Small Craft Advisory 59, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
429 PM AKST MON JAN 19 2015

.ANALYSIS AND UPPER LEVELS...
THE WEATHER MAP HAS A CLOSED UPPER LEVEL LOW SOUTH OF THE ALEUTIAN
ISLANDS WITH AN UPPER LEVEL RIDGE EXTENDING OUT OF THE PACIFIC
INTO THE BERING SEA THAT BENDS WESTWARD OVER THE LOW. THIS IS
LEAVING THE MAINLAND PART OF THE STATE IN NEARLY ZONAL FLOW EXCEPT
FOR A WEAK TROUGH THAT IS OVER WESTERN AND SOUTHWEST ALASKA WHICH
IS MOVING EASTWARD. THE 250 MB LOW IS WELL SOUTH OF THE FORECAST
AREA AS IT IS RUNNING SOUTH OF THE CLOSED UPPER LEVEL LOW.

AT THE SURFACE THERE IS WEAK HIGH PRESSURE OVER MOST OF MAINLAND
ALASKA. THERE IS A STRONG LOW AROUND 960 MB WELL SOUTH OF ADAK
AND ANOTHER LOW DEVELOPING SOUTHEAST OF KODIAK ISLAND. THIS SECOND
LOW WILL INITIALLY STRENGTHEN AS IT MOVES INTO THE GULF OF ALASKA
TONIGHT AND THEN QUICKLY ELONGATE AND WEAKEN BY TUESDAY NIGHT.
THIS WILL SHIFT THE STORM TRACK INTO SOUTHEAST ALASKA AT THAT
TIME.

&&

.MODEL DISCUSSION...
MODELS ALL SEEMED TO HAVE INITIALIZED WELL WITH THE LOW SOUTHEAST
OF KODIAK ISLAND HEADING TOWARD THE GULF OF ALASKA. THE MAIN
FEATURES OF THE COMPLEX LOW SOUTH OF THE ALEUTIANS ALSO
INITIALIZED WELL. THE MODELS ARE ALL VERY SIMILAR IN THE WAY THEY
MOVE THE LOWS AND THEN ELONGATE THEM INTO A FRONTAL BOUNDARY BY
WEDNESDAY AFTERNOON. THIS WILL STRETCH FROM SOUTH OF THE ALEUTIANS
THROUGH THE MIDDLE OF THE GULF OF ALASKA TOWARD YAKUTAT. THIS PATH
WILL BECOME THE AXIS OF THE MAIN WEATHER FEATURES FOR THE SECOND
HALF OF THE WEEK. BY THURSDAY THE MODELS ARE NOT IN GOOD AGREEMENT
AT ALL WITH THE PLACEMENT OF THE MAIN CENTER OF THE COMPLEX LOW
BUT ALL AGREE IT WILL BE LOCATED SOMEWHERE SOUTHWEST OF KODIAK
ISLAND. MODELS ARE ALSO IN REASONABLE AGREEMENT WITH A FRONT THAT
EXTENDS OUT OF THE COMPLEX LOW INTO THE NORTHERN GULF BY THURSDAY
NIGHT IN A FEATURE THAT WILL BRING PRECIPITATION TO AT LEAST THE
COASTAL AREAS AND POSSIBLY FARTHER INLAND THURSDAY THROUGH FRIDAY
NIGHT. DETAILS ON THE TEMPERATURE PROFILE OF THE FRONT AND THE
IMPACT ON PRECIPITATION TYPE IS WHERE THE MODELS REALLY DIVERGE.
THE ECMWF IS THE COLDEST SOLUTION WITH WEAK COLD ADVECTION OVER
SOUTHCENTRAL INLAND AREAS WHICH WOULD BRING IN SNOWFALL. THE NAM
AND GFS AND MUCH WARMER AND SHOW THE POSSIBILITY OF RAIN OR
FREEZING RAIN. THIS SHOULD BECOME A BIT CLEARER AS WE GET CLOSER
TO THE EVENT.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2...TUESDAY
AND WEDNESDAY)...ONE WEAK WAVE IS HELPING TO TRIGGER SOME SNOW AND
RAIN SHOWERS AS IT TRACKS FROM KODIAK ISLAND TOWARDS KACHEMAK BAY.
THIS FEATURE WILL RUN INTO THE HIGH PRESSURE CENTERED OVER THE
STATE AND BEGIN TO FALL APART OVER KACHEMAK BAY TUE MORNING. THIS
HIGH PRESSURE IS ALSO RESPONSIBLE FOR THE FOG/STRATUS TRAPPED IN
THE ANCHORAGE BOWL. THIS FOG SHOULD BEGIN TO DISSIPATE THROUGH THE
OVERNIGHT HOURS AS THE DOWN-INLET GRADIENT INCREASES.
MEANWHILE...A DEEPENING LOW IN THE GULF WILL BRING A STRETCH OF
GALE FORCE WINDS THROUGH THE NORTHEAST GULF TONIGHT AND TOWARDS
THE COAST BY MORNING. MOST OF THE PRECIPITATION ASSOCIATED WITH
THIS SHOULD REMAIN EAST OF THE AREA SO HAVE ONLY LEFT ISOLATED TO
SCATTERED RAIN AND SNOW SHOWERS IN THE FORECAST FROM VALDEZ TO
CORDOVA.

AFTER THAT...HIGH PRESSURE CENTERED OVER THE WESTERN HALF OF THE
MAINLAND WILL KEEP THE AREA DRY. WITH A WEAK TROUGH OF LOWER
PRESSURE SITUATED OVER THE GULF...THIS WILL KEEP A DECENT OFFSHORE
GRADIENT. THIS MEANS GUSTY OUTFLOW WINDS THROUGH THE TYPICAL AREAS
SUCH AS THOMPSON PASS...SEWARD...AND THE COPPER RIVER BASIN
THROUGH WED. THIS COULD MAKE WEDNESDAY ONE OF OUR SUNNIEST DAYS
FOR THE PAST FEW WEEKS WITH TEMPERATURES VERY NEAR NORMAL.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

A WEAK LOW WILL KEEP SNOW SHOWER THREATS ACROSS BRISTOL BAY AND
THE LOWER KUSKOKWIM VALLEY THROUGH TUESDAY BEFORE INCREASING
NORTHEAST WINDS DEVELOP ON WEDNESDAY...DRYING THE REGION OUT. COLD
TEMPERATURES WILL REMAIN OVER MUCH OF THE AREA...ESPECIALLY ACROSS
THE KUSKOKWIM DELTA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

A MODERATE GALE FORCE FRONT WILL DEVELOP ACROSS THE ALEUTIANS
THROUGH WEDNESDAY...WITH INCREASING NORTHEAST WINDS ACROSS THE
ENTIRE BERING SEA AND ALEUTIAN CHAIN. RAIN AND SNOW WILL GENERALLY
REMAIN OVER THE ALEUTIAN CHAIN...WITH DRIER CONDITIONS ACROSS THE
CENTRAL AND EASTERN BERING.

&&

.LONG TERM FORECAST (WEDNESDAY NIGHT THROUGH SUNDAY)...

THE FORECAST CHALLENGE IN THE LONG RANGE IS THE UPPER LEVEL STORM
SYSTEM THAT IS CURRENTLY CHURNING SOUTH OF THE ALEUTIANS. THIS
SYSTEM SLOWLY MOVES A FRONT INTO THE SOUTHERN BERING MID WEEK
WHICH THEN STALLS AS THE UPPER LOW BECOMES STATIONARY SOUTH OF THE
ALASKA PENINSULA. THE STORM SYSTEM WILL MOVE A WEAK FRONT ACROSS
THE ALASKA PENINSULA AND SOUTHWEST MAINLAND WEDNESDAY NIGHT AND
THEN TO THE NORTHERN GULF OF ALASKA ON THURSDAY. A WARMER AIR MASS
PUSHES SLOWLY ACROSS THE SOUTHERN MAINLAND THROUGH THE END OF THE
WEEK...ALTHOUGH THE WARM ADVECTION IS LIMITED IN NORTHWARD
PROGRESS DUE TO AN ARCTIC LOW PUSHING A COLDER AIRMASS THROUGH
NORTHWEST ALASKA. SHORTWAVES FROM BOTH OF THESE SYSTEMS INCREASE
CHANCES FOR PRECIPITATION ACROSS THE SOUTHERN MAINLAND INTO THE
WEEKEND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 130 155 172 173 174 175 176 177
         HEAVY FREEZING SPRAY 180 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...MSO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...KH