Small Craft Advisory 123, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
517 AM AKST MON FEB 9 2015

.ANALYSIS AND UPPER LEVELS...
A WEAK UPPER LEVEL LOW SITS OVER THE EASTERN ALEUTIANS WITH A
TROUGH EXTENDING OUT OVER THE NORTHERN GULF. THE LOW ITSELF IS
SLOWLY TRACKING SOUTHWEST WHILE THE TROUGH IS ELONGATING AND
SLOWLY PUSHING NORTH. THIS TROUGH IS CREATING A BROAD AREA OF
INSTABILITY THAT IS ALLOWING FOR MANY MINOR CIRCULATIONS TO FORM.
A SECOND LOW IN THE NORTH PACIFIC IS STALLING OUT SOUTH OF THE
EASTERN ALEUTIANS. HOWEVER...THE WARM FRONT ASSOCIATED WITH THIS
LOW CONTINUES TO PUSH NORTH WITH THOSE WARMER TEMPERATURES. IN
BETWEEN THESE TWO LOWS IS WEAK RIDGING THAT IS MAKING ITS WAY OVER
THE ALASKA PENINSULA.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT UNTIL THE DEVELOPMENT OF A TRIPLE
POINT LOW EARLY ON TUESDAY. THERE IS VARIATION WITH WHERE A CLOSED
LOW WILL FORM ANYWHERE FROM SOUTH OF KODIAK TO THE EASTERN GULF.
FOR THE MOST PART CONSENSUS IS FOR A LOW TO FORM IN THE EASTERN
GULF. TIMING IS ALSO AN ISSUE WITH THE EC BEING THE FASTEST WHILE
THE NAM LAGS BEHIND WITH A WEAKER LOW.

&&

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

A WEAKENING FRONTAL SYSTEM MOVING NORTH WILL BRING SNOW SHOWERS
ACROSS MUCH OF THE NORTH GULF COAST AND EASTERN KENAI. SNOW
SHOWERS WILL BE MORE ISOLATED AND PROBABLY INITIALLY VIRGA WEST
OF THE CHUGACH AS THE MORNING SOUNDING SHOWS DRY CONDITIONS
THROUGHOUT MOST OF THE AIR COLUMN. A SECONDARY FRONT APPROACHING
KODIAK ISLAND WILL BRING SNOW TO KODIAK WHICH SHOULD QUICKLY MIX
OR TURN TO RAIN THIS AFTERNOON. THIS FRONT WILL BRING MORE STEADY
SNOW TO THE NORTH GULF AND KENAI PENINSULA TUE NIGHT AND WED.

GAP FLOWS SHOULD DIMINISH ACROSS THE MATANUSKA VALLEY AND KEYSTONE
CANYON/THOMPSON PASS THIS AFTERNOON. LOCAL GALE FORCE WINDS ARE
EXPECTED FROM SOUTHERN COOK INLET TO SHELIKOF STRAIT TODAY. GALES
WILL BECOME MORE WIDESPREAD TONIGHT AND TUESDAY WITH THE APPROACH
OF THE NEXT NORTH ADVANCING FRONTAL BAND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK UPPER DISTURBANCE WILL GENERATE A FEW SNOW SHOWERS AS IT
LIFTS NORTHWARD THROUGH THE BRISTOL BAY REGION TODAY...WITH THE
KUSKOKWIM VALLEY AND DELTA MAINLY JUST SEEING AN INCREASE IN
CLOUDS THROUGH TUESDAY AS THE WAVE DISSIPATES OVERHEAD. A CHANCE
FOR SNOW WILL PERSIST ACROSS BRISTOL BAY INTO THE MIDDLE OF THE
WEEK AS A NORTH PACIFIC FRONT CROSSES THE ALASKA PENINSULA AND
THEN STALLS AND WEAKENS OVER THE SOUTHEASTERN BERING...WHILE OTHER
AREAS OF THE SOUTHWEST MAINLAND REMAIN GENERALLY DRY WITH GUSTY
NORTHEAST WINDS IN PERSISTENT OFFSHORE FLOW.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE FRONT CURRENTLY TRACKING TOWARDS THE ALASKA PENINSULA WILL
BRING ABUNDANT PRECIPITATION AND GUSTY WINDS TO THE SOUTHEASTERN
BERING OVER THE COMING DAYS AS IT STALLS AND GRADUALLY WEAKENS. A
BRIEF PERIOD OF BLOWING SNOW COULD ACCOMPANY THE ARRIVAL OF THE
FRONT THIS AFTERNOON FROM COLD BAY TO NEAR DUTCH HARBOR...BUT
THESE CONCERNS WILL BE SHORT LIVED AS TEMPERATURES QUICKLY WARM
AND PRECIPITATION BEGINS TO TRANSITION TO RAIN BY THIS EVENING.
MEANWHILE...A TIGHT PRESSURE GRADIENT BETWEEN HIGH PRESSURE NEAR
THE KAMCHATKA PENINSULA AND AN UPPER LOW OVER THE NORTH PACIFIC
WILL HELP TO MAINTAIN GUSTY GALE FORCE WINDS ACROSS MUCH OF THE
CENTRAL BERING THROUGH THE MIDDLE OF THE WEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...THE INITIAL FRONTAL
SYSTEM ASSOCIATED WITH THE LARGE UPPER LEVEL LOW WHICH WILL BE
SETTING UP STATION FOR QUITE A WHILE SOUTH OF THE ALASKA
PENINSULA WILL APPROACH THE NORTHERN GULF COAST TUESDAY NIGHT AND
ROTATE INLAND AS IT FALLS APART ON WEDNESDAY. NORTH TO
NORTHEASTERLY GAP WINDS WILL INCREASE OUT AHEAD OF THIS FRONT IN
LOCATIONS SUCH AS SEWARD...PRINCE WILLIAM SOUND...THOMPSON PASS
AND THE COPPER RIVER DELTA AS THE OFFSHORE GRADIENT TIGHTENS
FAIRLY RAPIDLY TUESDAY NIGHT. WITH A CONTINUING SUPPLY OF LOW
LEVEL COLD INLAND AIR AND OVERRUNNING MOISTURE...WILL NEED TO
KEEP AN EYE ON THESE LOCATIONS FROM A SNOW AND/OR MIXED
PRECIPITATION PERSPECTIVE THROUGH THE DAY WEDNESDAY. ALONG THE
WEST SIDE OF THE CHUGACH MOUNTAINS DOWNSLOPING EAST TO SOUTHEAST
FLOW WILL WRING OUT MUCH OF THE AVAILABLE MOISTURE KEEPING
PRECIPITATION AMOUNTS LIGHTER...AT LEAST FOR THIS INITIAL FRONT.

NUMEROUS ADDITIONAL TROUGHS AND FRONTAL SYSTEMS WILL ROTATE UP AND
OVER THE AREA THROUGH THE REMAINDER OF THE WEEK AND INTO NEXT
WEEKEND WITH EACH ONE WARMING AND MOISTENING THE AIR MASS A BIT
MORE. WHILE RECENT MODEL RUNS (COMPARED WITH THOSE OVER THE LAST
SEVERAL DAYS) HAVE BACK OFF A BIT ABOUT THE AMOUNT OF WARM AIR
BEING PUMPED UP INTO THE AREA BY SOUTHERLY FLOW AND ARE NOW
DIRECTING THE WETTER SYSTEMS A LITTLE FURTHER TO THE EAST...THE
TREND OF STEADILY INCREASING TEMPERATURES WITH PERIODIC ROUNDS OF
PRECIPITATION STILL LOOKS QUITE SOUND.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 119 120 127 128 130 131 132 136 137 138 139 150 155
               160 165 170 171 172 173 174 175 176 177 179 180
         HEAVY FREEZING SPRAY 127 128 130 139 140 165 179 180 185
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...DK
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...JR