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  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab PA Page Main Text Page