Small Craft Advisory 20, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
208 PM AKST TUE JAN 5 2016

.SHORT TERM...BENIGN WEATHER PATTERN FOR THE NEXT 24 HOURS OVER
SOUTHEAST ALASKA. THE MAIN STORY IS A PERSISTENT NORTHEASTERLY
GRADIENT ALONG THE COAST MOUNTAINS WHICH WILL BE SLIGHTLY ENHANCED
BY PRESSURE FALLS OVER THE EASTERN GULF TONIGHT AND WEDNESDAY.
THESE PRESSURE FALLS ARE IN RESPONSE TO AN UPPER LOW MOVING FROM
SOUTHWESTERN BRITISH COLUMBIA OVER THE SOUTHERN PANHANDLE TONIGHT
AND INTO THE EASTERN GULF ON WEDNESDAY.

NORTHERLY WINDS WILL BE STRONGEST IN THE VICINITY OF THE COAST
MOUNTAINS AS THE PRESSURE GRADIENT REMAINS TIGHTLY PACKED ALONG
THE MOUNTAIN RANGE. HAVE DECREASED WINDS IN LYNN CANAL OUTSIDE OF
TAIYA INLET DUE TO THIS AS WELL AS THE LACK OF COLD AIR IN CANADA
DRIVING THE NORTHERLY WINDS FARTHER SOUTH INTO THE CANAL. THE
STRONGEST WINDS WILL BE FELT NEAR TAIYA INLET WHERE THE SKAGWAY
AIRPORT HAS BEEN GUSTING TO 45-50 MPH TODAY. NORTHEASTERLY
PRESSURE GRADIENT FROM SKAGWAY TO TESLIN, YUKON IS 11 MB EARLY
THIS AFTERNOON AIDING IN THESE STRONG WINDS. EXPECT THIS GRADIENT
TO PERSIST THROUGH THE SHORT TERM PERIOD AND EVEN STRENGTHEN SOME
LATER TONIGHT AND EARLY WEDNESDAY. POTENTIAL OUTFLOW WINDS NEAR
DOWNTOWN JUNEAU AND DOUGLAS HAVE BEEN TONED DOWN TO 10 TO 15 MPH.
THINKING IS THE INVERSION WILL REMAIN BELOW RIDGE TOP RESULTING
IN WINDS STAYING ALOFT.

PRECIPITATION CHANCES REMAIN ZERO THROUGH THE PERIOD. AN INCREASE
IN CLOUD COVER CAN BE EXPECTED OVER THE SOUTHERN AND CENTRAL
PANHANDLE TONIGHT AND WEDNESDAY AS THE UPPER LOW MENTIONED ABOVE
MOVES THROUGH. INCLUDED PATCHY FOG IN PORTIONS OF THE CENTRAL AND
NORTHERN PANHANDLE INCLUDING JUNEAU...PETERSBURG...AND TENAKEE
INLET. AM NOT EXPECTING FOG TO BE AS WIDESPREAD AS THE PAST FEW
NIGHTS.

USED THE 12Z NAM/ECMWF FOR UPDATES TO THE INHERITED FORECAST.

.LONG TERM...UPPER RIDGE WILL REMAIN OVER WRN CANADA THROUGH MOST
OF THE LONG TERM PERIOD. WEAK ELY WAVE WILL MOVE TO THE ERN GULF
ON THU...BUT ANY PRECIP WITH THIS FEATURE IS EXPECTED TO STAY
MAINLY OFFSHORE. SURFACE PRESSURE GRADIENT WILL BE TIGHT FROM
SKAGWAY NWD WED NIGHT INTO FRI...WHICH SHOULD SUPPORT A
CONTINUATION OF STRONG WIND GUSTS TO 40 MPH. TIGHT GRADIENT IS NOT
EXPECTED TO BUILD S OVER LYNN CANAL...THUS LIMITED WINDS OVER THE
NRN CANAL TO SMALL CRAFT/25 KT OR LESS.

DEEP LAYER CYCLONE IS FORECAST TO MOVE N ACROSS THE ALEUTIANS
FRI/SAT...WHILE ASSOCIATED FRONTAL BOUNDARY PROGRESSES E OVER THE
GULF...REACHING THE PANHANDLE BY SAT AFTERNOON. THIS WILL INCREASE
THE PROBABILITY FOR SNOW/RAIN...THOUGH QPF AMOUNTS ARE NOT
EXPECTED TO BE PARTICULARLY LARGE DUE TO WEAK FORCING FOR ASCENT.
THEREAFTER...THE PATTERN BECOMES SLIGHTLY MORE PROGRESSIVE...AS
WEAK FRONTAL SYSTEMS ATTEMPT TO MOVE THROUGH/BREAK DOWN THE
CANADIAN RIDGE.

PRESSURE GRIDS WERE UPDATED WITH AN EC/NAM BLEND...TRANSITIONING
TO WPC FROM SAT ONWARD. REMAINDER OF THE FORECAST WAS UPDATED WITH
AN ENSEMBLE BLEND WERE NECESSARY...THOUGH THIS DID NOT RESULT IN
SUBSTANTIAL CHANGES TO THE INHERITED.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THROUGH WEDNESDAY AFTERNOON FOR AKZ018.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-031.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ022-041>043-051-052.

&&

TPS/GARNER

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