Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 311540 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1140 AM EDT FRI JUL 31 2015 .SYNOPSIS... HIGH PRESSURE OVER THE CENTRAL U.S. WILL NOSE INTO THE REGION THIS WEEKEND. A PERSISTENT TROUGH ALOFT WILL SIT OVER THE GREAT LAKES AND NORTHEAST AT THE SAME TIME. WEAK FRONTS WITH LITTLE MOISTURE MOVING DOWN ON THE NORTHWEST FLOW OVER THE GREAT LAKES WILL TRY TO BREAK DOWN THE HIGH PRESSURE. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... HIGH PRESSURE RIDGE EXTENDING NE INTO THE REGION FROM THE OHIO RIVER VALLEY WILL PROVIDE ABUNDANT SUNSHINE FOR THIS AFTERNOON WITH SFC DEWPOINTS IN THE UPPER 50S ACROSS THE MTNS AND L-M 60S THROUGHOUT THE LOWER SUSQ VALLEY. LATE TODAY AND TONIGHT...INCREASING MOISTURE...REFLECTED BY A FEW SW/NE ORIENTED RIBBONS OF HIGHER THETA-E AT 850 MB /AND 1.25-1.5 INCH PWATS/ WILL PUSH INTO THE REGION AHEAD OF AN UPPER TROUGH AND CFRONT DROPPING ESE FROM THE UPPER GLAKES. SFC BASED CAPE /VIA THE MORE AGGRESSIVE NAM/ WILL REMAIN UNDER 500 J/KG ACROSS THE SE HALF OF THE STATE...WHILE RAMPING UP TO OVER 1000 J/KG ACRS FAR NWRN PENN BY 00Z SAT. 14Z RUN OF THE 13KM RAP...AND A SIMILAR SOLUTION GIVEN BY THE 09Z SREF INDICATE THAT ENOUGH INSTABILITY TO PRODUCE SCTD SHRA/TSRA WONT ARRIVE ACROSS OUR FAR NW ZONES UNTIL AT LEAST 02Z SAT /ENHANCED BY COOLING MID LEVELS AND INCREASING UPPER LVL DIFFLUENCE/. THIS AGREES PRETTY WELL WITH OUR CURRENT GRIDDED POP VALUES AND TIMING. HOWEVER...WILL BE TRIMMING LOW-END 10-15 PERCENT POPS FOR OUR NW MTNS LATER THIS AFTERNOON. EARLIER SPC MRGL DY 1 RISK FOR NW PENN HAS BEEN TRIMMED BACK TO GENERAL TSRA /WHICH EXTENDS ACROSS THE NW HALF OF OUR CWA BY 12Z SAT/. TEMPS ARE ON TRACK TO REACH LATE AFTERNOON HIGHS THAT WILL BE SEVERAL DEG F ABOVE NORMAL. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/... UPSTREAM CONVECTION WILL TRY TO GET INTO THE NORTHWEST LATER THIS EVENING AND WILL PROBABLY SUCCEED IS MAKING ISOLD TO SCT SHOWERS/STORMS FOR THE NRN THIRD TO HALF OF THE CWA TONIGHT. BUT THE LOSS OF INSTABILITY AND THE STORMS RUNNING INTO DRIER AIR AND A GOOD CAP WILL LIKELY CAUSE THEM TO DIE OUT AS THEY GET TO PA. NIGHTTIME LOWS 55-65F. DEWPOINTS DON/T MOVE MUCH INTO SATURDAY...BUT BETTER DYNAMICS ALOFT AND SLIGHTLY LOWERED HEIGHTS WILL ALLOW FOR A FEW MORE STORMS TO FORM ON SAT AFTN/EVENING - BUT AGAIN CONFINED TO THE NRN HALF OF THE AREA DUE TO STRONG INVERSION IN THE SRN HALF. 8H TEMPS A LITTLE COOLER ON SAT VS FRI...SO MAX TEMPS WILL LIKELY BE SLIGHTLY COOLER AS WELL - ESP IN THE NW. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... LITTLE CHANGE IS ANTICIPATED IN WHAT SHOULD BE A STABLE LARGE SCALE FLOW PATTERN ACROSS THE CONUS DURING THE FIRST WEEK OF AUGUST. UPPER RIDGE WILL CONTINUE TO DOMINATE OUT WEST WHILE A BROAD UPPER TROUGH EXTENDS SWD FROM EASTERN CANADA ACROSS THE ERN U.S. TEMPERATURES SHOULD AVG NEAR NORMAL INTO EARLY NEXT WEEK BEFORE TRENDING COOLER LATER IN THE WEEK. CONFIDENCE IS LOW ON TIMING OF PCPN CHANCES ASSOCD WITH NRN STREAM FRONTAL SYSTEMS. DID NOT CHANGE A LOT. DID BACK OFF CLOUDS SOME AND HAVE THE HIGHEST POPS DURING THE DAYTIME HOURS. MAIN THING GOING FOR SHOWERS AND STORMS WILL BE HEATING WITH COLD AIR ALOFT AND WEAK SHORTWAVES MOVING ACROSS. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... SFC HIGH PRESSURE RIDGING NE INTO THE REGION WILL SUPPORT VFR CONDITIONS ACROSS MOST OR ALL OF THE REGION THROUGH AT LEAST EARLY SATURDAY MORNING. SCTD TSRA POSSIBLE BEGINNING LATE THIS EVENING INVOF KBFD...BUT THEY WILL BECOME MORE ISOLATED FURTHER SOUTH AND EAST OVERNIGHT AS INSTABILITY WANES. OUTLOOK... SAT...MAINLY VFR...SCATTERED SHOWERS/THUNDERSTORMS. SUN...MAINLY VFR. MON-TUE...MAINLY VFR...SCATTERED SHOWERS/THUNDERSTORMS. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LAMBERT NEAR TERM...LAMBERT SHORT TERM...DANGELO/LAMBERT LONG TERM...MARTIN/STEINBUGL AVIATION...LAMBERT

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