Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS61 KPBZ 270811
AFDPBZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
311 AM EST FRI FEB 27 2015

.SYNOPSIS...
A DISTURBANCE WILL BRING CHANCES FOR LIGHT SNOW THROUGH THIS
EVENING. DRY AND FRIGID CONDITIONS WILL END THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
SNOW QUICKLY TAPERING OFF WEST TO EAST ACROSS THE RIDGES AT THIS
HOUR...WILL COMPLETELY EXIT BY 12Z. CURRENT 11-3.9 MICRON FOG
CHANNEL SATELLITE IMAGERY SHOWING SKIES CLEARING QUICKLY BEHIND
THE EXITING SNOW. MID- AND HIGH-LEVEL MOISTURE HAS ALREADY
EVACUATED THE AREA...LEAVING ONLY THE LOW-LEVEL MOISTURE
ASSOCIATED WITH THE DWINDLING SNOW. THE RATE OF CLEARING IS A BIT
FASTER THAN PREVIOUS GUIDANCE INDICATED...BUT THE LATEST HI-RES
MODELS HAVE A GOOD HANDLE ON THIS. ULTIMATELY CUT BACK ON CLOUD
COVER THIS MORNING THROUGH MIDDAY WHERE AT LEAST MOSTLY SUNNY
CONDITIONS ARE EXPECTED.

DESPITE THE MORE POTENT LATE FEBRUARY SUNSHINE...TEMPERATURES WILL
REMAIN COLD THROUGH THE DAY AS COLD AIR CONTINUES TO ADVECT IN.
COLDEST 850MB TEMPERATURES NEAR -22C WILL BE DIRECTLY OVERHEAD
THIS AFTERNOON AS HIGH PRESSURE BUILDS.

AS THE SUN SETS TONIGHT...TEMPERATURES WILL FALL QUICKLY UNDER
CALM...DRY AND MOSTLY CLEAR CONDITIONS. THIS SHOULD OPTIMIZE
RADIATIONAL COOLING FOR MOST LOCATIONS...ESPECIALLY THOSE
LOCATIONS THAT RECEIVED A FRESH COATING OF SNOW. SFC HIGH PRESSURE
WILL BE DIRECTLY OVER THE FORECAST AREA PRE-DAWN SATURDAY. MODELS
CONTINUE TO SHOW WARMING OF THE MID-LEVELS TO THE TUNE OF 6 TO 8
DEGREES C ABOVE THE 00Z MINIMUMS. WITH A LACK OF FLOW BETWEEN THE
SFC AND 750MB...A NEAR SFC INVERSION WILL DECOUPLE THE ATMOSPHERE
AND DROP TEMPERATURES BELOW ZERO FOR MOST LOCATIONS...WELL BELOW
ZERO ACROSS THE NORTHERN ZONES.

AT THIS POINT...THE ONLY FLY IN THE OINTMENT FOR TEMPERATURES AS
LOW AS FORECAST IS POSSIBILITY OF HIGH CLOUDS SHIELDING THE
OUTGOING LONGWAVE RADIATION. THE 00Z NAM IS A LITTLE BIT FASTER IN
INTRODUCING HIGH CLOUDS IN RESPONSE TO A WEAK UPPER LEVEL WAVE.
ULTIMATELY TWEAKED SAT MORNING LOWS...WHICH INCLUDES BUMPING UP
TEMPERATURES ACROSS THE SRN 1/2 OF THE CWA BY A DEGREE OR TWO.

AFTER DAYBREAK SATURDAY...THE NEAR SFC TEMPERATURE INVERSION
SHOULD MIX OUT AND ALLOW FOR A QUICK WARM-UP UNDER MOSTLY SUNNY CONDITIONS.
TAX

&&

.SHORT TERM /SATURDAY/...
WITH HIGH PRESSURE OVERHEAD FRI NIGHT/SAT MORNING TEMPERATURES
SHOULD DROP SIGNIFICANTLY ONCE AGAIN...WITH THE HELP OF STRONG
RADIATIONAL COOLING AND SNOWPACK. TEMPERATURES SHOULD MODERATE ON
SATURDAY HOWEVER...AS WINDS SHIFT TO THE SOUTHWEST AND WARM
ADVECTION ENSUES.

NEXT SYSTEM WILL MAKE ITS APPROACH ON SUNDAY. AS OF NOW...THE
SURFACE LOW LOOKS TO MOVE RIGHT ACROSS THE FORECAST AREA...WITH
WARM ADVECTION AND 850 TEMPERATURES WARM ENOUGH TO BRING A MIX TO
AREAS SOUTH OF I 80...WITH MAINLY SNOW TO THE NORTH. A BRIEF
PERIOD OF FREEZING RAIN IS POSSIBLE BUT NOT ENOUGH CONFIDENCE IN
THE DETAILS TO INCLUDE AT THIS TIME. HAVE HIGHLIGHTED THIS FEATURE
IN THE HWO AS SOME ACCUMULATING SNOW MAY BE POSSIBLE...DEPENDING
ON THE TRACK AND WARM AIR ALOFT.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
A PATTERN CHANGE AND RELATIVE WARM UP THEN SETS UP THROUGH MUCH
OF NEXT WEEK AS WESTERN CONUS TROUGHING DEVELOPS. SHORTWAVES ARE
PROGGED TO EJECT OUT OF THE TROUGH AND MOVE ACROSS THE OHIO VALLEY
REGION IN SOUTHWEST FLOW...KEEPING PERIODIC RAIN AND SNOW CHANCES
THROUGH LATE WEEK. THE BEST CHANCE APPEARS TO BE WITH A
TUESDAY/TUESDAY NIGHT WAVE. MODEL QPF AMOUNTS APPEAR TO BE
OVERDONE IN THE WARM ADVECTION REGIME...BUT WILL MONITOR AS A
DECENT SNOWPACK REMAINS.

ENSEMBLE BASED WPC GUIDANCE OFFERED A REASONABLE START TO THE
FORECAST...THOUGH MADE ADJUSTMENTS TO THE LATEST GFS TO WARM SOME
TEMPS...WITH ADJUSTMENTS FOR PRECIP TYPE BASED ON GFS CRITICAL
THICKNESSES.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
SNOW AND ASSOCIATED MVFR CLOUD COVER IS CONTINUING TO WANE THIS
MORNING. THE LATEST SATELLITE IMAGERY REVEALS CLEARING SKIES WEST
TO EAST. MVFR CEILINGS MAY HOLD IN MGW AND LBE THIS MORNING FOR A
FEW MORE HOURS...BUT ALL SITES ARE EXPECTED TO BE VFR WITH MOSTLY
CLEAR SKIES BY DAYBREAK. HIGH PRESSURE WILL ENSURE VFR CONDITIONS
WITH WEAK SURFACE FLOW THROUGH THE BALANCE OF THE TAF PERIOD. TAX

OUTLOOK.../FRIDAY NIGHT THROUGH TUESDAY/...
RESTRICTIONS ARE LIKELY WITH CROSSING LOW PRESSURE SUNDAY INTO
MONDAY.

&&

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

&&

$$







USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.