Area Forecast Discussion
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000
FXUS61 KPBZ 080129
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
829 PM EST SUN FEB 7 2016

.SYNOPSIS...
LOW PRESSURE IS POISED TO SPREAD RAIN AND SNOW OVER THE REGION ON
MONDAY...AND SNOW ON TUESDAY AND WEDNESDAY.

&&

.NEAR TERM /THROUGH MONDAY/...
THE UPR OH REGION IS EXPECTED TO REMAIN DRY THROUGH MIDNGT WITH
RIDGING BETWEEN WRN GREAT LAKES AND SERN COASTAL LOW PRESSURE
SYSTEMS. TEMPERATURES WILL ONCE AGAIN BE ABOVE SEASONAL AVERAGES.

THE WRN LOW WL BE THE PROBLEM FOR THE NXT FEW DAYS AS IT IS FORECAST
TO DEEPEN OVR THE MIDWEST AND PLAGUE THE ARE WITH BROAD ASCENT...DEEP
MOISTURE...WITH SHORTWAVE SUPPORT ROTATING ARND THE CUTOFF LOW.

FOR TONIGHT...MOISTURE AND ASCENT VIA WARM ADVCTN AND WEAKLY
DIVERGENT FLOW ALOFT ARE LIKELY TO SUPPORT PRECIPITATION
DEVELOPMENT OVER WESTERN ZONES TOWARD MORNING...WITH EASTWARD
PROGRESSION AFTER DAYBREAK MONDAY AS PER SLOWER MDL CONSENSUS. AS
THAT SOLN SEEMS REASONABLE GIVEN SBSDNC ON THE WRN FLANK OF THE
EXPLODING SE COAST/WRN ATLANTIC LOW...HAVE ADJUSTED GRIDS FOR THAT
SCENARIO AND RETREATED FROM OVRNGT POPS.

PRECIP TYPE REMAINS AN ISSUE GIVEN THE AFOREMENTIONED WARM ADVECTION
AND LINGERING BOUNDARY LAYER WARMTH. EXPECT A RAIN/SNOW OR A
PRIMARY SNOW SITUATION WITH MELTING AT THE SFC AS THE SYSTEMS COLD
FRONT PLOUGHS TOWARD THE I 77 CORRIDOR DURING THE PREDAWN HOURS.
GIVEN THE TEMP LIMITATIONS AND SLOWER PROGRESSION...ANY LIGHT
ACCUMULATION IS NOT EXPECTED TO BE PROBLEMATIC FOR THE RUSH HOUR.

IN THE HIGHER ELEVATIONS...MODEL SOUNDINGS SUGGEST THE BOUNDARY
LAYER MAY BE COLD ENOUGH FOR PRECIPITATION TO REMAIN PRIMARILY
SNOW THROUGH THE EVENT THERE. THIS WILL LIKELY TRANSLATE INTO
SEVERAL INCHES OF SNOW DURING THE FIRST PUSH OF PRECIPITATION ON
MONDAY AFTERNOON AND EVENING. A WINTER WEATHER ADVISORY HAS BEEN
HOISTED FOR THESE AREAS TO COVER THIS. ALTHOUGH SEVERAL SUCCESSIVE
BOUTS OF SNOW WILL MOVE THROUGH THESE AREAS DURING SUCCESSIVE
PERIODS...IN COORDINATION WITH CHARLESTON/STERLING...THE DECISION
WAS MADE TO JUST COVER THE FIRST ROUND OF SNOW WITH AN ADVISORY
FOR THE MOMENT.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
SOME PROBLEMATIC TRENDS SEEM TO BE DEVELOPING IN THE MORE RECENT
MODEL RUNS VIS-A-VIS THE NORTHWARD PROGRESSION OF A SECONDARY LOW
LEVEL FRONTOGENETICAL REGION ON THE FRONT SIDE OF THE PUSH OF
GENUINE ARCTIC AIR. THE SIGNAL IS QUITE PRESENT ON THE
GFS...NAM...AND CANADIAN GLOBAL...HOWEVER THE LOCATION OF THE BEST
FORCING FOR ASCENT DOES VARY FROM MODEL-TO-MODEL. THE INCOMING 18Z
GFS DOES LINE UP FAIRLY WELL WITH THE CANADIAN GLOBAL...HOWEVER
THE NAM PLACEMENT IS QUITE A BIT FARTHER SOUTH WITH THE
FRONTOGENETICAL ZONE. THIS YIELDS A LOW CONFIDENCE FORECAST IN
TERMS OF NORTHWARD SPREAD OF MORE SUBSTANTIAL SNOW ON MONDAY NIGHT
INTO TUESDAY.

THE COMMON THEMES AMONGST THE GUIDANCE FROM MONDAY NIGHT INTO
TUESDAY GENERALLY REVOLVE AROUND GOOD DEFORMATION FROM THE SURFACE
TO 700 MB ALIGNING WITH FRONTOGENETICAL FORCING AND SOME ATLANTIC
MOISTURE FEED BACK INTO A TROWAL AIR STREAM THAT FEEDS TOWARD THE
OHIO VALLEY. HOWEVER...LOW LEVEL SPECIFICS WILL BE IMPORTANT.
THUS...THE FORECAST WAS FOCUSED ON INCREASING SNOW CHANCES AND
INTENSITY GENERALLY FROM PITTSBURGH SOUTHWARD THROUGH THE PERIOD
WITH BROAD ADVISORY TYPE ACCUMULATIONS DURING THE DURATION.
HOWEVER...IT IS QUITE POSSIBLE THAT THIS FGEN ZONE WILL LINGER IN
SOME PARTICULAR AREA DURING THAT INTERVAL. IF THAT SHOULD
OCCUR...GOOD MICROPHYSICAL SUPPORT FOR MODERATE TO HIGH RATIO
SNOWS COULD WELL RESULT IN WARNING TYPE ACCUMULATIONS IN THE
CORRIDOR IT LINGERS. FRIES

BY WEDNESDAY...THE CUTOFF LOW IS FORECAST TO BE FILLED/PHASED WITH
THE UPR OH UNDER THE AXIS OF A HIGH-AMPLITUDE ERN CONUS TROUGH.
SNOW SHOWER POTENTIAL WILL THUS CONTINUE AS INCREASINGLY COLDER
AIR IS POISED TO FLOW OVR THE REGION AS THAT AXIS SHIFTS EWD. IN
ADDITION...THE LATEST DETERMINISTIC TREND IS TO ROTATE A VORT
CENTER/SHORTWAVE INTO THE BASE OF THAT LOW. PRECIP PROBS WERE THUS
INCRSD FOR WEDNESDAY...CUMULATING IN CATEGORICAL NUMBERS FOR THE
HIGHER ELEVATIONS...BUT DRY ADVCTN AND INCREASING COLD IN THE
SNOW-SOURCE REGION SHOULD DEGRADE EFFICIENCY SO TOTALS WERE NOT
AMPED MUCH AT THIS STAGE OF THE FORECAST PROCESS.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
THE AFOREMENTIONED UPPER TROUGHING PTN IS PROGGED TO CONTINUE
FUNNELING COLD AIR OVR THE AREA THROUGH THE WEEKEND. SUB AVG TEMPS
CAN BE EXPECTED WITH READINGS ABOUT 20 DEGREES UNDER THE NORMALS
ANTICIPATED BY THE WEEKEND. THE I 80 CORRIDOR AND RIDGE ZONES WL
HAVE THE BETTER SNOW SHOWER POTENTIAL DURING THIS PERIOD GIVEN THE
COLD ...OFF-THE-LAKES UPSLOPING FLOW.

THE LONG TERM WAS CONSTRUCTED USING THE SUPERBLEND GUIDANCE.

&&

.AVIATION /02Z MONDAY THROUGH FRIDAY/...
LITTLE TO CHANGE AS VFR IS EXPECTED TO CONTINUE TONIGHT UNTIL
MOISTURE INCREASES IN ADVANCE OF THE COLD FRONT. TIMING OF
PRECIPITATION ONSET HAS CHANGED LITTLE BASED ON THE LATEST MODEL
RUNS...WITH SNOW OR RAIN/SNOW EXPECTED FROM WEST TO EAST ACROSS
THE TERMINALS. A DETERIORATION TO MVFR...WITH PATCHY IFR IS
ANTICIPATED AS THE BOUNDARY CROSSES STARTING 12Z AT ZZV...AND
PROGRESSING EASTWARD INTO WESTERN PA BY 18Z. FURTHER
DETERIORATION IS EXPECTED AS THE TERMINALS THAT EXPERIENCE RAIN
TRANSITION BACK TO SNOW.

.OUTLOOK.../TUESDAY THROUGH FRIDAY/...
RESTRICTIONS CAN BE EXPECTED THROUGH THU WITH THE AREA UNDR UPR TROFG.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...WINTER WEATHER ADVISORY FROM NOON MONDAY TO 1 AM EST TUESDAY
     FOR MDZ001.
OH...NONE.
PA...NONE.
WV...WINTER WEATHER ADVISORY FROM NOON MONDAY TO 1 AM EST TUESDAY
     FOR WVZ512-514.

&&

$$


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