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000
FXUS61 KCTP 141537
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1137 AM EDT TUE MAY 14 2013

.SYNOPSIS...
A RIDGE OF HIGH PRESSURE ALONG THE APPALACHIANS WILL SLIDE OFF
THE SOUTHEAST COAST THIS EVENING. LOW PRESSURE CROSSING
SOUTHEASTERN CANADA WILL SEND A WARM FRONT THROUGH THE REGION
EARLY WEDNESDAY...FOLLOWED BY A COLD FRONT LATER WEDNESDAY INTO
WEDNESDAY NIGHT. THE COLD FRONT WILL BECOME QUASI-STATIONARY SOUTH
OF THE MASON DIXON LINE WITH HIGH PRESSURE RETURNING FOR THE
SECOND HALF OF THE WEEK. TEMPERATURES WILL MODERATE THROUGH THE
END OF THE WEEK. THE BEST CHANCE OF RAIN WILL BE WITH THE FRONTAL
SYSTEM ON WEDNESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
MINOR TWEAKS TO THE SKY FOR TODAY...BUT LITTLE ELSE HAS BEEN
CHANGED WITH THIS 11 AM UPDATE. PREV DISC FOLLOWS...

DROPPED FR/FR FLAGS. THIS WILL PROBABLY BE THE LAST FROST/FREEZE
UNTIL OCTOBER.

AFTER AN UNSEASONABLY COLD START TO THE DAY...EXPECT EARLY
SUNSHINE TO GRADUALLY YIELD TO INCREASING CLOUDS AS A NNW-SSE
ORIENTED RIBBON OF CIRRUS AND ALTOCU SLIDES SEWD FROM THE GRT LKS.
THESE CLOUDS ARE ASSOCIATED WITH A RATHER STRONG SURGE OF H85-H7
WARM AIR/THETA-E ADVECTION ON THE FRONT-SIDE OF SFC WARM FRONT
EXTENDING SEWD FROM LOW PRES MOVG ACRS WRN ONT/UP OF MI. MDLS
GENERATE AN AREA OF SPOTTY PCPN OVR THE WRN 1/3 OF THE CWA LATE
THIS AFTN/EVE BEFORE SPREADING IT EWD OVERNIGHT. ZONE OF STG ISENT
LIFT/INC DEEP LYR MSTR AT NOSE OF WSWLY LLJ WILL SUPPORT A GRADUAL
INCREASE IN CHC POPS FROM WEST TO EAST LATE TNT INTO THE EARLY
MORNING HOURS WED...WHICH SEEMS TO FIT A CONSENSUS MDL SOLN. MDL
DATA ALSO SHOWS RELATIVELY HIGH ML CAPE /FOR THE NIGHTTIME HOURS/
AND PLUME OF VERY STEEP MID-LVL LAPSE RATES /7-8C PER KM/
ENCROACHING ON WRN PA BY 12Z WED. THE INSTABILITY MAY BE TOO HIGH
WITH MDL DEWPOINTS IN THE LOW 60S...AND THIS HAS IMPLICATIONS FOR
DAY 2.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
THE MODELS SHOW GOOD OVERALL AGREEMENT WITH LOW-AMPLITUDE 500MB
SHORTWAVE TROUGH AND ASSOCIATED SFC LOW PRES CROSSING SERN CANADA
ON DAY 2. AT THE SFC...PRECEDING WARM FRONT SHOULD PUSH EWD ACRS
CENTRAL PA EARLY WITH TRAILING PORTION OF LWR LKS COLD FRONT
DROPPING SEWD DURING THE AFTN...BCMG INCREASINGLY W-E ORIENTED
FROM PA WWD BACK INTO THE UPR OH VLY.

THE MAIN UNCERTAINTY IN THE SHORT RANGE CONTINUES TO CENTER AROUND
THE DEGREE OF DESTABILIZATION PROGGED AHEAD OF THE SFC COLD FRONT
SINKING SWD ACRS CENTRAL PA AND ADJ MID-ATLC STATES. PER SPC...THE
MDLS CONTINUE TO UNREALISTICALLY DEVELOP AN AREA OF 60+ TD/S OVER
THE MIDWEST AND EXPAND/ADVECT THIS RICH LLVL MSTR EWD ON DAY 2 -
WHICH CONTRIBUTES TO PRE-FRONTAL ML CAPE VALUES IN EXCESS OF 2000
J/KG ACRS PORTIONS OF S-CNTRL PA BY 21Z WED. THE LATEST THINKING
IS THIS AMT OF INSTABILITY IS TO HIGH...RESULTING FROM IN- SITU
MOISTENING FROM THE OVERESTIMATION OF BLYR EVAPOTRANS IN THE
MIDWEST...LEADING TO MODEL INDICATIONS OF SEVERE POTENTIAL WHICH
APPEAR TO BE OVERDONE. THEREFORE THE DAY 2 OUTLOOK MAINTAINED 5%
SVR PROBS AND A SEE TEXT CATEGORICAL OUTLOOK FOR THE AREA. HOWEVER
THE DOOR IS OPEN FOR UPGRADE TO SLGT RISK/GREATER SVR POTENTIAL
ONCE THE DEGREE OF MSTR/DESTABILIZATION CAN BE MORE ADEQUATELY
ASCERTAINED. AT ANY RATE...STILL THINK THERE WILL BE SOME
CONVECTIVE DEVELOPMENT WITH POTENTIAL FOR ORGANIZED STORM
STRUCTURES GIVEN SUFFICIENT 0-6KM SHEAR. WILL CONTINUE TO
HIGHLIGHT THE THREAT IN HWO AND SEE HOW THINGS EVOLVE. STAY TUNED.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
THE W-E ORIENTED "BACKDOOR" COLD FRONT SHOULD PUSH SOUTH OF THE
PA/MD LINE EARLY ON DAY 3 AND BECOME QUASI-STATIONARY OVER WV/VA
ON DAY 4. BOTH THE GEFS AND ECENS ARE ADVERTISING A GRADUAL
INCREASE IN BLOCKING AT HIGH LATITUDES THROUGH THE MEDIUM
RANGE...WHICH HAS FORCED THE MEAN POSITION OF THE Q-STNRY FRONTAL
ZONE SWD INTO THE SRN MID-ATLC STATES. THIS LEAVES HIGH PRES IN
CONTROL OVER CENTRAL PA THR-FRI. KEPT SOME LOW POPS ACRS THE FAR
SRN TIER ON THR FOR CONTINUITY...BUT OVERALL THR-FRI SHOULD BE
DRY. CONS TEMP BLEND YIELDED SLIGHTLY LOWER HIGHS FOR THE FIRST
HALF OF THE PERIOD AS THE LOW-LVL FLOW GRADUALLY VEERS FROM THE
NORTH/EAST TO SOUTH/EAST BY THE END OF THE WEEKEND. WAVY FRONTAL
BOUNDARY WILL RETURN NWD AS WARM FRONT DURING THE SECOND HALF OF
THE PERIOD...AS LOW PRES DEVELOPS INTO THE WRN GRT LKS. INCREASING
WARMTH AND MOISTURE IN THE WARM SECTOR SHOULD SPELL A BETTER CHC
FOR SHOWERS/TSTMS INTO EARLY NEXT WEEK.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
AN APPROACHING WARM FRONT WILL BRING INCREASING CLOUDS TO THE
REGION THIS AFTERNOON WITH LATE AFTERNOON SHOWERS POSSIBLE ACROSS
THE WESTERN PART OF THE STATE. MDL GUIDANCE SUGGESTS DRY AIR AT
LOW LVLS WILL PRECLUDE MUCH BUT VFR CONDS THROUGH THE FIRST HALF OF
THE EVENING. VFR CIGS AND VSBYS WILL DOMINATE INTO TOMORROW WHERE
THERE WILL BE A BETTER POSSIBILITY FOR SCATTERED SHOWERS AND
THUNDERSTORMS AFTER 12Z FOR THE WESTERN TAF SITES AND AFTER 17Z
FOR THE EASTERN TAF SITES.

.OUTLOOK...
WED...AM LOW CIGS POSS AT BFD. SCT TSRA IMPACTS POSS.
THU-FRI...NO SIG WX EXPECTED.
SAT...ISOLATED PM TSRA IMPACTS POSSIBLE.

&&

.CLIMATE...
NEITHER IPT NOR MDT SET/TIED A RECORD MIN THIS MORNING.
MDT...34 IN 1996 -- 35 THIS AM.
IPT...28 IN 1996 -- 30 THIS AM.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...DANGELO/STEINBUGL
NEAR TERM...DANGELO/STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...STEINBUGL
AVIATION...DANGELO/CERU
CLIMATE...