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Area Forecast Discussion
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000
FXUS61 KCTP 210921
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
521 AM EDT THU AUG 21 2014

.SYNOPSIS...
A WARM FRONT WILL PIVOT INTO CENTRAL PENNSYLVANIA THROUGH
TONIGHT. UPPER TROUGHING MOVING EAST FROM THE GREAT LAKES ACROSS
THE NORTHEAST STATES INTO THE CANADIAN MARITIME REGION WILL PUSH
THE FRONT BACK TO THE SOUTH ALONG THE EAST COAST THIS
WEEKEND...ALLOWING A LARGE AREA OF HIGH PRESSURE OVER NORTHERN
NEW ENGLAND TO RIDGE SOUTHWEST ALONG THE EAST-SIDE OF THE
APPALACHIANS THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
WET GROUND...LGT WINDS AND M/CLR SKIES WILL CONTINUE TO SUPPORT
LCL FOG/STRATUS DEVELOPMENT EARLY THIS MORNING. IT WILL BE A
MUGGY AND HUMID START TO THE DAY WITH TEMPS/DWPTS IN THE LOW-MID
60S. RETURNS ON THE RADAR SCOPE ARE VERY ISOLATED AND SHOULD STAY
THAT WAY THRU MID-LATE MORNING PER 00Z MESO MODEL CONSENSUS.

A BROAD ZONE OF WNW FLOW ALOFT WILL PERSIST AGAIN OVER THE
NORTHERN MID ATLANTIC STATES AS WEAKENING UPPER LOW SHIFTS EWD
FROM THE GREAT LAKES INTO NEW ENGLAND BY 12Z FRI. ALTHOUGH THE
HIGHEST PWS ARE PROGGED TO THE NORTH AND SW OF THE AREA TODAY
OVER UPSTATE NY AND THE OHIO VALLEY...MULTIPLE FACTORS SHOULD
AID IN THE DEVELOPMENT OF ISOLD TO SCT PM SHWRS/TSTMS INCLUDING
ADDNL S/WV ENERGY ROUNDING THE SRN PERIPHERY OF UPPER LEVEL TROUGH
PASSING TO THE NORTH...A MOIST/MODESTLY UNSTABLE AIRMASS AND
RELATIVELY STEEP MID LVL LAPSE RATES. HIGHEST POPS /40-60%/ ARE
DURING PEAK HEATING IN THE 18-00Z TIME WINDOW WHICH IS SUPPORTED
BY THE SSEO/WRF/RAP/HRRR.

WHILE THE NEAR TERM GUIDANCE SHOWS DECREASING CONVECTIVE CVRG
TONIGHT...WILL NEED TO WATCH UPSTREAM FOR ORGANIZED "RING OF FIRE"
CONVECTION DROPPING SEWD ALONG WARM FRONTAL ZONE DRAPED OVER THE
UPPER OH VLY. A BLEND OF THE 00Z HIRES MODEL QPF SUGGESTS THE
MAIN PCPN AXIS STAYS TO THE W/SW OF THE AREA FROM THE SRN GRT LKS
ACRS OH INTO WV.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
UPPER LOW WILL BE PASSING INTO NEW ENG BY FRI MORNING. 
HOWEVER..SHORT TERM MDL DATA ALL TRACKING A TRAILING SHORTWAVE SEWRD 
THRU CENTRAL PA FRIDAY PM...WHICH WILL LIKELY BRING ANOTHER ROUND OF 
SHRA/TSRA TO THE AREA. HIGHEST /LIKELY/ POPS PLACED ALONG AND SW OF 
QUASI-STATIONARY FRONT...WHICH MDLS PLACE ROUGHLY FROM KBFD SE TO 
KTHV. SOUTH AND WEST OF THIS BNDRY...UNSTABLE SOUNDINGS AND HIGH 
PWATS COULD RESULT IN LOCALLY HVY RAINFALL IN TSRA. CONVECTION-
ALLOWING MDLS PRODUCING ISOLATED SPOTS AMTS OF ARND 4 INCHES. 
HOWEVER...AVERAGE AMTS BASED ON BLENDED QPF SHOULD BE LESS THAN A 
HALF INCH. GEFS 925 TEMPS ARE SUPPORTIVE OF MAX TEMPS NR SEASONAL 
LEVELS FRIDAY. 

CONVECTION SHOULD DIMINISH AND PUSH SOUTH OF THE STATE FRIDAY 
NIGHT...AS SHORTWAVE DIVES SOUTH OF THE AREA. BEHIND THIS 
FEATURE...BACKDOOR COLD FRONT IS PROGGED TO WORK SWRD THRU CENTRAL 
PA FRI NIGHT. MOIST EASTERLY FLOW ASCENDING THE APPALACHIANS MAY 
PRODUCE LOW CLOUDS AND SPOTTY DRIZZLE LATE FRIDAY NIGHT.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
LARGE SFC HIGH OVR NEW ENG WILL BE THE PRIMARY DRIVER OF OUR WX THRU 
MOST OF THE EXTENDED FCST. MOIST...EASTERLY FLOW OFF THE ATLANTIC 
WILL LIKELY PRODUCE A DULL AND COOL SATURDAY...WITH AM LOW CLOUDS 
GIVING WAY TO A BIT OF BRIGHTENING BY AFTN. GEFS 925 TEMPS OF ONLY 
16C-18C IMPLY MAX TEMPS FROM JUST THE U60S OVR THE HIGH TERRAIN OF 
THE CENTRAL MTNS...TO THE M70S OVR THE SUSQ VALLEY. 

MED RANGE GUIDANCE INDICATES HIGH PRES AND ASSOC DRY AIR MASS WILL 
DRIFT SOUTH LATE THIS WEEKEND...BRINGING FAIR AND BRIGHTER WX TO 
CENTRAL PA. PTSUNNY SKIES SHOULD HELP TEMPS REBOUND A BIT ON 
SUNDAY...BUT STILL REMAIN BLW NORMAL.

EARLIER CONCERNS OF CENTRAL PA DEALING WITH RING OF FIRE CONVECTION 
APPEAR TO BE WANING...AS LARGE SCALE SUBSIDENCE AND DRY AIR ARE THE 
THEMES OF THE MED RANGE GUIDANCE EARLY NEXT WEEK BENEATH SFC RIDGE 
ALONG THE E COAST. FCST CONFIDENCE BEGINS LOWER BY THE MIDDLE OF 
NEXT WEEK...WHEN MED RANGE MDLS BEGIN TO DIVERGE. GEFS KEEPS RIDGE 
AND FAIR WX GOING THRU WED...WHILE ECMWF ENSEMBLE DATA INDICATES A 
WEAK COLD FRONT COULD PUSH SE INTO THE REGION. THUS...HAVE ADDED A 
LOW CHC OF TSRA WED. WHAT APPEARS CERTAIN IS THAT THE COOL TEMPS OF 
THIS WEEKEND WILL GIVE WAY TO A SLOW WARMING TREND THRU THE FIRST 
HALF OF NEXT WEEK...AS COOL AIR MASS MODIFIES UNDER STILL STRONG 
AUGUST SUN. GEFS AND EC ENS 850 TEMPS SUPPORT HIGH RETURNING TO ABV 
NORMAL BY WED. 

&&

.AVIATION /08Z THURSDAY THROUGH MONDAY/...
UPPER LEVEL S/WV CURRENTLY ROTATING ACROSS CENTRAL PA IS HELPING
TO SUSTAIN ISOLD CONVECTION OVER THE AIRSPACE EARLY THIS MORNING.
ONLY TERMINAL IMPACT ATTM APPEARS TO BE IPT WHICH SHOULD GET A
-SHRA WITH A FEW LTG STRIKES NEARBY 07-08Z. HRRR/COSPA DATA SHOWS
LINGERING SHOWERS DISSIPATING OR MOVG E THROUGH DAYBREAK. 

FOG AND LOW CLOUDS LKLY TO BE MORE OF A FACTOR EARLY THIS MORNING
GIVEN RECENT RAIN/WET GROUND...LIGHT WINDS AND HIGH BOUNDARY
LAYER MOISTURE/SFC DEWPOINTS IN THE 60S. CUT BACK ON EXTENT OF IFR
CONDS FROM PREVIOUS FCST WITH HIGHEST CONFIDENCE AT TERMINALS THAT
RECEIVED DECENT RAINFALL YESTERDAY. REDUCED CONDITIONS SHOULD
IMPROVE TO VFR BY MID-LATE MORNING. A CONSENSUS OF HIRES MDL
GUIDANCE INDICATES MORE DISORGANIZED/WDLY SCT SHRA AND TSTMS
DEVELOPING THIS AFTN. WILL LKLY ADD SOME MENTION INTO 12Z TAFS BUT
FOR NOW WENT WITH SCT-BKN 040-050. ANTICIPATE DECREASING CVRG OF
SHRA AND TSTMS INTO THE LATE EVE/OVERNIGHT PERIOD WITH AREAS OF
FOG/ST DEVELOPING AGAIN WITH SOME CLEARING/LGT WINDS/MOIST
AIRMASS. 

OUTLOOK... 
FRI-SAT...AM LOW CIGS/FOG FOLLOWED BY SCT SHOWERS/TSTMS AND BRIEF
MVFR/IFR RESTRICTIONS. 
SUN-MON...AM LOW CIGS PSBL. OTHERWISE MAINLY VFR.

&&

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

&&

$$
SYNOPSIS...STEINBUGL
NEAR TERM...STEINBUGL
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD
AVIATION...STEINBUGL



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