Area Forecast Discussion
Issued by NWS State College, PA

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000 FXUS61 KCTP 271132 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 732 AM EDT SUN JUL 27 2014 .SYNOPSIS... A STRONG COLD FRONT WILL BRING A CHANCE OF SEVERE THUNDERSTORMS TO THE AREA LATER TODAY AND THIS EVENING. LESS HUMID AIR WILL MOVE IN MONDAY...WITH MUCH OF THE UPCOMING WEEK AVERAGING COOLER THAN NORMAL. && .NEAR TERM /THROUGH TONIGHT/... SIMILAR TO LAST NIGHT...A DISTURBANCE MOVING THROUGH THE REGION EARLY WILL LEAVE RELATIVELY TRANQUIL CONDITIONS IN ITS WAKE FOR AT LEAST PART OF THE DAY. THE DAY WILL START OFF CLOUDY BUT OTHER THAN A FEW SCATTERED SHOWERS/TSTORMS MOVING THROUGH NRN AREAS...IT SHOULD BE DRY IN MOST LOCATIONS. I TRIED TO SHOW A MINIMUM OF SHOWER ACTIVITY THROUGH AT LEAST EARLY-MID AFTERNOON BENEFITING FROM A SHORTWAVE RIDGE THAT SHOULD MOVE THROUGH IN THE WAKE OF OUR DEPARTING CONVECTIVE SYSTEM. CONFIDENCE IN EXACTLY HOW THE LATE DAY CONVECTIVE EVENT PLAYS OUT IS LOW GIVEN HOW THE MCS THAT IS PASSING INTO VA NOW HAS DISTURBED THE LOW LEVEL FLOW. MODELS AGREE IN SWINGING A STRONG COLD FRONT THROUGH THE AREA LATER TODAY AND THIS EVENING. TIMING OF THE FRONT SUGGESTS A FAIRLY LATE DAY EVENT LOCALLY AS THE UPPER LOW DIVES OUT OF THE GR LAKES AND BOTTOMS OUT OVER PA. A STRONG UPPER LEVEL JET STREAK IS PROGGED TO DIVE INTO THE LOWER LAKES BY LATER THIS AFTERNOON. THE LOWER BRANCH OF THE INDIRECT TRANSVERSE CIRCULATION UNDER AND AHEAD OF THIS FEATURE IS MADE TO SUPPORT A WSW LOW LEVEL JET THAT HELPS PUSH A SURGE OF MOISTURE AND INCREASINGLY UNSTABLE AIR RAPIDLY BACK INTO THE REGION. WHETHER THE EVENTUAL COLD FRONT IS ACCOMPANIED BY A SINGLE STRONG SQUALL LINE OR SMALLER BROKEN SEGMENTS REMAINS UNCLEAR AND IS BEING HANDLED DIFFERENTLY BY ALL THE AVAILABLE HIGH RES SHORT RANGE GUIDANCE. MY THINKING IS STILL THAT GIVEN THE UNSEASONABLY STRONG SYSTEM AND THE DYNAMICS ACCOMPANYING IT...SEVERE WEATHER LOOKS LIKE A PRETTY GOOD BET. WITH THE 850 LOW AND JET EXPECTED TO SLIDE THROUGH NORTHERN PA...THE STRONG VEERING FLOW THROUGH THE LOW LEVELS WILL PROVIDE A FAIR AMOUNT OF SHEAR AND HELICITY SO WE CANNOT RULE OUT THE THREAT OF TORNADO DEVELOPMENT. THE FRONT SHOULD BE MOVING INTO EASTERN AREAS BY MIDNIGHT BRINGING A RAPID END TO THE SEVERE THREAT AS MORE STABLE AIR MOVES INTO THE REGION IN ITS WAKE. HOWEVER THE STRONG UPPER TROUGH/LOW WILL KEEP SHOWERS IN THE AREA RIGHT INTO MONDAY. QUESTION REMAINS IF SOME SORT OF DEFORMATION ZONE CAN FORM AND LINGER THE RAIN OVER NORTHERN AREAS LATER TONIGHT INTO THE DAY TOMORROW. OPERATIONAL ECMWF SUGGESTS THIS POSSIBILITY...BUT NOT SURE ENOUGH TO THINK ABOUT ANY FLOOD HEADLINES AT THIS HOUR. && .SHORT TERM /MONDAY/... GOING ON THE IDEA THAT DEFORMATION ZONE RAINS DO NOT LINGER OVER NORTHERN AREAS...RAINFALL WILL DIMINISH IN COVERAGE MONDAY AS THE FRONTAL BOUNDARY AND SURFACE LOW MOVE EAST OF THE AREA. THE LINGERING UPPER TROUGH AND COLD AIR ALOFT...COUPLED WITH MID SUMMER HEATING WILL HELP SUPPORT AT LEAST THE MENTION OF SCATTERED SHOWERS DURING THE DAY. BUT WITH THE DEEP MOISTURE BEING SHUNTED OFF TO THE EAST...THE SHOWERS WILL BECOME MORE HIT AND MISS AS THE DAY WEARS ON. MONDAY WILL BE THE FIRST IN A SERIES OF COOLER THAN NORMAL DAYS...WITH HIGHS AVERAGING SOME 5-10 DEG BELOW NORMAL. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... THE ANOMALOUSLY DEEP UPPER TROUGH WILL LINGER OVER THE EASTERN US THROUGHOUT THE UPCOMING WEEK. THIS WILL BRING REFRESHINGLY DRY CONDITIONS AS WE APPROACH THE LAST DAYS OF JULY. CAN`T IMAGINE A LOT OF FOLKS COMPLAINING ABOUT COMFORTABLE SLEEPING WEATHER WITH MILD DAYTIME HIGHS IN THE 70S TO LOWER 80S...AND LOW HUMIDITY. THE CHANCES FOR RAIN WILL BE LIMITED TO THE POSSIBILITY OF DIURNAL INSTABILITY POPPING OFF A FEW SHOWERS. MODELS ARE AGREEING BETTER ON THE PROSPECTS OF THE UPPER TROUGH RETROGRADING LATER IN THE WEEK..ALLOWING MODERATING TEMPERATURES AND INCREASINGLY HUMID AIR TO RETURN TO THE REGION. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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SHOWERS OUT OF THE AREA NOW. A FEW CLOUDS HERE AND THERE. MOST OF THE DAY SHOULD BE DRY...GIVEN WEAK RIDGE OF HIGH PRESSURE. MAIN ISSUE LATE TODAY INTO MONDAY WILL BE THE POTENTIAL FOR STRONG TO SEVERE STORMS. SOME SHOWERS COULD PERSIST FROM LATE MONDAY INTO MID WEEK ACROSS THE MOUNTAINS...GIVEN THE STRONG JULY SUN...AND HOW DEEP THE UPPER LVL TROUGH IS. MORE DETAIL BELOW. ANY EARLY LOW CIGS SHOULD MIX OUT OVR THE N MTNS...LEAVING WIDESPREAD VFR CONDS FOR THE REST OF THE DAY. MAIN AVIATION CONCERN WILL COME LATE TODAY AND TONIGHT...AS A POTENT LOW PRES SYSTEM APPROACHES FROM THE GRT LKS. LATEST MDL DATA POINTS TOWARD THE POSSIBILITY OF SOME STRONG TSRA ACROSS SOUTHERN PA DURING THE LATE AFTN AND EVENING. FURTHER NORTH...THE THREAT OF STRONG WGUSTS IS LOWER. HOWEVER...VSBY REDUCTIONS STILL APPEAR LIKELY IN SHRA/TSRA TONIGHT...ALONG WITH HEAVY RAIN. OUTLOOK... MON...LOW CIG AND SHOWERS AND STORMS. TUE-THU...ISOLATED SHOWERS ACROSS THE MOUNTAINS.
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&& .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...LA CORTE NEAR TERM...LA CORTE SHORT TERM...LA CORTE LONG TERM...LA CORTE AVIATION...FITZGERALD/MARTIN

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