Heavy Snow in Alaska, April 7, 2008

SOUTHEAST ALASKA FORECAST DISCUSSION
1100 AM ADT MON APR 7 2008

.SYNOPSIS...
.SHORT RANGE...THE LATEST SATELLITE IMAGERY SHOWS A WEAK
VERTICALLY STACKED LOW OVER THE NORTHERN GULF THAT HAS SLOWED
DOWN ITS EASTWARD PROGRESSION TO KEEP MODERATE TO HEAVY SNOW
SHOWERS OVER THE PAYA AREA THIS MORNING. THESE SHOWERS WILL
PERSIST INTO THE AFTERNOON SO A HEAVY SNOW WARNING WAS ISSUED
UNTIL 4 PM THIS AFTERNOON. THE REST OF THE PANHANDLE IS UNDER
MOSTLY CLOUDY SKIES WITH SCATTERED TO NUMEROUS SNOW SHOWERS
MOVING ONSHORE. SOME OF THESE SNOW SHOWERS WILL MIX WITH RAIN
OVER THE SOUTHERN THIRD THIS AFTERNOON WITH DAY TIME HEATING AND
WEAK WAA. SNOW AMOUNTS WILL VARY DEPENDING ON SHOWERS MOVEMENT
BUT ACCUMULATION WILL BE UP TO 1 INCH. THE WINDS ARE GENERALLY
LESS THAN 15 MPH WITH THE STRONGEST SOUTH WINDS OVER NORTHERN
LYNN CANAL TO 25 MPH WITH HIGHER GUSTS. THE WINDS OVER THAT AREA
WILL SLOWLY DIMINISH THROUGH THE DAY AS THE SURFACE RIDGE OVER
THE AREA SLIDES TO THE EAST.

THE UPPER LEVEL LOW OVER THE NORTHERN GULF ATTM WILL PHASE WITH A
SOUTHERN VORT MAX TO FORM A TROF OVER THE EASTERN GULF TONIGHT
AND MOVE OVER THE PANHANDLE THROUGH TUESDAY. THIS WILL INCREASE
THE ONSHORE FLOW ALONG WITH STRONG UPPER LEVEL DYNAMICS OVER THE
AREA. SO THERE WILL BE CATEGORICAL PRECIP OVER MOST OF THE
PANHANDLE TONIGHT WITH THE EXCEPTION TO THE NORTHERN GULF AND FAR
NORTHERN INNER CHANNELS AS THEY WILL SEE CHANCE TO LIKELY POPS
TONIGHT INTO TUESDAY. THERE WILL BE DECREASING TREND IN POPS
THROUGH TUESDAY AS THE UPPER LEVEL TROF MOVES THROUGH THE
PANHANDLE DURING THE DAY. SO WILL KEEP THE FAR NORTHERN AREAS ON
THE DRY SIDE FOR MOST OF THE DAY AND DROPPING THE POPS TO CHANCES
FROM WEST TO EAST BY THE AFTERNOON OVER THE REST OF THE AREA.

THE FORECAST CHALLENGE FOR TODAY WILL BE P-TYPE. THE COLD AIR
ALOFT WILL KEEP MOST OF THE PRECIP OVER THE NORTHERN HALF AS SNOW
THROUGH TONIGHT WITH THE SOUTHERN HALF MIXING WITH RAIN. AS FOR
TUESDAY THE SOUTHERN THIRD WILL CHANGE TO ALL RAIN WHILE THE
CENTRAL WILL SEE A MIX IN THE MORNING THEN BECOMING RAIN IN THE
AFTERNOON. THE NORTHERN AREAS MAY STAY ALL SNOW BUT WITH DAYTIME
HEATING THERE MAY BE SOME AREAS OF MIX PRECIP BY THE AFTERNOON.
ABJ

.LONG RANGE...CONSISTENCY OF MODEL OUTPUTS IS STILL POOR WITH THE
LATEST RUN BUT INITIAL CONDITIONS HAVE BECOME MUCH BETTER THAN
YESTERDAY TO YIELD AN AVERAGE CONFIDENCE WITH MODEL CONSENSUS.
WOULD LIKE TO STAY WITH THE LATEST GFS SOLUTIONS FOR THE LONG
TERM FORECAST TO MAINTAIN THE INHERITED GRIDS AS CLOSE AS
POSSIBLE WITH THE 12Z RUN. EXPECT NO BIG CHANGES FOR THE
AFTERNOON PACKAGE. AS THE PACIFIC HIGH CONTINUES MARCHING
EAST...A WEAK RIDGE FORMS SOUTH OF THE FORECAST AREA. THIS WILL
WEAKEN THE TROUGH ACROSS THE EASTERN GULF AND SOUTHEAST ALASKA
THROUGH WEDNESDAY. ALONG THE TRAILING EDGE...WIND MAY PICK UP TO
GENERATE BREEZY CONDITIONS OVER NORTHERN AND CENTRAL COASTAL
SECTIONS THROUGH WEDNESDAY. OTHERWISE...A QUASI-ZONAL FLOW WILL
FOLLOW THROUGH LATE FRIDAY AHEAD OF THE NEXT INCOMING TROUGH IN
THE CENTRAL GULF FRIDAY AFTERNOON. THIS TROUGH DEEPENS IN TIME AS
AN OMEGA BLOCK DEVELOPING EAST OF THE AREA. AS THE BLOCKING RIDGE
SLOWLY MOVING EAST AND THE TROUGH STARTS MOVING INTO THE EASTERN
GULF SATURDAY MORNING...A LEADING EDGE OF FRONTAL BOUNDARY WILL
DRIFT NORTHEASTWARD AND REACH SOUTHWEST COAST SATURDAY AFTERNOON
AND THE TROUGH WILL CONTINUE TO AFFECT THE PANHANDLE THROUGH
EARLY NEXT WEEK. AHN

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...HVY SNOW WRNG...AKZ017.
MARINE...SCA...PKZ022-036-041>043-051-052.