Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 222335
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
335 PM AKDT FRI MAY 22 2015

.ANALYSIS AND UPPER LEVELS...
THE REMNANTS OF TYPHOON DOLPHIN CONTINUE TO SPIN IN THE WESTERN
BERING SEA TODAY WITH A STRONG ZONAL JET PEAKING AT 150 KNOTS IN
THE NORTH PACIFIC. THE EXIT REGION OF THE JET IS SOUTH OF ADAK AND
IS SUPPORTING A STRONG FRONTAL FEATURE. IN ADDITION...WE ARE
SEEING LIGHTNING OVER SOME OF THE COASTAL WATERS NEAR ADAK WITH
COOLING TOPS ON IR IMAGERY AND LIGHTNING STRIKES VIA THE LIGHTNING
NETWORK. A STRONG UPPER LEVEL RIDGE REMAINS IN PLACE OVER THE
PANHANDLE THROUGH THE YUKON. AN UPPER LEVEL LOW NEAR 50N 160W
COMBINED WITH THE STRONG UPPER LEVEL RIDGE IS HELPING TO PUSH
MOISTURE NORTH THROUGH KODIAK ISLAND WEST AND STARTING TO REACH
THE NORTHERN GULF COAST AS WELL. OVERALL...THE RIDGE IS KEEPING
VERY WARM AND DRY AIR OVER EASTERN ALASKA. THE REMNANT LOW OF
TYPHOON DOLPHIN IS PRODUCING GALE FORCE WINDS NOW DOWN FROM THE
STORM FORCE WINDS YESTERDAY. HOWEVER...THERE IS A WELL DEFINED
FRONT MOVING THROUGH THE CENTRAL BERING SEA TODAY WITH GALE FORCE
WINDS AND MODERATE PRECIPITATION. DUE TO THE INCREASE IN MOISTURE
FROM THE RIDGE BEING PUSHED A BIT EAST LAST NIGHT INTO THIS
MORNING...SOME AREAS OF FOG HAVE DEVELOPED IN SOUTHWEST ALASKA AND
ALONG THE GULF COAST OF ALASKA THIS MORNING. IT IS LIKELY THAT THE
SAME AREAS WILL EXPERIENCE FOG AGAIN TOMORROW MORNING.

&&

.MODEL DISCUSSION...
THE LONG WAVE PATTERN DOES NOT CHANGE MUCH AT ALL OVER THE NEXT
WEEK. THEREFORE THE MODELS ARE IN FAIRLY GOOD AGREEMENT
THROUGHOUT THE TIME FRAME. OVER THE NEXT COUPLE DAYS...MODELS
AGREE ON ALL FRONTS WITH FORECAST CONFIDENCE HIGH. THE UPPER LEVEL
LOW SITUATED OVER THE NORTHERN PACIFIC NEAR 50N 160W TO PHASE WITH
THE FRONT MOVING THROUGH THE CENTRAL BERING TONIGHT. THIS WILL
CREATE A STRONGER FRONT WITH GALE FORCE WINDS ALONG SOUTHWEST
ALASKA COAST. STRONG WIND HEADLINES...RAIN...AND SOME HIGHER WATER
TO REACH THE COASTLINE OF SOUTHWEST ALASKA AS A RESULT TOO. THE
HIGH WATER WILL LIKELY REMAIN NEAR THE HIGH ASTRONOMICAL TIDE
LEVEL WITH MOSTLY ALONG COAST WAVE ACTION NOT ADDING TO THE HIGH
WATER. THE UPPER LEVEL LOW TO LIFT THROUGH SOUTH CENTRAL
SATURDAY/SATURDAY NIGHT BEFORE BEING TORN APART BY THE RIDGE OVER
EASTERN ALASKA SUNDAY. BEFORE BEING RIPPED APART BY THE
RIDGE...THE UPPER LOW WILL HELP TO SPREAD SHOWERS AND SOME WINDS
OVER SOUTH CENTRAL ALASKA. THIS UPPER LEVEL DISTURBANCE MAY ALLOW
FOR ISOLATED THUNDERSTORMS TO DEVELOP OVER THE MOUNTAINS IN THE
EASTERN COPPER RIVER BASIN AS WELL. HOWEVER...THE COPPER RIVER
BASIN WILL REMAIN DRY AND WARM WITH RED FLAG CONDITIONS THROUGH
SATURDAY. WINDS IN THE COPPER WILL ADD TO THE RED FLAG CONDITIONS
SATURDAY. RED FLAG CONDITIONS MOST LIKELY TO END SUNDAY WITH CLOUD
COVER.

AS DOLPHIN DIMINISHES IN THE EASTERN BERING SEA...A SECONDARY
LOW DROPS INTO THE WESTERN BERING SEA SUNDAY. THE REMNANT OF
DOLPHIN DISSIPATES SUNDAY AS THE NEXT LOW INTENSIFIES IN THE
WESTERN BERING SUNDAY NIGHT WITH A NEW JET CORE OF 160 KNOTS.

&&

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

ELONGATING MID-LEVEL SYSTEM WILL MOVE NORTH ACROSS THE WESTERN
GULF AND LOWER COOK INLET REGION THROUGH SATURDAY...THEN BEGIN TO
STALL AS THE ORIENTATION OF THE SYSTEM BECOMES NEARLY PARALLEL TO
THE MID-LEVEL FLOW. MID-LEVEL MOISTURE TRANSPORT IS PLENTY
SUFFICIENT FOR THIS TIME OF YEAR OFF OF THE GULF OF ALASKA AND
THE SNOW GROWTH LAYER (ALOFT) QUITE HIGH...SO THERE WILL NOT BE
ENOUGH OF A RAIN SHADOW EFFECT TO INHIBIT ALL LOCATIONS NORTH AND
WEST OF THE CHUGACH IN THE COOK INLET REGION SEEING AT LEAST SOME
RAINFALL OVER THE WEEKEND. THE MAIN INHIBITOR WILL BE INITIALLY
OVERCOMING DRIER AIR IN THE LOWER LEVELS OF THE ATMOSPHERE.

FIRE WEATHER...

TOWARD THE COPPER RIVER BASIN CONDITIONS WILL REMAIN DRY AND VERY
WARM WITH RED FLAG CONDITIONS PERSISTING THROUGH SATURDAY EVENING
FOR BOTH LOW HUMIDITY AND STRONG WIND. THE LONG STRETCH OF
CONSECUTIVE DAYS OF RED FLAG CONDITIONS SHOULD END SUNDAY AS
CLOUDS AND MID-LEVEL MOISTURE PUT A DAMPER ON CRITICAL FIRE
WEATHER CONDITIONS...THOUGH THERE WILL BE VERY LITTLE IF ANY RAIN
ACROSS MUCH OF THE BASIN...ESPECIALLY FROM GLENNALLEN NORTH AND
NORTHEAST.

THERE WILL ALSO BE AN EXTREMELY SLIGHT CHANCE OF A THUNDERSTORM
OCCURRING SATURDAY ALONG AND NORTH OF THE WRANGELL MOUNTAINS IN
THE NORTHEASTERN CORNER OF THE COPPER RIVER BASIN. THE THREAT IS
CONDITIONAL AS TO WHETHER INCREASING MID-LEVEL MOISTURE ARRIVES
IN ENOUGH TIME TO COINCIDE WITH PEAK HEATING. ANY STORM THAT MOVES
NORTH OFF OF THE MOUNTAINS WILL LIKELY BE DRY GIVEN THE EXTREMELY
DRY CONDITIONS IN THE LOWER LEVELS OF THE ATMOSPHERE.
AGAIN...CONFIDENCE IN AN ISOLATED DRY LIGHTNING STORM IS LOW AT
THIS TIME.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TONIGHT THROUGH SUN)...

THE MAJORITY OF THE SUBTROPICAL MOISTURE THAT HAS BEEN ADVECTED
NORTHWARD THE PAST 24-36 HOURS HAS PRETTY MUCH BEEN SHUT-OFF AS
EVIDENT ON RADAR REFLECTIVITY TRENDS DURING THE DAY AND ALSO
WATER VAPOR IMAGERY. THE LEFT OVER SUBTROPICAL MOISTURE CURRENTLY
RESIDES ACROSS THE KUSKOKWIM DELTA AND HAS BEEN GRADUALLY DRYING
OUT DURING THE DAY. SOUTHERLY TO SOUTHWESTERLY FLOW ALOFT IS
EXPECTED AS THE LONGWAVE TROUGH REMAINS ANCHORED OVER THE BERING
SEA...WHICH WILL ALLOW A SERIES OF UPPER LEVEL DISTURBANCES TO
IMPACT SOUTHWEST ALASKA. A QUICK 1-2 PUNCH WILL BE SEEN IN THE
NEXT 24 HOURS AS AN UPPER LEVEL LOW OVER THE NORTH PACIFIC WILL
BRING AN INCREASED CHANCE OF RAINFALL TO THE BRISTOL BAY
AREA...ESPECIALLY THE UPSLOPE AREAS OF THE ALASKA PENINSULA. THIS
UPPER LOW WILL PHASE INTO THE SURFACE FRONT/SHORTWAVE ENHANCED
TROUGH ASSOCIATED WITH THE APPROACHING EXTRA-TROPICAL REMNANTS OF
DOLPHIN CURRENTLY RESIDING OVER THE CENTRAL BERING SEA. THE MAIN
CONCERNS WITH THIS FOR SOUTHWESTER ALASKA WILL BE STRONG WINDS
OBSERVED THROUGH CHANNELED TERRAIN OF THE ALEUTIAN RANGE AND ALONG
COASTAL AREAS.

CROSS BARRIER FLOW ACROSS THE ALASKA AND ALEUTIAN RANGES WILL
INCREASE ON SATURDAY...WHICH WILL KEEP THE USUAL LEE SIDE AREAS
DRIER THAN SURROUNDING AREAS. THERE WILL BE FRAGMENTS OF SHORTWAVE
ENERGY AND A PERIOD OF DEEPER MOISTURE ALOFT WHICH WILL BRIEFLY
OVERCOME THE CROSS BARRIER FLOW...BUT IN GENERAL IT APPEARS THE
COASTAL AREAS AND UPSLOPE AREAS LOOK PRIMED FOR A MAJORITY OF THE
RAINFALL. THIS PATTERN IS EXPECTED TO CONTINUE THROUGH THE WEEKEND
WITH NO BIG SHIFT IN THE WEATHER PATTERN EXPECTED.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TONIGHT THROUGH SUN)...

AN AREA OF CONVECTION AND THUNDERSTORM ACTIVITY HAS BEEN OBSERVED
OVER THE COASTAL WATERS OF THE ALEUTIAN ISLANDS THIS AFTERNOON.
THIS IS IN RESPONSE TO A JET STREAK PASSING SOUTH OF THE UPPER
LEVEL TROUGH AND INTERACTING WITH A RELATIVELY UNSTABLE
ATMOSPHERE. THESE THUNDERSTORMS ARE EXPECTED TO WANE DURING THE
EVENING HOURS AS THE JET STREAK WEAKENS AND SLIDE EASTWARD.
LOOKING AT THE BIGGER PICTURE...THE REMNANTS OF DOLPHIN ARE
CURRENTLY TRACKING ACROSS THE WESTERN BERING SEA AND MOVING TO THE
SOUTHEAST. IT CONTINUES TO PUSH A GALE FORCE FRONT THROUGH THE
BERING SEA WHICH LOOKS TO STALL NEAR THE PRIBILOF ISLANDS TONIGHT.
COLD AIR WRAPPING BEHIND THE BERING SEA LOW WILL STEEPEN THE LOW
LEVEL LAPSE RATES AND ALLOW SOME OF THE STRONGER WINDS ALOFT TO
MIX DOWN. WITH THE PASSAGE OF THE AFOREMENTIONED JET STREAK...THERE
WILL BE NO ADDITIONAL MECHANISMS TO MIX THE STRONGEST WINDS DOWN.
BECAUSE OF THIS...HAVE OPTED TO KEEP WINDS AT MAX GALE ON THE BACK
SIDE OF THE LOW. IN GENERAL...A VERY WET AND ACTIVE PERIOD LOOKS
TO CONTINUE AS THE LOW GETS TRAPPED IN THE BERING SEA THANKS TO A
BUILDING RIDGE ACROSS THE INTERIOR OF ALASKA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

OPERATIONAL MODELS AND ENSEMBLES ARE IN AGREEMENT THAT THE RIDGE
OVER THE NORTHEAST PACIFIC AND ALCAN WILL PERSIST THROUGH NEXT
WEEK. ONSHORE FLOW ALONG THE WESTERN FLANK OF THE RIDGE WILL
BRING RAIN TO THE NORTH GULF COAST SUN NIGHT THROUGH MON. SHOWER
ACTIVITY WILL CROSS THE NORTHERN MOUNTAINS INTO SOUTHCENTRAL AK
THROUGH TUE. BRIEF RIDGE BUILDING WILL CUT OFF PRECIPITATION ON
WED...BUT ONSHORE FLOW WILL RESUME WITH COASTAL RAIN AND INLAND
SHOWERS AT THE END OF THE WEEK.

LOW PRESSURE WILL SPIN AROUND THE SOUTHERN BERING FOR THE NEXT
WEEK. ASSOCIATED FRONTS WILL MOVE TO SOUTHWEST AK BEFORE
DISSIPATING AGAINST THE RIDGE. THIS MEANS THAT RAIN AND SHOWERS
CAN BE EXPECTED OVER THE ENTIRE BERING AND ALEUTIAN CHAIN THROUGH
THE END OF THE WEEK. SOUTHEAST FLOW ACROSS THE ALEUTIAN
RANGE WILL BRING SHOWER ACTIVITY TO MUCH OF SOUTHWEST AK DURING
THE SAME PERIOD...ENHANCED AT TIMES BY THE FRONTS AS THEY DECAY
OVERHEAD.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 155 160 165 170 172 175 176 177
   178 180 181 185.
FIRE WEATHER...RED FLAG WARNING 141.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...JN
SOUTHCENTRAL ALASKA...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...DS


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