Area Forecast Discussion
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000
FXUS61 KPBZ 290225
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
925 PM EST SUN DEC 28 2014

.SYNOPSIS...
CLOUDS AND DRIZZLE WILL PERSIST THIS AFTERNOON. A RETURN TO
BELOW-NORMAL TEMPERATURES IS EXPECTED MONDAY...WITH UNSEASONABLY
COLD AIR EXPECTED ON WEDNESDAY.

&&

.NEAR TERM /THROUGH MONDAY NIGHT/...
A RAPID EROSION OF DEEP MOISTURE IS EVIDENT BASED UPON THE
ERADICATION OF RADAR RETURNS AND SUBSEQUENT DISSIPATION OF LIGHT
FOG IN SURFACE OBSERVATIONS OVER THE SOUTHEASTERN PORTIONS OF THE
FORECAST AREA. AT THE MOMENT...THE ONLY AREA SEEMINGLY WITH
ABUNDANT LOW LEVEL MOISTURE IS GENERALLY EAST OF THE LAUREL
RIDGE...AND THIS TOO SHOULD START TO DISSIPATE IN THE NEXT SEVERAL
HOURS. MODEL TIME HEIGHT SECTIONS FURTHER ENDORSE THIS IDEA AND
LARGELY ISOLATED SATURATION TO THE LAYER BELOW 5 KFT OR SO ACROSS
ONLY THE FARTHEST SOUTHEAST OF THE RIDGES. ADDITIONALLY...BASED
UPON EVENING OBSERVATIONS...DRIZZLE HAS BECOME A PREDOMINANT
P-TYPE AS OPPOSED TO RAIN...AND THIS FURTHER DEMONSTRATES THE
WEAKENING SATURATED LAYER. HOWEVER...WHILE THIS HAS BEEN
OCCURRING...COLD ADVECTION HAS CONTINUED UNABATED. THIS HAS
ALLOWED FOR OBSERVATIONS IN THE HIGHER ELEVATIONS TO FALL AS LOW
AS 30F AS OF THIS HOUR...WHICH IS A BIT DISCONCERTING.
HOWEVER...BOUNDARY LAYER RH VALUES SHOULD BE SAGGING AND DRIZZLE
WILL LIKELY BECOME LESS COMMON BY LATE THIS EVENING. BARRING ANY
RAPID TEMPERATURE DECLINES...IT WOULD SEEM ANTECEDENT GROUND HEAT
WILL LIKELY PRECLUDE MUCH IN THE WAY OF ANY ICING POTENTIAL FROM
FREEZING DRIZZLE...PARTICULARLY GIVEN THE FACT THAT FREEZING
TEMPERATURES ARE STILL A FAIRLY NEW DEVELOPMENT EVEN AMONGST THE
RIDGES. TO ACCOUNT FOR THIS...DRIZZLE AND FREEZING DRIZZLE HAVE
BEEN ADDED TO THE FORECAST FOR THE EVENING. DUE TO THE FACT THAT
ICE ACCRETION IS NOT EXPECTED TO BE PROBLEMATIC...HOWEVER...NO
HEADLINES ARE ANTICIPATED AT THIS TIME. FRIES

PREVIOUS DISCUSSION FOR MONDAY FOLLOWS...A SLGT INCR IN CLD CVR
WILL BE PSBL ON MON AS BNDRY LYR HEATS AND MIXES AND STRATOCU
DVLPS. SFC HIPRES WILL DOMINATE WX ON MON IN MOST AREAS...BUT A
SHRTWV TROF IS XPCD TO RIDE ALONG THE STALLED FRONTAL BNDRY IN SRN
WV. THIS TROF MAY AID IN NWD DVLPMT OF LGT PCPN FOR THE RDG ZONES
MON AFTN-MON EVE...WHERE INHERITED POPS WERE RETAINED.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
FAST AND LOW-AMPLITUDE FLOW WILL PERSIST IN THE GRTLKS RGN MID-WK.
SHRTWV TROF ENTERING NRN PLNS ON TUE MRNG WILL BE ACCOMPANIED BY
ARCTIC AMS...WHICH WILL MODIFY ONLY SLGTLY AS IT PROGRESSES ESEWD
INTO THE GRTLKS RGN.

THE WAVE WILL PASS THRU THE FCST AREA ON TUE...WITH COLD AIR XPCD
TO FOLLOW QUICKLY. MAXIMA WED WILL BE IN THE UPR TEENS-MID 20S F
OWING TO AGGRESSIVE COLD AIR. ARCTIC AIR ALSO HAS A TALENT FOR
SQUEEZING OUT ANY AVAILABLE MSTR. GIVEN RECENT WARMTH...THIS AMS
LKLY WILL INDUCE LAKE-ENHANCED SNOW DESPITE MODEL INDICATIONS TO
THE CONTRARY. CONSEQUENTLY...POPS WERE INCLD IN NRN ZONES FOR SNOW
SHWRS FROM TUE AFTN-WED AFTN WHEN THE FLOW WILL HAVE AT LEAST A
REASONABLY-ORIENTED DIRECTION. POPS IN RDG ZONES ALSO WERE CONTD
TUE AFTN-TUE EVE AS FLOW WILL HAVE UPSLP COMPONENT. BY WED MRNG...
SFC RDG AXIS WILL BUILD EWD AND SHOULD LWR INVERSION SUFFICIENTLY
TO PRECLUDE SGFNT PCPN IN THE RDGS.

TEMPS WED NGT WILL BE QUITE COLD...WITH MINIMA FALLING TO THE LOW-
MID TEENS. SINGLE-DIGIT WIND CHILLS ARE XPCD WED NGT.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
FLOW WILL BCM VRB AND EVENTUALLY LGT SWLY ON THU AS SFC HIPRES
CNTRD IN THE RGN MOVES EWD IN RESPONSE TO EJECTING SHRTWV TROF IN
SRN PLNS. THE EXIT OF HIPRES WILL HERALD A SLOW WARMING TREND INTO
THE WKEND.

POTENT SHRTWV TROF XPCD TO IMPACT FCST AREA FRI NGT THRU SAT NGT.
BOTH GFS AND ECMWF SHOW REMARKABLE CONSISTENCY...WITH THE SFC
FEATURE PASSING TO THE NW OF THE FCST AREA AND LEADING TO STRONG
WARM AIR ADVCTN THAT SHOULD KEEP PCPN MAINLY LIQUID. ONLY CAVEAT
WILL BE SUB-FREEZING TEMPS AT ONSET...WHICH COULD SPELL A FRZG
RAIN/SLEET SCENARIO. POPS WERE INCRD FRI AFTN-SAT NGT GIVEN
CERTAINTY IN OCCURRENCE OF PCPN...BUT UNCERTAINTY RMNS IN PCPN
TYPE. PCPN LKLY WILL BGN AS WINTRY MIX BFR CHGG TO ALL RAIN BY
MID-DAY SAT...SO THIS PSBLTY HAS BEEN INCLD IN HWO.

OTHER CONCERN WILL BE AMT OF PCPN. STRONG WARM ADVCTN AMID DP SWLY
FLOW AND POTENCY OF WAVE WILL PROMOTE SGFNT RAINFALL...WHICH COULD
LEAD TO LOCALIZED HYDROLOGIC ISSUES. FCST WILL NEED TO BE MONITORED
FOR THIS POTL.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
CIGS WILL CONTINUE THE GENERAL RISING TREND OVERNIGHT...ALTHOUGH
MVFR CONDITIONS WILL HOLD ON A BIT LONGER AT MORE EASTERN
LOCATIONS LIKE MGW AND LBE. HOLDING OFF ON MUCH FOG
OVERNIGHT...BUT THIS MIGHT HAVE TO BE REEVALUATED IF CLOUDS CLEAR
OUT QUICKLY. EXPECTING MOST SITES TO ACHIEVE VFR TOWARDS
15Z...ALTHOUGH MGW WILL BE ON THE EDGE OF AN AREA OF PRECIPITATION
TO THE SOUTH AND EAST.

OUTLOOK.../MONDAY THROUGH THURSDAY/...
PERIODIC RESTRICTIONS CAN BE EXPECTED FOR THE FIRST HALF OF THE
WEEK WITH COLD ADVCTN AND CROSSING DISTURBANCES.

&&

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

&&

$$






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