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
000
FXAK67 PAJK 260003 CCA
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE JUNEAU AK
403 PM AKDT SAT OCT 25 2014

.SHORT TERM...WEAKENING LOW SW OF HAIDA GWAII WILL MOVE SE AWAY
FROM THE AREA THRU SUN. A LOW PRESSURE TROF OVER THE ERN GULF WILL
PUSH SLOWLY INLAND OVER SE AK THRU SUN. A WEAK LOW OVER THE NW
GULF WILL MOVE TO THE NE GULF SUN AFTERNOON. USED BLEND OF THE 12Z
NAM WITH PREVIOUS FORECAST FOR TONIGHT AND SUN...ALTHOUGH DID
BLEND IN 15Z SREF FOR POPS.

MAIN FORECAST CONCERNS WILL BE PRECIP POTENTIAL...AND HOW MUCH FOG
WILL BE AROUND ESPECIALLY TONIGHT. RIGHT NOW LOOKS LIKE SCATTERED
SHOWERS ARE OVER THE ERN GULF ROUGHLY W OF A PAYA-BUOY 46084 LINE.
THINK THESE SHOWERS WILL BEGIN A SLOW EWD PUSH AS WEAK UPPER TROF
MOVES ONSHORE TONIGHT. THE SHOWERS MAY GET AS FAR E AS THE PAJN
AREA BY LATE TONIGHT. EXPECT THEM TO BE FAIRLY ISOLATED OVER THE
INNER CHANNELS THOUGH. THEN...AS A SHORTWAVE TROF INTENSIFIES OVER
THE NRN GULF AND PUSHES EWD SUN...AND LOW LEVEL TROF MOVES
INLAND...SHOWERS SHOULD BE ON THE INCREASE. BEST LIFT SHOULD
ARRIVE FOR SUN AFTERNOON OVER THE NRN AREA...AND HAVE POPS RISING
TO LIKELY FOR THAT PERIOD FOR MUCH OF THE N. WEAKER LIFT FURTHER S
WILL MEAN LESS SHOWER COVERAGE BUT EVEN THE SRN COASTAL AREA
SHOULD GET INTO SOME SHOWERS SUN...ESPECIALLY IN THE AFTERNOON.
ONLY KEEPING THE HYDER AREA OUT OF ANY SHOWERS THRU SUN AFTERNOON.

AS FOR THE FOG...THERE IS A POCKET OF FOG OVER THE PAJN AREA THAT
IS SLOWLY ERODING AROUND THE EDGES OF THE FOG BANK. THE FLOW IS
NOT FORECAST TO INCREASE IN THE AREA TONIGHT...AND TIDE WILL BE
FALLING DURING THE EVENING HOURS EXPOSING MORE WET GROUND...SO THE
FOG WILL LIKELY THICKEN AGAIN EARLY THIS EVENING. MAY ISSUE DENSE
FOG ADVY FOR THIS EVENING IN THE PAJN AREA. BIG QUESTION IS WHAT
HAPPENS LATER THIS EVENING AND OVERNIGHT AS CLOUDS MOVE IN. THINK
THESE CLOUDS WILL HELP DISSIPATE ANY REMAINING FOG IN THE PAJN
AREA LATER TONIGHT. FURTHER S...PATCHY FOG IS LIKELY TO DEVELOP
OVER THE SRN HALF OF THE AREA AS WINDS DIE OFF TONIGHT. THERE HAS
BEEN A LOT OF SUNSHINE THERE TODAY WHICH HELPED DRY OUT THE LOWER
LEVELS SOME...SO NOT EXPECTING THE FOG TO GET TOO THICK IN MOST
PLACES DOWN S.

OTHERWISE...WINDS WILL DIMINISH OVER THE INNER CHANNELS TONIGHT AS
LOW TO THE S OF THE AREA MOVES AWAY. TEMPS WILL BE TRICKY
ESPECIALLY OVER THE N WHERE CLOUDS SHOULD MOVE IN LATER THIS
EVENING. DECIDED TO ALLOW TEMPS TO DROP QUICKLY THIS EVENING FOR
MUCH OF THE NRN AREA...THEN RISE SLOWLY OVERNIGHT. TEMPS IN SOME
AREAS SHOULD DROP BELOW FREEZING...BUT RISE ABOVE FREEZING AS
CLOUDS MOVE IN LATER TONIGHT. ANY SHOWERS THAT DO FALL NEAR SEA
LEVEL TONIGHT AND SUN MORNING SHOULD REMAIN LIQUID AS MAIN
FREEZING LEVEL IS ABOVE 2000 FEET.

.LONG TERM...LONG RANGE FORECAST STARTS OUT FAIRLY QUIET AS THE JET
STREAM APPEARS TO BE IN A SPLIT FLOW PATTERN. THE STRONGER
SOUTHERLY JET EXTENDS ACROSS THE NORTHERN PACIFIC AIMED AT THE
PACIFIC NW. EMBEDDED IN IT IS THE REMAINS OF HURRICANE ANA WHICH
WILL BE SOUTH SOUTHWEST OF HAIDA GWAII BY SUN EVENING. THE
NORTHERN BRANCH IS TIED UP BY A LOW OVER THE NORTHERN BERING SEA
WITH ONLY A MUCH WEAKER PART OF IT SLIPPING INTO THE NORTHERN GULF
AND SOUTH CENTRAL ALASKA. THE WEAKER PART IS ACCOMPANYING A WEAK
UPPER TROUGH JUST AHEAD OF A BUILDING RIDGE IN THE WESTERN GULF.
THE BUILDING RIDGE AND TROUGH WILL BRIEFLY AFFECT THE THE
PANHANDLE ON MON BUT BOTH FEATURES GET QUICKLY SHOVED OUT OF THE
WAY BY THE BERING SEA UPPER LOW. THIS SPELLS THE END OF THE SPLIT
FLOW PATTERN AS THE BERING SEA LOW PLUNGES INTO THE GULF ON TUE
CONNECTING THE SOUTHERN STREAM JET UP WITH THE NORTHERN STREAM BY
WED. THE RESULTING DEEP UPPER TROUGH STICKS AROUND JUST TO OUR
WEST FOR WED AND THU BRINGING S UPPER FLOW TO THE PANHANDLE.
WESTERLY UPPER FLOW AGAIN RETURNS ON FRI.

AT THE SURFACE, THE WEAK UPPER TROUGH ON SUN NIGHT AND MON HAS
ENOUGH VIGOR THAT MOST OF THE PANHANDLE WILL SEE RAIN SHOWERS OUT
OF THIS. MOST AREAS ARE TOO WARM FOR SNOW YET, BUT THIS TROUGH IS
DRAGGING DOWN SOME MORE COOL AIR FROM INTERIOR ALASKA. AGAIN
NOTHING REALLY COLD YET BUT IT WILL BE ENOUGH TO LOWER SNOW LEVELS
ON THE BACK SIDE OF THE TROUGH AND FORM A 1020 MB HIGH IN THE
SOUTHERN YUKON LATE MON NIGHT. AREAS LIKE SKAGWAY, HAINES, AND
YAKUTAT MAY SEE SOME SNOW MIXING IN WITH THE RAIN SHOWERS JUST
BEFORE THE PRECIP ENDS LATE SUN NIGHT OR EARLY MON MORNING AS
1000-850 MB THICKNESSES DROP TO NEAR 1290 M SUN NIGHT. ANY
ACCUMULATIONS WILL BE LIGHT. MEANWHILE THE SOUTHERN PANHANDLE WILL
BE CLIPPED BY THE SYSTEM THAT HOLDS THE REMAINS OF HURRICANE ANA
ON MON. NOT EXPECTING MUCH EXCEPT FOR A FEW LIGHT RAIN BANDS AS
MOST OF THE TROPICAL MOISTURE AND ENERGY WILL REMAIN SOUTH OF THE
PANHANDLE.

FOCUS THEN SHIFTS NORTH AGAIN AS THE COOLER AIR DRAGGED DOWN BY
THE UPPER TROUGH SETTLES IN THE SOUTHERN YUKON SETTING UP AN
OUTFLOW EVENT THROUGH AT LEAST MID WEEK. NORTHERLY PRESSURE
GRADIENTS OF AROUND 6 MB BETWEEN JUNEAU AND SKAGWAY WILL PRODUCE
GALE FORCE WINDS FOR LYNN CANAL AND SMALL CRAFT WINDS FOR MANY OF
THE OTHER NORTHERN CHANNELS BY THE TIME TUE ROLLS AROUND. DOWNTOWN
JUNEAU AND DOUGLAS WILL HAVE TO BE WATCHED FOR A TAKU WIND EVENT AS
WELL. CROSS BARRIER FLOW IS FORECAST TO INCREASE TO 35 TO 45 KT ON
TUE. HOWEVER THE CRITICAL LEVEL IS NOT VERY WELL DEFINED OR
NON-EXISTENT AT THIS TIME SO SOME GUSTY WINDS ARE EXPECTED BUT
REALLY HIGH WINDS ARE NOT. THE SECONDARY EFFECT OF THIS OUTFLOW IS
THAT THE NORTHERN TWO THIRDS OF THE PANHANDLE WILL DRY AND CLEAR
OUT. SO THE POTENTIAL IS THERE FOR SOME COLD OVERNIGHT LOWS
THROUGH MID WEEK.

PAST TUE MODEL AGREEMENT SUFFERS AS THEY CAN NOT AGREE ON HOW THE
LOW DROPPING FROM THE BERING SEA PANS OUT. THE GENERAL CONSENSUS
IS THAT THERE WILL BE A SYSTEM WITH MULTIPLE LOW CENTERS IN THE
GULF BUT EXACTLY WHERE AND HOW STRONG IS UP FOR DEBATE. THE
GENERAL TRENT OVER THE LAST 24 HOURS SEEMS TO BE LINING UP MORE
WITH THE ENSEMBLE MEANS WITH A GENERAL LOW SOMEWHERE IN THE
CENTRAL GULF. THIS IS A WESTWARD TREND FROM WHAT THE PREVIOUS
FORECAST HAD. AS FOR THE PANHANDLE, PRECIP RETURNS SOMETIME WED OR
WED NIGHT AND WILL CONTINUE THROUGH THE END OF THE WEEK. AREAS
AROUND SKAGWAY, HAINES, AND YAKUTAT MAY BE COOL ENOUGH FOR SNOW
AT THE BEGINNING BUT WILL LIKELY WARM BACK UP AND CHANGE OVER TO
RAIN RATHER QUICKLY EXCEPT AT HIGHER ELEVATIONS.

LONG RANGE MODELS WERE IN DECENT AGREEMENT THROUGH AROUND TUE.
DECIDED ON USING THE NAM AND ECMWF FOR GUIDANCE THROUGH TUE AS
BOTH HAD DECENT REPRESENTATION OF THE PRESSURE GRADIENT AND
OUTFLOW ON MON INTO TUE NIGHT. PAST THIS POINT FAVORED THE WPC
DATA WITH ITS USE OF ENSEMBLE MEANS IN THE FORECAST AS THE
OPERATIONAL MODELS WERE DISPLAYING TOO MUCH DISAGREEMENT AND
CONSISTENCY ISSUES TO GET A CONFIDENT FORECAST OUT OF.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.

&&

$$

RWT/EAL

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.