Small Craft Advisory 791, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
131 PM AKDT SAT OCT 11 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW CENTERED NEAR CAPE NEWENHAM. THERE IS
A RIDGE OF HIGH PRESSURE OVER THE WESTERN BERING SEA AND ANOTHER
OVER THE YUKON TERRITORY. ASSOCIATED WITH THE UPPER LOW IS A
DISSIPATING SURFACE LOW/FRONTAL SYSTEM OVER SOUTH CENTRAL ALASKA
AS WELL AS A STRENGTHENING LOW OVER THE SOUTHWEST GULF OF ALASKA.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE COMING INTO BETTER AGREEMENT ON THE
DEVELOPING LOW IN THE GULF...BUT THERE IS STILL CONSIDERABLE
DISAGREEMENT ON THE STRENGTH AND LOCATION OF THE LOW EVEN JUST
24 HOURS INTO THE FORECAST. SOME PREFERENCE IS GIVEN TO THE ECMWF
SOLUTION...BUT WITH A BIT OF A NOD TOWARD THE REGIONAL GEM WHICH
IS STRONGER (BUT SLOWER). FORECAST CONFIDENCE IS A BIT BELOW
NORMAL FOR THE AFTERNOON PACKAGE.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...THE FRONT OVER THE AREA WILL WEAKEN AND
MOVE NORTH TONIGHT...THEN DISSIPATE SUNDAY MORNING. SNOW LEVELS
WILL DROP AS COLDER AIR WRAPPING AROUND THE UPPER PUSHES INTO THE
AREA. THE LOW CURRENTLY IN THE SOUTHWEST GULF WILL RAPIDLY MOVE
NORTH/NORTHEAST EAST TONIGHT AND STRENGTHEN. ON SUNDAY AFTERNOON
THE LOW WILL WRAP AROUND TO THE WEST AND APPROACH KODIAK ISLAND.
FRONTAL PRECIPITATION WILL REACH THE KENAI PENINSULA AND KODIAK
DURING THE AFTERNOON...BUT LIKELY NOT GET FAR INLAND AS THE MAIN
UPPER LOW DIVES SOUTHEAST INTO THE GULF. THE UPPER AND SURFACE
LOWS WILL BECOME VERTICALLY STACKED MONDAY MORNING...AND THEN
RAPIDLY MOVE SOUTHEASTWARD AND OUT OF THE AREA BY MONDAY EVENING.
ALTHOUGH FLOW ALOFT WILL REMAIN SLIGHTLY CYCLONIC MONDAY NIGHT AND
TUESDAY...LITTLE OR NO PRECIPITATION IS EXPECTED AS THE DYNAMICS
ARE WEAK AND OFFSHORE FLOW AT THE LOWER LEVELS WILL KEEP THINGS
SOMEWHAT DRY.

FOR SOUTHWEST ALASKA...THE UPPER LOW CENTERED NEAR CAPE NEWENHAM
WILL SLIDE SOUTHEAST AND BE OUT OF THE AREA BY MONDAY AFTERNOON.
LOW LEVEL FLOW IS FROM THE NORTH/NORTHWEST AND THIS WILL KEEP A
CHANCE OF SHOWERS OVER THE AREA...MAINLY IN THE KUSKOKWIM BASIN
AND DELTA REGIONS.

FOR THE BERING SEA/ALEUTIANS...NORTH TO NORTHWEST FLOW WILL
CONTINUE OVER THE EASTERN ALEUTIANS AND ALASKA PENINSULA THROUGH
TUESDAY WITH LOW PRESSURE OVER THE GULF AND HIGH PRESSURE TO THE
WEST. THE HIGH OVER THE WESTERN BERING WILL SLOWLY SLIDE EAST
THROUGH TUESDAY. BY MONDAY NIGHT A WEAK FRONT WILL WORK ITS WAY
INTO THE WESTERN ALEUTIANS AND THEN INTO THE CENTRAL ALEUTIANS ON
TUESDAY AS LOW PRESSURE MOVES IN FROM THE WEST DRIVEN BY A FAIRLY
STRONG JET OFF OF ASIA (AROUND 150 KNOTS).

&&

.LONG TERM FORECAST (WEDNESDAY THROUGH SATURDAY)...

AN ACTIVE WEATHER PATTERN LOOKS TO CONTINUE THROUGH NEXT WEEK AND
INTO THE WEEKEND AS MULTIPLE SURFACE AND UPPER LEVEL FEATURES
IMPACT THE BERING SEA AND MAINLAND ALASKA. OVERALL...A BROAD
LONGWAVE TROUGH EXTENDS FROM THE EAST COAST OF RUSSIA ALL THE WAY
TO THE PACIFIC COAST OF THE CONTINENTAL UNITED STATES. A SURFACE
LOW IN THE EASTERN GULF OF ALASKA WILL CONTINUE TO SLOWLY WEAKEN
AND DRIFT SOUTHEASTWARD TOWARD THE PANHANDLE...WHICH WILL BRING A
REPRIEVE OF RAIN AND SNOW TO SOUTHCENTRAL ALASKA AND THE GULF
COAST. BY LATE WEDNESDAY...A LOW IN THE NORTHERN PACIFIC WILL
BEGIN TO PHASE WITH THE LOW IN THE GULF OF ALASKA. HOWEVER...MUCH
OF THIS ENERGY WILL BE PUSHED INTO THE PANHANDLE WHERE PERIODS OF
HEAVY RAIN CAN BE EXPECTED...WHILE THE NORTHERN GULF COAST MAY SEE
SCATTERED SHOWERS IN RESPONSE TO THE OVERALL CYCLONIC FLOW OVER
THE GULF. AS SATURDAY ROLLS AROUND...THE RESULTANT LOW IN THE
EASTERN GULF WILL BEGIN TO PHASE WITH THE EXTRATROPICAL REMNANTS
OF TYPHOON VONGFONG...WHICH WILL BEGIN TO INCREASE RAIN CHANCES
ALONG THE NORTHERN GULF COAST. COLDER AIR WILL CONTINUE TO FILTER
IN ACROSS INTERIOR PORTIONS OF SOUTHCENTRAL ALASKA. THIS WILL LEAD
TO TEMPERATURE BEING BETWEEN 4 AND 7 DEGREES BELOW NORMAL THROUGH
THE BEGINNING OF NEXT WEEKEND.

OVER THE BERING SEA...A WEAK VERTICALLY STACKED LOW OVER RUSSIA
WILL PUSH A FRONT ACROSS THE NORTHERN HALF OF THE BERING SEA AND
PRIBILOF ISLANDS ON WEDNESDAY. BY WEDNESDAY AFTERNOON...THE
EXTRATROPICAL REMAINS OF TYPHOON VONGFONG WILL PUSH INTO THE WESTERN
BERING SEA/WESTERN ALEUTIANS AND LIKELY BRING GALE FORCE WINDS TO
THE ALEUTIAN ISLANDS AND SOUTHERN PORTIONS OF THE BERING SEA THROUGH
THE PERIOD. THE TIMING OF THE EXTRATROPICAL LOW HAS SLOWED 12 TO
18 HOURS FROM YESTERDAY AS A SLIGHTLY MORE AMPLIFIED TROUGH OVER
THE NORTH PACIFIC CREATES A BRIEF PERIOD OF SHORTWAVE RIDGING IN
ITS WAKE. REGARDLESS...A WET AND WINDY PERIOD IS EXPECTED THROUGH
FRIDAY WHEN HIGH PRESSURE BEGINS TO BUILD ACROSS THE WESTERN
BERING SEA.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 119 120 130 131 132 136 137 150 155 165 170
                   172 179 180 181 185.
FIRE WEATHER...NONE.

&&

LUDWIG/MCLAY OCT 14