Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 291642
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1242 PM EDT MON JUN 29 2015

.SYNOPSIS...
A WEAK RIDGE OF HIGH PRESSURE WILL BRING DRY WEATHER AND MILDER
TEMPERATURES TO MOST OF CENTRAL PENNSYLVANIA TODAY. A FRONTAL
SYSTEM MOVING THROUGH THE OHIO VALLEY INTO THE LOWER GREAT LAKES
WILL LIKELY BRING INCREASING CLOUDS AND SHOWERS TO THE AREA LATER
TONIGHT INTO TUESDAY MORNING...FOLLOWED BY SCATTERED THUNDERSTORMS
TUESDAY AFTERNOON. EXPECT AN UNSETTLED WEATHER PATTERN TO PERSIST
INTO THE UPCOMING HOLIDAY WEEKEND AS A BROAD BUT WEAKENING UPPER
LEVEL TROUGH REMAINS POSITIONED OVER THE LOWER 48 EAST OF THE
CONTINENTAL DIVIDE.

&&

.NEAR TERM /THROUGH TONIGHT/...
WEAK SFC RIDGE DRIFTING NE ACROSS THE REGION THIS AFTERNOON WILL
CONTINUE TO PROVIDE FAIR/DRY WEATHER THIS AFTERNOON /AND EARLY THIS
EVENING FOR MOST LOCATIONS EAST OF THE ALLEGHENIES/.

THE SW EDGE OF COOLER TEMPS/STEEPER LOW-MID LEVEL LAPSE RATES WAS
DEPARTING THE CWA...BUT WILL RESULT IN SCT-BKN FLAT CU THIS
AFTERNOON.

LATER TODAY...QUICKLY NE ADVANCING WARM FRONT AND THE LEADING
EDGE OF ANOMALOUSLY STRONG SSWRLY FLOW AT 850 MB AND HIGHER PWAT
AIR WILL ACCOMPANY A WARM FRONT TO BRING A QUICK INCREASE IN
CLOUDS WITH A CHC FOR SHOWERS BY EARLY THIS EVENING ACROSS MAINLY
THE NW MTNS.

AREAS EAST OF THE ALLEGHENY PLATEAU WILL SEE INCREASING CLOUDS
LATE TODAY/EARLY TONIGHT...BUT THE CHC FOR SHOWERS WILL BE MUCH
LOWER UNTIL AT LEAST 04Z TUESDAY.

MODEL CONSENSUS FAVORS SHOWERS OVER NW PA TONIGHT WITH MODEST QPF
AMOUNTS IN THE 0.25 TO 0.50 INCH RANGE AS THE SFC LOW REACHES LAKE
ERIE BY 12Z TUE.

HIGH TEMPS THIS AFTERNOON WILL VARY FROM THE L70S NORTH TO AROUND
80F IN THE SE.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
THE LEAD SHORTWAVE IS FCST TO WEAKEN INTO THE LOWER GREAT LKS
EARLY TUESDAY. HOWEVER...SEVERAL ADDITIONAL SHORTWAVES CRESTING
THE WRN CONUS MEAN RIDGE WILL DIG SEWD THROUGH THE UPPER/MID MS
VALLEY...HELPING TO CARVE OUT A SIGNIFICANT MID LVL TROUGH THAT
SHOULD GRADUALLY SHIFT EWD ACROSS THE OH VALLEY ON TUESDAY/D2 AND
THE NORTHERN MID ATLC STATES ON WEDNESDAY/D3.

THE LATEST SHORT RANGE MODEL GUIDANCE INDICATES CENTRAL PA WILL
BE IN THE WARM SECTOR BY TUESDAY AFTERNOON...WITH SEASONALLY
STRONG BOUNDARY LAYER HEATING EXPECTED AHEAD OF WEAK COLD FRONT OR
WIND SHIFT APPROACHING FROM THE OH VALLEY. TSTMS ARE PROJECTED TO
DEVELOP WITHIN A CORRIDOR OF MODEST INSTABILITY AND STEEP LOW
LLVL LAPSE RATES FROM THE MID SOUTH NEWD ALONG THE APPALACHIANS
INTO CENTRAL PA. DEEP LAYER SHEAR VALUES WITHIN THIS CONVECTIVE
ZONE ARE SUPPORTIVE OF ORGANIZED MULTI-CELL UPDRAFTS AND LINE
SEGMENTS...AND THEREFORE SPC HAS MAINTAINED A MARGINAL RISK FOR
D2. TSTM ACTIVITY WILL BE TIED TO DIURNAL HEATING MAXIMUM WITH A
DECREASING COVERAGE/WEAKENING TREND EXPECTED DURING THE EVENING
HOURS.

THE SEVERE WEATHER RISK IS FCST TO SHIFT EWD ON D3/WED AS
THE MAIN MID-LVL TROUGH EJECTS NEWD ACROSS THE UPPER OH VALLEY
INTO UPSTATE NY/CENTRAL PA BY 18Z. THE CONVECTIVE ENVIRONMENT
SHOULD BE SIMILAR TO D2 WITH THE AXIS OF BEST INSTABILITY/LOW LVL
LAPSE RATES SHIFTED SLIGHTLY EWD INTO ERN PA. LOOK FOR ANOTHER
ROUND OF TSTMS TO DEVELOP ALONG/AHEAD OF SFC COLD FRONT AND POSE
AT LEAST A LOW RISK OF DAMAGING WINDS AND PERHAPS SOME HAIL.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
THE LATEST GLOBAL DETERMINISTIC MODELS AND ENSEMBLE MEANS ARE
STARTING TO SUGGEST THAT THE HIGHLY AMPLIFIED RIDGE/TROUGH
PATTERN OVER THE LOWER 48 WILL START TO FLATTEN OUT WITH
TIME...PERHAPS REVERTING BACK TO A MORE TYPICAL SUMMERTIME MID-
LATITUDE FLOW REGIME WITH THE MAIN BELT OF ZONAL WESTERLIES
ALIGNED NEAR THE US/CANADIAN BORDER AND SUBTROPICAL RIDGING
EXPANDING ACROSS THE SOUTHERN UNITED STATES.

DESPITE A SERIES OF MID-LEVEL DISTURBANCES MOVING DOWNSTREAM OF
THE WRN THROUGH FROM THE UPPER/MID MS VALLEY THROUGH THE MID ATLC
REGION...500MB HEIGHTS SHOULD BE IN RECOVERY MODE WHICH SHOULD
ALLOW DAYTIME TEMPERATURES TO TREND WARMER INTO THE JULY 4TH
HOLIDAY WEEKEND. CONFIDENCE IN THE PCPN PATTERN REMAINS LOW
ALTHOUGH THERE SEEMS TO BE SOME MODEL AGREEMENT IN FOCUSING RAINS
THU/FRI ALONG THE D3/WEDNESDAY COLD FRONT...WHICH APPEARS TO
BECOME QUASI-STNRY FROM SRN NJ WSWWD ALONG THE MASON DIXON LINE
LATE THIS WEEK.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
ALL AIRFIELDS HAVE RETURNED TO VFR CONDITIONS AND THEY ARE
EXPECTED TO PERSIST THROUGH MUCH OF THE DAY.

UNSETTLED PATTERN WITH A SERIES OF FRONTS AFFECTING THE REGION
MUCH OF NEXT WEEK. BEST CHANCES OF RESTRICTIONS WILL BE TUESDAY
INTO WEDNESDAY.

OUTLOOK...
TUE- WED...MAINLY VFR...BUT SOME POSSIBLE RESTRICTIONS IN
SHRA/TSRA.
THU-THU...AGAIN MAINLY VFR....BUT RESTRICTIONS POSSIBLE IN SHRA
AND POSSIBLE TSRA.

&&

.CLIMATE...
JUNE 2015 HAS BEEN A WET MONTH ACROSS MUCH OF CENTRAL PA. THROUGH
6/28...OUR TWO LCD CLIMATE SITES /HARRISBURG AND WILLIAMSPORT/ ARE
RANKED 8TH AND 6TH RESPECTIVELY FOR THE WETTEST JUNE ON RECORD.

&&

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

&&

$$
SYNOPSIS...LAMBERT/STEINBUGL
NEAR TERM...LAMBERT/STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...STEINBUGL
AVIATION...JUNG/LAMBERT/GARTNER
CLIMATE...



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