Small Craft Advisory 290, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
535 AM AKDT THU APR 2 2015

.ANALYSIS AND UPPER LEVELS...
IN THE UPPER LEVELS THE MAIN SYNOPTIC FEATURES ARE THE TROUGH
OVER CENTRAL ALASKA AND A LARGE COMPLEX LOW IN THE GULF OF ALASKA.
ANOTHER LOW IS SITUATED OVER THE NORTHERN KAMCHATKA PENINSULA WITH
AN AMPLIFIED RIDGE EXTENDING FROM THE NORTH PACIFIC OVER THE
CENTRAL AND EASTERN BERING SEA. THE UPPER LOW OVER THE GULF IS
SUPPORTING THE WEAKENING SURFACE LOW OVER THE SOUTHERN GULF. THIS
LOW HAS AN OCCLUDED FRONT THAT IS WRAPPING NORTH AND WEST AROUND
THE LOW ACROSS THE WESTERN AND NORTHERN GULF. WEAK UPPER
DISTURBANCES CONTINUE TO ROTATE NORTH TO WEST ACROSS SOUTHCENTRAL
ALASKA...TAPPING INTO A RATHER UNSTABLE ATMOSPHERE TO PRODUCE
PERIODS OF RAIN AND OUT OVER THE OPEN WATERS...SCATTERED TO
NUMEROUS RAIN/SNOW SHOWERS OVER THE NORTH GULF COAST...AND
ISOLATED TO WIDELY SCATTERED RAIN/SNOW SHOWERS ON THE INLAND SIDE
OF THE CHUGACH/KENAI MOUNTAIN RANGE.

OUT WEST...THE KAMCHATKA LOW HAS A MARGINAL GALE-FORCE FRONT
PUSHING NORTH ALONG A LINE THIS MORNING FROM THE WESTERN BERING TO
THE CENTRAL ALEUTIANS. OVER THE CENTRAL AND EASTERN BERING INTO
SOUTHWESTERN ALASKA...LOW STRATUS WITH RELATIVELY LIGHT WINDS
PREDOMINATES.

&&

.MODEL DISCUSSION...
OVER THE WESTERN BERING...THE GALE FORCE FRONT WILL CONTINUE TO
MOVE NORTH THROUGH THE WESTERN AND CENTRAL BERING SEA THROUGH
FRIDAY AS THE PARENT LOW MOVES NORTH INTO EASTERN RUSSIA. A FAIRLY
STRONG DISTURBANCE WILL WRAP AROUND THE SOUTHERN END OF THE
KAMCHATKA LOW AND IMPACT THE WESTERN AND CENTRAL ALEUTIANS
THURSDAY NIGHT INTO FRIDAY. MUTUAL AMPLIFICATION OF THE SURFACE
LOW AND THE STRONG UPPER LEVEL DISTURBANCE WILL LIKELY PRODUCE
GALE-FORCE WINDS WITH THE DEVELOPING SURFACE LOW AS IT ENTERS THE
SOUTHERN BERING. THERE IS THE POTENTIAL FOR A NARROW BAND OF
STORM-FORCE GUSTS ON THE BACK SIDE OF THE LOW AS COLDER AIR ALOFT
WRAPS INTO THE BACK SIDE OF THE SYSTEM LATE THURSDAY NIGHT INTO
FRIDAY...BUT THE TIMING AND LOCATION WHERE THIS OCCURS IS STILL
SOMEWHAT IN DOUBT...WITH AN EC/GEM COMBO THE PREFERRED MODEL
CHOICE AND THE GFS SOMEWHAT OF AN OUTLIER AS MODEL DISAGREEMENT
BEGINS TO INCREASE BY FRIDAY OVER THIS REGION.

THE GULF LOW WILL CONTINUE TO MOVE EAST-SOUTHEAST ACROSS THE FAR
SOUTHERN GULF...AND THIS WILL HELP BRING A MORE NORTHERLY AND
DRIER FLOW (AND A BIT MORE STABLE) PATTERN ACROSS SOUTHCENTRAL
ALASKA BY THU AFTERNOON. THIS WILL USHER IN A RETURN OF THE
OUTFLOW GAP TYPE WINDS THROUGH THE CHUGACH MOUNTAINS...THOUGH WE
CURRENTLY DO NOT ANTICIPATE WINDS RISING TO WARNING LEVELS. A
BLEND OF MODELS WITH VERY LITTLE OVERALL CHANGE SYNOPTICALLY IS
PREFERRED IN THIS REGION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LOW COMPLEX OVER THE GULF AND ASSOCIATED FRONT WILL CONTINUE
TO SLIP SOUTH AND EAST THIS AFTERNOON AND TONIGHT. IN
RESPONSE...SHOWERS ALONG THE GULF COAST WILL DIMINISH. OUTFLOW
WINDS CONDITIONS ARE EXPECTED TO DEVELOP THIS MORNING OVER THE
EASTERN KENAI AND NORTH GULF COAST...SLOWING WEAKENING THIS
AFTERNOON. PRESSURE/THERMAL GRADIENTS WILL INCREASE AGAIN SOME
TONIGHT ALLOWING FOR OUTFLOW/GAP WINDS TO REDEVELOP. AN UPPER
TROUGH DROPPING SOUTH OUT OF THE INTERIOR TO OVER SOUTHCENTRAL FRI
AFTERNOON/FRI NIGHT LOOKS A LITTLE MORE INTENSE THEN EARLIER MODEL
RUNS. CURRENT THINKING IS TO INTRODUCE SHOWERS ALONG THE TALKEETNA
MOUNTAINS..AK RANGE...AND COPPER RIVER BASIN DURING THESE TIME
PERIODS.

GULF...GALES OVER THE NORTHERN GULF WILL DIMINISH THROUGH THIS
AFTERNOON...BUT WILL HOLD ON OVER THE WESTERN GULF THROUGH LATE
THIS EVENING BEFORE DIMINISHING.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE DOMINATE WEATHER FEATURES TODAY FOR SW ALASKA WILL BE THE
WEAKENING COMPLEX LOW IN THE GULF OF ALASKA AND THE SHORTWAVE
RIDGE CURRENTLY MOVING EASTWARD ALONG THE CENTRAL ALEUTIANS AND
BERING SEA. THIS IS KEEPING THE REGION IN GENERALLY DRY NORTHERLY
FLOW WHICH WILL LIMIT ANY PRECIPITATION TO THE LIGHT FLURRIES
ALONG THE WESTERN COAST AND THE SOUTHWESTERN PORTION OF THE
ALASKA PENINSULA THIS MORNING. A WELL DEFINED FRONT WILL BEGIN TO
PUSH INTO THE EASTERN BERING SEA AND SW ALASKA FRIDAY MORNING FROM
THE WEST...BRINGING WITH IT WARM SOUTHERLY FLOW AND INCREASING
PRECIPITATION CHANCES...MAINLY ALONG THE COASTAL AREAS AND THE
ALASKA PENINSULA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A SHORTWAVE RIDGE CURRENTLY OVER THE CENTRAL BERING WILL CONTINUE
TO PUSH EASTWARD TODAY AS A FRONT ASSOCIATED WITH A LOW NOW NEAR
NORTHEASTERN RUSSIA PUSHES THROUGH THE EASTERN ALEUTIANS AND THE
PRIBILOF ISLANDS THROUGH TOMORROW MORNING. A DEVELOPING NORTH
PACIFIC LOW WILL ENTER THE REGION NEAR AMCHITKA EARLY FRIDAY
MORNING AND RAPIDLY MOVE TO NEAR THE PRIBILOFS BY LATE FRIDAY
NIGHT. THIS LOW AND ITS ASSOCIATED FRONT WILL BRING MAINLY RAIN TO
THE ALEUTIANS AND A RAIN/SNOW MIX TO THE PRIBILOFS TOMORROW.
MARINE AREAS SOUTH OF 56N CAN EXPECT WIDE SWATHS OF GALE FORCE
WINDS AS THE LOW RAPIDLY MOVES TO THE EAST.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE SOUTHCENTRAL REGION WILL HAVE MOSTLY SUNNY SKIES WITH LIGHT
WINDS THROUGH THE WEEKEND...EXCEPT FOR SOME SCATTERED RAIN
SHOWERS ALONG THE NORTHERN GULF ASSOCIATED WITH A DISSIPATING
WEAK LOW PRESSURE NEAR CAPE SUCKLING. THE COPPER RIVER BASIN WILL
HAVE A CHANCE FOR SNOW SHOWERS WITH AN UPPER LEVEL WEAK
DISTURBANCE MOVING THROUGH THE WEEKEND. THE BERING SEA WILL HAVE A
STORM FORCE LOW TRACKING JUST WEST OF NUNIVAK ISLAND ON SATURDAY
BEFORE MOVING INLAND IN KUSKOKWIM DELTA ON SUNDAY. THIS SYSTEM
WILL BRING WARMER TEMPERATURES WITH THE PREDOMINANT PRECIPITATION
FALLING AS SNOW EXCEPT WITH RAIN MIXING IN AT TIMES OVER THE
INLAND AREAS. THE NEXT NORTH PACIFIC LOW WILL ENTER THE WESTERN
ALEUTIANS BY SUNDAY MORNING AND WILL TRACK EASTWARD ALONG THE
LOWER BERING SEA INTO THE BRISTOL BAY REGION BY TUESDAY. THIS WILL
BRING WIDESPREAD RAIN OUT AHEAD OF THE SYSTEM AND RAIN/SNOW
MIXTURE ON THE BACKSIDE OF THE LOW...EXCEPT FOR ALL SNOW SHOWERS
FARTHER NORTH IN THE BERING WITH THE COOLER TEMPERATURES. THIS
PRECIPITATION WILL SPILL OVER INTO THE SOUTHCENTRAL REGION BY
TUESDAY GOING INTO WEDNESDAY. THIS WILL BRING MORE WARM
TEMPERATURES WITH WIDESPREAD RAIN FROM THE SOUTHWESTERN GULF AREA
SPREADING NORTHWARD INTO THE NORTHERN GULF THROUGH THE MIDWEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...119 120 131 132 150 173 174 175 176 177 185.
         HEAVY FREEZING SPRAY WARNING...180.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...BC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RLF
LONG TERM...PLD