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000
FXUS61 KPBZ 011419
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
919 AM EST SUN FEB 1 2015

.SYNOPSIS...
LOW PRESSURE WILL BRING WINTRY WEATHER SUNDAY INTO MONDAY WITH
COLD TEMPERATURES FOR TUESDAY MORNING. ANOTHER COLD FRONT FOR THE
WEDNESDAY NIGHT WILL REINFORCE COLD AIR FOR THE LATTER PART OF
THE WEEK.

&&

.NEAR TERM /THROUGH MONDAY/...
SNW CONTS TO OVERSPREAD THE RGN AS AN INITIAL SHRTWV CROSSES THE
RGN AHD OF A DVLPG SFC LOW AND DIGGING UPR TROF. CRITICAL
THICKNESSES AND MRNG SOUNDINGS INDICATE SNW WL CONT TO BE THE PCPN
TYPE THIS MRNG...BEFORE WRM ADVCTN MIXES AND EVENTUALLY CHGS THE
PCPN OVR TO RAIN S OF I 70 LATE. NO CHGS TO HEADLINES ATTM BUT WL
REEVALUATE AFT REVIEWING 12Z GUIDANCE.

PREVIOUS DISC...SECOND WARM PUNCH ACCOMPANIES APPROACH OF H850 LOW
TONIGHT...WHICH WILL TRACK ACROSS NORTHERN OHIO TO ERIE BY 12Z
MONDAY. INCREASING SW FLOW WILL BRING A RENEWED FEED OF
MOISTURE...AND ALSO THE H850 ZERO LINE TO JUST SOUTH OF I-80.
THUS...SNOW WILL MIX WITH RAIN AND FREEZING RAIN...BEFORE TURNING
TO ALL RAIN FOR THE MAJORITY OF THE CWA BY 06Z MONDAY. SURFACE LOW
PASSES NEAR OR JUST SOUTH OF PIT LATE TONIGHT...WHICH WILL TURN
WINDS TO MORE OF A WESTERLY COMPONENT AND START TO BRING COLDER
AIR BACK IN. EXPECT MOST OF OHIO TO TURN BACK TO SNOW BY 12Z
MONDAY...WITH REST OF CWA FOLLOWING IN QUICK ORDER LATER MONDAY
MORNING. POPS DECREASE AS WELL WITH DEEPER MOISTURE BEING SHUNTED
OFF TO THE EAST.

AFTER COLLABORATION...ELECTED TO DOWNGRADE COLUMBIANA AND BEAVER
COUNTIES TO AN ADVISORY...AND LEFT ALL OTHER HEADLINES INTACT FOR
NOW.  WILL NOT BE SURPRISED IF A FURTHER NORTHWARD MOVEMENT OF
WARNINGS/ADVISORIES IS NEEDED LATER TODAY DEPENDING ON EVENTUAL
STRENGTH OF WARM SURGE.  FOREST/VENANGO/MERCER STILL PICTURED AS
REMAINING MOSTLY SNOW...ALTHOUGH A BRIEF MIX WILL STILL BE POSSIBLE
TONIGHT.  WINTRY MIX AND RAIN WILL HOLD BACK ACCUMULATIONS SOUTH OF
THERE.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY/...
DRY SLOT WILL BEGIN PUSHING EAST OF THE CWA LINE BY MON MORNING AS
WE TRANSITION TO COLD ADVECTION IN THE WAKE OF THE LOW. 12Z MON
MARKS A GOOD TRANSITION POINT IN THE SYSTEM AS MOST PRECIP WILL HAVE
FULLY CHANGED OVER TO SNOW AS THE SFC LOW MOVES EAST THROUGH PA.
STRATIFORM SNOW WILL STILL BE PRESENT THROUGH MID-MORNING AS THE
MID-LEVEL DEFORMATION BAND EVIDENT ON THE LATEST NAM SWINGS
THROUGH...DESPITE A STOUT 500MB JET THAT WILL INJECT DRY AIR INTO
AXIS OF THE UPPER LOW. COPIOUS MOISTURE STILL EXISTS FROM THE SFC TO
700MB AND REMAINS THROUGH THE EARLY EVENING AS THE BOTTOM DROPS OUT
ON THE MID-LEVEL TEMPS.

VERY STRONG CAA WILL BRING 850MB TEMPS DOWN NEARLY 20C IN THE MATTER
OF 12HRS. THE DENDRITIC GROWTH ZONE WILL DROP LIKE AN ANCHOR TO THE
SFC ALLOWING EVERY BIT OF MOISTURE TO PRECIPITATE OUT IN THE FORM OF
SNOW. RAPID COOLING OF THE MID-LEVELS WILL TRANSLATE TO THE SFC
CAUSING ADDITIONAL PROBLEMS AS SFC TEMPS ARE EXPECTED TO DECREASE
THROUGH THE DAY. THIS WILL MEAN THAT UNTREATED PAVEMENT SURFACES
COULD SEE FLASH FREEZING...AND THAT SLICK SPOTS COULD EXIST EVEN IN
THE ABSENCE OF EARLIER HEAVY SNOW OR MIXED PRECIPITATION.

SNOW SHOWERS IN COLD AIR BEHIND THE UPPER LOW COULD PRODUCE AROUND
AN INCH OF FLUFFY ACCUMULATION ACROSS MUCH OF THE LOWLAND
COUNTIES...WITH A LITTLE MORE IN THE RIDGES OF PA/MD/WV AND UP
NORTH. EXPECTING FLUFFY SNOW SHOWERS TO FINALLY TAPER DOWN TO
FLURRIES AND THEN FULLY CEASE BY MIDNIGHT MON AS THE MOISTURE DRIES
UP. TEMPERATURE FORECAST TUES MORNING IS TRICKY...AS SOON AS THE
COLD AIR ARRIVES...ITS GONE AND WAA BEGINS TO KICK IN BY DAY BREAK
TUES. WILL REMAIN BELOW GUIDANCE TUES MORNING AS WE DECOUPLE UNDER
HIGH PRESSURE WITH CLEARING SKIES AND A LINGERING SNOWPACK. CALM
SFC WINDS MAY PRECLUDE THE NEED FOR A WIND CHILL ADVISORY ALONG THE
NORTH TUES MORNING...BUT IT WILL BE DOWNRIGHT COLD REGARDLESS.
TAX

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
THE TEMPORARY EXODUS OF HIGH PRESSURE MARKS THE BEGINNING OF THE
EXTENDED AS A WEAK LOW MOVES THROUGH THE SRN GREAT LAKES BY
MID-WEEK. THIS RELATIVELY DRY SYSTEM SHOULD PRODUCE LIGHT SNOW ALONG
THE NRN PERIPHERY OF THE CWA WEDS INTO THURS...BUT JUST AS
IMPORTANT...THE TRAILING COLD FRONT WILL REINFORCE THE UPPER LEVEL
TROF AS COLD AIR POURS IN TOWARDS THE END OF THE WEEK. HIGH PRESSURE
WILL ENSURE A DRY START TO THE WEEKEND...BUT ANOTHER LOW IS POISED
TO IMPACT THE AREA BY NEXT SUN.
TAX

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
INITIAL BAND OF LIGHT SNOW IN PLACE...WITH MOSTLY MVFR CIG AND
IFR VSBY. EXPECT THIS BAND TO LIFT OUT BY MIDDAY. FKL/DUJ SHOULD
REMAIN IN THE SNOW FOR THE MOST PARTY WITH LOW MVFR/IFR. LOW
CONFIDENCE FORECAST FOR THE AFTERNOON. RENEWED MOISTURE PUSH
TONIGHT AS SURFACE LOW APPROACHES...WITH ALL SITES EXPECTED TO
DROP DOWN TO IFR AND PERHAPS LIFR. FKL/DUJ WILL CONTINUE WITH
SNOW...WHILE OTHER SITES CHANGE TO RAIN OR HAVE A PERIOD OF WINTRY
MIX. DID NOT INCLUDE ICY PRECIP TYPES YET...HOPING FOR MORE
CLARITY IN FUTURE FORECASTS. COLDER AIR RETURNS TO ZZV JUST BEFORE
THE END OF THE TAF PERIOD...WITH RAIN CHANGING BACK TO SNOW.


OUTLOOK.../MONDAY THROUGH THURSDAY/...
WIDESPREAD RESTRICTIONS CAN BE EXPECTED INTO MONDAY AS A LOW
PRESSURE SYSTEM CROSSES THE REGION. NEXT CHANCE FOR WIDESPREAD
RESTRICTIONS WILL BE WITH A WEDNESDAY COLD FRONT.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...WINTER WEATHER ADVISORY UNTIL NOON EST MONDAY FOR OHZ039>041-
     048>050-057>059.
PA...WINTER WEATHER ADVISORY UNTIL NOON EST MONDAY FOR PAZ020-021-
     029-073-074.
     WINTER STORM WARNING UNTIL NOON EST MONDAY FOR PAZ007>009-
     013>016-022-023.
WV...WINTER WEATHER ADVISORY UNTIL NOON EST MONDAY FOR WVZ001>003.

&&

$$