Small Craft Advisory 983, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
100 PM AKST SUN DEC 8 2013

.ANALYSIS AND UPPER LEVELS...
A RIDGE REMAINS OVER THE SOUTHERN MAINLAND...THOUGH THE HIGHEST
HEIGHTS HAVE NOW BEGUN TO RETREAT TO THE SOUTHEAST. WIDESPREAD
SUBSIDENCE CONTINUES TO PRODUCE A SIGNIFICANT TEMPERATURE INVERSION
IN THE LOWER ATMOSPHERE...WITH DENSE FOG LOCKED IN PLACE PRIMARILY
AROUND THE COOK INLET REGION. WITH NO SIGNIFICANT MECHANISMS TO MOVE
OR ALTER THE AIRMASS THIS FOG REMAINS STAGNANT AND PERSISTENT. A
TIGHTER PRESSURE GRADIENT OVER THE ALASKA PENINSULA IS SPREADING
SLOWLY NORTHWARD TOWARD BRISTOL BAY WITH LIGHT RAIN AND GUSTY
SOUTHEAST WINDS. MEANWHILE OUT WEST...A COMPLEX LOW SOUTH OF THE
ALEUTIANS IS SENDING WEAK IMPULSES OF RAIN AND WIND THROUGH THE AREA
WITH FAIRLY MINOR IMPACT. OVERALL...TEMPERATURES ACROSS MUCH OF THE
STATE REMAIN ABOVE NORMAL AS THE JET STREAM REMAINS OVER THE NORTHERN
HALF OF THE STATE...WELL NORTH OF ITS USUAL POSITION FOR THIS TIME OF
YEAR.

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD OVERALL AGREEMENT ON THE RIDGE OVER SOUTHERN
ALASKA CONTINUING TO BREAK DOWN OVER THE COMING DAYS. THE FIRST
DISTURBANCE TO ENTER THE AREA WILL BE A WEAK SHORTWAVE MOVING IN FROM
THE GULF TOMORROW MORNING...AND WILL BRING GENERALLY LIGHT
PRECIPITATION TO THE SOUTHWEST MAINLAND AND EVEN PARTS OF
SOUTHCENTRAL. THERE IS LARGER UNCERTAINTY REGARDING AN UPPER TROUGH
THAT DROPS DOWN FROM THE NORTH ON TUESDAY. MODELS HAVE STRUGGLED WITH
HOW QUICK AND HOW STRONG THIS FEATURE WILL BE...BECAUSE IT WILL HAVE
LARGE IMPLICATIONS FOR HOW FAR NORTH THE IMPACTS FROM A LOW IN THE
GULF ARE ABLE TO SPREAD BY THE MIDDLE OF THE WEEK. IN THE LAST 24
HOURS MODELS HAVE ALL TRENDED TOWARD THIS UPPER LOW ARRIVING IN
SOUTHERN ALASKA IN TIME TO KEEP MOST OF THE GULF MOISTURE TO THE
SOUTH. THUS WILL KEEP CHANCES FOR PRECIP FOR THE MIDDLE OF THE WEEK
CONFINED TO THE COASTLINE AT THIS TIME.

.SHORT TERM FORECAST...
SOUTHCENTRAL...WITH FLOW IN THE LOWEST SEVERAL THOUSAND FEET OF THE
ATMOSPHERE NON-EXISTENT THE FOG AROUND SOUTHCENTRAL WILL HARDLY BUDGE
THROUGH TOMORROW MORNING. AS MID-LEVEL CLOUDS APPROACH ASSOCIATED
WITH THE AFOREMENTIONED TROUGH FOG SHOULD LIFT A BIT. HOWEVER...THIS
ADDED WEAK LIFT ALSO INCREASES THE LIKELIHOOD OF SOME DRIZZLE OR
FREEZING DRIZZLE TO DEVELOP FROM THE WESTERN KENAI UP TO ANCHORAGE
AND THE MAT-SU VALLEY. MEASURABLE PRECIP IS NOT EXPECTED AT THIS
TIME...AND THUS DO NOT EXPECT ANY ICE ACCUMULATION EVEN IN AREAS THAT
DO REMAIN BELOW FREEZING. STARTING MONDAY EVENING THE ATMOSPHERE WILL
BEGIN A GRADUAL COOL-DOWN AS SEASONABLY COOL AIR FILTERS INTO THE
REGION FROM THE NORTH IN THE WAKE OF THE RETREATING RIDGE. NEXT
CHANCE FOR SNOW IS WEDNESDAY...THOUGH AS MENTIONED IN THE MODEL
DISCUSSION THE TREND IS TOWARD THE LOW IN THE GULF REMAINING TOO FAR
SOUTH TO HAVE MAJOR IMPACT.

SOUTHWEST...THE ATMOSPHERE IS IN A GENERALLY SIMILAR STATE TO
SOUTHCENTRAL...WITH WARM AIR ALOFT AND LOCALIZED AREAS OF BELOW
FREEZING TEMPERATURES AT THE SURFACE. LIFT ASSOCIATED WITH THE
SHORTWAVE APPROACHING THE REGION WILL BE A BIT STRONGER ACROSS THE
SOUTHWEST MAINLAND...AND THUS EXPECT A BETTER CHANCE OF MEASURABLE
(BUT STILL LIGHT) PRECIP ACROSS THE AREA TONIGHT AND TOMORROW.
PRECIPITATION TYPE WILL BE WIDELY VARIABLE ACROSS THE AREA...WITH THE
HIGHEST LIKELIHOOD OF FREEZING RAIN ACROSS WESTERN BRISTOL BAY ZONE
AND INTERIOR PORTIONS OF THE DELTA. WITH MINOR ICE ACCUMULATIONS
EXPECTED A FREEZING RAIN ADVISORY REMAINS IN EFFECT BEGINNING THIS
EVENING.

BERING SEA AND ALEUTIANS...AS THE STORM TRACK SLOWLY SHIFTS FROM
SOUTH OF THE ALEUTIANS INTO THE GULF REGION MOST OF THE BERING WILL
REMAIN IN FAIRLY BENIGN FLOW OVERALL. A WEAK LOW WILL SPIN UP OVER
THE WESTERN BERING MONDAY NIGHT...BUT IMPACTS WILL BE LOCALIZED AND
FAIRLY MINIMAL AS WEAK UPPER LEVEL SUPPORT WILL PREVENT THIS LOW FROM
MUCH INTENSIFICATION. GENERALLY MILD TEMPERATURES WILL CONTINUE
THROUGH THE MIDDLE OF THE WEEK BEFORE A MORE NORTHERLY FLOW GRADUALLY
TAKES HOLD.

.LONG TERM FORECAST...
EXTENDED MODELS ARE STARTING TO AGREE ON THE GENERAL IDEA THAT THE
MAINLAND WILL SLOWLY SINK BACK INTO NORTHERLY FLOW AND COLD
TEMPERATURES BY THE END OF THE COMING WEEK. THE STORM TRACK WILL
SHIFT INTO THE SOUTHERN GULF...WHICH IS LIKELY TO KEEP THE MAINLAND
COLD AND DRY HEADING INTO NEXT WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...DENSE FOG ADVISORY 101 111 121 145
MARINE...NONE
FIRE WEATHER...NONE

AMD DEC 13