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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPBZ 271747
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1247 PM EST TUE JAN 27 2015

.SYNOPSIS...
LIGHT SNOW AND FLURRIES WILL PERSIST TODAY BEFORE HIGH PRESSURE
BUILDS AND DECREASES CLOUDS TONIGHT. A COLD WEDNESDAY MORNING WILL FOLLOW.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
ONLY MINOR TWEAKS TO HOURLY TRENDS WERE NEEDED FOR THE EARLY AFTN
UPDATE AS LGT DEFORMATION ZONE SNOW CONTS...ALBEIT WEAKLY. THAT
ZONE WL SHIFT EWD AND CONT TO WEAKEN AS NEW ENGLAND LOW LIFTS
NEWD.

OTHERWISE...DRY SFC HIGH PRES WL BLD EWD UNDR NNWLY FLOW ALOFT
TNGT. A CLEARING SKY...LGT WIND...AND WIDESPREAD SNOW COVER WL
SPPRT A TEMP SIGNIFICANT TEMP DROP WITH SINGLE DIGITS ANTICIPATED
FOR THE ENTIRE AREA...WITH READINGS ARND...OR A FEW DEGREES BELOW
ZERO ANTICIPATED FOR COUNTIES NORTH OF PITTSBURGH. THESE ADJUSTMENTS
WERE COMPLETED WITH A BLEND OF GUIDANCE TRENDS AND PERSISTENCE.
-- End Changed Discussion --

&&

.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
-- Changed Discussion --
WEDNESDAY HIGHS WERE LIMITED TO ROUGHLY 10 DEGREES UNDR THE AVGS
WITH SFC HIGH PRES SLIDING ACRS THE UPR OH REGION. SHRTWV RIDGING
WL MAINTAIN DRY CONDITIONS THROUGH WEDNESDAY NIGHT...BUT STRENGTHENING
WARM ADVCTN IN ADVN OF TROUGH DIGGING RAPIDLY TWD THE WRN LAKES WL
IMPROVE THE THURSDAY MRNG LOWS.

THE NAM...GFS...ECMWF FORECASTED CENTER TRACK OF THAT SYSTEM RMNS
N OF THE REGION...HENCE CONTD WARM ADVCTN ON THE ERN FLANK IS
EXPECTED TO LIMIT SNOW ACCUMULATION POTENTIAL. HOWEVER...THE
SCENARIO WL FAVOR A WINTRY MIX COMPLICATED BY COLD SURFACES
LEFTOVER OVR FM THE PREVIOUS TWO NGTS.

ANY PCPN THAT DOES TURN TO RAIN WL STILL HAVE THE POTENTIAL TO
FREEZE ON CONTACT. IN ADDITION...THE DRY LAYER WHICH IS PROGGED TO
LIMIT PCPN ONSET IN THE MRNG MAY OFFSET A WEAKER WARM ADVCTN
REGIME VIA WET BULBING. BOTTOM LINE IS THAT FORECAST WL FEATURE A
WINTRY MIX WITH A CHANGE TO SNOW WITH PASSAGE OF THE SYSTEMS COLD
FRONT ON THURSDAY EVENING. A HAZARDOUS WEATHER OUTLOOK WAS ALSO
INCLUDED FOR THE FREEZING RAIN POTENTIAL. QPF WAS COMPLETED USING
HPC GUIDANCE TRIMMED FOR LOCAL POP TRENDS WITH SNOW TOTALS
ADJUSTED FOR SFC TEMP EXPECTATIONS.

IN THE WAKE OF THE FRONT...COLD TEMPS WL AGAIN VISIT THE REGION.
DEPTH OF COLD AT MOMENT LKS SUFFICIENT TO SPPRT SNOW SHWRS...SO
LIKELY POPS WERE MAINTAINED OVR THE RIDGES PAST DAYBREAK DESPITE
DRY ADVCTN AND LACK OF ANY REINFORCING LAKE ERIE MSTR DUE TO ICE.
-- End Changed Discussion --

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
COLD ARCTIC HIGH SHIFTS EAST INTO SATURDAY WITH SNOW SHOWERS IN
NORTHWEST FLOW FRIDAY ENDING FRIDAY NIGHT. WITH 850MB TEMPS
PROGGED NEAR -20C BY 00Z SATURDAY TEMPERATURES FRIDAY WILL BE
STEADY OR FALL. CLOUDS SHOULD BEGIN TO BREAK AS CENTER OF HIGH
MOVES INTO REGION FRIDAY NIGHT...WITH LOWS BELOW ZERO NORTH AND
SINGLE DIGITS SOUTH. IF CONDITIONS GO CLEAR AND CALM FRIDAY NIGHT
MAY GO BELOW ZERO ACROSS THE ENTIRE REGION. TEMPERATURES RECOVER
TO MAINLY THE 20S SATURDAY. A SIGNIFICANT STORM LOOKS POSSIBLE FOR
SUNDAY INTO EARLY MONDAY BEFORE ARCTIC AIR RETURNS TO START THE
WORK WEEK.

&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...

-- Changed Discussion --
MVFR CIGS WILL CONTINUE THROUGH THE AFTERNOON INTO THE EVENING
HOURS. MVFR/VFR VISIBILITY SNOW WILL ALSO CONTINUE...WITH AN
OCCASIONAL IFR VISIBILITY POSSIBLE. SNOW SHOULD COME TO AN END
DURING THE EVENING HOURS. CEILINGS SHOULD BEGIN TO SLOWLY LIFT AS
CLOUDS SCATTER OUT DURING THE LATE EVENING INTO EARLY MORNING HOURS.
CLEAR SKIES ARE EXPECTED BY SUNRISE. A GUST TO 15-20 KTS IS POSSIBLE
THROUGH MIDNIGHT WITH WINDS VEERING FROM NORTHWEST TO WEST...AND
WINDS SHOULD DROP UNDER 5 KT FOR WEDNESDAY.

.OUTLOOK.../WEDNESDAY THROUGH SUNDAY/...
WIDESPREAD RESTRICTIONS ARE EXPECTED ON THURSDAY WITH CROSSING LOW
PRESSURE. FREEZING PRECIPITATION IS POSSIBLE AT ALL TERMINALS
THURSDAY WITH PRECIPITATION CHANGING OVER TO SNOW BY MIDNIGHT
FRIDAY. RESTRICTIONS WILL CONTINUE INTO FRIDAY. VFR CONDITIONS ARE
EXPECTED SATURDAY...WITH ANOTHER SET OF RESTRICTIONS POSSIBLE SUNDAY.
-- End Changed Discussion --

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...NONE.
OH...NONE.
PA...NONE.
WV...NONE.

&&

$$

15/33