Heavy Snow in Alaska, March 14, 2007

SOUTHEAST ALASKA FORECAST DISCUSSION
630 AM ADT WED MAR 14 2007

.SYNOPSIS...
.SHORT RANGE...NOT A TREMENDOUS DIFFERENCE IN THE WEATHER PATTERN
FROM YESTERDAY. LARGE SCALE LOW REMAINS OVER THE NORTHERN GULF OF
ALASKA THIS MORNING. THE ONE BIG DIFFERENCE IS THAT THERE IS AN
EXTENSIVE AMOUNT OF STRATIFORM CLOUD COVER OVER THE EASTERN GULF
INSTEAD OF THE CUMULUS OF THE PREVIOUS FEW DAYS. HOWEVER...THERE
ARE STILL SUBSTANTIAL AREAS OF SHOWERS REMAINING OVER THE
PANHANDLE AND ADJACENT GULF WATERS. THERE WILL BE SOME BEGINNINGS
OF CHANGE TO THE PATTERN LATE IN THE SHORT TERM PERIOD. ANOTHER
LARGE SCALE LOW NOW OVER THE NORTHERN PACIFIC IN THE VICINITY OF
40N/160W WILL BEGIN TO APPROACH THE SOUTHERN GULF LATE THURSDAY
AND INTO FRIDAY. THIS WILL HELP TO EJECT THE CURRENT LOW
NORTHWESTWARD AS IT BEGINS TO WEAKEN.

THE MODELS WERENT IN TOO BAD AGREEMENT AGAIN THIS MORNING AND
THIS FORECAST WAS BASED LARGELY ON THE NAM95. PERSISTENT ONSHORE
FLOW ACROSS MOST OF THE AREA WILL MAINTAIN THE POTENTIAL FOR
SHOWERS ACROSS THE ENTIRE PANHANDLE. THE POSITION OF THE LOW JUST
WEST OF YAKUTAT HAS ALLOWED HEAVY SNOW TO OCCUR THERE THIS
MORNING AND SHOULD CONTINUE INTO THE MID MORNING HOURS. SCATTERED
SNOW SHOWERS WILL CONTINUE ACROSS A LARGE PART OF THE NORTHERN
AND CENTRAL PANHANDLE AGAIN TODAY. THERE WILL LIKELY BE ENOUGH
WARMER AIR ACROSS THE SOUTHERN ZONES TO ALLOW THE SHOWERS TO
BECOME ALL RAIN BY NOON OR SHORTLY THEREAFTER.

DETERMINING SNOW TOTALS WILL ONCE AGAIN BE DIFFICULT. AT THIS
TIME...BELIEVE TOTALS FOR THE MOST PART WILL REMAIN BELOW WARNING
OR ADVISORY CRITERIA...WITH THE EXCEPTION OF YAKUTAT. THERE COULD
BE ISOLATED SPOTS THAT SEE ADVISORY VALUES...BUT NOT ENOUGH TO
WARRANT THE ISSUANCE OF AN ADVISORY.

.LONG RANGE...FAIR AGREEMENT IN MODELS THROUGH THE WEEKEND IN
KEEPING AN ACTIVE WEATHER PATTER ACROSS THE AREA AND NOW MODELS
STARTING TO SUGGEST A MAJOR PATTERN CHANGE FOR PANHANDLE BY
MIDDLE OF NEXT WEEK. USED A MIX OF OFFICIAL, 00Z GFS40/LR, NAM40,
AND MOS FOR GRIDS TODAY.

UPPER AND SURFACE LOW OVER NORTHERN GULF WILL START TO MOVE OFF
TO W AND DISSIPATE FRIDAY AS A NEW LOW DEVELOPING IN THE NORTH
PACIFIC LIFTS NORTH INTO THE EASTERN GULF AND DEEPENS TO AROUND
980 MB. THIS LOW CONTINUES NORTHWEST AND WEAKENS SATURDAY AS
BROAD SURFACE RIDGE BUILDS NORTH ALONG PACIFIC COAST. THE
ASSOCIATED FRONT LIFT NORTH AND SPREAD WARMER AIR MASS INTO
SOUTHERN HALF FRIDAY THEN MOVE OFF TO EAST SATURDAY WITH A RETURN
TO CAA SATURDAY AND SUNDAY.

SE-NE GALES MOVE INTO EASTERN GULF THURSDAY NIGHT AND FRIDAY WITH
A NW GALE IN OFFSHORE WATERS ON BACK SIDE OF LOW. HAVE KEPT INNER
CHANNELS AT SMCR FOR SE WINDS THURSDAY FRIDAY BUT AS LOW PULLS
INTO SE GULF SHOULD SEE GALE FORCE NORTH WINDS WITH FREEZING
SPRAY THROUGH NORTHERN CHANNELS THURSDAY NIGHT AND FRIDAY. EXPECT
SNOW TO SPREAD ACROSS SOUTHERN ZONES THURSDAY NIGHT AND CHANGE
OVER TO RAIN POSSIBLY HEAVY AT TIMES BY FRIDAY. FOR NOW THINK
AREAS NORTH OF CSP-FFIA2 LINE WILL STAY SNOW FOR THE ENTIRE EVENT
AND COULD SEE SIGNIFICANT ACCUMS FRIDAY THROUGH SATURDAY.
SOUTHWEST FLOW ON BACK SIDE OF LOW WILL BRING MORE RAIN AND SNOW
SHOWERS TO THE AREA SATURDAY NIGHT AND SUNDAY. FOR INNER CHANNELS
THIS BECOMES A SE SMCR.

ANOTHER LOW CUTS ACROSS SOUTHERN PANHANDLE MONDAY WITH MORE RAIN
FOR SOUTHERN AND SNOW LIKELY NORTH. WINDS LOOK LIKE THEY WILL
REACH MIN GALE IN COASTAL AND POSSIBLE SOUTHERN WATERS. CURRENTLY
GFS SUGGESTING SNOW LEVELS WILL BE OVER 6K FEET SOUTHERN THIRD.
BY WEDNESDAY A SECOND WARM SYSTEM PUSHES ITS WAY ACROSS THE GULF
AND THROUGH ALL BUT FAR NORTHERN PANHANDLE. THIS SYSTEM COULD BE
THE LIGHT AT THE END OF THE...SNOW TUNNEL.

.AJK...WATCHES/WARNINGS/ADVISORIES
PUBLIC...HEAVY SNOW WARNING TIL 10 AM ADT AKZ017
MARINE...SCA PKZ011>013-036-041>043-051>052

MLR/MM