Small Craft Advisory 227, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT SUN MAR 16 2014

.ANALYSIS AND UPPER LEVELS...
A LONGWAVE TROUGH REMAINS ENTRENCHED ACROSS THE BERING SEA...WITH
BROAD SOUTHWEST FLOW AT THE MID AND UPPER LEVELS CONTINUING TO GUIDE
STORMS ORIGINATING FROM THE BERING SEA INTO THE SOUTHERN MAINLAND.
THE MOST PROMINENT FEATURE ON THE MORNING WEATHER MAP IS A STRETCHED
OUT FROM THE GULF ACROSS SOUTHWEST ALASKA AND BACK TO A PARENT LOW
OVER THE WESTERN BERING. THIS FRONT IS BRINGING STRONG WINDS AND
SNOW/BLOWING SNOW TO THE BRISTOL BAY AND KUSKOKWIM DELTA REGIONS
TODAY. KODIAK ISLAND IS ALSO SEEING STRONG WINDS AND HEAVY SNOW...BUT
ENOUGH WARM AIR HAS BEEN TRANSPORTED NORTHWARD TO LEAD TO ONLY
LOCALIZED AREAS OF SIGNIFICANT BLOWING SNOW. FURTHER EAST...LINGERING
LOW CLOUDS AND FLURRIES AROUND ANCHORAGE HAVE SPOILED AN OTHERWISE
SUNNY MORNING ACROSS MUCH OF INTERIOR SOUTH CENTRAL. CLOUDS ARE NOW
THICKENING UP AHEAD OF THE APPROACHING FRONT WITH SNOW ALREADY
FALLING OVER THE SOUTHERN KENAI PENINSULA.

.MODEL DISCUSSION...
THE MODELS REMAIN IN GOOD OVERALL AGREEMENT...BUT SEEM TO BE A TAD
SLOW ON FRONTAL PROGRESS INTO SOUTHERN ALASKA THIS MORNING. MODELS
ALSO ARE CONTINUING TO STRUGGLE WITH TRIPLE POINT LOW DEVELOPMENT
NEAR THE BARREN ISLANDS THIS EVENING. THE ECWMF AND GEM ARE TRYING TO
BRING A WEAK CIRCULATION UP COOK INLET TONIGHT...WHILE THE NAM IS
TRYING TO SLIDE MOST OF THE LOW-LEVEL ENERGY OFF TO THE EAST AND
TOWARD PRINCE WILLIAM SOUND. IT IS INCREASINGLY LIKELY THAT THERE
WILL BE A WEAK CIRCULATION THAT FOLLOWS EACH PATH...AND WILL TREND
THAT DIRECTION WITH THE FORECAST. THE LARGEST IMPACTS FROM THIS
DISCREPANCY WILL BE IN THE DISTRIBUTION OF SNOWFALL ACROSS THE
REGION...WITH THE WESTERN TRACK UP COOK INLET MORE FAVORABLE FOR SNOW
AROUND ANCHORAGE.

.SHORT TERM FORECAST...
SOUTHCENTRAL...THE BIG STORY IS THE FRONT MOVING UP THROUGH DEEP
LAYER SOUTHWEST FLOW. KODIAK ISLAND IS IN THE MIDST OF FRONTAL
PASSAGE AT THIS TIME....WITH THE HEAVIEST PRECIPITATION ABOUT TO MOVE
OFF TO THE NORTH. THE EASTERN KENAI PENINSULA WILL GET THE BULK OF
PRECIPITATION FROM THE FRONT OVER THE NEXT 24 HOURS...BUT THE BIG
QUESTION IS HOW MUCH DOWNSLOPING WILL OCCUR FROM KENAI UP TO
ANCHORAGE AND THE MATANUSKA VALLEY. DIFLUENT AND STRONG SOUTH OR
SOUTHWEST FLOW ALOFT FAVORS A SCENARIO WHERE LIGHT SNOW DOES MAKE IT
OVER TO THE LEE OF THE MOUNTAINS...THUS WILL MODIFY FORECAST TO
REFLECT INCREASING CHANCES OF ONGOING LIGHT SNOWFALL AS THE FRONT
PUSHES NORTHWARD TONIGHT. A BETTER CHANCE FOR ACCUMULATING SNOW FOR
ANCHORAGE COMES TOMORROW AS AN EMBEDDED UPPER TROUGH MOVES UP COOK
INLET AND PROVIDES SOME ADDITIONAL ATMOSPHERIC LIFT.
ELSEWHERE...THOMPSON PASS IS LIKELY TO SEE SOME BLOWING SNOW AS THE
FRONT REACHES THE NORTH GULF COAST TOMORROW MORNING...BUT NOT
THINKING WILL REACH WARNING OR ADVISORY LEVELS AT THIS TIME BASED ON
RAPID FRONTAL WEAKENING AND ONLY MODEST UPPER MOMENTUM TO PUSH THE
FRONT INTO THE COASTAL MOUNTAINS.

SOUTHWEST...AN IMPROVING TREND WILL GRADUALLY SPREAD INLAND THIS
EVENING AS STRONG SOUTHEAST WINDS BECOMING WEAKER AND SHIFT TO THE
SOUTHWEST BEHIND THE FRONT. HOWEVER DO NOT EXPECT SIGNIFICANT
CLEARING OR DRYING EVEN BEHIND THE FRONT...AS CYCLONIC ONSHORE FLOW
AT ALL LEVELS WILL CONTINUE TO GENERATE NUMEROUS SNOW SHOWERS WITH
GUSTY WINDS THROUGH MONDAY NIGHT. THESE SHOWERS ARE LIKELY TO BECOME
MORE WIDESPREAD AND SIGNIFICANT MONDAY EVENING OVER BRISTOL BAY AS
THE ORIGINAL LOW FROM THE WESTERN BERING AND ASSOCIATED UPPER TROUGH
MOVE THROUGH THE ONSHORE FLOW AND IMPACT THE COAST.

BERING SEA AND ALEUTIANS...
THE ORIGINAL LOW CENTER IN THE WESTERN BERING IS IN THE PROCESS OF
YIELDING ENERGY TO A DEVELOP CENTER NORTHEAST OF THE PRIBILOF
ISLANDS. STRONG WINDS IN THE BASE OF THIS ORIGINAL CIRCULATION
CONTINUE TO BRING STRONG WINDS IN A NARROWLY FOCUSED BAND TO THE
CENTRAL ALEUTIANS WHICH WILL DIMINISH DURING THE EVENING HOURS.
ELSEWHERE...COLD AIR ADVECTION AND INSTABILITY SNOW SHOWERS WILL
CONTINUE ACROSS MOST OF THE ALEUTIAN REGION THROUGH TOMORROW
AFTERNOON.

.LONG TERM FORECAST...
THE OVERALL WEATHER PATTERN WILL GRADUALLY TRANSITION DURING THE
COURSE OF THE COMING WEEK...WITH HIGH PRESSURE BUILDING OVER THE
NORTHERN BERING AND INTERIOR ALASKA. THIS WILL SHUNT THE STORM TRACK
TO THE SOUTH OF THE GULF OF ALASKA...KEEPING MOST OF THE ACTIVE
WEATHER IN THE ALASKAN DOMAIN OVER THE BERING SEA. TEMPERATURES WILL
MODERATE BACK TOWARD NORMAL FOR MUCH OF THE MAINLAND WITH AN INCREASE
IN SUNSHINE FOR THE LATTER HALF OF THE WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER WEATHER ADVISORY 155 161
MARINE...GALE 119 120 125 129 155 165 170 172 173 174 175 176 177 178
         HVY FREEZING SPRAY 139 140 179
FIRE WEATHER...NONE

AMD MAR 14