNER

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