Area Forecast Discussion
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000
FXAK67 PAJK 281452
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
552 AM AKST SUN DEC 28 2014

.SHORT TERM...VERY QUIET THROUGH MONDAY MORNING RELATIVELY
SPEAKING...EVEN FOG HAS BEEN NEARLY ABSENT THROUGH THE NIGHT FOR
THE AREA. HIGH PRESSURE AND DRY CONDITIONS NOW DOMINATING THE AREA
AND MAIN CHALLENGE TONIGHT HAS BEEN THE WIND FORECASTS IN RESPONSE
TO THE BUILDING ANTICYCLONE JUST TO OUR NORTH AND EAST. THE HIGH
BUILDS TO 1050+ MB AND MOVES SLOWLY SOUTHEASTWARD FOR THE NEXT 24+
HOURS. NORTHERN LYNN IS NOW EDGING TOWARDS GALE BUT WE DON`T HAVE
THEM PAST SCA UNTIL 21Z. GRADIENT STEADILY INCREASES TODAY BETWEEN
SKAGWAY AND JUNEAU...ONLY QUESTION WILL BE WHEN THE GALE LEVELS
ARE ACTUALLY REACHED. CURRENT SCA INCLUDES SOUTHERN LYNN. ALSO A
WEAK TO MODERATE TAKU WIND EPISODE IS EXPECTED FOR JUNEAU-DOUGLAS
AS CROSS BARRIER FLOW IS FORECAST BY THE HIGH-RES MODELS TO GET TO
40+KT LATER TODAY. THE ARW HAS NORTHEASTERLY SURFACE WINDS NEAR
JUNEAU AT 35KT FOR 00Z. PER BUFKIT SOUNDINGS DOESN`T APPEAR THAT
GUSTS WILL GET MUCH ABOVE 40KTS AS A CLASSIC MOUNTAIN WAVE
SIGNATURE IS NOT THERE. WE HAVE 40KT GUSTS IN THE ZONE BEGINNING
18Z THROUGH 03Z. SUMNER STRAIT GETS INTO THE ACT WITH SCA FROM 18Z
ONWARDS FOR OUTFLOW WINDS ON ITS EASTERN REACHES. FIVE FINGERS IS
CURRENTLY AT SCA LEVEL WINDS....STEPHENS PASSAGE CONTINUES FOR SCA
THROUGH 12Z MONDAY IN THE CURRENT PACKAGE. CROSS SOUND, ICY STRAIT
AND FREDERICK GET IN ON THE ACT TOO IN THE NEXT FEW HOURS. TWEAKED
THE SURFACE WINDS THROUGH 15Z MONDAY TO LINE UP THE DIRECTIONS A
BIT BETTER WITH THE CHANNELS...AND A BIT OF ENHANCEMENT ON THE
CENTRAL PANHANDLE ON CHANNEL SPEEDS. OTHERWISE DRY AND MOSTLY
CLEAR CONDITIONS CONTINUE THROUGH PERIOD WITH THE EXCEPTION OF THE
YAKUTAT AREA WHERE UPPER CLOUDS ARE ALREADY ON A GRADUAL INCREASE.
GALES MOVE INTO THE FAR WESTERN OUTER WATERS BY 12Z MONDAY. CURRENT
GRIDS MATCHED WITH NEW EC/NAM/GFS RUNS VERY WELL ON SCALES ABOVE
LOCAL...WITH ONLY SMALLER-SCALE TWEAKS NECESSARY.

.LONG TERM...GENERAL PATTERN THINKING REMAINS THE SAME AS PAST
SEVERAL DAYS. HIGH AMPLITUDE RIDGE WILL SHIFT TO THE SOUTH AND
EAST AHEAD OF AN APPROACHING FRONT IN THE GULF. THIS WEAK FRONT
WILL REACH THE PANHANDLE LATER TUESDAY INTO WEDNESDAY. MODEL
DISAGREEMENT INCREASES BY LATE WEEK, BUT THINKING REMAINS THAT
HIGH PRESSURE WILL BUILD BACK IN WITH NORTHERLY PRESSURE GRADIENT
STRENGTHENING AGAIN.

MONDAY WILL BE ANOTHER DRY DAY ACROSS THE PANHANDLE WITH HIGH
PRESSURE IN CONTROL. AS THE RIDGE BEGINS TO FLATTEN LATER MONDAY
INTO TUESDAY, HIGH CLOUDS WILL SPREAD INTO THE PANHANDLE FROM THE
WEST IN RESPONSE TO THE APPROACHING FRONT. THIS FRONT WILL BE
SIGNIFICANTLY WEAKENING AS IT MOVES INTO THE EASTERN GULF AS THE
PARENT LOW AND MAIN DYNAMICS ARE FAR TO THE WEST. THE MAIN MODEL
DIFFERENCE THAT HAS ARISEN IS HOW SHARP THE RIDGE AHEAD OF THIS
FRONT WILL BE AND WHERE THE RIDGE AXIS WILL SET UP. THIS WILL
DETERMINE HOW MUCH SOUTHERLY FLOW IS ABLE TO DEVELOP. THE
ECMWF/GFS HAVE A SHARPER RIDGE AND 2 MB OF SOUTHERLY GRADIENT
BEGINNING MONDAY NIGHT. THE NAM IS MUCH WEAKER AND KEEPS A LIGHT
NORTHERLY GRADIENT UNTIL WEDNESDAY MORNING. THIS HAS IMPLICATIONS
ON HOW MUCH WARM AIR IS ADVECTED NORTH BEFORE PRECIPITATION BEGINS
LATE TUESDAY. HAVE OPTED TO LEAN TOWARDS THE WARMER ECMWF SOLUTION
WITH SNOW OR RAIN/SNOW MIX AT SEA LEVEL FROM GUSTAVUS-JUNEAU NORTH
THEN QUICKLY CHANGING TO RAIN LATE TUESDAY NIGHT. LITTLE
ACCUMULATION IS EXPECTED. IF FUTURE RUNS CONTINUE TO SHOW THIS
SCENARIO, THE AMOUNT OF SNOW CURRENTLY IN THE FORECAST IS LIKELY
OVERDONE.

MANY QUESTIONS LATE WEEK AS MODEL DISAGREEMENT CONTINUES. THE
ECMWF CONTINUES TO SHOW AN INTERESTING SCENARIO WITH SOME ENERGY
PUSHING THROUGH A WEAKNESS IN THE RIDGE INTO THE SOUTHEAST GULF.
THIS OCCURS AS A SURFACE HIGH BUILDS INTO THE AREA FROM THE NORTH
WITH THE ARCTIC FRONT PUSHING SOUTH OVER THE PANHANDLE. THE 00Z
ECMWF AT THIS TIME HAS LIMITED PRECIPITATION TO THE SOUTHERN HALF
OF THE PANHANDLE. THE GEM HAS A SIMILAR SOLUTION BUT IS A BIT
FARTHER SOUTH. THE GFS IS THE DRIEST OF MODELS KEEPING ANY
PRECIPITATION FAR TO THE SOUTH. OPTED TO LEAVE FORECAST AFTER DAY
4 AS IS, BUT THIS WILL HAVE TO CONTINUE TO BE MONITORED OVER THE
COMING WEEK. HOWEVER, MODELS DO SEEM TO AGREE THAT THERE WILL BE
COLDER AIR SPILLING BACK INTO THE PANHANDLE BY NEXT WEEKEND.

USED MAINLY THE 00Z ECMWF FOR UPDATES TO THE FORECAST. FORECASTER
CONFIDENCE IS AVERAGE BUT DECREASES BY LATE WEEK WITH MODEL
DISAGREEMENT.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 9 AM AKST THIS MORNING THROUGH THIS AFTERNOON
     FOR AKZ025.
MARINE...GALE WARNING FOR PKZ012-052.
         SMALL CRAFT ADVISORY FOR PKZ013-021-022-031-034-035-041>043-051.

&&

$$

WESLEY/TPS

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