Heavy Freezing Spray Warning 138, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT WED MAR 14 2012

.MODEL DISCUSSION...

MODELS IN REASONABLY GOOD AGREEMENT. NAM PREFERRED IN THE SHORT TERM
FOR ITS HIGHER RESOLUTION. TRENDED MID AND LONG RANGE FORECASTS
TOWARDS HPC GUIDANCE. ALL MODELS STRUGGLING WITH PRESSURE GRADIENT
ALONG GULF COAST AND WITH TIMING OF SHORT WAVES ALOFT.

.UPPER LEVELS...

AN UPPER LEVEL CUT OFF LOW CENTERED OVER SOUTHWEST ALASKA DRIFTS
WESTWARD INTO THE SOUTHERN BERING SEA OVER THE NEXT 36 HOURS
WEAKENING SLIGHTLY IN THE PROCESS. MEANWHILE RIDGING OVER EASTERN
ALASKA DAMPENS AND A NEW UPPER LOW FORMS SOUTH OF KODIAK ISLAND. THE
WESTERN CENTER GRADUALLY WEAKENS AND DISSIPATES BY LATE FRIDAY NIGHT
WHILE THE EASTERN CENTER MOVES INTO THE NORTHERN GULF OF ALASKA AND
BECOMES THE DOMINANT FEATURE ALOFT.

.ANALYSIS AND SHORT TERM FORECAST...

COMPLEX LOW PRESSURE PERSISTS IN THE GULF OF ALASKA THROUGH THE
REMAINDER OF THE WEEK...SPREADING CLOUDS AND LIGHT PRECIPITATION
ACROSS SOUTHCENTRAL ALASKA. A SERIES OF SHORT WAVES ALOFT
CIRCULATING ABOUT THE LOW ALOFT MAY TRIGGER PERIODS OF INTENSE BUT
BRIEF SNOWFALL. THE PRESSURE GRADIENT ALONG THE GULF COAST WILL
ALTERNATIVELY SLACKEN AND TIGTHEN AS VARIOUS SMALL SURFACE WAVES
CYCLE THROUGH THE GULF. GUSTY WEST TO NORTHEAST WINDS BLOWING
THROUGH CHANNELED AREAS OF THE CHUGACH AND KENAI MOUNTAINS WILL
DIMINISH BY AFTERNOON BUT SHOULD REDEVELOP EARLY THURSDAY. WEST
WINDS OF 20 TO 35 MPH FROM EAST TURNAGAIN ARM TO WHITTIER ARE
PRODUCING LOCALIZED WHITE OUT CONDITIONS IN SNOW AND BLOWING SNOW.
CONDITIONS ARE EXPECTED TO IMPROVE BY EARLY AFTERNOON WHEN WIND
SPEEDS ARE EXPECTED TO DROP SIGNIFICANTLY.

OUT WEST...A TROUGH OF LOW PRESSURE EXTENDING ALONG THE ALASKA
PENINSULA AND ALEUTIAN CHAIN WILL DISSIPATE BY TOMORROW MORNING.
BROAD NORTHWESTERLY FLOW DEVELOPS ACROSS THE WHOLE OF THE BERING SEA
BY LATE TONIGHT AND PERSISTS INTO THE WEEKEND. AN EXTENSIVE
AREA OF SNOW AND RAIN SHOWERS EXTENDS ACROSS THE ALASKA PENINSULA
AND ALEUTIAN CHAIN. SHOWERS ARE EXPECTED TO LINGER THROUGH THURSDAY
AFTERNOON. A THICK DECK OF STRATUS AND PATCHY FOG SHOULD SET UP
ACROSS THE BERING BEHIND THE EXITING TROUGH LINE.

.LONG TERM FORECAST...

NO CHANGE IN AIRMASS EXPECTED THROUGH THE WEEKEND OR INTO THE COMING
WEEK...THE FLOW PATTERN AT THE SURFACE REMAINS WEAK AND THE MAIN JET
STREAM WILL REMAIN WELL SOUTH OF THE STATE. MAINLAND ALASKA CAN
EXPECT UNSEASONABLY COOL TEMPERATURES TO CONTINUE. CLOUDINESS AND
PERIODS OF LIGHT SNOW WILL ALSO PERSIST...ESPECIALLY FOR COASTAL
AREAS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...HEAVY SPRAY...140 150 155 165 170 411 412 413 414
FIRE WEATHER...NONE.

ASB MAR 12