Small Craft Advisory 154, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
434 AM AKST WED FEB 18 2015

.ANALYSIS AND UPPER LEVELS...THE WEATHER ROUNDUP ACROSS THE REGION
THIS MORNING FEATURES THE UPPER LEVEL LOW PULLING AWAY TOWARD THE
BERING STRAIT AND A FAIRLY WEAK SURFACE LOW MOVING ALMOST DUE
NORTH OVER THE EASTERN GULF. IN BETWEEN THESE TWO LOWS THE
MAJORITY OF THE MAINLAND REMAINS UNDER WEAK SOUTH TO SOUTHWESTERLY
FLOW. UPPER LEVEL WINDS ARE VERY LIGHT WITH THE ONLY SIGN OF JET
ACTIVITY WELL TO OUR SOUTH IN THE NORTH PACIFIC. THIS JET IS
PROVIDING SOME SUPPORT TO A BROAD LOW COMPLEX THAT WILL EVENTUALLY
MAKE ITS WAY INTO THE CENTRAL ALEUTIANS LATE TONIGHT INTO EARLY
THURSDAY.

&&

.MODEL DISCUSSION...MODELS ARE ALL IN RELATIVELY GOOD AGREEMENT
THROUGH THE FIRST 48 HOURS (THU AFTERNOON) THEN CONTINUE TO
MAINTAIN THE SAME IDEA...EVEN THOUGH SOME OF THE DETAILS DIFFER.
FORECASTS THIS EVENING TRENDED TOWARDS THE HIGHER RESOLUTION
MODELS (NAM/GEM REGIONAL) IN THE SHORTER TERM AND THEN
TRANSITIONED TO AN ECMWF APPROACH. THE BIGGEST TREND WAS TO SLOW
DOWN THE NORTHWARD PROGRESSION OF THE FRONT FROM THE NORTH
PACIFIC. INITIALLY IT WAS LOOKING LIKE THU MIGHT BE THE NICEST DAY
OF THE WEEK FOR PARTS OF SOUTHCENTRAL...BUT IF THE FRONT DOES
INDEED SLOW DOWN...FRI COULD BE QUITE NICE AS WELL.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2...WED AND
THU)...AFTER RECORD HIGH TEMPERATURES OCCURRED ACROSS MUCH OF THE
AREA ON TUE...WE WILL SEE THINGS TREND SLIGHTLY COOLER BUT STILL
REMAIN WELL ABOVE NORMAL TODAY. STARTING OFF THE MORNING...TEMPS
ARE ALREADY ON THE ORDER OF 5 TO 15 DEGREES COLDER THAN
YESTERDAY. WITH MOST PLACES BELOW FREEZING...THIS COULD MAKE FOR A
SLICK MORNING COMMUTE WITH STANDING WATER FROM YESTERDAY
REFREEZING ON SURFACES. AREAS FROM THE SUSITNA VALLEY TOWARDS THE
GULF COAST WILL CLIMB INTO THE LOWER 30S TO LOWER 40S WHILE THE
COPPER RIVER BASIN WILL CLIMB INTO THE MID 20S. THE WEAK LOW IN
THE EASTERN GULF IS REACHING A BIT FURTHER WEST THAN INITIALLY
THOUGHT...BUT IT DOES STILL LOOK LIKE THE PRECIP WILL BE CONFINED
TO AREAS FROM THE PRINCE WILLIAM SOUND EAST. THEN THU SHOULD BE QUITE
A SPECTACULAR DAY ACROSS MUCH OF THE AREA...PENDING THE
DEVELOPMENT OF ANY FOG/LOW STRATUS. A SHARP...FAST SHORTWAVE RIDGE
WILL PASS THROUGH THE AREA KEEPING SKIES MOSTLY CLEAR AND WINDS
LIGHT. TEMPERATURES WILL REMAIN RELATIVELY MILD AND WITH AN EVER-
INCREASING SUN ANGLE...IT SHOULD FEEL QUITE WARM OUTSIDE. THE ONLY
HINDRANCE TO THIS IS THE POTENTIAL FOR FOG...ESPECIALLY ALONG THE
KNIK ARM. EVEN IF IT WAS TO DEVELOP...IT WOULD LIKELY REMAIN
CONFINED TO THE MORNING HOURS AS DRIER AIR CONTINUES TO MOVE IN
THROUGH THE DAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...WED AND THU)...THE
UPPER LEVEL LOW IS MAKING FOR AN EXTENDED PERIOD OF LIGHT
PRECIPITATION STRETCHING FROM THE KUSKOKWIM DELTA THROUGH BRISTOL
BAY. PRECIPITATION HAS TURNED TO ALL SNOW THROUGH THE DELTA
OVERNIGHT BUT WARM TEMPERATURES CONTINUE TO SUPPORT MOSTLY RAIN
THROUGH BRISTOL BAY. AS THE UPPER LEVEL LOW CONTINUES TO SLIDE
NORTH AND FALL APART THROUGH THE DAY...WE SHOULD SEE PRECIPITATION
BECOME MORE SHOWERY THIS AFTERNOON BEFORE COMING TO AN END
OVERNIGHT. THIS COULD SET THE STAGE FOR PATCHY FOG. THE EXTENT OF
THE FOG SHOULD BE LIMITED THOUGH AS WEAK COLD AIR ADVECTION
CONTINUES OVERNIGHT. THROUGH THE DAY THURSDAY...WE SHOULD SEE A
SWITCH TO SOUTHEASTERLY FLOW BRINGING IN WARM AIR ADVECTION WITH
850 MB TEMPERATURES RISING FROM ROUGHLY -6C TO NEARLY +1C AS THE
NEXT WARM FRONT APPROACHES. FOR NOW IT DOES NOT APPEAR THAT ANY
PRECIPITATION ASSOCIATED WITH THIS FRONT WILL REACH THE COAST
UNTIL NEARLY MIDNIGHT THU NIGHT. AS IT DOES SPREAD INLAND...IT
COULD MAKE FOR MORE MIXED PRECIPITATION ISSUES ON
FRIDAY...ESPECIALLY FOR THE COLDER VALLEYS OF THE DELTA AND LOWER
KUSKOKWIM VALLEY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2...WED AND
THU)...THE AREA REMAINS UNCHARACTERISTICALLY QUIET. ONE AREA OF
LOW PRESSURE IS MOVING NORTH TOWARDS THE BERING STRAIT WHILE IT
FALLS APART. THE NORTH PACIFIC LOW TRIES TO STRENGTHEN AS IT
APPROACHES THE CENTRAL AND EASTERN ALEUTIANS...BUT IT OUT-RUNS ITS
UPPER LEVEL SUPPORT LEAVING IT ONLY TO PUSH A WEAK WARM FRONT
THROUGH THE AREA. THERE WILL BE SOME MINIMUM GALE FORCE WINDS
ASSOCIATED WITH THIS LOW. IT WILL CONTINUE TO BE THE MAIN WEATHER
PLAYER AS IT ONLY DRIFTS EVER SO SLOWLY EAST WHILE WEAKENING
THROUGH THIS TIME.

&&

.LONG TERM FORECAST (FRIDAY FEBRUARY 20TH - THROUGH WEDNESDAY
FEBRUARY 25TH)...

ONCE AGAIN...ALASKA WILL BE ASSAULTED BY ANOTHER ROUND OF WARM AND
MOIST NORTH PACIFIC MARITIME AIR FRIDAY THROUGH MONDAY. THE FIRST
NORTH PACIFIC FRONT WILL MOVE ACROSS THE EASTERN BERING SEA AND
SOUTHWEST ALASKA FRIDAY BEFORE MOVING EAST INTO THE GULF OF ALASKA
SATURDAY AND SUNDAY. SOME RAIN AND SNOW WILL BE POSSIBLE INLAND AS
THE FRONT MOVES NORTH...BUT THIS WILL RAPIDLY TURN TO ALL RAIN
INLAND AS WARM AIR ERODES ANY COLD AIR NEAR THE SURFACE. TEMPS
WILL SKYROCKET WELL ABOVE NORMAL ONCE AGAIN...WITH HEAVY
PRECIPITATION IMPACTING MOST OF THE GULF COAST AND KODIAK ISLAND.
THE TROUGH WILL MOVE EAST LATE MONDAY AND TUESDAY...BRINGING A
BRIEF REPRIEVE FROM THE WARM AND WET PATTERN. UNCERTAINTY
NATURALLY GROWS HEADING INTO MIDWEEK...BUT THE SUITE OF GLOBAL
NUMERICAL MODELS ARE HINTING AT A SLIGHTLY MORE PROGRESSIVE WAVE
PATTERN ALOFT ACROSS THE REGION.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 150 155 172 175-177 180.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...MSO
SOUTHCENTRAL ALASKA...MSO
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MSO
LONG TERM...JRA