Storm Warning 58, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
209 PM AKST MON DEC 28 2015

.SHORT TERM...FAIRLY ACTIVE WEATHER AS A GALE FORCE FRONT PUSHES
TOWARDS THE PANHANDLE THIS EVENING THEN DISSIPATES OVERNIGHT.
PRECIPITATION SHIELD SPREADING FROM YAKUTAT INTO NORTHERN AND
CENTRAL PANHANDLE, WHILE SOUTHERN PANHANDLE REMAINS DRY.

THE START OF THE SHORT TERM FORECAST PERIOD WILL FEATURE A
WEAKENING WEATHER FRONT PUSHING INTO THE PANHANDLE. EXPECT 35 TO
40 KT GALE FORCE WINDS ON THE OUTSIDE WATERS THIS EVENING,
DIMINISHING OVERNIGHT. THE HIGH RESOLUTION NMM MODEL IS SHOWING
ENHANCED SOUTHERLY WINDS IN THE LOWER LEVELS ACROSS THE NORTHERN
PANHANDLE. THUS, PUT IN 25 TO 30 KT SOUTHERLY SMALL CRAFT WINDS
FOR LYNN CANAL, NORTHERN CHATHAM STRAIT, AND GLACIER BAY. ALSO PUT
IN 25 TO 30 KT EASTERLY SMALL CRAFT WINDS FOR CROSS SOUND, ICY
STRAIT, AND STEPHENS PASSAGE. LATE THIS MORNING, THE WINDS IN
HAINES FLIPPED FROM LIGHT WEST TO EAST WIND 10 TO 20 MPH, AND THE
TEMPERATURES JUMPED FROM AROUND 20 DEGREES TO THE LOW 30S DUE TO
THE MUCH WARMER WATER TEMPERATURES OF NORTHERN LYNN CANAL. AREAS
SUCH AS JUNEAU, GUSTAVUS, AND HOONAH ALSO SEE AN ENHANCEMENT IN
SOUTHEASTERLY WIND THIS MORNING. DO EXPECT SOUTHEASTERLY WIND OF
10 TO 20 MPH TO PERSIST THROUGH THE EVENING BEFORE TAPERING OFF AS
THE FRONT DISSIPATES OVER THE PANHANDLE.

AFTERNOON TEMPERATURES ROSE TO THE LOW TO MID 30S FOR MOST OF THE
PANHANDLE. WITH PRECIPITATION, CLOUD COVER, AND WIND, EXPECT THE
TEMPERATURES TO SLOWLY FALL OR BE STEADY OVERNIGHT. THE WARMER
AIR IS ALREADY FILTERED INTO THE OUTER COAST INCLUDING YAKUTAT,
ELFIN COVE, AND SITKA. DO EXPECT PRECIPITATION IN THESE AREAS TO
STAY AS RAIN PRIMARILY. FOR GUSTAVUS, ANGOON, AND HOONAH, DO
EXPECT A RAIN SNOW MIX WITH LITTLE OR NO SNOW ACCUMULATION. FOR
JUNEAU, WHERE THERE IS A LITTLE BIT MORE COLDER AIR, PRECIPITATION
SHOULD STAY AS MOSTLY SNOW. HOWEVER, QPF AMOUNTS WILL DECREASE AS
ONE MOVES MORE INLAND (OR EAST). THUS, ONLY EXPECT UP TO 1 INCH OF
SNOW ACCUMULATION, WITH THE HIGHEST AMOUNTS WITHIN MENDENHALL
VALLEY. FOR HAINES AND SKAGWAY, WHERE THERE IS A GREATER SUPPLY
OF COLD AIR, PRECIPITATION WILL STAY MOSTLY SNOW. UP TO 3 INCHES
OF SNOW EXPECTED NEAR THE BORDER AND WHITE PASS.

BY WEDNESDAY MORNING, CHANGEOVER TO RAIN WILL BE EXPECTED IN
HOONAH, GUSTAVUS, AND HOONAH. CHANGEOVER TO RAIN WILL MOVE INTO
JUNEAU AREA BY WEDNESDAY AFTERNOON. SNOW LEVEL ON THE OUTER COAST
WILL RISE ABOVE 2000 FEET. HIGHS ON WEDNESDAY WILL BE A FEW DEGREES
WARMER THAN TUESDAY.

FORECAST CONFIDENCE IS ABOUT AVERAGE. AS ALWAYS, PRECIPITATION
MICROPHYSICS POST SIGNIFICANT FORECAST CHALLENGES. USED HIGH
RESOLUTION NMM MODEL IN UPDATING THE WIND FIELD, AND USED ECMWF/GEM
IN REFRESHING THE PRECIPITATION RELATED FIELDS.

.LONG TERM...BULK OF THE LONG TERM PERIOD WILL BE CHARACTERIZED BY
PERSISTENT TROUGHING OVER THE ALEUTIANS ANCHORED BY A 160 KT
ZONAL JET TO ITS S OVER THE N PAC. THIS PATTERN WILL YIELD A
CONTINUOUS SERIES OF UPPER TROUGHS EJECTING NE ACROSS THE GULF AND
PANHANDLE. AS A RESULT...AN EXTENDED PERIOD OF WET AND MILD
WEATHER IS EXPECTED ACROSS SERN AK.

THE FIRST DISTURBANCE TO IMPACT THE REGION WILL MOVE N OVER THE
GULF DURING WED...AND WILL FEATURE A GALE FORCE FRONT THAT IS
FORECAST TO STALL OVER THE OUTSIDE WATERS DUE TO HIGHLY MERIDIONAL
FLOW ALOFT. MODEL GUIDANCE SHOWS PW VALUES NEAR 2 STANDARD
DEVIATIONS ABOVE CLIMO SPREADING N TO YAKUTAT/AKZ017...WHICH
PERSISTS THROUGH THU MORNING. MODERATE TO HEAVY RAINFALL APPEARS
PROBABLE AS A RESULT. THE GULF FRONT THEN GETS KICKED EWD TO THE
PANHANDLE COAST ON THU AS A RIDGE BREAKS DOWN OVER BC IN RESPONSE
TO AN UPPER IMPULSE EJECTING NE. HIGH PW AIRMASS SUBSEQUENTLY
SHIFTS E AIDING IN LOCALLY MODERATE/HEAVY RAINFALL OVER THE
CNTRL/SRN PANHANDLE THU/THU NIGHT.

BEYOND THU...MODEL GUIDANCE REMAINS IN FAIR AGREEMENT WITH LARGE-
SCALE FEATURE EVOLUTION...SHOWING CONTINUED MOIST SSWLY FLOW
ALOFT SPREADING ACROSS THE GULF. THE STRONG SLY FLOW REGIME WILL
ALSO PROMOTE WARM BOUNDARY LAYER TEMPERATURES...FAVORING
HIGHS IN THE 30S/40S...AS WELL AS FREEZING/SNOW LEVELS RISING
TO 1000 FT NEAR SKAGWAY...AND 4000 FT NEAR KLAWOCK.

INHERITED FORECAST WAS IN LINE WITH LATEST MODEL GUIDANCE...THUS
NO MAJOR DEVIATIONS WERE NECESSARY. DID BUMP UP QPF VALUES
SLIGHTLY DURING THE MIDDLE OF THE WEEK. PRESSURE GRIDS WERE LEFT
UNCHANGED THROUGH FRI...THEN NUDGED TOWARD 12Z WPC GUIDANCE.
TEMPERATURE GRIDS WERE LEFT VIRTUALLY UNTOUCHED.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ042-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-022-031>033-035-036-041-
     053.

&&

RCL/GARNER

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