281
FXUS61 KCTP 170520
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1220 AM EST SUN NOV 17 2024
SYNOPSIS
WE'LL HAVE A DRY, BREEZY AND MILDER START TO THE WEEKEND WITH
PARTIAL CLEARING AND AN ELEVATED RISK FOR WILDFIRE SPREAD ACROSS
EAST CENTRAL PA. A WEAK AND LOW PRECIP COLD FRONT WILL SLIDE
ACROSS THE NORTH LATE SUNDAY NIGHT INTO MONDAY, FOLLOWED BY A
WARM FRONT BRINGING A FEW SHOWERS ACROSS WEST CENTRAL PA LATE
TUESDAY.
THE NEXT CHANCE FOR WIDESPREAD PRECIPITATION WILL COME IN THE
FORM OF WIDESPREAD RAIN SHOWERS WEDNESDAY NIGHT INTO THURSDAY,
THEN A LIKELY CHANGEOVER TO SNOW ACROSS THE HIGHER TERRAIN OF
NORTHERN AND WESTERN PA WITH A MIX OF RAIN AND WET SNOW SHOWERS
IN THE VALLEYS.
NEAR TERM /UNTIL 6 AM THIS MORNING/
745 PM UPDATE... NIGHTTIME MICROPHYSICS SATELLITE IMAGERY HAS
SHOWN LITTLE OVERALL CHANGE TO THE EXTENT OF THE STRATOCUMULUS
DECK ACROSS ROUGHLY THE WESTERN THIRD OF THE COMMONWEALTH SO FAR
THIS EVENING.
MODEL SOUNDING/MOISTURE PROGS STILL INDICATE A GRADUAL REDUCTION
IN THE DEPTH OF THE MOIST LAYER OVERNIGHT, BUT THIS MAY WELL
RESULT IN A LOWERING OF THE CLOUD DECK AND DEVELOPMENT OF RIDGE
TOP FOG, WHERE IT IS CURRENTLY CLOUDY. FARTHER TO THE EAST,
WHERE SKIES HAVE CLEARED, EFFICIENT RADIATIONAL COOLING
OVERNIGHT COULD RESULT IN AT LEAST PATCHY VALLEY FOG. THESE
SCENARIOS SEEM TO BE WELL HANDLED IN THE CURRENT GRIDDED
FORECAST, SO LITTLE DEVIATION FROM THIS WAS MADE.
BY DAYBREAK, WE SHOULD SEE READINGS RANGING ACROSS THE 30S OVER
THE VAST MAJORITY OF CENTRAL AND NORTHWESTERN PA.
PREVIOUS DISCUSSION... A LOW STRATUS DECK CONTINUES TO BLANKET
MUCH OF THE CENTRAL AND NW MTNS THIS AFTERNOON, WITH MOISTURE
TRAPPED BETWEEN 2000-5000 FT, BENEATH A SUBSIDENCE INVERSION.
MODEL SOUNDINGS INDICATE SOME OF THE CLOUD AREA ACROSS THE
CENTRAL MOUNTAINS WILL CONTINUE TO ERODE PRIOR TO SUNSET, BUT
CLOUDS WILL HOLD STRONG IN THE NW INTO THE OVERNIGHT HOURS, AND
PERHAPS EXPAND EAST AGAIN AFTER DARK.
A FAIRLY TIGHT GRADIENT BETWEEN UPSTREAM HIGH PRESSURE OVER THE
GRT LKS AND LOW PRESSURE OFF OF THE EAST COAST WILL RESULT IN
GUSTY NORTHWEST WINDS AS HIGH AS 30 MPH IN SOUTHEASTERN ZONES
INTO EARLY THIS EVENING. SEE FIRE WX SECTION FOR LATEST
THINKING CONCERNING FIRE WEATHER.
A NORTH-SOUTH ORIENTED SURFACE HIGH PRESSURE RIDGE IS PROGGED
TO PUSH INTO PA TONIGHT, RESULTING IN DIMINISHING WIND. LATEST
SREF AND NAMNEST BOTH INDICATE PATCHY FOG IS POSSIBLE,
ESPECIALLY ACROSS THE NORTH AND WEST, AS THE SUBSIDENCE
INVERSION STRENGTHENS AND THE LOW CLOUD DECK PUSHES CLOSER TO
THE GROUND.
SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY NIGHT/
FAIR WEATHER AND LIGHT WIND ARE EXPECTED ON SUNDAY UNDER THE
HIGH PRESSURE SYSTEM. HOWEVER, WARM ADVECTION ALOFT IN ADVANCE
OF A SHORTWAVE OVER THE GRT LKS IS LIKELY TO SPREAD A VEIL OF
CIRRUS OVER THE REGION, ESPECIALLY IN THE NORTH. PROGGED 850MB
TEMPS SURGE TO 20 DEGREES ABOVE CLIMO SUNDAY. HOWEVER, WEAK
MIXING UNDER THE SURFACE RIDGE WILL RESULT A MORE MODEST WARMUP
WITH HIGHS IN THE 50S TO AROUND 60F.
A NORTHERN STREAM SHORTWAVE WILL PIVOT ACROSS THE EASTERN GREAT
LAKES INTO NEW ENGLAND LATE SUNDAY NIGHT INTO EARLY MONDAY.
THIS FEATURE WILL SEND A WEAK COLD FRONT THROUGH THE REGION
AND TRIGGER SOME LIGHT RAIN SHOWERS DOWNWIND OF LAKE ERIE CLOSE
NEAR AND TO THE NORTH OF THE NY BORDER. RIDGING SFC AND ALOFT
RETURNS FOR THE REST OF MONDAY, BRINGING DRY CONDITIONS WITH
MILDER DAYTIME TEMPERATURES IN THE 55-65F RANGE (+10-15 DEGREES
ABOVE THE HISTORICAL AVERAGE).
UPPER LEVEL RIDGING OVER PA SHOULD PROVIDE THE REGION WITH MILD
AND MOSTLY RAIN-FREE CONDITIONS TUESDAY. HOWEVER, WARM ADVECTION
ASSOCIATED WITH A WEAKENING SHORTWAVE LIFTING INTO THE GRT LKS
MAY PRODUCE A FEW SHOWERS, MAINLY OVER THE NW MTNS. FOCUS THEN
SHIFTS TO A CUT-OFF UPPER LOW DROPPING INTO THE MIDWEST.
LONG TERM /WEDNESDAY THROUGH SATURDAY/
OUR SUITE OF ENSEMBLE PREDICTION SYSTEMS IS IN GENERALLY GOOD
AGREEMENT ON THE LARGE-SCALE PATTERN NEXT WEEK, LEADING TO
REASONABLY HIGH CONFIDENCE.
THE PATTERN LOOKS TO BECOME MORE AMPLIFIED, AS A DEEPENING UPPER
LOW AND TRAILING TROUGH AXIS DIGS INTO THE EASTERN GREAT LAKES
AND NORTHEASTERN STATES. THIS EVOLUTION IS STILL EXPECTED TO
BRING A STRONG COLD FRONT ACROSS THE COMMONWEALTH DURING THE
MID-WEEK PERIOD, ACCOMPANIED BY WIDESPREAD SHOWERS, WITH OUR
COLDEST AIR MASS OF THE SEASON THUS FAR TO FOLLOW FOR THE END OF
THE WEEK INTO NEXT WEEKEND.
GIVEN THE AFOREMENTIONED COLD AIR, ALONG WITH WELL ABOVE NORMAL
WATER TEMPERATURES ON THE GREAT LAKES, THE STAGE IS SET FOR A
PROLONGED PERIOD OF LAKE ENHANCED AND UPSLOPE SHOWERS. MUCH OF
THESE SHOWERS SHOULD BE IN THE FORM OF SNOW OVER THE HIGHER
TERRAIN OF THE ALLEGHENIES, WITH A RAIN AND WET SNOW MIX
ANTICIPATED IN THE VALLEYS FARTHER EAST AND SOUTH. ALTHOUGH IT
IS TOO EARLY TO START TALKING ABOUT ACCUMULATIONS, IT DOES
APPEAR QUITE PROBABLE THAT THE GROUND WILL BE WHITENED OVER THE
ELEVATED TERRAIN OF NORTHWESTERN PA, ALONG WITH PARTS OF THE
LAUREL HIGHLANDS.
THE AFOREMENTIONED UPPER LOW WILL BE SLOW TO LIFT OUT, SO FAIRLY
COLD TEMPERATURES WILL PROBABLY NOT MODERATE MUCH UNTIL THE
EARLY PART OF THE FOLLOWING WEEK.
AVIATION /05Z SUNDAY THROUGH THURSDAY/
MAINLY CLEAR OUTSIDE THE OFFICE WHEN I CAME IN AT 1130, BUT I
COULD SEE SOME LOWER CLOUDS WELL TO THE WEST. NOT REALLY SOLD
ON FOG LATER AT BFD AND OTHER SITES, BUT WILL HOLD ONTO IT FOR
NOW, AS WE DID GET A BIT OF RAIN LATELY. THUS NO BIG CHANGES
FOR THE 06Z TAF PACKAGE AT THIS POINT. OVERALL REALLY GOOD
WEATHER THE NEXT FEW DAYS FOR MID NOVEMBER.
EARLIER DISCUSSION BELOW.
MVFR CEILINGS CONTINUE AT BFD AND UNV THIS EVENING, WHILE THE
REST OF CENTRAL PENNSYLVANIA IS CURRENTLY VFR. VFR CONDITIONS
ARE EXPECTED TO CONTINUE THROUGH THE NIGHT EAST OF UNV, WHILE
AREAS TO THE WEST WILL SEE CEILING AND VISIBILITY RESTRICTIONS
DEVELOP. MODEL SOUNDINGS SUGGEST THAT AS UPPER LEVEL RIDGING
BUILDS IN FROM THE WEST, LOW LEVEL MOISTURE WILL BECOME TRAPPED
BENEATH A SUBSIDENCE INVERSION. THIS WILL LEAD TO IFR/LIFR
CEILINGS AT BFD AND JST, AS WELL AS THE POTENTIAL FOR IFR/LIFR
VISIBILITIES. WHILE CONFIDENCE IN LOW CLOUDS AND FOG IS HIGHEST
AT BFD/JST (80-90%), IT IS POSSIBLE THAT FOG DEVELOPS FARTHER TO
THE EAST AS WELL (AOO/UNV/IPT). THERE IS A MUCH LOWER CHANCE OF
ANY FOG DEVELOPING AT MDT/LNS.
FOG AND LOW CLOUDS WILL GRADUALLY DISSIPATE DURING THE MORNING
AND WILL GIVE WAY TO VFR CONDITIONS AREA-WIDE BY THE AFTERNOON.
WINDS WILL BE LIGHT THROUGH THE 00Z TAF PERIOD, WITH WEST-
NORTHWEST WINDS AROUND 3-5 KNOTS.
OUTLOOK...
SUN NIGHT - EARLY MON...CFROPA. MVFR CIGS/VIS IN -SHRA, MAINLY
N HALF.
MON PM-TUES...NW FLOW. IFR/MVFR CIGS NW, VFR SE.
WED...RESTRICTIONS POSS, MAINLY NW. MORE WIDESPREAD RESTRICTIONS
WITH RAIN AND LLWS WED NIGHT.
THU...RESTRICTIONS LIKELY WITH RAIN AND SNOW SHOWERS.
FIRE WEATHER
THE FIRE WEATHER WATCH HAS BEEN CANCELLED AS CONFIDENCE HAS
INCREASED THAT RH VALUES WILL REMAIN ABOVE 30 PERCENT ACROSS THE
AREA PREVIOUSLY IN THE WATCH. ALTHOUGH CRITICAL FIRE WEATHER
CONDITIONS ARE NO LONGER EXPECTED, THERE IS STILL AN INCREASED
RISK OF WILDFIRE SPREAD AND A SPECIAL WEATHER STATEMENT HAS BEEN
ISSUED TO DISCUSS THIS RISK. FOR AREAS EAST OF THE SUSQUEHANNA
RIVER, MINIMUM RELATIVE HUMIDITY VALUES WILL RANGE FROM THE
UPPER 30S TO THE LOW 40S PERCENT ACCOMPANIED BY WIND GUSTS
BETWEEN 25 AND 35 MPH. THE LOWEST RH VALUES ARE EXPECTED IN
EASTERN SCHUYLKILL COUNTIES, WHERE THEY MAY BRIEFLY DROP TO
NEAR 30 PERCENT (35 PERCENT CHANCE). THE 1-HR AND 10-HR FUEL
MOISTURES ARE ALSO ABOVE CRITICAL LEVELS, EXPECTED TO REMAIN
ABOVE 10 PERCENT TODAY PER DCNR REPORTS.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...LAMBERT/COLBERT
NEAR TERM...JUREWICZ/LAMBERT/COLBERT
SHORT TERM...LAMBERT/COLBERT
LONG TERM...JUREWICZ/FITZGERALD/NPB
AVIATION...MARTIN/BAUCO
FIRE WEATHER...COLBERT
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