717
FXUS61 KCTP 191819
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
119 PM EST TUE NOV 19 2024
SYNOPSIS
*MOSTLY CLOUDY AND RELATIVELY MILD WITH PATCHY RAIN AND DRIZZLE
TONIGHT
*GUSTY RAIN SHOWERS LATER WEDNESDAY WILL PRECEDE THE FIRST TASTE
OF WINTER WEDNESDAY NIGHT THROUGH FRIDAY
*THE FIRST SNOW ACCUMULATION OF THE SEASON IS EXPECTED IN THE
ALLEGHENY MOUNTAINS WITH SEVERAL INCHES POSSIBLE AT PEAK
ELEVATIONS IN THE LAUREL HIGHLANDS BY THE WEEKEND
NEAR TERM /THROUGH TONIGHT/
A PATCH OF LIGHT RAIN ASSOCIATED WITH A MINOR SHORT WAVE TROUGH
WILL PASS THROUGH THE AREA STARTING VERY SHORTLY. AS OF 18Z, NO
PRECIP HAS YET BEEN NOTED AT ANY CENTRAL PA METAR LOCATIONS.
BUT, SOMERSET AND JOHNSTOWN SHOULD GET WET BY 19Z. PERHAPS NOT
MEAS. RAINFALL, BUT WET. MOST OF THE LIGHT RAIN WILL FALL IN
THE EVENING HOURS. HOWEVER, THE CLOUDS THICKEN AND LOWER OVER
MUCH OF THE CWA AFTER MIDNIGHT, LEADING TO AREAS OF DRIZZLE AND
FOG, ESP ON THE RIDGE TOPS. QPF WILL BE <0.10", WITH THE NE
HARDLY GETTING 0.01".
SHORT TERM /WEDNESDAY/
SFC LOW PRESSURE CONSOLIDATING OVER LH/LE AND WRN PA WILL RESULT
IN A WEAK SOUTHEASTERLY UPSLOPE FLOW OFF OF THE ATLANTIC WILL
YIELD A LOW STRATUS OVER MUCH OF THE AREA WED, ESPECIALLY OVER
THE CENTRAL MTNS. SOME LIFTING AND SOME BREAKS ARE POSSIBLE IN
THE AFTN, ESP IN THE E/SE. FALLING HEIGHTS AND SURGING PWATS
ALONG A SOUTHERLY LOW LEVEL JET SHOULD THEN BRING IN THICKEN
CLOUDS FROM ALOFT AND SHRA/RA ACROSS THE ENTIRE AREA WED AFTN IN
THE W AND EVENING FOR THE E. WE HAVE UNDERCUT NBM MAX TEMPS
WED, DUE ITS WARM BIAS IN EASTERLY FLOW/CAD SCENARIOS.
REGARDLESS, WEDNESDAY WILL BE THE LAST MILD DAY FOR A WHILE AS
COOLER, MORE SEASONABLE AIR ARRIVES BY THURSDAY.
LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/
FOCUS THEN SHIFTS TO A VIGOROUS BOWLING BALL CUT-OFF UPPER LOW
BARRELING EAST SOUTHEASTWARD THROUGH THE GREAT LAKES.
RECENT GUIDANCE ALL TRACKS A SURFACE COLD/OCCLUDED FRONT THROUGH
CENTRAL PA WED EVENING IN ADVANCE OF THE UPPER LOW APPROACHING
FROM THE GRT LKS. STRONG LARGE SCALE FORCING AHEAD OF THE UPPER
LOW AND LOW LEVEL CONVERGENCE ALONG THE FRONT SUPPORTS A HIGH
CHANCE OF RAIN WED NIGHT. SHALLOW CONVECTION IS POSSIBLE NEAR OR
ALONG THE COLD FRONT GIVEN RAPIDLY COOLING TEMPERATURES ALOFT.
THE MOST LIKELY RAINFALL BY LATE WED NIGHT IS IN THE 0.25 TO
0.75 INCH RANGE, WITH THE HIGHEST TOTALS OVER THE EASTERN PART
OF THE FORECAST AREA.
GUIDANCE INDICATES A DRY SLOT WILL WORK INTO CENTRAL PA THURSDAY
MORNING, THEN A PERIOD OF CHILLY AND UNSETTLED WEATHER LOOKS
CERTAIN LATE THIS WEEK, AS THE UPPER LOW PIVOTS ACROSS SOUTHERN
PA AND PINWHEELS NEAR THE NJ COAST. A DEEP MOIST NORTHWEST FLOW
ON THE WESTERN PERIPHERY OF THE EXITING UPPER LOW SHOULD RESULT
IN A LONG DURATION, UPSLOPE/OROGRAPHIC AND LAKE ENHANCED
PRECIPITATION EVENT FOCUSED OVER THE ALLEGHENY MTNS AND
PARTICULARLY THE LAUREL HIGHLANDS THROUGH THE END OF THE WEEK.
MODEL THERMAL PROFILES CURRENTLY LOOK COLD ENOUGH TO SUPPORT THE
FIRST ACCUMULATING SNOW OF THE SEASON ACROSS THE HIGHER
ELEVATIONS OF THE ALLEGHENIES THURSDAY INTO FRIDAY, BUT
SNOWFLAKES COULD EXTEND SOUTHEAST OF THE ALLEGHENY FRONT INTO
THE CENTRAL RIDGE AND VALLEY REGION AT TIMES.
THE LAUREL HIGHLANDS ARE POISED TO PICK UP THE MOST SNOW DUE TO
ENHANCED OROGRAPHIC FORCING, FAVORABLY NW FLOW TRAJECTORY, AND
COLDER SURFACE TEMPS. THURSDAY NIGHT LOOKS LIKE THE BEST SHOT AT
SEEING ADVISORY CRITERIA TOTALS OVER SOMERSET COUNTY WITH WPC
PWPF SHOWING HIGH PROBS (>70%) FOR SNOWFALL POTENTIALLY
EXCEEDING 4" AT ELEVATIONS ABOVE 2500FT. WE MODIFIED THE HWO TO
HIGHLIGHT THIS AREA.
IN ADDITION TO FREQUENT PRECIPITATION AND BELOW NORMAL DAYTIME
TEMPERATURES, GUSTY WEST-NORTHWEST WINDS ARE ALSO ANTICIPATED
FRIDAY AND SATURDAY, AS A TIGHT GRADIENT DEVELOPS WEST OF AN
INTENSIFYING SURFACE LOW OVER NEW ENGLAND. LATEST EPS PLUMES
INDICATE GUSTS OF AROUND 30MPH ARE LIKELY BOTH DAYS. PERSISTENT
CLOUD COVER AND COOLER TEMPERATURES ALOFT WILL KEEP HIGH
TEMPERATURES 5-10 DEGREES BELOW AVERAGE LATE THIS WEEK, WHILE
OVERNIGHT LOWS ARE CLOSE TO NORMAL.
LINGERING LAKE EFFECT OVER THE W MTNS SHOULD DWINDLE BY SUNDAY
AFTERNOON, AS INVERSION HEIGHTS FALL AND HIGH PRESSURE
APPROACHES FROM THE WEST. MILDER CONDITIONS LOOK LIKELY NEXT
MONDAY AHEAD OF AN APPROACHING COLD FRONT, WHICH COULD PRODUCE
LATE DAY RAIN SHOWERS.
AVIATION /18Z TUESDAY THROUGH SUNDAY/
THE UPPER LOW TO OUR WEST WILL WOBBLE A DEEP TROUGH AXIS OVER
THE UPPER OH VALLEY AND SHOVE A LARGE PATCH OF RAIN ACROSS PA
FROM W TO E WED EVENING AND EARLY NIGHT. AFTER A BIG DRY SLOT
NOSES IN, MOST PRECIP SHOULD PAUSE FOR CENTRAL PA, AT LEAST
UNTIL THE CENTER OF THE DEEP CLOSED LOW WOBBLES CLOSER. THE COLD
AIR ALOFT UNDER THE BIG UPPER LOW, NW LLVL FLOW, AND LAKE
WARMTH/MOISTURE WILL MAKE FOR A PERSISTENT PATTERN OF SHRA/SN
INTO SAT AM. EXPECT EXTREMELY POOR FLYING CONDITIONS FOR BFD AND
JST THURS NIGHT INTO SAT AM AS NUMEROUS SHOTS OF PRECIP AND LOW
CIGS AFFECT THE N AND W.
OUTLOOK...
THU-SAT...RESTRICTIONS LIKELY WITH RAIN AND SNOW SHOWERS,
MAINLY ACROSS THE MOUNTAINS (BFD AND JST). MVFR MUCH OF THE TIME
FOR UNV/IPT/AOO. WINDY.
SUN...NO SIG WX.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...DANGELO/STEINBUGL
NEAR TERM...DANGELO
SHORT TERM...DANGELO
LONG TERM...FITZGERALD/DANGELO
AVIATION...DANGELO
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