Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 250044
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
444 PM AKDT SUN MAY 24 2015

.ANALYSIS AND UPPER LEVELS...

THE UPPER RIDGE HAS RETREATED OVER WESTERN CANADA. A BROAD
BAROCLINIC ZONE EXTENDS FROM NW ALASKA...MATSU...TO OVER THE
CENTRAL GULF. RAIN AND LOW CLOUDS ARE ASSOCIATED WITH THIS FEATURE
WHICH BROUGHT WETTING RAINS TO MUCH OF SOUTHCENTRAL COASTS AS WELL
AS AREAS WEST OF THE COPPER RIVER BASIN OVERNIGHT AND TODAY. RAIN
CONTINUES TO SPREAD ACROSS THE NORTHERN GULF THIS AFTERNOON.
WAVES EMBEDDED IN THE BROAD CYCLONIC FLOW AROUND AN UPPER LOW CENTER
OVER THE EASTERN BERING SEA IS PRODUCING GENERALLY CLOUDY
CONDITIONS WITH AREAS OF RAIN AND SHOWERS ACROSS MUCH OF THE
BERING SEA...ALEUTIANS...AK PEN AND SW MAINLAND. GUSTY WESTERLY
WINDS ALONG THE ALEUTIANS AND SOUTHERLY WINDS ACROSS THE EASTERN
BERING SEA/AK PEN WERE ALSO EVIDENT. WATER VAPOR IMAGERY ALSO
SHOWS A DEVELOPING UPPER WAVE MOVING JUST EAST OF THE KAMCHATKA
PEN AND SURFACE FIELDS INDICATE CORRESPONDING PRESSURE FALLS
ASSOCIATED WITH A DEVELOPING SURFACE LOW. A BROAD ZONAL JET IS
ALSO EVIDENT ACROSS THE NORTH PACIFIC ALONG 40N.

&&

.MODEL DISCUSSION (SHORT TERM)...
THE MODELS OVERALL ARE IN GOOD AGREEMENT AND SIMILARLY HANDLE THE
SYNOPTIC FEATURES...PARTICULARLY THE DEVELOPING LOW MOVING INTO
THE BERING SEA MON. IN THE SHORT TERM (THRU TUE) THE NAM WILL BE
USED IN THE EAST WITH A ECMWF/NAM BLEND IN THE WEST.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (SUNDAY AND MONDAY)...

UPPER DISTURBANCE BRINGING RAIN TO PRINCE WILLIAM SOUND NORTH
THROUGH THE TALKEETNA MOUNTAINS WILL SLOWLY DIMINISH IN COVERAGE
OVER THE NEXT 24 HOURS. SCATTERED TO OCCASIONALLY NUMEROUS SHOWERS
WILL OCCUR THROUGH THE NIGHT AS ANOTHER DISTURBANCE MOVES NORTH
FROM THE WESTERN GULF AND KODIAK ISLAND REGION NORTH ACROSS THE
KENAI PENINSULA AND THE UPPER COOK INLET REGION.

WITH THE DISSIPATION OF THE PRIMARY STABILIZING FRONTAL SYSTEM
OVER SOUTHCENTRAL...INSTABILITY WILL SLOWLY INCREASE AND CHANGE
PRECIPITATION OVER TO DIURNAL CONVECTIVE SHOWERS. THIS SHOWER
ACTIVITY WILL DEVELOP OVER THE MOUNTAINS EARLY IN THE AFTERNOON
AND THEN MOVE NORTH TO NORTH-NORTHWEST OFF THE MOUNTAINS THROUGH
THE AFTERNOON INTO EARLY EVENING...RESULTING IN CONTINUED SPORADIC WET
CONDITIONS THROUGH THE REMAINDER OF THE HOLIDAY WEEKEND FOR
ANCHORAGE AND THE MAT-SU BOROUGHS AS WELL AS THE KENAI PENINSULA.

FOR TUESDAY...INSTABILITY WILL CONTINUE TO INCREASE ESPECIALLY
INLAND...WITH MORE INTENSE CONVECTIVE SHOWER ACTIVITY AND THE
SLIGHT POTENTIAL FOR SOME THUNDERSTORMS PARTICULARLY OVER THE
NORTHEAST COPPER RIVER BASIN NEAR AND ALONG THE ALASKA RANGE...AS
WELL AS OVER THE TALKEETNA MOUNTAINS.

.FIRE WEATHER...

SHOWERY CONDITIONS WILL IMPACT SOUTHCENTRAL ALASKA THROUGH
TUESDAY...THOUGH THE COPPER RIVER BASIN WILL REMAIN DRIEST.
INSTABILITY BEGINS TO INCREASE ENOUGH TUESDAY AFTERNOON AND
EVENING SUCH THAT A SLIGHT CHANCE OF THUNDERSTORMS HAS BEEN
INTRODUCED TO THE NORTHEAST COPPER RIVER BASIN NEAR AND ALONG THE
ALASKA RANGE AS INCREASINGLY EAST TO NORTHEAST FLOW MAY TAP INTO
AND ADVECT SOME INSTABILITY OVER THE YUKON REGION TOWARD THE
AREA.

&&

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

A WEAK BOUNDARY ACROSS THE SOUTHWEST WILL BE THE FOCUS FOR
SCATTERED TO NUMEROUS SHOWERS OVERNIGHT AS A DEVELOPING UPPER
LEVEL LOW SLIDES ACROSS THE ALASKA PENINSULA TO KODIAK ISLAND.
RAIN ACTIVITY TAPERS OFF MONDAY NIGHT AS THIS SYSTEM SHIFTS EASTS
AND WEAK RIDGING BUILDS ACROSS BRISTOL BAY. TUESDAY AFTERNOON AND
EARLY EVENING A FEW CONVECTIVE SHOWERS MAY DEVELOP MAINLY ALONG
THE ALASKA AND ALEUTIAN RANGES...OTHERWISE MILD CONDITIONS ACROSS
THE REGION.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

LOW PRESSURE PUSHES A FRONT INTO SHEMYA TONIGHT AND INTO THE
CENTRAL BERING BY MONDAY AFTERNOON. GUSTY GALE WINDS AND RAIN ARE
EXPECTED ALONG THE FRONTAL PASSAGE WITH THE FRONT SWINGING INTO
THE EASTERN BERING MONDAY NIGHT. THIS SYSTEM IS NOT IMPRESSIVELY
DEEP FOR THIS TIME OF YEAR...HOWEVER THIS SYSTEM IS WELL ORGANIZED
WITH THE UPPER LOW STACKED DIRECTLY OVER THE SURFACE LOW MAKING
IT POTENT ENOUGH TO BRING GUSTY WINDS ACROSS A LONG FETCH OVER THE
WATER. THIS COMBINATION WILL HELP MAXIMIZE WAVE HEIGHTS AROUND 20
FEET. THIS STORM SHOULD BE MONITORED FOR UPDATES AS IT MAY BE
POTENTIALLY STRONGER THAN CURRENT MODELS ARE PROJECTING.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE OVERALL PATTERN REMAINS UNCHANGED...WITH A PERSISTENT RIDGE
REAMPLIFYING OVER THE GULF AND MUCH OF EASTERN ALASKA MAINLAND
DURING THE WEEK. THIS RIDGE WILL PERSIST OVER THE AREA INTO NEXT
WEEKEND...AND BEGIN TO EXTEND INTO THE WESTERN MAINLAND AS WELL BY
MID WEEK. SOUTHERLY FLOW ALONG THE WESTERN FLANK OF THE RIDGE WILL
KEEP RAIN SHOWERS ALONG PARTS OF THE GULF COAST AND INLAND AREAS
AROUND SOUTHCENTRAL THROUGH TUE NIGHT. AS THE RIDGE INCREASES IN
STRENGTH AND EXTENDS FURTHER WESTWARD...ONSHORE FLOW AND
PRECIPITATION WILL TAPER OFF TUESDAY NIGHT THROUGH THURSDAY OVER
MUCH OF THE MAINLAND...KEEPING MUCH OF THE PRECIPITATION
ASSOCIATED WITH AN APPROACHING BERING SEA FRONT MAINLY OVER THE
SOUTHWESTERN COAST. MODELS THEN SHOW THE RIDGE BUILD IN OVER THE
SOUTHWEST MAINLAND...KEEPING DRIER CONDITIONS OVER THE INLAND
AREAS INTO THE WEEKEND.

FURTHER WEST...A BROAD AREA OF LOW PRESSURE WILL PERSIST OVER MUCH
OF THE THE BERING...WITH A SERIES OF LOW PRESSURE SYSTEMS AND
ASSOCIATED FRONTS TRACKING THROUGH THE ALEUTIANS AND BERING
THROUGH MUCH OF THE WEEK. THIS WILL GIVE THE ALEUTIANS AND BERING
LITTLE TO NO BREAK FROM WET AND WINDY CONDITIONS THROUGH MUCH OF
THE WEEK. THE NEXT NORTH PACIFIC LOW WILL TRACK THROUGH THE
WESTERN ALEUTIANS THURSDAY BEFORE WEAKENING OVER THE WESTERN
BERING DURING THE DAY FRIDAY. THE ASSOCIATED FRONTAL SYSTEM WILL
BRING ANOTHER ROUND OF GUSTY WINDS AND RAIN TO THE CENTRAL
ALEUTIANS THURSDAY...THEN WEAKEN AS IT TRACKS EASTWARD OVER THE
ALASKA PENINSULA BY FRIDAY. MODELS CONTINUE TO STRUGGLE WITH THE
TRACK AND STRENGTH OF THIS SYSTEM...KEEPING FORECAST CONFIDENCE
LOWER FOR THE LONG TERM FORECAST OUT WEST. HOWEVER MODELS ARE IN
FAIR AGREEMENT WITH THE THE RIDGE OVER THE GULF AND MUCH OF THE
SOUTHERN MAINLAND...RAISING CONFIDENCE SLIGHTLY REGARDING THE
PRECIPITATION BEING CONFINED TO MOSTLY THE THE BERING AND
ALEUTIAN CHAIN INTO NEXT WEEKEND.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 170 173 174 176 178 179 185
FIRE WEATHER...NONE.

&&

$$

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


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