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FXAK68 PAFC 280305 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
423 PM AKDT WED MAY 27 2015

.ANALYSIS AND UPPER LEVELS...
THERE IS A LARGE STACKED LOW OVER THE BERING SEA WITH ANOTHER LOW
DEVELOPING SOUTH OF ATTU ISLAND THIS AFTERNOON. THE RIDGE REMAINS
IN PLACE OVER THE MAINLAND WITH A CLOSED LOW OVER THE PANHANDLE. THE
SOUTHERN LOW IS COUPLED WITH A 140 KNOT JET AND GOOD
BAROCLINICITY. THE CURRENT LOW IN THE BERING SEA WILL DIMINISH AS
IT FILLS AND LOSES OVERALL UPPER LEVEL SUPPORT. THE FRONT
ASSOCIATED WITH THE LOW IN THE BERING SEA WEAKENED OVERNIGHT BUT
IS RE-INTENSIFYING AS A SHORT WAVE TROUGH LIFTS THROUGH SOUTHWEST
ALASKA TODAY AND TONIGHT. THE PRECIPITATION WILL LIKELY NOT PUSH
INTO THE KUSKOKWIM VALLEY. THE SHORT WAVE TROUGH WILL PUSH INTO
THE RIDGE OF HIGH PRESSURE OVER THE INTERIOR TOMORROW. THE CLOSED
LOW OVER THE PANHANDLE KEEPING SOME MOISTURE SPILLING INTO THE
COPPER RIVER BASIN. THE AIR MASS IS UNSTABLE ENOUGH OVER THE
COPPER RIVER BASIN FOR SHOWERS BASIN WIDE AND ISOLATED THUNDERSTORMS
POSSIBLE NORTH AND EAST OF GLENNALLEN. IN BETWEEN THE FRONT AND
THE CLOSED LOW...MOSTLY CLEAR SKIES ARE PREVAILING.

&&

.MODEL DISCUSSION...
GIVEN THE STRONG LONG WAVE PATTERN...MODELS OVER THE NEXT FEW DAYS
ARE IN FANTASTIC AGREEMENT. THEREFORE...FORECAST CONFIDENCE IS
HIGH THROUGH FRIDAY.

THE RIDGE OVER THE STATE HAS REBOUNDED A BIT TODAY. CLEAR SKIES
REIGN OVER MOST OF THE INTERIOR OUTSIDE OF THE WEST COAST AND
COPPER RIVER BASIN. THERE WAS LITTLE STRATUS LAST NIGHT/THIS
MORNING AS WELL AS OPPOSED TO LAST NIGHT. A CLOSED LOW OVER THE
PANHANDLE IS KEEPING CLOUDS AND A CHANCE OF RAIN AND POSSIBLE
ISOLATED THUNDERSTORMS OVER THE COPPER RIVER BASIN. A SHORT WAVE
TROUGH IS RE-INVIGORATING THE FRONT ALONG THE WEST COAST AND WILL
LIFT NORTH AND EAST OVERNIGHT AND TOMORROW SPREADING SHOWERS AND
POSSIBLE THUNDERSTORMS INLAND. OVER SOUTH CENTRAL
ALASKA...THUNDERSTORM DEVELOPMENT WILL LIKELY BE LIMITED TO NORTH
OF GLENNALLEN. IN THE MEANTIME...A LOW STRENGTHENS IN THE WESTERN
ALEUTIAN ISLANDS THURSDAY. WINDS AROUND THE LOW WILL BE STRONG BUT
NOT EXPECTED TO PUSH INTO THE STORM FORCE RANGE AT THIS TIME.
PUSHED ACROSS THE BERING SEA AND ALEUTIAN ISLANDS WITH GOOD
BAROCLINICITY AND JET SUPPORT...A FRONT WILL MOVE INTO THE CENTRAL
BERING SEA THURSDAY AFTERNOON AND TO THE EASTERN BERING FRIDAY 
AFTERNOON. THE RIDGE WILL BUILD OVER THE MAINLAND THURSDAY AND 
FRIDAY WITH DAYTIME TEMPERATURES BECOMING 5 TO 10 DEGREES ABOVE 
NORMAL AND POSSIBLY EVEN TO RECORD LEVELS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE IS THE DOMINANT FEATURE OVER THE SOUTHCENTRAL WHICH
IS STARTING A DRYING TREND AND CAUSING THE CLEAR SKIES TO SPREAD.
THIS WILL CONTINUE THROUGH FRIDAY DROPPING RH VALUES TO AROUND 30
PERCENT IN THE COPPER RIVER BASIN AND SUSITNA VALLEY. UNDER THE
EFFECTS OF THE HIGH PRESSURE RAIN WILL BE LIMITED TO ISOLATED
SHOWERS MAINLY ALONG THE ALASKA RANGE. HOWEVER...ON THURSDAY A
TROUGH WILL PUSH THROUGH THE COPPER RIVER BASIN PROVIDING ENOUGH
INSTABILITY FOR ISOLATED THUNDERSTORMS. WINDS SHOULD BE LIGHT FOR
MOST OF THE SOUTHCENTRAL WITH SEA BREEZES DEVELOPING IN THE
AFTERNOON.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE FRONTAL SYSTEM CURRENTLY STRETCHING ACROSS BRISTOL BAY AND
WESTERN ALASKA WILL SHIFT INLAND TONIGHT THEN NORTHEAST AND CLEAR
OF THE AREA THURSDAY MORNING AS AN UPPER LEVEL TROUGH SWINGS
THROUGH. CONDITIONS WILL DRY OUT QUICKLY WITH SHOWERS ENDING
THURSDAY AFTERNOON AS RIDGING BUILDS OVER SOUTHWEST ALASKA. THE
NEXT FRONTAL SYSTEM WILL APPROACH THE COAST THURSDAY NIGHT HOWEVER
A STRENGTHENING UPPER LEVEL RIDGE INLAND SHOULD KEEP THE BULK OF
THE PRECIPITATION OFFSHORE MAINLY JUST IMPACTING THE WESTERN CAPES
AND ALASKA PENINSULA. THE FRONTAL SYSTEM WILL REMAIN STALLED NEAR
THE COAST FRIDAY THEN WEAKEN AND SHEAR APART SATURDAY. FURTHER
INLAND CONDITIONS WILL CONTINUE TO WARM AND DRY UNDER THE
PERSISTING UPPER LEVEL RIDGE.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE OLD BERING LOW NOW VERTICALLY STACKED WITH THE LARGE UPPER
LOW OFF OF THE KAMCHATKA PENINSULA WILL CONTINUE TO GRADUALLY FILL
AND WEAKEN TONIGHT AND DISSIPATE THURSDAY. A COLD UPPER LEVEL
TROUGH SWINGING IN FROM THE WEST COMBINED WITH A STRONG JET STREAM
WILL RAPIDLY STRENGTHEN THE NEW LOW DEVELOPING SOUTH OF THE
ALEUTIANS TODAY. THE ASSOCIATED RATHER STRONG FRONTAL SYSTEM WILL
APPROACH THE WESTERN AND CENTRAL ALEUTIANS TONIGHT BRINGING A SOLID
SWATH OF STRONG GALES WITH IT. THE SURFACE LOW WILL CROSS THE
ALEUTIAN AROUND THE KISKA AND AMCHITKA AREA THURSDAY MORNING.
WIDESPREAD GALES WILL FOLLOW THE LOW NORTH ACROSS THE BERING
THURSDAY AND FRIDAY BEFORE IT EVENTUALLY WEAKENS AND TRACKS OFF
TO THE NORTHWEST AND OUT OF THE AREA FRIDAY NIGHT AND SATURDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7 - SATURDAY THROUGH WEDNESDAY)...
A VERY HIGH AMPLITUDE PATTERN WILL BE IN PLACE ON SATURDAY WITH A
BLOCKING RIDGE EXTENDING FROM THE HIGH ARCTIC (BEAUFORT/CHUKCHI SEAS)
SOUTHWARD ACROSS MAINLAND ALASKA AND DOWN INTO THE NORTHEAST PACIFIC.
UPSTREAM A CORRESPONDING TROUGH WILL EXTEND FROM EASTERN RUSSIA
SOUTHEASTWARD ACROSS THE BERING SEA AND ALEUTIANS TO THE NORTH-
CENTRAL PACIFIC. THE STORM TRACK WILL REMAIN ON THE WESTERN EDGE
OF THIS TROUGH...MAINLY AFFECTING THE FAR WESTERN BERING SEA AND
WESTERN ALEUTIANS. THE REST OF THE REGION WILL BE DOMINATED BY
GENERALLY WEAK FLOW AND FORCING. 

THE BIG HEADLINE FOR THIS WEEKEND INTO EARLY NEXT WEEK WILL BE 
HOT AND DRY CONDITIONS ACROSS SOUTHCENTRAL AND INTERIOR SOUTHWEST
ALASKA. THE KEY TO THIS WARMTH IS ENERGY DROPPING OUT OF THE
CANADIAN ARCTIC SLIDING DOWN THE EAST SIDE OF THE UPPER RIDGE
ACROSS EASTERN MAINLAND ALASKA. THIS WILL ADVECT DRIER AIR FROM
THE INTERIOR AND HINDER OR PREVENT FORMATION OF SEA BREEZES ALONG
THE GULF COAST. IF THESE UPPER WAVES ACTUALLY TRACK SOUTHWARD INTO
THE GULF THERE IS POTENTIAL FOR GUSTY NORTHERLY WINDS WHICH WOULD
RESULT IN EVEN HOTTER AND DRIER CONDITIONS. THERE ARE MODEL
DIFFERENCES IN THE TIMING AND TRACK OF UPPER LEVEL WAVES. THUS IT
IS DIFFICULT TO NAIL DOWN THE DETAILS AT THIS POINT IN TIME.
HOWEVER...CHANCES ARE THAT CRITICAL FIRE WEATHER CONDITIONS WILL
DEVELOP SOMETIME OVER THE WEEKEND.

AS STEADY PARADE OF UPPER WAVES ALONG THE EASTERN PERIPHERY OF THE
RIDGE WILL CAUSE IT TO RETROGRADE WESTWARD EARLY NEXT WEEK. THIS
WILL RESULT IN A COOLING TREND BEGINNING TUESDAY ALONG WITH A
MORE FAVORABLE CONDITIONS FOR SHOWERS AS WE HEAD THROUGH THE
WEEK.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 170 172 173 174 175 176 177 178 179 181 185.
FIRE WEATHER...NONE.

&&

$$

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

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