920
FXUS61 KCTP 190417
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1117 PM EST MON NOV 18 2024
SYNOPSIS
A RIDGE OF HIGH PRESSURE WILL BUILD ACROSS PENNSYLVANIA
TONIGHT, THEN A WEAKENING SHORTWAVE WILL GRAZE THE AREA AS IT
LIFTS NORTH THROUGH THE GREAT LAKES LATE TUESDAY. A CUT-OFF
UPPER LOW WILL TRACK FROM THE GREAT LAKES INTO PENNSYLVANIA
LATE THIS WEEK, PRECEDED BY AN OCCLUDED FRONT PASSAGE WEDNESDAY
NIGHT.
NEAR TERM /UNTIL 7 AM TUESDAY MORNING/
SURFACE RIDGING BUILDING ACROSS THE REGION WILL ENSURE FAIR
WEATHER AND LIGHT WINDS TONIGHT ACROSS CENTRAL PA. WARM
ADVECTION NORTH OF A STALLED FRONT IN THE OHIO VALLEY WILL
RESULT IN MOSTLY CLOUDY SKIES ACROSS THE SOUTHWEST PORTION OF
THE FORECAST AREA, WHILE THE REST OF THE REGION EXPERIENCES A
MOSTLY CLEAR START TO THE NIGHT, THEN VARIABLE CLOUDINESS LATE.
LATEST SREF AND NAMNEST BOTH TARGET THE N MTNS FOR VALLEY FOG
LATE TONIGHT ASSOCIATED WITH EFFICIENT RADIATIONAL COOLING AND
TUMBLING TEMPS THE FIRST HALF OF THE NIGHT. FURTHER SOUTH,
DEWPOINT DEPRESSIONS ARE ALREADY LOW ACROSS THE SOUTHWEST
COUNTIES CLOSER TO THE STALLED FRONT. ANY BREAKS IN THE CLOUD
COVER IN THAT AREA SHOULD ALSO RESULT IN PATCHY LATE NIGHT
VALLEY FOG.
EXPECT MIN TEMPS TO RANGE FROM THE LOW 30S IN THE VALLEYS OF
NORTHERN PA, WHERE CONDITIONS ARE MOST FAVORABLE FOR RADIATIONAL
COOLING, TO THE MID 40S OVER SOMERSET COUNTY, WHERE SKIES SHOULD
REMAIN MOSTLY CLOUDY OVERNIGHT.
SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY/
UPPER LEVEL RIDGING OVER THE AREA SHOULD PROVIDE CENTRAL PA
WITH MILD AND RAIN-FREE CONDITIONS FOR MOST OF TUESDAY. WEAK
MIXING UNDER THE RIDGE AXIS SHOULD RESULT IN SLIGHTLY LOWER
TEMPS TUESDAY, DESPITE WARMING ALOFT. SEE NO REASON TO DEVIATE
FROM NBM GUIDANCE, WHICH PROJECTS HIGHS IN THE 50S TO NEAR 60F
ACROSS THE LOWER SUSQ VALLEY.
WARM ADVECTION ASSOCIATED WITH A WEAKENING SHORTWAVE LIFTING
INTO THE GRT LKS SHOULD LEAD TO INCREASING CLOUDS LATE
TUESDAY/TUESDAY NIGHT WITH THE CHANCE OF A LITTLE LIGHT RAIN,
MAINLY OVER THE W MTNS. ANY LIGHT RAIN SHOULD TAPER OFF
FROM WEST TO EAST LATE TUE EVENING, AS THE LOW LEVEL JET AND
DEEPEST MOISTURE EXITS. HOWEVER, MODEL SOUNDINGS INDICATE PATCHY
DRIZZLE MAY LINGER OVER THE ALLEGHENIES, WHERE THE SFC-850MB
LAYER REMAINS NEARLY SATURATED AND A LIGHT SOUTHEAST FLOW
ASCENDS THE HIGH TERRAIN. LATEST ENSEMBLE QPF SUGGEST MOST
LIKELY RAINFALL BY LATE TUE NIGHT RANGES FROM NEAR A TENTH OF AN
INCH ACROSS THE LAUREL HIGHLANDS, TO LITTLE IF ANY RAIN IN THE
SUSQ VALLEY.
FOCUS THEN SHIFTS TO A CUT-OFF UPPER LOW DROPPING INTO THE
MIDWEST. MODEL SOUNDINGS INDICATE AN EASTERLY FLOW OFF OF THE
ATLANTIC WILL LIKELY YIELD STRATUS OVER MUCH OF THE AREA WED,
ESPECIALLY OVER THE CENTRAL MTNS. FALLING HEIGHTS AND SURGING
PWATS ALONG A SOUTHERLY LOW LEVEL JET SHOULD THEN BRING
THICKENING CLOUDS AND AN INCREASING CHANCE OF SHOWERS ACROSS THE
ENTIRE AREA BY LATE WEDNESDAY OR WED EVENING. 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 MONDAY/
RECENT GUIDANCE ALL TRACKS A SURFACE COLD/OCCLUDED FRONT THROUGH
CENTRAL PA WED EVENING IN ADVANCE OF AN 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 SHOWERS WED NIGHT. WITH REGARDS TO RAINFALL WED
EVENING, EARLIER SPREAD AMONG ENSEMBLE MEMBERS HAS DIMINISHED.
MOST LIKELY RAINFALL BY LATE WED NIGHT BASED ON THE 18Z EPS
PLUMES IS IN THE 0.25 TO 0.75 INCH RANGE, WITH THE HIGHEST
TOTALS OVER THE EASTERN PART OF THE FORECAST AREA.
THE TRIPLE POINT MAY CLIP THE EXTREME SOUTHEAST PART OF THE
FORECAST AREA WED EVENING. I HAD INITIALLY PUT IN SCHC THUNDER
FOR LATER WED FOR THE SE, BUT WITHDREW IT WITHOUT SUPPORT FROM
OTHER FORECASTERS.
CURRENT GUIDANCE INDICATES A DRY SLOT WILL WORK INTO CENTRAL PA
THU MORNING, THEN A PERIOD OF CHILLY AND UNSETTLED WEATHER LOOKS
CERTAIN LATE THIS WEEK, AS THE UPPER LOW TRACKS ACROSS PA. A
DEEP MOIST NORTHWEST FLOW ON THE WESTERN PERIPHERY OF THE
EXITING UPPER LOW SHOULD RESULT IN PERSISTENT LAKE-ENHANCED,
OROGRAPHIC PRECIPITATION FOCUSED OVER THE W MTNS THURSDAY NIGHT
INTO AT LEAST THE FIRST HALF OF NEXT WEEKEND. 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 AT TIMES.
THE LAURELS (SPECIFICALLY SOMERSET CO WHICH HAS THE HIGHEST
ELEVS OF PA) IS POISED TO PICK UP THE MOST SNOW DUE TO ENHANCED
OROGRAPHIC FORCING AND COLDER SURFACE TEMPS. THURSDAY NIGHT
LOOKS LIKE THE BEST SHOT AT SEEING ADVISORY CRITERIA TOTALS OVER
SOMERSET COUNTY. AFTER THAT, MUCH OF THE LATEST GUIDANCE
BECOMES A BIT TO WARM TO SUPPORT SNOW, OR AT LEAST ACCUMULATING
SNOW.
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 /04Z TUESDAY THROUGH SATURDAY/
CONDITIONS ARE GENERALLY VFR ACROSS A LARGE CHUNK OF CENTRAL
PENNSYLVANIA THIS EVENING. THE EXCEPTION BEING KJST WHERE A MVFR
CEILING PERSISTS ACROSS THAT HIGHER ELEVATION SITE. EXPECT THIS
TO CONTINUE OVERNIGHT.
ELSEWHERE, VFR WILL PERSIST OVERNIGHT AND INTO TUESDAY
AFTERNOON. PATCHY FOG IS POSSIBLE ACROSS THE NORTHWEST MOUNTAINS
AND LAURELS BY TUESDAY MORNING. NOT ENOUGH CONFIDENCE (<20%) TO
INCLUDE FOG AT ANY TAF SITES AT THIS POINT (HIGHEST PROBABILITY
AT JST/BFD, POSSIBLE AT IPT, UNV, AND AOO).
CLOUDS WILL BEGIN TO INCREASE TOMORROW AHEAD OF A WARM FRONT
THAT WILL BRING LIGHT SHOWERS TO WESTERN AIRFIELDS TUESDAY
AFTERNOON. RESTRICTIONS SHOULD HOLD OFF UNTIL AFTER 21Z IN THE
WEST WITH IFR CONDITIONS DEVELOPING OVERNIGHT.
OUTLOOK...
TUE NIGHT...RESTRICTIONS LIKELY WEST
WED...RESTRICTIONS LIKELY, MAINLY NW. MORE WIDESPREAD
RESTRICTIONS WITH RAIN AND LLWS WED NIGHT.
THU-FRI...RESTRICTIONS LIKELY WITH RAIN AND SNOW SHOWERS, MAINLY
ACROSS THE MOUNTAINS. WINDY.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
SYNOPSIS...FITZGERALD
NEAR TERM...FITZGERALD
SHORT TERM...FITZGERALD/BANGHOFF
LONG TERM...FITZGERALD/DANGELO
AVIATION...TYBURSKI
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page