Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 260006
AFDAFC

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

.ANALYSIS AND UPPER LEVELS...

A HIGHLY AMPLIFIED JET STREAM PATTERN CONTINUES ACROSS THE
STATE...WITH A SOUTH-SOUTHEASTERLY JET STREAK FROM THE CENTRAL
ALEUTIANS NORTH INTO FAR EASTERN RUSSIA...A NORTHWESTERLY JET
STREAK OVER THE SOUTHWEST COAST AND ALASKA PENINSULA...AND A WEAK
SOUTHERLY JET STREAK EXTENDING NORTH FROM THE WESTERN GULF INTO
SOUTHCENTRAL ALASKA. THIS PATTERN PRETTY MUCH DEFINES THE TROUGH-
RIDGE PATTERN IN THE MID-LEVELS...WITH AN UPPER LEVEL LOW
CURRENTLY CLOSING OFF AS IT MOVES FROM BRISTOL BAY INTO THE
SOUTHWEST GULF OF ALASKA. IMMEDIATELY UPSTREAM...A NARROW YET
RAPIDLY AMPLIFYING UPPER LEVEL RIDGE IS BUILDING OVER THE EASTERN
BERING ITSELF IMMEDIATELY DOWNSTREAM OF A LARGE UPPER LEVEL LOW
AND ASSOCIATED SURFACE LOW OVER THE WESTERN BERING SEA.

THE UPPER LEVEL LOW CURRENTLY CLOSING OFF NEAR KODIAK ISLAND IS
EXTREMELY ENERGETIC...WITH NUMEROUS DISTURBANCES BRINGING SHOWER
ACTIVITY TO MUCH OF SOUTHCENTRAL AND SOUTHWEST ALASKA. KING SALMON
HAS UNOFFICIALLY SET A NEW MAY RAINFALL RECORD WITH THIS MORNING`S
RAINFALL.

&&

.MODEL DISCUSSION (SHORT TERM)...
MODELS ARE IN GOOD AGREEMENT...ESPECIALLY THE EC AND GFS OUT
WEST WHERE A STRENGTHENING LOW WILL MOVE ACROSS THE WESTERN AND
CENTRAL ALEUTIANS AND INTO THE BERING SEA THURSDAY INTO FRIDAY.

BACK IN THE IMMEDIATE SHORT TERM...THE UPPER LOW CLOSING OFF AS IT
MOVES TOWARD THE SOUTHWEST GULF WILL MOVE EAST TOWARD THE NORTHERN
PANHANDLE INTO MID-WEEK BEFORE MOVING INLAND. THE RAPIDLY BUILDING
RIDGE IN THE MEANTIME WILL CONTINUE TO BUILD AS IT MOVES OVER THE
MAINLAND BY WEDNESDAY. AN UPPER LEVEL WAVE THAT PEELS OFF FROM THE
MAIN UPPER LOW OVER THE BERING WILL THEN MOVE NORTH AND EAST INTO
SOUTHWEST ALASKA AND BRING A MORE STABLE REGIME TO THAT REGION AS
IT ATTEMPTS TO MOVE OVER THE RIDGE LATER IN THE WEEK.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA...
AN UPPER LEVEL LOW WILL PUSH EAST ACROSS THE GULF WHICH WILL
ALLOW FOR INSTABILITY ACROSS THE SOUTHCENTRAL. THIS WILL LEAD TO
SHOWERS DEVELOPING INTO TUESDAY...PRIMARILY ALONG THE MOUNTAINS.
THERE IS ALSO THE POSSIBILITY THAT THIS COULD LEAD TO THUNDERSTORM
DEVELOPMENT TUESDAY AFTERNOON ALONG THE ALASKA RANGE AND TALKEETNA
MOUNTAINS BUT CONFIDENCE IS LOW. HIGH PRESSURE WILL THEN MOVE IN
FROM THE SOUTHWEST KEEPING SHOWER ACTIVITY PUSHED NORTH ALONG THE
ALASKA RANGE. WINDS SHOULD PRIMARILY BE LIGHT WITH THIS PATTERN
WITH THE EXCEPTION OF SEA BREEZE DEVELOPMENT IN THE AFTERNOON
THROUGH WEDNESDAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
SHOWERS ASSOCIATED WITH THE UPPER LEVEL LOW CENTERED OVER THE BRISTOL
BAY AREA AND SEVERAL SMALL SHORTWAVES ROTATING AROUND IT WILL GRADUALLY
TAPER OFF TONIGHT THROUGH TUESDAY MORNING AS THIS FEATURE SHIFTS
EAST. A FAIRLY UNSTABLE AIR MASS WILL BRING THE POTENTIAL FOR
ISOLATED THUNDERSTORMS OVER THE LOWER KUSKOKWIM VALLEY THIS
AFTERNOON AND EVENING. UPPER LEVEL RIDGING WILL BUILD ALONG THE
COAST TUESDAY THEN SHIFT INLAND TUESDAY NIGHT AS A FRONTAL SYSTEM
ARRIVES AND STALLS ALONG THE WEST COAST.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE LARGE VERTICALLY STACKED UPPER LEVEL LOW CURRENTLY IN THE
SOUTHWESTERN BERING WILL GRADUALLY FILL AS IT LIFTS NORTH THROUGH
TUESDAY THEN CURVES WEST TUESDAY NIGHT AND WEDNESDAY. A WAVE
DEVELOPING ALONG THE ASSOCIATED FRONTAL SYSTEM STRETCHED OVER THE
CENTRAL ALEUTIANS WILL KEEP GALES GOING ALONG THE FRONTAL TONIGHT
THROUGH MIDDAY TUESDAY AS IT LIFTS NORTHEAST ACROSS THE BERING.
THE NEXT POTENTIALLY RATHER STRONG FRONTAL SYSTEM WILL APPROACH
THE WESTERN AND CENTRAL ALEUTIANS FROM THE SOUTH LATE IN THE DAY
WEDNESDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE OVERALL PATTERN REMAINS UNCHANGED...WITH A PERSISTENT RIDGE
DOMINATING MUCH OF THE SOUTHERN MAINLAND AND GULF THROUGH THE END
OF THE WEEK...AND A SERIES OF NORTH PACIFIC LOWS TRACKING THROUGH
THE ALEUTIANS AND BERING SEA THROUGH EARLY NEXT WEEK. DRIER
CONDITIONS ARE EXPECTED OVER MUCH OF THE SOUTHERN MAINLAND AS THE
RIDGE BUILDS OVER THE AREA THROUGH THE WEEK. THIS IS ALSO EXPECTED
TO BRING SOME OF THE WARMEST TEMPERATURES SO FAR THIS SUMMER TO THE
COPPER RIVER BASIN...MATSU VALLEY...AND PARTS OF THE SOUTHWEST
MAINLAND WITH TEMPERATURES CLIMBING INTO THE 70S. THE STRENGTH OF
THIS RIDGE WILL KEEP THE RAINY AND WINDY CONDITIONS CONFINED
MOSTLY TO THE BERING SEA AND ALEUTIANS THROUGH EARLY NEXT WEEK.
HOWEVER...MODELS ARE HINTING AT THE POTENTIAL FOR CONVECTIVE
SHOWERS TO DEVELOP OVER PARTS OF THE SOUTHCENTRAL MAINLAND LATER
IN THE WEEK...AS INSTABILITY INCREASES OVER THE AREA WITH THE
PASSING OF AN UPPER LEVEL TROUGH THURSDAY AFTERNOON/EVENING.
MODELS REMAIN IN FAIR AGREEMENT WITH THESE FEATURES/PATTERN OVER
THE SOUTHERN MAINLAND AND GULF...KEEPING FORECAST CONFIDENCE OVER
THE EASTERN DOMAIN SLIGHTLY ABOVE AVERAGE.

FURTHER WEST...THE ALEUTIANS AND BERING SEA WILL SEE LITTLE TO NO
BREAK FROM WET AND WINDY CONDITIONS THROUGH MUCH OF THE WEEK. THE
ABOVE MENTIONED NORTH PACIFIC LOW WILL STRENGTHEN AS IT TRACKS
THROUGH THE WESTERN/CENTRAL ALEUTIANS THURSDAY...BEFORE RECURVING
TO THE NORTHWEST OVER THE WESTERN BERING FRIDAY. THE ASSOCIATED
FRONTAL SYSTEM WILL BRING GUSTY WINDS AND RAIN TO THE
WESTERN/CENTRAL ALEUTIANS THURSDAY...THEN WEAKEN AS IT TRACKS
EASTWARD OVER THE ALEUTIAN CHAIN THROUGH THE END OF THE WEEK. AS
THE INITIAL FRONTAL SYSTEM DISSIPATES OVER THE EASTERN ALEUTIANS
AND ALASKA PENINSULA SUNDAY...ANOTHER FRONTAL SYSTEM BEGINS TO
TRACK OVER THE WESTERN ALEUTIANS/BERING FROM THE WEST. THIS
SYSTEM WILL BRING ANOTHER ROUND OF RAIN AND GUSTY WINDS TO THE
WESTERN AND CENTRAL ALEUTIANS/BERING SUNDAY THROUGH MONDAY. MODELS
HAVE COME INTO BETTER AGREEMENT WITH THESE FEATURES OVER THE
WESTERN DOMAIN IN THE MOST RECENT MODEL RUNS. HOWEVER...THEY ARE
STILL STRUGGLING WITH THE FINER DETAILS IN BOTH TIMING AND
STRENGTH. THUS FORECAST CONFIDENCE HAS SLIGHTLY INCREASED OVER THE
WESTERN DOMAIN THROUGH MUCH OF THE LONG TERM...BUT STILL REMAINS
BELOW AVERAGE.

&&
.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 170-176 185
FIRE WEATHER...NONE.

&&
$$

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


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