Gale Warning 280, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
340 PM AKDT TUE OCT 8 2013

.SHORT TERM...A STRONG WEATHER FRONT IS QUICKLY MOVING INTO THE
PANHANDLE. MODERATE TO HEAVY RAIN HAS BEEN FALLING IN YAKUTAT ALL
DAY AND WIND GUSTS OF 40 KT HAVE ALREADY BEEN REPORTED AT BERING
GLACIER WITH MUCH HIGHER VALUES FURTHER WEST. THE HEAVY RAIN AND
STRONG WINDS WILL MOVE INTO THE CENTRAL PANHANDLE THIS EVENING
AND OVER THE SOUTHERN AREAS LATE TONIGHT. WINDS THROUGH THE
NORTHERN INSIDE WATERS HAVE ALREADY INCREASED TO GALE FORCE TODAY
AND EXPECT A BRIEF PERIOD OF 50 KT STORM FORCE WINDS IN NORTHERN
LYNN CANAL THIS EVENING.

THIS FRONT IS BRINGING IN WARMER AIR ALOFT FROM THE TROPICS...SO
DO NOT EXPECT THE TEMPERATURE TO FALL MUCH OVERNIGHT. BEHIND THE
FRONT THE TEMPERATURE WILL FALL OR RATHER...NOT RISE MUCH DURING
THE DAY WEDNESDAY. THEREFORE HAVE DECREASED MAX TEMPERATURES
SLIGHTLY DUE TO THE CAA AND NOT EXPECTING MUCH SOLAR HEATING UNDER
MOSTLY CLOUDY TO CLOUDY SKIES. THE CAA WILL CAUSE INSTABILITY
BEHIND THE FRONT AND CHANGE THE RAIN TO SHOWERS. HAVE INCLUDED A
SLIGHT CHANCE OF THUNDERSTORMS OUT OVER THE GULF LATE TONIGHT
THROUGH TOMORROW WHERE THE INSTABILITY WILL BE THE GREATEST.

WINDS WILL REMAIN STRONG ONCE THE WINDS SHIFT TO THE WEST BEHIND
THE FRONT. THIS WILL ENHANCE THE SHOWERS THROUGH THE DAY ALONG
WEST FACING MOUNTAIN SLOPES AND ESPECIALLY ALONG THE COASTAL
MOUNTAINS. SEE THE HYDROLOGY SECTION ABOUT RAINFALL AMOUNTS AND
RIVERS.

ONLY MADE MINOR CHANGES TO THE FORECAST AS MODELS HAVE BEEN IN
GOOD AGREEMENT WITH THIS FRONT. MOST CHANGES WERE MADE FOR LOCAL
EFFECTS. FORECAST CONFIDENCE IS ABOVE AVERAGE.

.HYDROLOGY...TOTAL RAINFALL AMOUNTS OF AROUND AN INCH TO 2 INCHES
THROUGH MID DAY TOMORROW WILL CAUSE LOCAL RIVERS AND STREAMS TO
HAVE SHARP RISES. HOWEVER, WITH WATER LEVELS CURRENTLY LOW...DUE
TO THE LOWER FREEZING LEVELS...AND WITH THE FRONT LOOKING TO MOVE
FAIRLY QUICKLY DO NOT EXPECT ANY RIVER TO REACH BANKFULL. HOWEVER
LEVELS SHOULD BE MONITORED IN CASE THE FRONT SLOWS OR STALLS
KEEPING HEAVY RAIN OVER AN AREA FOR A LONGER PERIOD OF TIME.

 &&

 .LONG TERM...WED NIGHT THROUGH THU IS NOT LOOKING TOO BAD AS WE
ARE LEFT WITH REMAINING SHOWERS IN THE POST FRONTAL ENVIRONMENT.
THE MAIN CONCERN IS THE SW SWELL THAT WILL BUILD IN THE GULF DUE
TO THE DOMINATE SW FLOW. GIVEN THE LONG FETCH SWELL HEIGHTS WILL
REACH 11 TO 13 FT OUT OF THE SW ON WED NIGHT AND CONSEQUENTLY
WAVE HEIGHTS WILL REACH 20 FT AT THE SAME TIME. SWELL AND WAVE
HEIGHTS WILL GRADUALLY DECREASE THROUGH FRI.

 THE NEXT SYSTEM TO AFFECT THE AREA LATE WEEK COMES WITH LOADS OF
UNCERTAINTY ATTACHED TO IT AS THE FORECAST MODELS STRUGGLE WITH
DETERMINING HOW IT WILL DEVELOP. SOME MODEL RUNS FROM LAST NIGHT
HAD DEVELOPED A 990 MB LOW JUST SOUTH OF THE GULF ON THU NIGHT
AND SENDING IT INTO THE SOUTHERN PANHANDLE DUE TO A STRONG JET
STREAK AND SHARPER UPPER TROUGH MOVING OVER HEAD. WHILE OTHERS
DIDN'T EVEN HAVE THE FEATURE OR HAD IT WEAKER, SLOWER AND FARTHER
SOUTH. SINCE THEN, MODELS HAVE BEEN TRENDING AWAY FROM THE
STRONGER OF THE SOLUTIONS FOR THE SURFACE LOW. LATEST RUNS OF THE
ECMWF AND THE GEM (BOTH OF WHICH, SHOWED THE STRONGER LOW IN
THEIR PREVIOUS RUNS) NOW SHOW A WEAKER (AROUND 1006 MB) AND
FARTHER SOUTH TRACK MORE IN LINE WITH WHAT SOME OF THE OTHER
MODELS (UKMET, AND SREF) WERE SHOWING YESTERDAY. WITH NO CURRENT
MODEL RUNS SUPPORTING THE PREVIOUS FORECAST OF THE STRONGER LOW
MOVING INTO THE SOUTHERN PANHANDLE, I HAVE DECIDED TO BREAK AWAY
FROM CONSISTENCY AND GO TOWARD A BLEND OF THE 12Z ECMWF/GEM/SREF
FOR A WEAKER, SLOWER, AND FARTHER SOUTH TRACK TO THE LOW ON FRI
AND FRI NIGHT. THIS RESULTS IN A LIGHTER WIND AND SOMEWHAT LOWER
PRECIP FORECAST FOR FRI AND FRI NIGHT IN THE SE GULF AND SOUTHERN
PANHANDLE. THE REST OF THE PANHANDLE WILL STILL BE DEALING WITH
SOME RAIN FROM A WEAK FRONT THAT IS NOT ASSOCIATED WITH THE LOW
FARTHER SOUTH.

 ONCE WE GET CLEAR OF THE LATE WEEK SYSTEM, A RIDGE WILL BEGIN TO
BUILD OVER THE EASTERN GULF AND PANHANDLE BRINGING DRIER WEATHER
TO THE AREA FOR SAT AND SUN. EARLY NEXT WEEK IS LOOKING WET AGAIN
AS ANOTHER FRONT MAKES ITS WAY ACROSS THE GULF. MODELS ARE IN
BETTER AGREEMENT WITH THIS RIDGE AND FRONT BUT THEN CHOKE AGAIN
ON THE WAVES THAT FOLLOW THE FRONT MID NEXT WEEK. ALL IN ALL I
DON'T HAVE A LOT OF CONFIDENCE IN THE LONG RANGE FORECAST FROM
FRI ONWARD GIVEN THAT THE MODELS ARE JUMPING BETWEEN SEVERAL
SOLUTIONS AT THE MOMENT. DECIDED TO STICK WITH THE WPC DATA FOR
THE WEEKEND AND BEYOND FOR ITS USE OF ENSEMBLE DATA TO EVEN OUT
THE DIFFERENCES.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 1 AM AKDT WEDNESDAY THROUGH WEDNESDAY MORNING
     FOR AKZ026-027.
         STRONG WIND FROM 10 PM AKDT THIS EVENING THROUGH WEDNESDAY
     MORNING FOR AKZ020-021-024-025.
         STRONG WIND THROUGH WEDNESDAY MORNING FOR AKZ018-022-023.
         STRONG WIND FROM 1 AM AKDT WEDNESDAY THROUGH WEDNESDAY MORNING
     FOR AKZ028.
         STRONG WIND FROM 7 PM AKDT THIS EVENING THROUGH WEDNESDAY
     MORNING FOR AKZ019.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ017.
MARINE...STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-013-021-022-031>036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ053.

&&

FERRIN/EAL