Small Craft Advisory 491, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
339 PM AKDT MON SEP 3 2012

.SHORT TERM...WET WEATHER CONTINUES OVER THE AREA AS SOME WEAK
FRONTAL BANDS MOVE THROUGH THE AREA. MOSTLY LIGHT PRECIP AND LESS
THEN 20 KT WINDS HAVE BEEN NOTED WITH THIS SYSTEM SO FAR. THE
EXCEPTIONS TO THIS ARE NORTHERN LYNN CANAL AND SKAGWAY WHERE S
WINDS 20 TO 25 KT HAVE BEEN BLOWING ALL MORNING, AND THE NORTHERN
GULF WHERE A BARRIER JET HAS CAUSED MIN GALE FORCE WINDS AROUND
THE AREA OF CAPE SUCKLING AND SMALL CRAFT WINDS ALONG THE REST OF
THE NORTHERN GULF.

INTO TONIGHT AND TOMORROW, ONSHORE FLOW AND A UPPER LEVEL TROUGH
MOVING THROUGH THE AREA WILL KEEP RAIN AND CLOUDY SKIES IN THE
FORECAST FOR MOST OF THE SHORT RANGE PERIOD. POPS DO NOT LESSEN
ACROSS THE AREA UNTIL AT LEAST TOMORROW MORNING FOR THE WESTERN
HALF OF THE PANHANDLE AND TOMORROW AFTERNOON FOR THE EASTERN HALF
AS THE TROUGH AND ASSOCIATED VORTICITY FINALLY MOVE INTO CANADA.
HELPING THE DRYING TREND OUT TOMORROW IS A BUILDING SURFACE RIDGE
OVER THE EASTERN GULF AND PANHANDLE THAT APPEARS TO BE STRONGER
AND SHARPER THEN THE ONE THAT WAS TRYING TO BUILD BEFORE THE
CURRENT SYSTEM EARLY THIS WEEKEND.

WINDS IN THE NORTHERN GULF WILL RELAX THIS EVENING AS THE FRONT
HELPING TO PRODUCE THE BARRIER JET RECEDES INTO CANADA. LYNN CANAL
AND SKAGWAY WILL BE ANOTHER STORY. SOUTHERLY WINDS, ALREADY
BLOWING AT ABOUT 20 KT CURRENTLY WILL INCREASE LATER THIS EVENING
AS A LOW FORMS UNDER THE EXIT REGION OF A WEAK 500 MB JET STREAK
ALONG THE RETREATING FRONT IN THE SOUTHERN YUKON. WINDS WILL
INCREASE TO 30 KT LATER TONIGHT AS THE SKAGWAY TO JUNEAU GRADIENT
DECREASES TO -3 MB. WINDS IN THE OTHER NORTH-SOUTH CHANNELS IN THE
NORTHERN PANHANDLE WILL HAVE SOME HIGHER WINDS AS WELL LATER
TONIGHT BECAUSE OF THIS. WINDS WILL DIMINISH A BIT DURING THE
MORNING AS THE LOW WEAKENS AWAY DUE TO THE LOSS OF ITS UPPER
SUPPORT, BUT WILL REMAIN SOMEWHAT HIGH AND MAY INCREASE AGAIN IN
THE AFTERNOON AS THE SURFACE RIDGE BUILDS TOMORROW. WINDS
ELSEWHERE WILL BE 20 KT OR LESS IN MOST PLACES.

SHORT RANGE MODELS ARE IN DECENT AGREEMENT THROUGH TOMORROW.
DECIDED ON USING THE NAM FOR THE DETAILS THAT IS COULD PROVIDE
OVER THE AREA. FORECAST CONFIDENCE IS ABOVE AVERAGE.

&&

.LONG TERM...A FLAT RIDGE WILL BE MOVING INLAND OVER SOUTHEAST
ALASKA TUESDAY NIGHT THAT TILTS TO THE SOUTHEAST AND MOVES OUT OF
THE AREA WEDNESDAY EVENING. NEXT FRONT MOVES TO PAYA AREA
WEDNESDAY MORNING AND THEN SLOWLY SINKS SOUTHWARD THROUGH
WEDNESDAY NIGHT. A FLAT RIDGE BUILDS OVER THE GULF THURSDAY AND
FRIDAY WITH A FEW DISTURBANCE MOVING OVER THE TOP OF THE RIDGE IN
MODERATE WESTERLY FLOW. A MODERATELY STRONG FRONT WITH A TRIPLE
POINT LOW WEST OF CDE EXPECTED NEXT WEEKEND.

ONSHORE FLOW OVER FLAT RIDGE WILL KEEP CLOUDS ACROSS THE AREA WITH
A CHANCE OF RAIN FOR NORTHERN PANHANDLE TUESDAY NIGHT. SOUTHERN
AREAS COULD SEE BREAKS IN CLOUDS ON WEDNESDAY AS RIDGE AXIS MOVES
THROUGH.

NEXT FRONT MOVES TO YAKUTAT AREA WEDNESDAY MORNING. THIS FRONT IS
UNDER A 140 KT SW JET MAX AND HAS DEEP MOISTURE. EXPECT A BARRIER
TYPE JET TO SET UP ACROSS THE NORTHERN GULF WHICH WILL INCREASE ESE
WINDS TO GALE FORCE. THIS WEAKENS TO SMCR FOR COASTAL WATERS
WEDNESDAY AFTERNOON. RAINFALL WILL BE HEAVY AT TIMES FOR YAKUTAT
ON WEDNESDAY AND POSSIBLE ALONG THE NORTHERN COAST WEDNESDAY
NIGHT. THE FRONT WEAKENS AS IT DROPS SOUTH AND PRECIP IS EXPECTED
TO DIMINISH ACROSS SOUTH CENTRAL WITH ONLY A CHANCE OF RAIN FOR
SOUTHERN.

BEHIND THIS FRONT ANOTHER FLAT RIDGE BUILDS OVER THE GULF WHICH
KEEPS ONSHORE FLOW INTO THE PANHANDLE THURSDAY AND FRIDAY. THERE
ARE AT LEAST 2 SMALL TROUGHS THAT PUSH ACROSS THE TOP OF THE RIDGE
AND HAVE KEPT A CHANCE OF FOR THIS.

MODELS IN GOOD AGREEMENT THROUGH THE LONG TERM. USED NAM TO UPDATE
TUESDAY NIGHT AND WEDNESDAY AND MADE LITTLE IN THE WAY OF CHANGE
TO LATER PERIODS.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
         SMALL CRAFT ADVISORY FOR PKZ012-013-031-036-043-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042.

&&

EAL/MM