Small Craft Advisory 401, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
513 AM AKDT SUN MAY 10 2015

.ANALYSIS AND UPPER LEVELS...
THE REMNANTS OF THE NORTH PACIFIC LOW THAT BROUGHT WIDESPREAD RAIN
TO THE GULF COAST LAST WEEK HAS BECOME VERTICALLY STACKED AS IT
CONTINUES TO SLOWLY WEAKEN OVER THE WESTERN GULF. RAIN SHOWERS
OVER THE WESTERN GULF COAST ARE BEGINNING TO DIMINISH AS
SHORTWAVES CONTINUE TO MOVE INLAND. OVER THE ALEUTIANS...AN
ELONGATED LOW STRETCHING FROM THE NORTH CENTRAL BERING INTO THE
EASTERN ALEUTIANS IS BRINGING GUSTY SOUTHERLY WINDS AND RAIN TO
THE AREA. THIS SYSTEM IS TRACKING TO THE EAST TOWARDS THE GULF
WHERE IT WILL ABSORB THE GULF LOW LATE TONIGHT.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN VERY GOOD AGREEMENT WITH THE DEVELOPING LOW
SOUTH OF THE AKPEN THROUGH MONDAY...WITH JUST SOME MINOR
DISAGREEMENT WITH LOW POSITION AND INTENSITY THAT SHOULD HAVE
MINIMAL IMPACT ON THE OVERALL FORECAST CONFIDENCE. ON
TUESDAY...LARGER DISCREPANCIES ARISE WITH THE STRENGTH OF THE NEXT
NORTH PACIFIC LOW THAT WILL APPROACH THE WESTERN ALEUTIANS. THE
MODELS ARE ALL TRENDING STRONGER...WITH GOOD AGREEMENT THAT THIS
WILL BE AT LEAST A GALE FORCE LOW...BUT THE GFS HAS BEEN
CONSISTENTLY STRONGER WITH THIS LOW. THE GEM GLOBAL WAS THE
PREFERRED MODEL WITH THIS NEXT LOW...WHICH IS ROUGHLY A BLEND
BETWEEN THE STRONGER GFS AND WEAKER EC SOLUTIONS.

&&

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

A COLD UPPER LEVEL LOW IS MOVING OVER SOUTHCENTRAL
ALASKA FROM THE GULF OF ALASKA. THIS LOW WILL HELP KEEP THE
ATMOSPHERE GENERALLY UNSTABLE THE NEXT FEW DAYS. THE SURFACE
LOW IN THE GULF OF ALASKA CONTINUES TO PUSH SOME MOISTURE INTO
SOUTHCENTRAL ALASKA BUT IT WILL MOVE FAR ENOUGH TO THE SOUTHEAST
BY TONIGHT TO NOT HAVE MUCH MORE EFFECT OVER THE AREA. MOST OF
THE SHOWERS WILL BE RELEGATED TO THE NORTH GULF COAST. SOME BREEZY
CONDITIONS WILL DEVELOP ONCE AGAIN THIS AFTERNOON INTO EVENING IN
THE NORMAL CHANNELED TERRAIN AREAS BUT THESE WINDS ARE NOT
EXPECTED TO BE AS STRONG AS THE PREVIOUS COUPLE OF DAYS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE WEATHER OVER MOST OF SOUTHWEST ALASKA WILL BE FAIRLY QUIET
TODAY AS A RIDGE OF HIGH PRESSURE MOVES THROUGH THE REGION.
EXPECT SCATTERED SHOWERS TODAY MAINLY ALONG THE ALASKA/ALEUTIAN
RANGE AND THE KILBUCK MOUNTAINS. A FRONT LYING JUST OFF THE
KUSKOKWIM COAST THIS MORNING WILL PRODUCE AREAS OF RAIN MAINLY
FROM KIPNUK NORTHWARD. THIS FRONT HAS A DEEP SOUTHERLY FETCH...SO
MODERATE RAINFALL AMOUNTS ARE EXPECTED.

AS THIS FRONT MOVES EASTWARD TONIGHT INTO MONDAY...SCATTERED TO
NUMEROUS SHOWERS WILL MOVE INLAND. WINDS WILL INCREASE TODAY AS
THE FRONT APPROACHES THE COAST WITH THE STRONGEST WINDS EXPECTED
ALONG THE WESTERN CAPES OF BRISTOL BAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
AN ACTIVE PATTERN IS IN STORE FOR THE BERING SEA AND THE ALEUTIAN
ISLANDS OVER THE NEXT 48 HOURS AS THREE DIFFERENT SYSTEMS IMPACT
THE REGION. FIRST...THE LOW THAT HAS BEEN TRANSITING THE CENTRAL
BERING THE LAST 24 HOURS WILL STALL NEAR GAMBELL MONDAY MORNING.
THE ASSOCIATED FRONT WILL SLOWLY MOVE INLAND OVER THE
SOUTHWESTERN MAINLAND BY TOMORROW. THIS FRONT HAS AMPLE MOISTURE
AND SHOULD PRODUCE STEADY RAINFALL AND AREAS OF FOG ALONG THE
FRONT ALL THE WAY INTO THE NORTHEAST BERING SEA. AIDING THIS FRONT
IN PRODUCING RAINFALL IS A SECOND LOW MOVING EASTWARD SOUTH OF THE
ALASKA PENINSULA INTO THE GULF OF ALASKA. THIS LOW WILL BRING
ADDITIONAL FORCING AND AMPLE MOISTURE WITH A DEEP SOUTHERLY
FETCH...SO RAINFALL AMOUNTS OF UP TO AN INCH AND A HALF ARE
POSSIBLE OVER THE NEXT 24 HOURS WITH THE HEAVIEST TOTALS ALONG THE
WESTERN ALASKA PENINSULA. WINDS ALONG THE EASTERN ALEUTIANS AND
ALASKA PENINSULA WILL INCREASE TODAY AS THIS LOW MOVES EASTWARD
AND A WEAK RIDGE MOVES THROUGH BEHIND IT. A SMALL AREA OF GALE
FORCE WINDS ARE EXPECTED BRIEFLY SOUTH OF UNIMAK ISLAND TONIGHT.

AS THE RIDGE MOVES INTO THE BERING...WINDS SHOULD RELAX UNTIL
TUESDAY AFTERNOON AS A LOW IN THE NORTHEAST PACIFIC OCEAN WILL
RAPIDLY INTENSIFY AND MOVE TO JUST SOUTH OF THE WESTERN ALEUTIANS.
THIS SYSTEM WILL HAVE A VERY DEEP MOISTURE SOURCE AND THE
ASSOCIATED FRONT IS EXPECTED TO BRING A WIDE SWATH OF RAINFALL TO
MOST OF THE WESTERN AND CENTRAL ALEUTIAN ISLANDS. WINDS ALONG THE
FRONT ARE CURRENTLY EXPECTED TO REACH GALE FORCE OVER THE WESTERN
ALEUTIANS. THERE ARE SOME SIGNIFICANT DIFFERENCES IN THE MODELS
WITH THE STRENGTH OF THIS LOW /A PRESSURE OF 972MB FOR THE GFS
AND ABOUT 982MB FOR THE EC/...SO A MIDDLE GROUND WAS TAKEN FOR THE
WIND FORECAST TUESDAY NIGHT. IF THE STRONGER SOLUTION DOES
OCCUR...A MUCH WIDER AREA OF UPPER GALE FORCE WINDS IS POSSIBLE

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE NORTH PACIFIC LOW POSITIONED IN THE CENTRAL GULF WILL
GRADUALLY MOVE EASTWARD BEFORE DISSIPATING BY TUESDAY AFTERNOON.
THIS SYSTEM WILL BRING MOISTURE TO THE NORTHERN GULF AND THE
MAJORITY OF THE PRECIPITATION WILL BE ALONG THE COASTAL
AREAS. AN AMPLIFIED RIDGE OF HIGH PRESSURE WILL BEGIN TO MOVE
INTO THE SOUTHCENTRAL REGION FROM THE WEST BY WEDNESDAY...BEFORE
AN UPPER LEVEL CLOSED HIGH PRESSURE DEVELOPING IN THE INTERIOR BY
FRIDAY. THIS WILL BRING WARMER TEMPERATURES WITH DIURNAL SHOWERS
IN THE AFTERNOON AND EVENING ACCOMPANIED BY A THERMAL TROUGH
FORMING IN THE INTERIOR AS WERE HEADING INTO THE MIDWEEK TIME
FRAME. THE MODELS WERE IN DECENT AGREEMENT WITH THESE FEATURES
AND FORECAST CONFIDENCE IS AVERAGE.

ON THE BERING SEA SIDE...THE NORTHERN BERING WILL HAVE A WEAK LOW
DISSIPATING BY EARLY TUESDAY MORNING. WHILE...THE WESTERN
ALEUTIANS WILL HAVE A NORTH PACIFIC GALE FORCE LOW APPROACHING BY
LATE MONDAY EVENING WITH AN ASSOCIATE WEATHER FRONT MOVING
THROUGH THE CENTRAL ALEUTIANS. THIS SYSTEM WILL TRANSITION INTO
A BROAD AREA OF LOW PRESSURE OVER THE BERING SEA. THIS WILL BRING
WIDESPREAD RAIN WITH GUSTY WINDS THROUGH THE EARLY PART OF NEXT
WEEK BEFORE TRANSITIONING TO SHOWERY PRECIPITATION BY MIDWEEK.
DOWNSTREAM...AN AMPLIFIED RIDGE BUILDS THROUGH THE EASTERN
BERING/ALEUTIANS BY MONDAY AND MOVES EASTWARD. THIS WILL BRING
WARMER TEMPERATURES THROUGH THURSDAY. THE MODELS CONTINUE TO
STRUGGLE WITH THE PLACEMENT/STRENGTH OF THIS NORTH PACIFIC LOW.THE
FORECAST CONFIDENCE REMAINS BELOW AVERAGE.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE
MARINE...GALE WARNING 155 172
FIRE WEATHER...NONE

&&

SYNOPSIS AND MODEL DISCUSSION...DEK
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RF
LONG TERM...PLD