Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 251216
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
416 AM AKDT MON MAY 25 2015

.ANALYSIS AND UPPER LEVELS...

IN THE BRISTOL BAY AREA AN UPPER LEVEL LOW IS FORMING WITH AN
ASSOCIATED TROUGH EXTENDING THROUGH THE EASTERN ALEUTIANS NEAR
PORT MOLLER INTO THE PACIFIC. THE SOUTHWEST/SOUTHCENTRAL ALASKA
HAS EMBEDDED SHORTWAVES SWINGING THROUGH TOWARDS THE INTERIOR.
THIS IS BRINGING PERIODS OF RAIN TO THE NORTHERN GULF COASTLINES
AND STREAMING INTO THE INTERIOR. THE RADAR IMAGERY IS SHOWING
NUMEROUS RAIN SHOWERS THROUGH THE BRISTOL BAY INTERIOR AND THE
KUSKOKWIM DELTA REGION THIS MORNING. THIS IS PRODUCED BY THE
ONSHORE FLOW AND WITH EMBEDDED SHORTWAVES MOVING THROUGH THE
SOUTHWEST ALASKA AREA. SURFACE OBSERVATIONS IN THE SOUTHCENTRAL
REGION HAVE BEEN REPORTING LIGHT RAIN AND DRIZZLE WITH CONTINUED
ONSHORE FLOW ACCOMPANIED BY LOW STRATUS. WHILE...AN UPPER LEVEL
RIDGE IS EXTENDING THROUGH THE CENTRAL ALEUTIANS NORTHWARD INTO
THE NORTHERN BERING SEA. UPSTREAM JUST WEST OF SHEMYA THERE IS A
CLOSED VERTICALLY STACKED LOW AT 300 MB WITH A 115 KNOT SOUTHERLY
JET STREAK POSITIONED THROUGH KISKA EXTENDING INTO THE WESTERN
BERING SEA. THIS JET STREAK IS SUPPORTING THE GALE FORCE LOW AT
THE SURFACE JUST WEST OF SHEMYA THIS MORNING. THE SATELLITE
IMAGERY IS SHOWING A NICE COMMA CLOUD SHIELD WITH THIS SYSTEM
PUSHING THROUGH THE WESTERN ALEUTIANS AND A FRONTAL BOUNDARY
MOVING THROUGH THE CENTRAL ALEUTIANS THIS MORNING.


&&

.MODEL DISCUSSION (SHORT TERM)...

THE MODELS ARE IN GOOD AGREEMENT WITH THE LOW IN THE WESTERN
BERING SEA AS IT TRACKS TOWARD THE KAMCHATKA PENINSULA THROUGH THE
MIDWEEK. THE NEXT NORTH PACIFIC LOW THE MODELS ARE HANDLING FAIRLY
WELL AS IT TRACK FROM THE SOUTH TOWARDS THE WESTERN ALEUTIANS BY
WEDNESDAY. WHILE...THE GULF WILL HAVE HIGH PRESSURE BUILD INTO THE
REGION THROUGH REST OF THE WEEK. THE FORECAST CONFIDENCE REMAINS
ABOVE AVERAGE FOR THE NEXT SEVERAL DAYS.

&&

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

SOUTHERN ALASKA WILL REMAIN UNDER SOUTHEAST FLOW TODAY...AFFECTED
PRIMARILY BY AN UPPER LEVEL TROUGH THAT IS NEARLY STATIONARY OVER
THE ALASKA PENINSULA AND SOUTHERN KODIAK ISLAND. THIS IS A
GENERALLY MOIST WIND DIRECTION...AND CLOUD-COVER IS INDEED
PLENTIFUL THIS MORNING ACROSS MOST OF THE AREA. SHOWERS ARE
CONTINUING ACROSS THE NORTHERN GULF AND COOK INLET AREAS...AND
WILL CONTINUE FOR MOST OF THE DAY ESPECIALLY IF ANY BREAKS OF SUN
ARE ABLE TO DEVELOP AND PROVIDE A DIURNAL BOOST TO INSTABILITY.
THE COPPER BASIN SHOULD BE THE FIRST TO SEE SOME BREAKS OF SUN
DEVELOP...A TREND ALREADY STARTING TO DEVELOP LOOKING AT EARLY
MORNING SATELLITE IMAGERY. BY THIS EVENING THE UPPER TROUGH WILL
BEGIN TO TRANSITION INTO A WEAK UPPER LOW...WHICH WILL HAVE THE
EFFECT OF CHANGING THE MEAN FLOW ACROSS THE AREA TO A MORE
EASTERLY DIRECTION AND A BIT DRIER. THIS WILL ALLOW CLOUD- COVER
TO DIMINISH IN A MORE MEANINGFUL WAY IN MOST AREAS TONIGHT INTO
TUESDAY MORNING...A TREND THAT WILL CONTINUE FOR THE REST OF THE
WEEK. AS HIGH PRESSURE BEGINS TO BUILD BACK INTO THE GULF FROM THE
SOUTH FAIRLY ROBUST SEA BREEZES ARE EXPECTED TO DEVELOP BEGINNING
TUESDAY...WHICH WILL ALSO KEEP COASTAL TEMPERATURES MODERATED EVEN
IN THE FACE OF INCREASING SUNSHINE.

ON TUESDAY THE COPPER BASIN WILL LIKELY BE THE SCENE OF SOME
FAIRLY WIDESPREAD DIURNAL SHOWER ACTIVITY AS THE THERMAL TROUGH
STARTS TO BUILD BACK INTO THE AREA. AT THE SAME TIME...MODEST
UPPER LEVEL SUPPORT FROM THE UPPER LOW IN THE GULF WILL MOVE
THROUGH THE AREA. THE INSTABILITY DOES NOT LOOK TO BE UNUSUALLY
STRONG...BUT WITH LONG DAYLIGHT HOURS AND SOME CONTRIBUTION OF
DYNAMICS THERE IS A SLIGHT CHANCE OF THUNDERSTORMS TO ALSO
DEVELOP...MAINLY ALONG THE NORTHERN MOUNTAIN RANGES (ALASKA RANGE
AND TALKEETNA MOUNTAINS).

&&

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

A SLOW MOVING UPPER LOW MOVING ACROSS THE EASTERN BERING AND
BRISTOL BAY CONTINUES TO SUPPORT AREAS OF RAIN...ESPECIALLY ACROSS
THE BRISTOL BAY ZONE INTO THE SOUTHEAST PORTION OF THE KUSKOKWIM
DELTA. AS THIS FEATURE SHIFTS EAST TODAY...RAIN SHOULD TURN TO
SHOWERS AIDED BY DIURNAL HEATING...WITH THE POSSIBILITY OF A FEW
ISOLATED THUNDERSTORMS NEAR THE ALASKA RANGE IN THE AFTERNOON AND
EARLY EVENING. SHOWERS WILL DIMINISH IN COVERAGE AND INTENSITY ON
TUESDAY AS THE LOW WEAKENS AND MOVES INTO THE GULF OF ALASKA. A
FAST MOVING FRONT WILL MOVE INTO THE COASTAL REGIONS TUESDAY
NIGHT...BRINGING GUSTY SOUTHEAST WINDS AND MORE LIGHT RAIN.

&&

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

A LOW END GALE FORCE FRONT WILL MOVE ACROSS THE BERING SEA THROUGH
TUESDAY NIGHT...BRINGING A QUICK SHOT OF RAIN TO THE ENTIRE BERING
AND ALEUTIAN CHAIN. THE STRONGEST WINDS WILL BE AHEAD OF THE FRONT
WITH GUSTY SOUTHERLY WINDS. AREAS OF FOG WILL ALSO MOVE INTO THE
BERING...ESPECIALLY OVER THE CENTRAL AND NORTHERN BERING. ISOLATED
TO SCATTERED SHOWERS WILL REMAIN OVER THE WESTERN AND CENTRAL
BERING AND ALEUTIANS AS THE FRONT QUICKLY SPEEDS EASTWARD.

&&

.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. AS THIS RIDGE BUILDS THROUGH THE WEEK...IT
WILL BRING SOME OF THE WARMEST TEMPERATURES SO FAR THIS SUMMER IN
THE COPPER RIVER BASIN AND THE MATSU VALLEY WITH TEMPERATURES IN
THE 70S.

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. LOOK FOR THE LOWER KUSKOKWIM
VALLEY TO SEE ITS WARMEST TEMPERATURES THIS SUMMER WITH HIGH
TEMPERATURES IN THE 70S AS THE RIDGE BUILDS INTO THE AREA BY END
OF WEEK.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING...170 173 174 175 176 185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...PLD
SOUTHCENTRAL ALASKA...AD/RF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA
LONG TERM...TP/PLD


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