Winter Storm and High Wind in Alaska, March 7 to 8, 2012

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
551 AM AKST WED MAR 7 2012

.SHORT TERM...A STALLED FRONT EXTENDS FROM THE CENTRAL PANHANDLE
SWWD TO A DEVELOPING LOW OVER THE NE PAC. THE FRONT WILL BEGIN TO
MOVE NWWD AS A WARM FRONT TODAY...AND BE FROM THE NRN PANHANDLE
SWWD INTO THE ERN GULF BY LATE TONIGHT. THE DEVELOPING LOW IS
NEAR 43N/153W AND WILL MOVE NNE TO NEAR 51N/145W AND DEEPEN TO
AROUND 982 MB BY LATE TONIGHT. USED THE 00Z GFS FOR THIS FORECAST
PERIOD.

MAIN CONCERNS WILL BE TIMING...TYPE...AND AMOUNTS OF PRECIP.
RIGHT NOW RADAR/SAT/OBS SHOW PRECIP INCREASING ALONG THE CENTRAL
COASTAL AREA AND SWD. THIS WILL CONTINUE TODAY AND DEVELOP NWD TO
THE NRN AREA THIS AFTERNOON AS MID-LEVEL FLOW BACKS TO S-SW AND
DEEP LAYER WARM ADVECTION DEVELOPS. THE PRECIP SHOULD SLOWLY
DEVELOP NWWD OVER THE NE GULF COASTAL AREA TONIGHT...LIKELY
REACHING THE PAYA AREA AROUND MIDNIGHT.

AS FOR PTYPE...SOME COOLER AND DRIER AIR IS SITTING OVER THE NRN
THIRD OF THE PANHANDLE...MAINLY ALONG AND N OF A PAJN-PAEL LINE.
COLDEST AIR IS AROUND PAYA. AS PRECIP DEVELOPS NWD AND WITH LOWER
LEVEL FLOW EXPECTED TO BE ON THE LIGHT SIDE TO START...MIXED
PRECIP OR SNOW SHOULD DEVELOP ALONG THE PAJN-PAEL CORRIDOR LATE
THIS MORNING AND CONTINUE INTO THE AFTERNOON. AS FRONT MOVES NWD
AND SE WINDS PICK UP...ANY SNOW SHOULD CHANGE TO RAIN ALONG THE
PAJN-PAEL CORRIDOR BY EARLY EVENING. DO NOT EXPECT MORE THAN AN
INCH OR 2 OF SNOW THERE.

FURTHER N IN PAHN/PAGY AREAS WHERE AIRMASS IS COLDER AND LOW
LEVEL N-NW FLOW WILL PERSIST...PRECIP SHOULD START AS SNOW. THEY
SHOULD REMAIN SNOW THROUGH TONIGHT ALTHOUGH PRECIP WILL LIKELY
CHANGE TO RAIN OVER THE FAR SOUTHERN PART OF THE PAHN ZONE.
STILL...LOOKS LIKE A SIGNIFICANT SNOWFALL WILL OCCUR UP N
ESPECIALLY AT HIGHER ELEVATIONS...SO HAVE ISSUED A WINTER STORM
WARNING FOR THOSE ZONES. LOOKS LIKE 4 TO 10 INCHES OF SNOW WILL
FALL OVER THE FAR N TONIGHT...WITH THE MOST NEAR WHITE PASS.

IN THE PAYA AREA...WHERE THE DEEPEST COOLER AIR IS...PRECIP
SHOULD DEVELOP AS SNOW TONIGHT AS FRONT MOVES NWWD TOWARD THEM.
LOWER LEVEL FLOW WILL BE NELY SO THAT WILL KEEP COLD AIR IN
PLACE...WHICH SHOULD ALLOW FOR PRECIP TO REMAIN ALL SNOW TONIGHT.
QUESTION MARK FOR THEM IS HOW HEAVY PRECIP WILL GET. THAT WILL
DEPEND ON FLOW AROUND 850 MB. IF IT BECOMES NELY PRECIP WILL BE
DIMINISHED DUE TO DOWNSLOPE DESPITE STRONG LIFT GOING ON ABOVE
THAT LAYER. IF IT IS MORE SELY...PRECIP COULD BE SIGNIFICANT
TONIGHT. THE GFS MODEL HAS FLOW MORE SELY WHICH WOULD FAVOR
HEAVIER PRECIP. HAVE ISSUED WINTER STORM WATCH BEGINNING AT
MIDNIGHT TONIGHT FOR THE PAYA AREA GIVEN THAT SIGNIFICANT SNOW IS
LIKELY...BUT NOT CERTAIN AT THIS POINT.

OTHERWISE...WINDS WILL PICK UP OVER THE SERN GULF AND SRN INNER
CHANNELS AS LOW MOVES NNE TOWARD THAT AREA. SHOULD SEE GALES OVER
THE SE GULF AND CLARENCE STRAIT TONIGHT...WITH SCA OVER THE
REMAINING SRN CHANNELS. SCA ELY WINDS ARE LIKELY IN ICY STRAIT AND
CROSS SOUND LATER TONIGHT AS WELL AS THE E-CENTRAL GULF. ONLY THE
FAR NERN GULF IS EXPECTED TO REMAIN BELOW SCA LEVEL WINDS BUT SEAS
WILL BE AROUND OR ABOVE 8 FT ESPECIALLY TONIGHT SO SCA FOR SEAS
WILL BE OUT FOR THEM.

&&

.LONG TERM...THE DEVELOPING LOW WILL BE MOVING NORTHEASTERN GULF
THURSDAY AFTERNOON AND THE MOISTURE PLUME DRIVES NORTH INTO THE
PANHANDLE WITH THE MID TROPIC SOURCE REGION...SO AREAS LOCALLY
HEAVY PRECIPITATION THROUGH THU NIGHT AND EARLY FRIDAY. THE SNOWS
OVER THE NORTHERN SECTIONS SHOULD BE TRANSITIONING TO RAIN ON
THURSDAY. THERE IS A FAIR COLD POOL THAT FOLLOWS THE TROUGH BEHIND
THE FRONT AND THIS WILL SHIFT THE RAIN BACK TO SNOW SHOWERS.

ANOTHER LOW SLIPS OUT OF THE BERING SEA AND INTO THE GULF OF
ALASKA WITH ITS FRONTAL SYSTEM FOR LATE FRIDAY. THE GENERAL
PRECIPITATION TYPE SHOULD BE SNOW WITH THIS SYSTEM

THE GENERAL FORECAST TREND DOES NOT LOOK LIKE THE CHANGES ARE THAT
LARGE AS I STAYED WITH THE SAME PATTERN OF THE GFS SOLUTION WITH
HPC FAVORED IN THE LATER PERIODS.

FORECAST CONFIDENCE IS AVERAGE OR BETTER INTO THE WEEKEND AND THEN
LOWERING TO AVERAGE IN THE EXTENDED TIME RANGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER STORM WARNING FROM 3 PM THIS AFTERNOON TO NOON AKST
     THURSDAY FOR AKZ019.
         WINTER STORM WARNING FROM 6 PM THIS EVENING TO NOON AKST
     THURSDAY FOR AKZ018.
         WINTER STORM WATCH FROM LATE TONIGHT THROUGH THURSDAY MORNING
     FOR AKZ017.
MARINE...GALE WARNING FOR PKZ036-041-042.
         SMALL CRAFT ADVISORY FOR PKZ021-022-033>035-043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051-052.

&&

RWT/BEZENEK