AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
516 PM EDT MON MAY 20 2013
.SYNOPSIS...
A WARM FRONT WILL MOVE SLOWLY NORTHEAST ACROSS THE STATE THIS
AFTERNOON AND EVENING. INCREASING WARMTH AND HUMIDITY WILL
OVERSPREAD THE REGION THROUGH THE MID-WEEK IN THE WAKE OF THIS
FRONT. EXPECT WELL ABOVE NORMAL AFTERNOON TEMPERATURES ACROSS THE
WESTERN HALF OF THE STATE THIS AFTERNOON...AND IN ALL AREAS TUESDAY
AND WEDNESDAY. TEMPERATURES WILL COOL BACK BELOW NORMAL WITH DRIER
CONDITIONS BY THE WEEKEND AS A VERY COLD AIRMASS DROPS OUT OF
CENTRAL CANADA INTO THE GREAT LAKES AND NORTHEASTERN UNITED STATES.
&&
.NEAR TERM /UNTIL 10 PM THIS EVENING/...
EARLIER LOW STRATUS HAS TRANSITIONED INTO WIDESPREAD SCT-BKN FAIRLY
SHALLOW CU/STRATO CU FIELD ACROSS THE CWA AT MID AFTERNOON.
A RIBBON OF CONVECTION /NO THUNDER YET/ WAS DEVELOPING ACROSS THE
LAUREL WHERE EARLIER CLEARING AND HI LEVEL HEATING HAS RAMPED UP
MIXED LAYER CAPES TO AROUND 1500 J/KG. WARMING ALOFT SHOULD KEEP ANY
TSRA RATHER LOW-TOPPED AND ISOLATED LATE TODAY.
TEMPS ACROSS THE CENTRAL AND WEST ARE RIGHT AROUND THEIR FCST HIGHS
IN THE UPPER 70S TO LOWER 80S FOR HIGHS...AND SLIGHTLY COOLER IN THE
MID 70S ACROSS THE EAST. A FEW SPOTS IN SCENT PENN /JUST EAST OF THE
LAURELS/ COULD TOUCH 85F WHERE THE MEAN...DOWNSLOPING SWRLY LLVL
FLOW MAXIMIZING THE ADIABATIC WARMING OF THE 14C AIR RESIDING AT THE
850 MB LEVEL.
ALTHOUGH ALL MDL SOUNDINGS CONTINUE TO INDICATE THE ISOLD/SCT SHRA
THAT ARE SEEN FORMING OVER THE PAST HOUR OR SO...IN THE SRN TIER AND
ANOTHER AREA OVER THE NWRN MTS...BROADLY DIVERGENT LLVL FLOW WILL
ACT TO NEGATE ANY ORGANIZED AREAS OF DEEP CONVECTION THROUGH THE
REST OF THE DAYLIGHT HOURS.
WILL INCREASE POPS TO HIGH CHC/ LOW LIKELY ACROSS THE SW MTNS ...BUT
CONTINUE TO KEEP POPS OVER THE NE HALF OF THE CWA BELOW 20 PERCENT.
&&
.SHORT TERM /10 PM THIS EVENING THROUGH 6 PM TUESDAY/...
MORE LOW STRATUS AND FOG ARE LIKELY LATE TONIGHT SINCE WILL
DEWPOINTS REMAIN HIGH AND WINDS WILL FALL OFF TO LIGHT AND VARIABLE.
WILL COUNT ON A FEW DEG C OF WARMING ALOFT AND LACK OF LLVL FORCING
IN THE WAKE OF THE SLOWLY NWD LIFTING WARM FRONT TO QUICKLY
DISSIPATE ANY LINGERING SHOWERS/STORMS THIS EVENING...AND LEAVE POPS
LESS THAN 20 PCT FOR THE BULK OF THE NIGHT. INCREASING CONVECTION
/OVER WRN LOWER MICHIGAN ATTM/ CRESTING THE UPPER RIDGE TO OUR WEST
COULD SNEAK INTO THE NW BY MORNING...BUT THIS IS JUST WORTH A LOW
CHC POP AT THIS POINT. MINS WILL AGAIN BE MUGGY UPPER 50S AND LOWER
60S.
TUESDAY...WE WILL BE BE WELL INTO THE WARM SECTOR AHEAD OF THE STORM
CRAWLING IN FROM THE NORTHERN PLAINS/MIDWEST/UPPER LAKES. THE WARM
SECTOR AIR WILL BE QUITE WARM FOR THIS TIME OF YEAR...HAVING SPENT
PLENTY OF TIME COOKING OVER THE MS AND OH VALLEYS WITH GOOD GULF
INFLOW. TEMPS THERE RIGHT NOW ARE ABOUT 10F ABOVE AVERAGES.
THEREFORE...SUMMERTIME TEMPS OF UPPER 70S IN THE HILLS TO MID 80S IN
THE VALLEYS ARE EXPECTED ON TUESDAY. ALONG WITH THE WARM
TEMPERATURES...THE DEWPOINTS WILL BE SOLIDLY IN THE 60S. THIS
WARM...MOIST AIR AND A WEAKENING RIDGE MOVING OVERHEAD AND A LITTLE
TO OUR EAST WILL CREATE A GOOD SITUATION FOR SCT AFTN CONVECTION.
&&
.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
THE LARGE UPPER LEVEL LOW BRINGING SEVERE WEATHER THROUGHOUT THE
MIDWEST WILL SLOWLY MAKE ITS WAY EASTWARD. THIS FLOW SHOULD BRING A
RATHER UNSETTLED PERIOD THROUGH THE WORK WEEK. AS THE UPPER LEVEL
RIDGE CONTINUES TO BREAK DOWN...STORMS WILL SLOWLY APPROACH. SEVERE
OUTLOOK FOR DAY3/WED HAS THE WESTERN HALF OF THE CWA IN THE SLIGHT
RISK. SOUTHEASTERLY MOISTURE...COUPLED WITH INSTABILITY FROM THE
FRONT AND DAYTIME HIGHS IN THE 80S SHOULD ALLOW FOR A SUFFICIENT
ENVIRONMENT FOR DAYTIME STORMS/SHOWERS. SHEAR SHOULD BE
DECENT...ESPECIALLY AS MID RANGE MODELS ARE HINTING AT A LLJ THROUGH
WEDNESDAY AFTERNOON. THURSDAY WILL AGAIN FEATURE SCT/NMRS TSRA. THE
MED RANGE GUID IS NOW PRETTY SOLID WITH A THURS NIGHT/EARLY FRIDAY
PASSAGE OF THE COLD FRONT ASSOCD WITH THE SYNOPTIC SCALE STORM. MUCH
COOLER AIR AND DRIER CONDITIONS SHOULD FOLLOW FOR THE WEEKEND. ECMWF
HAS BACKED OFF ON THE COLD-NESS OF THE AIR MOVING DOWN WITH THE BIG
1030MB HIGH FOR THE WEEKEND...THOUGH IT LOOKS LIKE THE ZERO C LINE
AT 8H COULD CLIP THE NORTHWESTERN CORNER OF PA. MIN TEMPS FOR
SATURDAY MORNING WILL BE COOL BUT HAVE KEPT THEM IN THE LOW 40S TO
UPPER 30S. DRIER AIR ASSOCIATED WITH THIS FRONT SHOULD KEEP
PRECIPITATION OUT OF THE FORECAST THROUGH THE WEEKEND...WITH WEAK
HIGH PRESSURE BUILDING THROUGH SUNDAY. MEMORIAL DAY MAY SEEM SOME
CLOUDINESS AS THE RIDGE BREAKS DOWN TO DUE NORTHWESTERLY FLOW.
MOISTURE FROM A WEAK SHORTWAVE COULD BRING PRECIPITATION ALONG THE
MASON DIXON MONDAY EVENING...YET DUE TO IT BEING ON THE EDGE OF THE
FORECAST MUCH COULD CHANGE.
&&
.AVIATION /21Z MONDAY THROUGH SATURDAY/...
LATE AFTN RADAR LOOP SHOWING A FEW SHRA/TSRA HAVE DEVELOPED OVR
THE LAUREL HIGHLANDS. A BRIEF VSBY REDUCTION IS POSSIBLE AT
AOO/JST/UNV THRU ARND 00Z. ANY REMAINING SHRA/TSRA SHOULD
DISSIPATE AFTER SUNSET...AS BLYR COOLS/STABILIZES.
HIGH DEWPOINTS AND LIGHT WINDS WILL LEAD TO AREAS OF FOG AFTER
06Z TUESDAY. BULK OF MDL GUIDANCE TARGETS THE EASTERN HALF OF THE
STATE FOR THE LOWEST /LIKELY BLW 1SM/ VSBYS...DUE TO A NEARLY CALM
WIND.
AM FOG SHOULD BURN OFF BTWN 13-16Z TUESDAY. HOWEVER...PM TSRA WILL
AGAIN BE AN AVIATION CONCERN. THE BEST CHC OF A TSRA AND
ACCOMPANYING BRIEF VSBY REDUCTION WILL BE DURING THE PM HOURS
ACROSS THE N MTNS AND SOUTHWARD ALONG THE LAUREL HIGHLANDS.
.OUTLOOK...
TUE-THU...LOW CLOUDS/FOG POSS EARLY. SCT PM THUNDERSTORM IMPACTS
POSSIBLE.
FRI AND SAT...NO SIG WX EXPECTED.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...DANGELO/LAMBERT
LONG TERM...LA CORTE/CERU
AVIATION...FITZGERALD/LAMBERT
