488
FXUS61 KPBZ 181146
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
646 AM EST SAT JAN 18 2025
SYNOPSIS
RAIN AND SNOW RETURNS TODAY. IMPACTFUL SNOW POSSIBLE FOR THE
HIGHER TERRAIN OF WEST VIRGINIA THIS SUNDAY AND SUNDAY NIGHT,
FOLLOWED BY AN EXTREME COLD OUTBREAK NEXT MONDAY THROUGH
WEDNESDAY. A WARMING TREND IS EXPECTED BY AT LEAST THURSDAY OF
NEXT WEEK.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- RAIN AND SNOW CHANCES INCREASE OVERNIGHT
- SLIGHT CHANCE OF FREEZING RAIN AT ONSET
- RAIN CONTINUES TODAY, A MIX OF SNOW AND RAIN NORTH OF
PIT/RIDGES
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CURRENT TRENDS SHOWS PRECIPITATION MOVING INTO THE REGION THIS
MORNING. WITH STILL SOME LINGERING 10 TO 15 DEGREE DEW POINT
DEPRESSIONS ACROSS THE AREA. THIS IS EFFECTIVELY KEEPING PRECIP
FROM REACHING THE SURFACE WHILE AIR TEMPERATURES WARM AND
EVENTUALLY, THE ROAD TEMPERATURES. THIS WILL KEEP FZRA LESS OF A
POTENTIAL AND EVEN THE NBM PROBS ARE GIVING A LESS THAN 10%
PROBABILITY OF ANY ACCRUAL OF ICE.
THE LOWER ATMOSPHERE WILL FINALLY BEGIN TO SATURATE BY 12Z WITH
RAIN AND SNOW TO THE NORTH, AND SNOW OVER THE RIDGES PRETTY MUCH
AT ONSET. ANY MIX IN THE SOUTHERN LOWER ELEVATIONS SHOULD
CHANGE TO RAIN SOUTH OF RT 422 BY MID MORNING, WITH SNOW MIXED
WITH RAIN TO THE NORTH. SNOW ACCUMULATION TO THE NORTH SHOULD BE
LIMITED TO LESS THAN AN INCH WITH TEMPERATURES ABOVE FREEZING.
ACCUMULATION OVER THE RIDGES WILL BEGIN BY THIS AFTERNOON. THIS
WILL UNFOLD AS A SURFACE COLD FRONT WILL THEN APPROACH AND
CROSS THE REGION LATE SATURDAY AFTERNOON, CONTINUING THE PRECIP
CHANCES.
AS THE FRONT DIPS ACROSS THE AREA, TEMPERATURES ARE EXPECTED TO
VERY GRADUALLY DECREASE ACROSS THE AREA THROUGH THE PERIOD. THIS
WILL MEAN THAT ALL SNOW WILL BE THE PREDOMINANT PRECIPITATION
TYPE AS WE HEAD INTO THE TONIGHT PERIOD.
SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/
KEY MESSAGES:
- SLOW COLD FRONT PASSAGE WITH ANOTHER DISTURBANCE RIDING ALONG
THE HIGH TERRAIN.
- WINTER STORM WARNINGS GO INTO EFFECT FOR WV RIDGES.
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THERE HAS BEEN INCREASING CONFIDENCE IN AN IMPACTFUL WINTER
SYSTEM FOR THE WEST VIRGINIA RIDGES AS ANOTHER CYCLONE DEVELOPS
AND MOVES UP THE FRONT, SHOVELING MOISTURE BACK INTO THE COLD
SECTOR OF THE LOW FOR THE HIGH TERRAIN. THE WINTER STORM WATCH
HAS BEEN UPGRADED TO A WARNING IN THE WV RIDGES.
THE LATEST MODEL UPDATES SUGGEST THAT THE LOW TRACK WILL STILL
BE SUCH TO IMPACT THE WV RIDGES. WHILE SOME SNOW MAY BE POSSIBLE
THIS AFTERNOON INTO THE EVENING, THE ACCUMULATING AND IMPACTFUL,
SNOW WILL BEGIN LATE TONIGHT. THERE HAS BEEN A BIT OF SHIFTING
INTO THE LOW TRACK OF THE PAST 24 HOURS WITH THE MAIN SWATH OF
SNOW STILL BEING OVER THE WV MOUNTAINS. IN FACT, WHERE THE
DEFORMATION ZONE SETS UP SEEMS TO BE OVER THE WV RIDGES MORE
BUT THE LOWER ELEVATIONS AND PA RIDGES SUGGEST MORE ADVISORY
CRITERIA BASED ON THE SOUTHERLY TRACK. NBM PROBABILITIES FOR 3
INCHES OF SNOW OR MORE ONLY SHOWS SOME 30% TO 50% VALUES IN THE
LOWER ELEVATIONS OF SW PA (SOUTH OF PIT) AND LOWER ELEVATIONS OF
LOWER WV (NOT INCLUDING THE PANHANDLE). IT SEEMS AN ADVISORY
WILL BE NEEDED BUT DECIDED TO ALLOW 1 MORE RUN OF MODEL/ENSEMBLE
DATA TO FURTHER PIN DOWN THE AXIS OF THE HEAVIER SNOW.
UPSLOPE SNOW SHOWERS ALONG THE RIDGES, AND SOME LAKE EFFECT TO
THE NORTH WILL KEEP THE SNOW POTENTIAL IN PLACE THROUGH SUNDAY
NIGHT AS THE COLDER AIR CONTINUES TO ADVECT INTO THE REGION AND
INCREASING SNOW RATIOS. THE PERIOD OF HEAVIEST SNOW APPEARS TO
ALIGN WITH 12Z TO 18Z SUNDAY. THE BULK OF THE MOISTURE WILL THEN
BEGIN TO EXIT THE AREA BY SUNDAY EVENING, BUT WITH THE COLDER
AIR CONTINUING TO FILTER INTO THE REGION AND RATIOS INCREASING,
ACCUMULATING SNOWFALL WILL CERTAINLY CONTINUE SUNDAY EVENING
THROUGH SUNDAY NIGHT AS TEMPERATURES BEGIN TO DIP BACK TO BELOW
NORMAL TEMPERATURES.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/
KEY MESSAGES:
- SNOW SHOWERS CONTINUE ON SUNDAY AND MONDAY IN NORTHWEST FLOW.
- ARCTIC OUTBREAK WITH DANGEROUSLY COLD TEMPERATURES AND WIND
CHILLS LIKELY NEXT WEEK.
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EXTREME COLD MONDAY THROUGH WEDNESDAY...
CONFIDENCE HAS INCREASED ENOUGH ON DANGEROUS COLD WITH
SIGNIFICANT IMPACTS TO ISSUE AN EXTREME COLD WATCH. EXTREMELY
LOW TEMPERATURES AND WIND CHILL TEMPERATURES ARE EXPECTED TO
IMPACT THE REGION MONDAY THROUGH WEDNESDAY. ARCTIC AIR WILL DIP
DOWN OUT OF FAR NORTHERN CANADA ACROSS THE EASTERN UNITED STATES
BEGINNING SUNDAY NIGHT.
THE COLD IMPACTS THROUGH AT LEAST WEDNESDAY MORNING REMAIN HIGH
CONFIDENCE. THERE IS HIGH AGREEMENT AMONG ENSEMBLE CLUSTERS OF
THE 500MB HEIGHT AND TEMPERATURE TRENDS OF DEEP TROUGHING ACROSS
THE EASTERN CONUS, DIPPING TEMPERATURES AS LOW AS 35 DEGREES
BELOW NORMAL. LONG-RANGE GUIDANCE (NAEFS) HAS 850MB AND 700MB
TEMPERATURES EARLY NEXT WEEK NEAR THE 1ST PERCENTILE
(TEMPERATURES THIS TIME OF YEAR ARE WARMER THAN THIS 99% OF THE
TIME).
CONFIDENCE HAS INCREASED THAT THE COLDEST DAYTIME HIGH OF THE
PERIOD MAY BE MONDAY (MIDDLE SINGLE DIGITS) WITH THE INITIAL
INTRUSION OR ARCTIC AIR, BUT CLEAR SKIES AND THE POTENTIAL FOR
DECOUPLING AND COLD AIR DRAINAGE OVERNIGHT MEAN THAT THE COLDEST
MORNING MAY BE TUESDAY AND WEDNESDAY MORNING. GIVEN THE COMPLEX
TERRAIN AND MICRO-METEOROLOGICAL COLD AIR DRAINAGE PROCESSES,
LOW TEMPERATURES WILL LIKELY BE VARIABLE ACROSS THE AREA WITH
THE COLDEST POCKETS IN SHELTERED VALLEYS. EXPOSED RIDGE TOPS
MAY BE A BIT WARMER, BUT ALSO EXPOSED TO THE WIND. ALL IN ALL,
LOW TEMPERATURES IN THE HIGH NEGATIVE SINGLE DIGITS AND LOW
NEGATIVE TEENS WITH WIND CHILLS AS LOW AS -25F FOR THE LOWLANDS
AND -30F FOR THE RIDGES.
FORECAST CONFIDENCE DECREASES WEDNESDAY, WITH GEFS DOMINATED
ENSEMBLES SHOWING A BRIEF BOUT OF SHORTWAVE REJOINING BRINGING
TEMPERATURES UP TO THE HIGH 10S, WHILE THE EURO ENSEMBLES HOLD
COLDER WITH CONTINUED HIGHS IN THE SINGLE DIGITS. UNDER THE
SURFACE HIGH, EFFICIENT RADIATIVE COOLING IS STILL EXPECTED TO
DROP WIND CHILL TEMPERATURES CLOSE TO ADVISORY CRITERIA THURSDAY
MORNING. EVEN WITH THE BIMODAL SOLUTION, THE WATCH EXTENDS
THROUGH 15Z TO ACCOUNT FOR ONE MODE AND ALSO THE CUMULATIVE
IMPACTS OF THE EXTREME COLD TO THIS POINT.
THE TIME TO BEGIN PREPARING IS NOW. UNPROTECTED PIPES CAN FREEZE AND
BURST. PROLONGED EXPOSURE TO THE COLD MAY LEAD TO HYPOTHERMIA.
FROSTBITE CAN OCCUR IN AS LITTLE AS 30 MINUTES FOR EXPOSED SKIN. IT
IS ENCOURAGED TO BRING MOVABLE PLANTS INDOORS. EXTREME CARE IS
ENCOURAGED FOR THE PROTECTION OF PETS AND ANIMALS. RESCHEDULING ANY
EVENTS, ESPECIALLY OUTDOOR EVENTS, IS ENCOURAGED.
BY THE END OF NEXT WEEK (THURSDAY, FRIDAY, SATURDAY), THERE IS
STILL HIGH CONFIDENCE THAT RIDGING BUILDS IN AND WARMS HIGH
TEMPERATURES INTO THE LOW 30S AND UPPER 20S WITH LOWS IN THE LOW
20S TO UPPER 10S, WHICH IS STILL A HARE BELOW AVERAGE.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
SHORTWAVE MOVEMENT WITH WARM, MOIST ADVECTION AHEAD OF IT WILL
CONTINUE TO SPREAD MAINLY RAIN OVER THE REGION TODAY. MVFR CIGS
WILL DEVELOP WITHIN 2 HOURS OF PRECIPITATION ONSET, WITH IFR
HIGHLY LIKELY (60-90% PROBABILITY) BY 18Z. DUE TO AN INITIALLY
DRY ENVIRONMENT, WET-BULB PROCESSES MAY CREATE A MIX OF SNOW
SHORTLY AFTER ONSET AT FKL/DUJ WITH LOWER CONFIDENCE ON WHETHER
IT WILL FULLY TRANSITION BACK TO RAIN.
PASSAGE OF THE SHORTWAVE DURING THE AFTERNOON WILL BEGIN WEAK
COLD ADVECTION AND START A TRANSITION FROM RAIN TO SNOW FROM
THE NW TO THE SE. FOR SITES LIKE FKL/DUJ, THIS COULD OCCUR AS
EARLY AS 18Z AND IS MORE LIKELY BY 22Z. THE REST OF THE
TERMINALS ARE EXPECTED TO EXPERIENCE THE TRANSITION BETWEEN
22Z-02Z TONIGHT. THIS WILL COINCIDE WITH WIND SHIFT TO THE NW
ALONG WITH A SLIGHT RISE IN CEILINGS TO MVFR AND FALL TOWARD IFR
VSBY DUE TO GREATER MIXING AND EFFECTS OF SNOW.
SNOW IS LIKELY TO END BY 06Z AT ALL TERMINALS THOUGH UPSLOPE
FLOW MAY MAINTAIN HIGH TERRAIN SNOW INTO MONDAY MORNING.
OUTLOOK...
A DEEPER UPPER TROUGH WAVE AND A LIFTING SURFACE LOW TO THE
SOUTHEAST WILL INCREASE SNOW CHANCES SUNDAY, FAVORING LOCATIONS
SE OF PITTSBURGH. UNCERTAINTY REMAINS LARGE IN LOCATION OF THE
HEAVIER SNOW BANDS THAT ARE EXPECTED TO DEVELOP (WHETHER NEAR
KPIT OR WELL SE OF THE REGION); THIS VARIANCE MEANS LARGE
VARIANCE IN POTENTIAL SNOWFALL ACCUMULATIONS AND RATES. HIGHER
CONFIDENCE EXISTS IN AT LEAST LIGHTER SNOW DEVELOPING FOR MOST
TERMINALS BY 15Z SUNDAY, WHICH SHOULD MAINTAIN MVFR CONDITIONS
WITH POTENTIAL FOR IFR VSBYS.
ARCTIC TEMPERATURES ARRIVE SUNDAY NIGHT INTO NEXT WEEK BEHIND
THIS EXITING SYSTEM. EXPECT A RETURN OF VFR CONDITIONS, BUT
PERIODS OF GUSTY WIND AND PROLONGED SUB-FREEZING TEMPERATURE
THAT INCLUDES MANY HOURS WITH NEGATIVE WIND CHILLS.
CLIMATE
A PERIOD OF ANOMALOUSLY COLD WEATHER IS EXPECTED TO PASS MONDAY
THROUGH WEDNESDAY THAT WILL CHALLENGE MANY STANDING JANUARY
TEMPERATURE RECORDS. ATTACHED BELOW ARE THE STANDING
CLIMATOLOGY FOR LOCAL SITES. PITTSBURGH HAS A FULL RECORD,
WHILE OTHER SITES ARE PARTIAL RECORDS AND MAY NOT BE FULLY
REFLECTIVE OF HISTORICAL TEMPERATURES:
JANUARY 20TH: HIGH MINIMUM LOW MINIMUM
PITTSBURGH, PA 1F (1985) -18F (1985)
WHEELING, WV 13F (1940) -1F (1940)
MORGANTOWN, WV 3F (1985) -17F (1985)
NEW PHILADELPHIA, OH -3F (1994) -22F (1994)
ZANESVILLE, OH -2F (1985) -17F (1985)
DUBOIS, PA -2F (1985) -19F (1985)
JANUARY 21ST: HIGH MINIMUM LOW MINIMUM
PITTSBURGH, PA 5F (1984) -18F (1985)
WHEELING, WV 12F (2000) -2F (1924)
MORGANTOWN, WV 2F (1985) -18F (1985)
NEW PHILADELPHIA, OH -8F (1985) -19F (1985)
ZANESVILLE, OH 7F (1985) -22F (1984)
DUBOIS, PA 0F (1985) -22F (1985)
JANUARY 22ND: HIGH MINIMUM LOW MINIMUM
PITTSBURGH, PA 10F (1961) -14F (1936)
WHEELING, WV 11F (2014) -4F (2014)
MORGANTOWN, WV 11F (2014) -5F (1984)
NEW PHILADELPHIA, OH 5F (1984) -15F (1994)
ZANESVILLE, OH 13F (2014) -11F (2011)
DUBOIS, PA 8F (2013) -11F (1984)
BELOW IS THE LOWEST DAILY HIGH AND DAILY LOW TEMPERATURES OF THE
21ST CENTURY. THIS ENCOMPASSES ALL DAYS OF ALL MONTHS RUNNING
FROM JANUARY 2000 TO PRESENT:
HIGH MINIMUM LOW MINIMUM
PITTSBURGH, PA 4F (01/07/2014) -10F (01/17/2009)
(02/20/2015)
WHEELING, WV 5F (01/07/2014) -10F (01/07/2014)
MORGANTOWN, WV 7F (01/07/2014) -9F (01/28/2014)
(01/28/2014) (01/29/2014)
NEW PHILADELPHIA, OH 6F (01/16/2009) -18F (01/28/2014)
(01/28/2014)
(02/15/2015)
ZANESVILLE, OH 6F (01/28/2014) -20F (01/29/2014)
DUBOIS, PA 0F (01/07/2014) -17F (02/16/2015)
IN ADDITION, PITTSBURGH HAS NOT SEEN A DAYTIME HIGH BELOW 4F
SINCE JANUARY OF 1994. PITTSBURGH HAS ALSO HAS NOT SEEN 2
CONSECUTIVE DAYS OF HIGH TEMPERATURES LESS THAN 10F SINCE
JANUARY OF 1997. IF YOU EXTEND THIS STATISTIC TO 3 DAYS, YOU
WOULD HAVE TO GO BACK TO FEBRUARY 1899.
THE LAST TIME PITTSBURGH'S MINIMUM TEMPERATURE WAS LESS THAN OR
EQUAL TO -5F WAS DECEMBER 2022. LAST TIME IT WAS BELOW OR EQUAL
TO -10F WAS FEBRUARY 2015. FOR 2 CONSECUTIVE DAYS OF LOWS LESS
THAN OR EQUAL -10F, YOU WOULD HAVE TO GO BACK TO JANUARY OF
1994.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...EXTREME COLD WATCH FROM LATE SUNDAY NIGHT THROUGH THURSDAY
MORNING FOR PAZ007>009-013>016-020>022-029-031-073>078.
OH...EXTREME COLD WATCH FROM LATE SUNDAY NIGHT THROUGH THURSDAY
MORNING FOR OHZ039>041-048>050-057>059-068-069.
WV...EXTREME COLD WATCH FROM LATE SUNDAY NIGHT THROUGH THURSDAY
MORNING FOR WVZ001>004-012-021-509>514.
WINTER STORM WARNING FROM 1 AM SUNDAY TO 9 AM EST MONDAY FOR
WVZ512>514.
SYNOPSIS...WM/MILCAREK
NEAR TERM...SHALLENBERGER
SHORT TERM...MILCAREK/SHALLENBERGER
LONG TERM...MILCAREK
AVIATION...FRAZIER
CLIMATE...MILCAREK
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