331
FXUS61 KCTP 221829
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
229 PM EDT WED MAY 22 2019
SYNOPSIS
A RIDGE OF HIGH PRESSURE WILL DRIFT OFF THE MID ATLANTIC COAST
THIS EVENING. A COLD FRONT WILL MOVE THROUGH THE AREA THURSDAY,
FOLLOWED BY BREEZY, COOLER AND DRY WEATHER FOR FRIDAY.
THE HOLIDAY WEEKEND WILL BRING WARMER TEMPERATURES, HIGHER
HUMIDITY AND A RENEWED CHANCE FOR SHOWERS.
NEAR TERM /THROUGH TONIGHT/
MID AND HIGH CLOUDS ARE BLEEDING OVER THE TOP OF THE BIG
EASTERN UPPER RIDGE. AS THE SURFACE HIGH MOVES OFF TO OUR EAST,
BRINGING THE LOW LEVEL FLOW AROUND TO THE SE, EVENTUALLY GUSTING
10-15 MPH.
THE HRRR IS CONSISTENT IN BRINGING THE CHANCE OF SHOWERS BACK
INTO MY NWRN ZONES BETWEEN ABOUT 4-6PM. RADAR AND OBSERVATIONS
DO SHOW SOME LIGHT SHOWERS MOVING OUT OF OH WITH RAIN AT ERI AS
OF 2PM. WHILE MOST OF THE REGION WILL REMAIN DRY, WE DID
INCLUDE A 20-30% POP FROM MID AFTERNOON INTO THE EVENING.
THE PROSPECTS FOR THE OVERNIGHT A TAD LESS CERTAIN. THERE IS A
GOOD CHANCE A DYING AREA OF SHOWERS WILL WORK ACROSS, BUT
LOOKING AT THE VARIOUS FLAVORS OF THE HREF LENDS LITTLE
CONFIDENCE ABOUT HOW BIG AN AREA ACTUALLY SEES RAIN BY MORNING.
I USED BLENDED POPS THAT TRACKED THE BEST CHANCE OF RAIN FROM NW
PA DOWN OVER CENTRAL PA INTO MY SERN ZONES BY SUNRISE.
WITH CLOUDS AND SHOWERS, LOWS WILL ONLY DROP BACK INTO THE 50S.
SHORT TERM / THURSDAY THROUGH 6 AM THURSDAY/
AFTER A FAIR EVENING WITH A GENERALLY LIGHT SOUTHERLY WIND,
CLOUDS WILL THICKEN UP FROM THE WEST LATE AND SHOWERS/ISOLATED
EMBEDDED TSRA WILL MOVE INTO OUR NORTHWESTERN ZONES AFTER 02Z
NEAR THE NOSE OF A +2-3 SIGMA WESTERLY 850 MB WIND MAX AND MUCH
HIGHER PWAT AIR (30-35MM OR +2-3 SIGMA). MIN TEMPS WILL ONLY
SETTLE INTO THE 50S TO AROUND 60F.
LONG TERM /THURSDAY THROUGH WEDNESDAY/
THE SHOWERS WILL SPREAD FURTHER EAST ACROSS THE NORTHERN HALF
OF PA THROUGH THE MID MORNING HOURS THURSDAY (AND END
TEMPORARILY OVER THE LOWER SUSQ VALLEY AND WESTERN POCONOS FOR
ABOUT A 4-HOUR PERIOD DURING THE LATE MORNING AND EARLY
AFTERNOON), BEFORE A RATHER EXTENSIVE AREA OF CONVECTION
(HIGHLIGHTED BY EMBEDDED SUPERCELL STORMS) MOVES EAST THROUGH
THE ENTIRE REGION NEAR A SFC WARM FRONT/LEE TROUGH BETWEEN
17-23Z THURSDAY. A COLD FRONT WILL SLIDE SE ACROSS THE REGION
LATE THU AFTERNOON AND EVENING, ACCOMPANIED BY ANOTHER, ALBEIT
MORE BRIEF ROUND OF SHOWERS AND TSRA.
MULTIPLE INGREDIENTS ARE PRESENT THURSDAY AFTERNOON AND EVENING
FOR A RATHER SIGNIFICANT SEVERE STORM OUTBREAK WITH NUMEROUS
FAST-MOVING SUPERCELLS AND MINI BOW ECHOES WITHIN SHORT TSRA
LINES. SPC UPGRADED THE PREVIOUS SLIGHT RISK FOR DAY 2 TO AN
ENHANCED RISK FOR MUCH OF OUR CWA. THIS UPGRADES SEEMS WARRANTED
AS LLVL DIRECTIONAL SHEAR IS IMPRESSIVE AND STRONG LEADING TO
BROAD-LOOP HODOGRAPHS AND THE BASE OF 50KT WESTERLY AND WNW
WINDS ONLY AROUND 5KFT AGL DURING THE MID AFTERNOON TO EARLY
EVENING HOURS THURSDAY.
THIS IS A CLASSIC SUPERCELL AND POTENTIAL LARGE HAIL-PRODUCING
ENVIRONMENT AS STORM RELATIVE INFLOW/UPDRAFT HELICITY WILL BE
UNUSUALLY HIGH INVOF SFC WARM FRONT/LEE TROUGH ACROSS NCENT PA
AND THE SUSQ VALLEY DURING THE AFTERNOON HOURS. LOW LCLS UNDER
3000 FT AGL COVERING MUCH OF CENTRAL AND EASTERN PA AND STRONG
LLVL SHEAR WILL LEAD TO 0-1KM EHIS OF 2-4(M^2/SEC^2) NEAR THE
WARM FRONT/LEE TROUGH OVER THE CENTRAL AND EASTERN ZONES BETWEEN
21Z THU AND 00Z FRI. THE THREAT OF SEVERAL TORNADO-PRODUCING
SUPERCELLS WILL OCCUR ACROSS THIS SAME REGION FROM MID AFTERNOON
TO AROUND DUSK.
IN ADDITION TO THE ANTICIPATED HAIL AND ISOLATED TORNADO
THREAT, THE SUPERCELLS AND THEIR STRONG UPDRAFTS WILL
OCCASIONALLY COLLAPSE INTO FAST MOVING MINI BOW/SPEARHEAD ECHOES
THAT HAVE THE POTENTIAL FOR PRODUCING LOCALIZED, STRAIGHT LINE
WINDS IN EXCESS OF 75 MPH AND SWATHS OF WIND DAMAGE.
STORM TOTAL QPF WILL LIKELY AVERAGE BETWEEN 3 AND 6 TENTHS OF AN
INCH GIVEN THE FAST STORM MOTION. LOCALIZED ONE INCH AMOUNTS ARE
POSSIBLE WHERE TWO OR MORE TSRA OCCUR.
IN THE WAKE OF THE THURSDAY'S ACTIVE WEATHER, A SLIGHTLY COOLER
AND DRIER DAY IS IN STORE FOR FRIDAY. BY SATURDAY THE HUMIDITY
WILL BEGIN TO RETURN ALONG WITH A CHANCE OF MAINLY DIURNAL
SHOWERS/STORMS. AS A WEAK SHORTWAVE ONCE AGAIN RACES OVER THE
TOP OF THE EASTERN RIDGE. WE LOOK TO GET A BREAK ON SUNDAY AS
THE 12Z MODELS SHOW A MAINLY DRY DAY, BUT BY THE MONDAY-TUESDAY
TIMEFRAME MORE SHOWERS BECOME POSSIBLE AS WE STAY IN FAST FLOW
ALOFT NEAR THE TOP OF THE SUBTROPICAL RIDGE.
AVIATION /19Z WEDNESDAY THROUGH MONDAY/
A RIDGE OF HIGH PRESSURE TODAY WILL SLIDE OFF THE MID ATLANTIC
COAST THIS EVENING.
WIDESPREAD VFR CAN BE EXPECTED TODAY AND MUCH OF TONIGHT, WITH
SCATTERED RESTRICTIONS POSSIBLE WITH A DYING AREA OF SHOWERS AND
THUNDERSTORMS THAT WILL TRAVERSE THE AREA DURING THE EVENING AND
OVERNIGHT.
WINDS STARTING OFF LIGHT AND VARIABLE WILL BECOME S-SE 5-10 KT,
EVENTUALLY GUSTING INTO THE TEENS.
ENHANCED WEATHER IMPACTS EXPECTED ON THURSDAY FROM MID-
AFTERNOON THROUGH THE EVENING HOURS AS STRONG TO SEVERE
THUNDERSTORMS IMPACT THE REGION.
OUTLOOK
THU...VFR INTO THE AFTERNOON, THEN STRONG THUNDERSTORMS
DEVELOPING MID-AFTERNOON LASTING INTO THU NIGHT.
FRI...CEILING RESTRICTIONS POSS NW EARLY, THEN MAINLY VFR.
SAT...RESTRICTIONS IN VICINITY OF SHOWERS/THUNDERSTORMS. TSTMS
MORE NUMEROUS NORTH, SCATTERED SOUTH.
SUN...RESTRICTIONS POSSIBLE NEAR SCATTERED TSTMS, MAINLY WEST.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...LA CORTE
NEAR TERM...LA CORTE
SHORT TERM...LAMBERT
LONG TERM...LA CORTE/LAMBERT
AVIATION...LA CORTE
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