Small Craft Advisory 145, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SAT FEB 15 2014

.ANALYSIS AND UPPER LEVELS...
A BROAD AREA OF SNOW ASSOCIATED WITH A FRONTAL TROUGH AND OVERRUNNING
WAS EVIDENT ACROSS MUCH OF THE EASTERN GULF AND COPPER RIVER BASIN.
MODERATE TO HEAVY SNOWFALL WAS LIKELY OVER THE SOUTHERN COPPER RIVER
BASIN. THERE WERE SEVERAL SURFACE LOWS OVER THE GULF UNDER THE
BROADENING COLD UPPER TROUGH. 500 MB TEMPS THIS MORNING AT KODIAK AND
ANCHORAGE WERE AROUND -40C. UNSTABLE CONDITIONS UNDER THE TROUGH WAS
EVIDENCED BY WIDESPREAD SNOW SHOWERS ACROSS MUCH OF THE GULF. OUT
WEST...THE WEAKENING FRONTAL TROUGH EXTENDING ACROSS THE SOUTHERN
BERING SEA WAS MOVING SOUTH. COLD NORTHERLY FLOW WAS EXPANDING SOUTH
AND WEST ACROSS MUCH OF THE BERING SEA WITH WIDESPREAD OPEN AND
CLOSED CELL CU EVIDENT ON SAT IMAGERY. THE SOUTHWEST MAINLAND WAS
GENERALLY UNDER FAIR SKIES WITH DRY OFFSHORE FLOW.

.MODEL DISCUSSION(SHORT TERM)...
THE UPPER LEVELS ARE FAIRLY SIMILAR ON THE HANDLING OF UPPER WAVES
AND THE POSITIONING OF SYNOPTIC FEATURES. THE SURFACE PATTERN AND QPF
FIELDS ARE SOMEWHAT NOISY IN THE EAST WITH NUMEROUS WAVES PROPAGATING
NORTH THROUGH THE GULF. THE PATTERN IN THE WEST IS CONSIDERABLY MORE
STABLE WITH BROAD NORTHERLY FLOW SETTING UP OVER MUCH OF THE BERING
SEA/ALEUTIANS THROUGH TONIGHT AND CONTINUING INTO EARLY NEXT WEEK.

.SHORT TERM FORECAST...
.SOUTHCENTRAL ALASKA...
SNOW ASSOCIATED WITH A FRONTAL TROUGH AND LOW MOVING INTO THE COPPER
RIVER BASIN WILL LIFT NORTH LATE TONIGHT. CONDITIONS WILL BECOME
INCREASING MORE UNSTABLE OVER ACROSS THE GULF AND SOUTHCENTRAL ALASKA
OVER THE NEXT DAY OR SO WAS COLD AIR MOVING NORTH WITH BROADENING
UPPER TROUGH AND EMBEDDED SHORT WAVES. WIDESPREAD SNOW
SHOWERS...LOCALLY MODERATE TO HEAVY AT TIMES...ARE EXPECTED TO SPREAD
ACROSS THE REGION OVER THE NEXT COUPLE OF DAYS.

SOUTHWEST ALASKA...CLOUDS AND CHANGES OF SNOW SHOWERS WILL INCREASE
ACROSS THE SOUTHWEST MAINLAND AS THE UPPER LOW RETROGRADES NW TONIGHT
AND SUN. SKIES WILL ONCE AGAIN START TO CLEAR MON AS THE MAIN UPPER
LOW CENTER SHIFTS FURTHER SOUTH. THE UPPER LOW MOVING OVERHEAD WILL
BRING MORE ARCTIC AIR FROM THE INTERIOR CONTINUING THE BELOW ZERO
TEMPERATURES THROUGH EARLY NEXT WEEK. WINDS WILL REMAIN GENERALLY
LIGHT FROM THE NORTH WITH STRONGER WINDS TOWARD THE KUSKOKWIM DELTA
COAST.

.BERING SEA AND ALEUTIANS...INSTABILITY SHOWERS CONTINUE OVER THE
CENTRAL AND EASTERN BERING SEA. TEMPERATURES ALOFT AND LOW LEVEL
WINDS WILL REMAIN CONDUCIVE FOR SNOW SHOWERS THROUGH EARLY NEXT WEEK.
A FRONT OVER THE WESTERN/CENTRAL BERING SEA WILL DISSIPATE AND GIVE
WAY TO NORTHERLY FLOW AND SNOW SHOWERS THIS EVENING. THE APPROACHING
FRONT MON NIGHT WILL BRING A CHANCE OF SNOW TO THE WESTERN ALEUTIANS.

.LONG TERM FORECAST...
SOUTHERN ALASKA AND THE BERING ARE IN FOR A PATTERN CHANGE FROM THE
CURRENT OUTFLOW WIND AND BITTER COLD BY THE MIDDLE OF NEXT WEEK. THE
UPPER LOW OVERHEAD NOW WILL WEAKEN AND SHIFT TO THE EAST. AN
INCREASING ZONAL FLOW INFLUENCED BY THE EAST ASIAN JET STRENGTHENING
WILL DEVELOP ALONG THE BAROCLINITY BETWEEN THE ARCTIC AIR STREAMING
OFF THE MAINLAND AND WARMER NORTH PACIFIC REGIME. WITH AN ABSENCE OF
A TRUE BLOCKING PATTERN CONFIDENCE IS HIGHER THAN NORMAL FOR THE
DEVELOPMENT OF A MORE ACTIVE WARMER/WETTER PATTERN FOR SOUTHCENTRAL
BY NEXT WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER WEATHER ADVISORY FOR SNOW 141
MARINE...GALES 170 172 173 174 175 176 177 185 411 412 413 414.
FIRE WEATHER...NONE

RMC FEB 14