Area Forecast Discussion
Issued by NWS

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
000
FXAK67 PAJK 072331
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
331 PM AKDT TUE JUL 7 2015

.SHORT TERM...THE RIDGE OF HIGH PRESSURE THAT HAS PERSISTED OVER
THE EASTERN GULF FOR THE PAST FEW DAYS IS WEAKEN AND SHIFTING TO
THE SOUTH AND EAST. A WEAK FRONTAL BAND ASSOCIATED WITH A PARENT
LOW IN THE BERING SEA IS SLOWLY MOVING EAST OVER TOP OF THE RIDGE.
LIGHT RAIN HAS BEEN REPORTED IN YAKUTAT EARLY THIS AFTERNOON AND
THE BAND OF RAIN WILL CONTINUE TO MAKES IT WAY TO THE EAST INTO
THE NORTHERN PANHANDLE BY LATE TONIGHT. PRECIPITATION THAT DOES
FALL OVER THE NORTHERN PANHANDLE LATE TONIGHT AND TUESDAY MORNING
WILL BE VERY LIGHT AND EXPECT AT THE MOST 0.10" OF RAINFALL. THERE
IS VERY WEAK FORCING WITH THIS FEATURE AS THE PARENT LOW IS
SEVERAL HUNDRED MILES AWAY.

MARINE STRATUS MADE IT INLAND AGAIN THIS MORNING INTO ICY STRAIT
AND ALONG THE OUTER COAST. IT CAME INLAND IN GUSTAVUS AND SITKA AS
AN ELEVATED LAYER ABOUT 1K OFF THE GROUND WHILE THE ELFIN COVE AND
YAKUTAT AREAS SAW SOME REDUCTION TO VISIBILITY WITH LOWER
CEILINGS AND FOG. DO HAVE A CONCERN THAT STRATUS COULD MAKE ITS
WAY FARTHER NORTH INTO CLARENCE STRAIT LATE TONIGHT AND WEDNESDAY
MORNING AS NORTHWESTERLIES SUBSIDE WITH THE RIDGE. DECIDED TO
LEAVE THIS OUT OF THE FORECAST BUT WILL BE SOMETHING TO KEEP AN
EYE ON.

BIGGEST FORECAST PROBLEM OF THE SHORT TERM WAS A PIECE OF
UPPER LEVEL ENERGY MOVING INTO THE CENTRAL PANHANDLE WEDNESDAY
AFTERNOON. THIS WILL BRING A PERIOD OF MORE SIGNIFICANT, BUT NOT
HEAVY RAINFALL TO A PORTION OF THE PANHANDLE. THERE IS MODEL
DISAGREEMENT ON THE EXACT TRACK OF THIS FEATURE WITH THE 12Z ECMWF
TAKING A FURTHER NORTH TRACK WITH THIS MORE SIGNIFICANT RAINFALL
IMPACTING LOCATIONS AS FAR NORTH AS ICY STRAIT AND OVER INTO
JUNEAU. THIS WAS A SHIFT FROM PREVIOUS MODEL RUNS SO DID NOT JUMP
ON THE FARTHER NORTH SOLUTION AT THIS POINT. THE 12Z GFS ON THE
OTHER HAND TAKES IT OVER THE SOUTHERN PANHANDLE. OPTED TO GO WITH
THE MIDDLE OF THE ROAD APPROACH AS THE 12Z NAM TAKES IT OVER THE
CENTRAL PANHANDLE. BUT GENERALLY EXPECT A PERIOD OF STEADIER
RAINFALL TO BEGIN OVER BARANOF ISLAND OVER INTO THE CENTRAL
PANHANDLE LATE WEDNESDAY AFTERNOON.

TIGHTENING PRESSURE GRADIENT OVER THE NORTHERN PANHANDLE HAS
RESULTED IN GUSTY WINDS IN LYNN CANAL AND SKAGWAY THIS AFTERNOON.
EXPECT THIS TO PERSIST THROUGH THE EVENING BEFORE DIMINISHING LATE
TONIGHT. AS THE RIDGE AXIS PUSHED EAST EARLY THIS AFTERNOON WINDS
INCREASED TO SMALL CRAFT LEVELS AND SHIFTED TO THE SOUTHWEST AT
CROSS SOUND. ALSO EXPECT WINDS IN THAT AREA TO DIMINISH THIS
EVENING AS THE PRESSURE GRADIENT WEAKENS.

.LONG TERM...HIGH PRESSURE RIDGE OVER THE AK GULF AND PANHANDLE
CONTINUES TO BREAK DOWN THROUGH THE REST OF THE WEEK AS SURFACE
LOW EXTENDING FROM MAIN LOW IN THE BERING SEA MOVE INTO THE AK
GULF BY THE WEEKEND. A SHORT WAVES WILL TRACK OVER THE SOUTH
CENTRAL PANHANDLE BEFORE THE WEEKEND BUT AS IT IS MAINLY UPPER
LEVEL FEATURES SO NOT EXPECTING MUCH IN THE WAY OF RAIN OR WINDS.
THIS TRANSITION TO MORE TYPICAL SE AK WEATHER WITH COOLER
TEMPERATURES AND HIGHER RAIN POTENTIAL WILL CONTINUE THROUGH MOST
OF THE LONG RANGE WITH A SHORT BREAK ON FRIDAY. GREATEST POTENTIAL
FOR RAINFALL WILL BE START OF NEXT WEEK WHEN MORE SUBSTANTIAL
SURFACE LOW MOVES INTO THE GULF.

REMNANTS OF WAVE MOVING OVER THE WEAKENING RIDGE WILL CROSS OVER
THE CENTRAL PANHANDLE, KEPT CHANCE POPS DUE TO THE LIMITED
DYNAMICS. STILL NOT MUCH IN THE WAY OF QPF SO KEEPING PRECIP AS LIGHT. THERE
IS A SPLIT BETWEEN MODELS ON THIS SYSTEM WITH THE ECMWF MOVING
PRECIP FROM THE WAVE FURTHER NORTH THAN NAM/GFS/GEM. 850 MB
ONSHORE FLOW WILL KEEP MORE CLOUD COVER OVER MOST OF THE REGION
WITH SOME BREAKS OCCURRING ON FRIDAY AS LAST OF THE HIGH PRESSURE
RIDGE MOVES OVER THE PANHANDLE INTO BRITISH COLUMBIA. AS WE MOVE
INTO THE WEEKEND STARTING TO SEE BETTER ORGANIZED SYSTEMS FORM IN
THE GULF. LATEST RUNS SHOW NEXT LOW MOVING INTO THE SOUTHEAST GULF
THEN SWINGING A BIT TO THE NORTH. EXTENDED PATTERN SHOWS MORE
WAVES CROSSING INTO THE GULF, SO EXPECT PRECIP TO BE AT OR BIT
ABOVE NORMAL THIS TIME OF YEAR.

WITH ONLY WEAK FORCING WINDS WILL BE GENERALLY LIGHT. EXCEPTIONS
REMAIN LYNN CANAL WHICH WILL STILL HAVE S 20 KT WINDS WITH
GRADIENT BETWEEN SEMI PERSISTENT LOW OVER THE YUKON AND HIGHER
PRESSURE OVER THE PANHANDLE. NEW MODELS DID HAVE A SHIFT IN
WINDS OVER THE GULF FROM WEST TO EAST THURSDAY INTO FRIDAY. GULF
WINDS WILL START TO PICK UP AFTER THE WEEKEND AS THE MORE
ORGANIZED SYSTEMS MOVE IN.

NEW MODEL RUNS FELL MORE IN LINE WITH THE SHORT WAVE MOVING INTO
THE GULF. WHILE PRESSURE FIELDS WERE PRETTY CLOSE ECMWF WAS
OUTLIER ON POP. THROUGH DAY 4 UPPER LEVEL PATTERN DIFFERENCES WERE
MINOR BUT AS SURFACE FEATURES ARE WEAK MODEL PRESSURE FIELDS NEVER
QUITE LINED UP, SO HAD SOME WIND DIRECTION DIFFERENCE OVER THE
INNER CHANNELS. STARTING TO SEE OPERATIONAL MODELS FALL IN LINE
AFTER DAY 5 BUT NOT ENOUGH, SO KEPT WITH THE WPC ENSEMBLE BLEND.
FORECAST CONFIDENCE IS ABOVE AVERAGE THEN DROPS BY THE WEEKEND.

&&

.HYDROLOGY...WARM TEMPERATURES OVER THE PAST FEW DAYS HAS LED TO
NEAR BANK FULL CONDITIONS ON THE TAIYA RIVER. THE RIVER IS EXPECTED
TO CREST AROUND 16.1 FT THIS EVENING BEFORE FALLING AGAIN
OVERNIGHT. COOLER TEMPERATURES IS EXPECTED TO LOWER WATER LEVELS
THROUGH THE REMAINDER OF THE WEEK.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-041.

&&

$$

TPS/PRB

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU







USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.