Heavy Snow in Alaska, March 12 to 13, 2006

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM AST SUN MAR 12 2006

.SYNOPSIS...
.SHORT RANGE...DEEP POLAR VORTEX OVER YUKON DROPPING SLOWLY SOUTH
THROUGH MONDAY NIGHT AND OVER PAJN BY 12Z TUE. A VORT MAX
ROUNDING BASE OF THIS UPPER LOW FORECAST TO DROP SOUTH INTO
EASTERN GULF TONIGHT AND INITIATE CYCLOGENISIS TO WEAK
CIRCULATION JUST OF PASI COAST ALONG ARCTIC FRONT. AHEAD OF UPPER
LOW...A WEAK SOUTHERLY FLOW IN MID LEVELS HAS BROUGHT SOME
MOISTURE AND MODERATION TO TEMPERATURES INTO CENTRAL AND SOUTHERN
PANHANDLE THIS MORNING. CLOUDS WILL CONTINUE TO THICKEN ACROSS
COAST AND SOUTHERN HALF OF PANHANDLE TODAY WITH DEVELOPING LOW
PROVIDING ENOUGH LIFT BY THIS EVENING FOR AREAS OF LIGHT SNOW IN
SOUTH CENTRAL AND SOUTHERN  WITH FLURRIES AS FAR NORTH AS PAJN
INTO EARLY EVENING. OVERALL AMOUNTS WILL BE LIGHT TONIGHT. AS
REMNANTS OF OLD FRONT...CURRENTLY IN CENTRAL GULF...BECOMES
ABSORBED BY DEVELOPING LOW NEAR PANHANDLE...CLOUDS AND PRECIP
INCREASE ACROSS SOUTHERN HALF MONDAY WITH 1 TO 2 INCHES OF NEW
POSSIBLE FOR ZONE 26 AND NORTHERN PORTIONS OF 27 AND 28. PAKT AND
PANT EXPECTED TO WARM ABOVE FREEZING ON MONDAY WITH PRECIP
FALLING AS A  MIX OF SNOW AND RAIN AND WILL LEAVE ACCUMULATIONS
AT AROUND 1 INCH. PRECIP CONTINUES AS ALL SNOW FOR ZONE 29 MONDAY
NIGHT WITH AMOUNTS INCREASING TO 3 TO 5 INCHES FOR HYDER BY
TUESDAY MORNING.

SECOND SHOT OF ARCTIC AIR MAKING ITS WAYS SOUTH INTO NORTHERN
LYNN CANAL TODAY...NORTH CENTRAL TONIGHT AND ACROSS SOUTH CENTRAL
MONDAY. COLD AIR FINALLY CLEARS ALL OF SOUTHERN ZONES LATE MONDAY
NIGHT. OVERNIGHT LOW TEMPERATURES WITH THIS AIR MASS EXPECTED TO
BE NEAR RECORD LEVELS BY MONDAY NIGHT NORTHERN HALF. STRONG WINDS
ALSO ACCOMPANYING COLDER TEMPS WITH 10 TO 20 MB FORECAST ACROSS
COAST MOUNTAINS. THIS WILL EASILY SUPPORT GALES THROUGH INNER
CHANNELS AND WITH 50 KT CROSS BARRIER FLOW NEAR MTN RIDGES WILL
ALSO HAVE GUSTS TO 55 MPH AND POTENTIAL FOR TAKU WINDS IN JUNEAU
AREA AND PLAN ON SPREADING WIND ADVISORIES SOUTH THROUGH INNER
CHANNELS MONDAY AND MONDAY NIGHT. THE WIND AND COLD WILL COMBINE
FOR WIND CHILLS DROPPING TO 20 BELOW PAHN/PAGY AND TO 50 BELOW
ZERO FOR WHITE PASS SO WILL KEEP WIND CHILL ADVISORY IN PLACE.
HEAVY FREEZING SPRAY IS EXPECTED THROUGH NORTHERN INNER CHANNELS
AND NEAR OCEAN ENTRANCES THROUGH MONDAY NIGHT.

.LONG RANGE...BY TUE MRNG THERE WL BE A HI AMP 250MB RDG ACRS THE
ERN BERING SEA AND WRN AK.  THE RDG IS ACTUALLY TWO RDGS THAT ARE
MEGG OVR WRN AK.  THERE WL BE A NLY JET ON THE FNT SD OF THE
LEADING RDG THAT WL PUSH SWD ACRS THE ERN GLF AK AND WKN THRU
TUE NGT.  THE UPR RDG WL UNIFY INTO A LG 250MB HI OVR THE BERING
STS AND CHUKCHI SEA ALSO TUE NGT.

THERE IS A SGFNT 250MB LOW OVR THE SEA OF OKHOTSK W/ AN ASSOCD
JET THAT WL PUSH EWD ACRS THE NRN PAC AND GENLY BREAK THRU THE
LOWR PTN OF THE 250MB RDG.  THIS WL CUT OFF A LG CLSD UPR HI OVR
THE CHUKCHI SEA W/ A NR ZONAL JET ALNG THE ALEUTAIN CHAIN AND
ACRS THE GLF AK THRU FRI MRNG.  THIS IS REPORTED AS A GD SNOW
PATN FOR SE AK BUT XPCT THIS PATN TO BE TRANSITORY AS LOW PRESS
PUSHS ACRS INTR AK AND OVR NW CAN DRIVING THE 250MB HI NWD THRU
NXT SUN.

MOST MDLS IN GD AGRMNT BY TUE MRNG THAT THERE WL BE A STG CD ARC
SFC HI INVOF AK/CAN BORDER.  THERE WL ALSO BE A 998MB LOW JUST
INLD FM DXN ENT THAT WL CONT TO CAUSE VERY STG LOW LVL WNDS ALNG
THE ERN GLF CST AND SE AK...SPCLY THE NRN INNR CHNLS.  ALSO
ASSOCD W/ THE WNDS WL BE A VERY CD AMS THAT WL HAVE PUSHD OVR
MOST OF THIS FCST AREA BUT SPCLY THE NRN INNR CHNLS.

THE SFC LOW DVLPS DUE TO MID LVL (700MB - 500MB) LOW THAT PUSHS
SWD UNDR THE NLY 250MB JET ACRS SE AK TUE AND RMNS OVR THE ERN
GLF AK.  IT WL WKN AND DRFT WNWWD OVR THE N CNTRL GLF AK THRU
FRI MRNG.

AS THE NR ZONAL JET PUSHS ACRS THE N PAC A SFC LOW WL DVLP AND
MOV ENEWD ACRS THE PAC TO BE INVOF OF WA/OR THRU THU NGT OR FRI
MRNG. THIS LOW WL BEGIN A SERIES OF LOWS THAT PROGRESSIVELY MOV
FARTHER N ACRS THE NERN PAC AND OVR THE GLF AK IN ASSOCN W/ THE
INCRG ZONAL JET OVR THE GLF AK.  THE FIRST SYS TO EFFECT THE ERN
GLF CST AND SE AK WL PROB BE NXT SAT AS A WK LOW MOVS OVR THE
NERN GLF AK.  W/ THE CD AIR STILL OVR MOST OF SE AK AND ERN GLF
CST THIS SYS WL PROB PROD SNW TO MOST AREAS SAT.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...WIND CHILL ADVISORY 18 THROUGH 6 AM TUE
         WIND ADVISORY 18 19 IN EFFECT THROUGH 6 PM MON
         WIND ADVISORY 20 21 22 25 STARTING 6 AM MON
         WIND ADVISORY 23 24 26 STARTING 6 PM MON

MARINE...GALE 11-12 THROUGH MON NIGHT
         GALE 21 22 31 32 STARTING LATE TONIGHT
         GALE 33 34 35 STARTING MON AFTERNOON
         SMCR WITH STORM FORCE GUSTS OUT OF INTERIOR PASSES 43 51