Small Craft Advisory 431, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
214 PM AKDT FRI MAY 30 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL LOW IN THE EASTERN BERING SEA IS MOVING EAST AS
ANOTHER UPPER CENTER IS BRANCHING OFF FROM THIS ACROSS THE ALASKA
PENINSULA. THIS LOW IS BRING COLD AIR ALOFT WITH IT INTO SOUTHWEST
ALASKA THAT WILL PUSH INTO THE SOUTH CENTRAL REGION LOWERING THE
FREEZING LEVELS. THE ASSOCIATED SURFACE LOWS ARE THREE WEAKER LOWS
ONE JUST NORTH OF THE ALASKA PENINSULA A SECOND CENTER IS WEST OF
NUNIVAK ISLAND AND THE THIRD IS IN THE NORTON SOUND AREA. THE
UPPER LOW SOUTH OF KODIAK ISLAND IS SUPPORTING THE STRONG SURFACE
LOW THAT IS MOVING NORTH NORTHEAST TOWARD THE NORTH GULF COAST. IN
ADVANCE OF THIS INCOMING LOW A RIDGE HAS BUILT IN ALONG THE COAST
RESULTING IN THE ISALLOBARIC PUSH CAUSING THE STRONG WIND ACROSS
THE CHUGACH MOUNTAINS AND THROUGH PORTAGE PASS ALONG TURNAGAIN
ARM.

&&

.MODEL DISCUSSION...
THE NAM CONTINUES TO BE THE OUTLIER TODAY THOUGH IT IS COMING MORE
INTO AGREEMENT WITH THE GFS AND ECMWF IN THE SHORT TERM.
DIFFERENCES BECOME MORE PRONOUNCED AS WE PROGRESS THROUGH THE
WEEKEND AS THE NAM PUSHES THE UPPER LOW MORE NORTH AND EAST THAN
THE GFS ECMWF AND UKMET. OVERALL THE GEM REGIONAL AND ECMWF ARE
THE PREFERRED MODELS.

&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...WE ARE STILL ON TRACK WITH THE STRONG GAP
WINDS TODAY THAT ARE EXPECTED TO DECREASE TONIGHT AS THE FRONT
PASSES THROUGH. THE STRONG CROSS BARRIER FLOW RESULTED IN THE
TYPICAL DOWN SLOPE RAIN SHADOW ON THE LEE OF THE KENAI MOUNTAINS.
THE DOWN SLOPING SHOULD DIMINISH SIGNIFICANTLY TOWARD THE MORNING
ALLOWING FOR HEAVIER RAIN SATURDAY MORNING. FOLLOWING THE FRONTAL
PASSAGE THE PRECIPITATION WILL BECOME MORE SHOWERY ON SATURDAY.
THE HEAVIEST PRECIPITATION WILL BE ALONG THE COASTAL AREAS...WHILE
MORE INLAND AREAS LIKE THE COPPER RIVER BASIN AND UPPER SUSITNA
VALLEY WILL BE QUITE A BIT DRIER. THE MODELS ARE STILL BRINGING IN
THE COLDER AIR AND WE ARE STILL EXPECTING A FEW DAYS OF BELOW
NORMAL TEMPERATURES THROUGH THE WEEKEND BEFORE RETURNING TO NORMAL
OR SLIGHTLY ABOVE NORMAL NEXT WEEK. WITH THIS COLDER AIR THE
FREEZING LEVELS WILL DROP ACROSS SOUTH CENTRAL ALASKA AND WE WILL
VERY LIKELY SEE SNOW ON THE MOUNTAINS ABOVE 2000 TO 2500 FEET THIS
WEEKEND.

SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...
WE ARE STILL EXPECTING THE RAIN TO CONTINUE THROUGHOUT SOUTHWEST
ALASKA THROUGH SATURDAY THOUGH IT WILL BECOME MORE SHOWERY IN THE
SOUTHWEST FLOW AND CONSIDERING THE COLD AIR ALOFT WILL SUPPORT A
MORE CONVECTIVE ENVIRONMENT. THE COLD AIR ASSOCIATED WITH THIS
SYSTEM IS LIKELY TO RESULT IN A MIX OF RAIN AND SNOW OVERNIGHT
INTO THE MORNING HOURS ALONG THE BERING SEA COAST AND ESPECIALLY
AT HIGHER ELEVATIONS IN THE MOUNTAINS OF SOUTHWEST ALASKA. BY
SUNDAY MORNING THE UPPER TROUGH SHOULD SWING THROUGH AND WE EXPECT
A BIT OF AN IMPROVEMENT TO THE OVERALL WEATHER FOR SOUTHWEST
ALASKA AS THE CLOUDS WILL BE MORE BROKEN ALLOWING MORE SUN TO
SHINE THROUGH ALONG WITH THE SHOWERS BECOMING MORE SCATTERED.

IN THE ALEUTIANS TO LOW SOUTH OF SHEMYA WILL CONTINUE TO ELONGATE
TO THE EAST AND WEAKEN. FOLLOWING THIS LOW A HIGH WILL BUILD INTO
THE CENTRAL ALEUTIANS SAT AFTERNOON THEN SLIDE OFF TO THE EAST
WITH A GENERALLY FLAT RIDGE PERSISTING ACROSS THE ALEUTIANS AND
BERING SEA. A WEAK SURFACE TROUGH WILL SLIDE ACROSS THE TOP OF
THIS RIDGE BRINGING ANOTHER SHOT OR RAIN TO THE PRIBILOF ISLANDS
SUNDAY AFTERNOON.

&&

.LONG TERM FORECAST...
TEMPERATURES WILL RETURN TO NORMAL OR EVEN BE SLIGHTLY ABOVE
NORMAL BY THE MIDDLE OF NEXT WEEK AS UPPER RIDGING BUILDS OVER THE
EASTERN BERING SEA EXTENDING TO THE SOUTH CENTRAL REGION AND THE
UPPER LOWS REMAIN SOUTH OF THE ALEUTIANS AND IN THE GULF OF
ALASKA.

&&
AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 119 125.
FIRE WEATHER...NONE.

SAM MAY 14