700
FXUS61 KPBZ 191140
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
640 AM EST THU DEC 19 2024
SYNOPSIS
DRY AND CHILLY TODAY. SNOW SHOWERS RETURN FRIDAY AHEAD OF
COLDER TEMPERATURES AND MORE SNOW SHOWERS FOR THE WEEKEND. DRY
WEATHER TO START NEXT WEEK WITH MODERATING TEMPERATURES.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- SCATTERED SNOW SHOWERS AND FLURRIES POSSIBLE SOUTHEAST OF LAKE
ERIE.
- RISK FOR FREEZING DRIZZLE IN THE MOUNTAINS OF WV OVERNIGHT.
- DRY WITH BELOW NORMAL TEMPERATURES.
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SURFACE HIGH PRESSURE WILL SLIDE ACROSS PA TODAY. THIS WILL
KEEP THE AREA DRY. A BLANKET OF STRATOCU SHOULD REMAIN OVER THE
REGION AS COLDER AIR ALOFT HOLDS STEADY IN THE ZONAL FLOW ALOFT.
HIGHS TODAY WILL BE CLOSE TO 5 DEGREES BELOW NORMAL.
SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/
KEY MESSAGES:
- SNOW SHOWER CHANCES RAMP BACK UP ON FRIDAY.
- LAKE EFFECT AND UPSLOPE SNOW POSSIBLE ON SATURDAY.
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THE NEXT TROUGH WILL APPROACH AND DEEPEN TONIGHT INTO FRIDAY
BRINGING WITH IT ANOTHER ROUND OF SNOW SHOWERS. THE SURFACE LOW
LOOKS TO TRACK JUST TO OUR SOUTH. FORECAST SOUNDINGS ARE
BULLISH ON ALL SNOW AS THE ENTIRE TEMPERATURE PROFILE, WITH THE
EXCEPTION OF RIGHT AT THE SURFACE, REMAINS BELOW 0C.
ADDITIONALLY, SOUNDINGS ARE SHOWING MOISTURE ALOFT WHICH WILL
LIE WITHIN THE DGZ AND FEED ICE NUCLEI INTO THE LOWER CLOUDS.
LOWERED HIGHS A COUPLE OF DEGREES DUE TO THE CLOUDS AND SNOW.
ACCUMULATION PROBABILITIES REMAIN LOW AT LESS THAN 20% FOR >1",
OUTSIDE OF THE RIDGES. PROBS THERE FOR > 1 INCH ARE RUNNING 30
TO 60%.
UPPER TROUGHING LINGERS FOR THE WEEKEND AS SURFACE LOW PRESSURE
MOVES UP THE NEW ENGLAND COAST AND HIGH PRESSURE BUILDS IN FROM THE
GREAT LAKES. GRADIENT INDUCED NORTHWESTERLY FLOW BETWEEN THE HIGH
AND DEPARTING LOW PRESSURE IS FAVORING AN INVIGORATION OF LAKE
EFFECT SNOW. THERE IS A SURPRISINGLY DECENT SIGNAL FOR A LAKE HURON
TO LAKE ERIE PRECIPITATION BAND EXTENDING DOWN INTO THE WESTERN
PART OF OUR CWA ON SATURDAY. INCREASING SUBSIDENCE FROM THE
HIGH SUGGESTS THE DEPTH OF THE MOISTURE SHOULD BE SHALLOW, BUT
CLUSTERS ALL SUPPORT ONE LAST WAVE AND SHOT OF COLDER AIR ALOFT
MOVING THROUGH THE DEPARTING UPPER TROUGH. EXACT PLACEMENT OF
ANY BANDING STILL REMAINS ELUSIVE, SO SPATIAL INCONSISTENCIES
REMAIN, BUT THE OCCURRENCE OF IT IS BECOMING HIGHER CONFIDENCE.
THE OTHER LOCATION TO WATCH WILL BE THE RIDGES OF BOTH PA AND
WV WHERE DEEP LAYER NORTHWESTERLY FLOW WILL RUN INTO THE HIGHER
ELEVATION AND AID IN UPSLOPE DRIVEN SNOWFALL. HERE,
PROBABILITIES ARE HIGHER FOR ADVISORY CRITERIA (3 INCHES) AT
AROUND 45-55% WITH THE HIGH END OF THE GOAL POSTS SITTING AT
WARNING CRITERIA (6 INCHES). THE HIGH END SOLUTION IS ONE THAT
EMANATES FROM A DEEPER TROUGH WITH STRONGER LOW-LEVEL
FLOW/CONVERGENCE. WILL AWAIT BETTER AGREEMENT AMONG THE GUIDANCE
AS WE GET CLOSER AND CAN IRON OUT THE SMALL-SCALE VARIATIONS
THAT WILL BE OF HIGHER CONSEQUENCE.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
KEY MESSAGES:
- COLD BUT DRY END TO THE WEEKEND.
- MODERATING TEMPERATURES WITH MID-WEEK POSSIBLE MID-WEEK
PRECIPITATION CHANCES.
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SUNDAY SHOULD FEATURE THE DEPARTURE OF THE TROUGH AS HEIGHTS RISE
THROUGH THE DAY. SINKING SUBSIDENCE WILL SHUT OFF SNOW CHANCES AS
EACH FLAVOR OF ENSEMBLE CLUSTER RETURNS DRY CONDITIONS. TEMPS WON'T
REBOUND MUCH AT ALL, AND IN FACT, SUNDAY AND SUNDAY NIGHT ARE
FAVORED TO BE THE COLDEST OF THE PERIOD. HIGHS ECLIPSING 30 DEGREES
ARE LOW PROBABILITY AND SINGLE DIGIT OVERNIGHT LOWS ARE RANGING FROM
40-80% PROBABILITY NORTH AND EAST OF PITTSBURGH.
HIGH PRESSURE REMAINS DOMINANT WITH BUILDING HEIGHTS INTO NEXT WEEK.
A WEAK WAVE LOOKS TO MOVE THROUGH IN ZONAL FLOW RETURNING
PRECIPITATION CHANCES BY MID-WEEK, THOUGH THE SOURCE REGION FOR
MOISTURE BEING TO OUR NORTH AND WEST ISN'T SUGGESTING NOTABLE
PRECIPITATION ACCUMULATION. FOR THE WHITE CHRISTMAS DREAMERS OUT
THERE, LONG RANGE ENSEMBLES SUGGEST SUB-FREEZING TEMPERATURES
BEING MORE LIKELY CHRISTMAS EVE THAN CHRISTMAS DAY. IT'S STILL A
WEEK AWAY, SO PLENTY OF DETAILS TO IRON OUT AT THIS POINT.
AVIATION /12Z THURSDAY THROUGH MONDAY/
CEILINGS ARE STRADDLING THE VFR/MVFR THRESHOLD ACROSS THE REGION
UNDERNEATH A SOLID STRATOCUMULUS DECK. EXPECT CEILINGS TO FLOAT
DOWN INTO MVFR RANGE AREAWIDE UNDER WEAK COLD ADVECTION - HREF
PROBABILITIES OF SUCH ARE 70 PERCENT OR GREATER ACROSS THE
UPPER OHIO VALLEY.
THESE PROBABILITIES FALL OFF TO 60 PERCENT OR LESS LATER TODAY.
THIS SEEMS REASONABLE, AS TEMPERATURE ADVECTION WILL TREND
TOWARDS WARM LATER TODAY AS SURFACE HIGH PRESSURE MOVES EAST.
THIS WILL HELP TO LIFT CEILINGS BACK TO VFR BY SUNSET AT ALL
TERMINALS.
TONIGHT, CEILINGS SHOULD DRIFT BACK DOWN TO MVFR AS LOW PRESSURE
APPROACHES THE GREAT LAKES. A WARM FRONT MAY GENERATE SOME
LIGHT SNOW SHOWERS NORTH OF PITTSBURGH TOWARDS 12Z, WITH LITTLE
IMPACT FORESEEN THROUGH THE END OF THE TAF PERIOD.
OUTLOOK...
RESTRICTIONS AND SNOW ARE LIKELY TO RETURN EARLY FRIDAY WITH
CROSSING LOW PRESSURE. RESTRICTIONS MAY LINGER THROUGH AT LEAST
SATURDAY AS COLD ADVECTION UNDER NORTHWEST FLOW PROMOTES THE
CONTINUATION OF LAKE-EFFECT CLOUDS AND POSSIBLY A FEW SCATTERED
LIGHT SNOW SHOWERS. THE NEXT CHANCE FOR VFR LOOKS TO BE SATURDAY
NIGHT OR SUNDAY.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
SYNOPSIS...22
NEAR TERM...22
SHORT TERM...22/MLB
LONG TERM...MLB
AVIATION...CL/RACKLEY
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