Small Craft Advisory 694, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
347 PM AKST SUN NOV 6 2011

.SHORT TERM...AN OCCLUDED FRONT ALONG THE IMMEDIATE COAST WILL
MOVE ACROSS SOUTHEAST ALASKA THROUGH THE EVENING AND WILL EXIT
THE SOUTHEAST CORNER LATER TONIGHT. THE ASSOCIATED LOW OVER
SOUTHWEST ALASKA WILL EMERGE IN THE NORTHWEST GULF THIS EVENING
AND REMAIN NEARLY STATIONARY THROUGH MONDAY. A COLD TROUGH
EXTENDING SOUTH OF THIS LOW WILL ROTATE INTO THE EASTERN GULF
TONIGHT AND ACROSS SOUTHEAST ALASKA ON MONDAY. GALE FORCE
WESTERLY FLOW WILL CONTINUE ACROSS THE GULF.

 RADAR SHOWING FRONTAL BOUNDARY MOVING TOWARDS SITKA AT THIS TIME
AND EXPECT TO SEE WINDS SHIFT FROM ESE TO A SSW THIS AFTERNOON.
MODERATE SE GRADIENT THROUGH THE INNER CHANNELS KEEPING SOLID
SMCR IN LYNN CANAL, STEPHENS PASSAGE, AND CLARENCE INTO THE EARLY
EVENING BEFORE SLOWLY DIMINISHING OVER NIGHT. SAR IMAGERY SHOWING
 GALE FORCE WNW WINDS OVER THE OFFSHORE WATERS AND JUST STARTING
TO SPREAD INTO THE SOUTHEAST GULF.

 HAVE WIDESPREAD RAIN ACROSS ALL PANHANDLE EXCEPT FOR LINGERING
SNOW AND A NARROW BAND OF FREEZING RAIN WORKING NW ALONG THE
HAINES HIGHWAY. EXPECT THIS LINGERING WINTER WEATHER TO END BY
LATE AFTERNOON AND PLAN ON EXPIRING WSW WITH AFTERNOON UPDATE.
ONCE SE WINDS ARRIVE EXPECT TEMPS TO SHOOT UP INTO THE UPPER 30S
OR LOWER 40S WITH SNOW LEVELS RISING TO AROUND 2000 FT. LOWS
SHOULD BE ABOVE FREEZING ACROSS THE ARE TONIGHT.

 WILL BEGIN WEAK CAA ADVECTION BEHIND LEADING FRONT THIS EVENING
BUT STRONGER CAA WILL ACCOMPANY SECONDARY TROUGH AND THINK THIS
WILL CHANGE PRECIP BACK TO A MIX OF RAIN AND SNOW WITH ICE
PELLETS IN HEAVIER SHOWERS MONDAY. PAYA WILL HAVE BEST CHANCE OF
GOING BACK TO ALL SNOW BY MONDAY AFTERNOON AS COLD POOL MOVES
OVERHEAD. STABILITY WILL DROP AS COLD AIR MOVES IN AND CAN NOT
RULE AN ISOLATED THUNDERSTORM OVER NORTHERN COASTAL WATERS AS
EARLY AS THIS EVENING AND SPREADING TO SOUTHERN COASTAL WATERS ON
MONDAY.

 GOOD MODEL AGREEMENT THROUGH THE SHORT TERM. USED THE GFS TO
UPDATE GRIDS WITH ONLY MINOR CHANGES TONIGHT AND MONDAY.

.LONG TERM...THE MODELS ARE IN FAIR AGREEMENT THROUGH MID WEEK
THEN DIFFERENCES IN THE DETAILS SHOW UP LATE WEEK INTO NEXT
WEEKEND. OVERALL NOT MUCH CHANGE IN THE FORECAST FROM PREVIOUS THE
INCREASED TEMPS SOME AND THAT CHANGED SOME MIXED PRECIP TO ALL
LIQUID THROUGH THE WEEK. TEMPS WILL VARY AND BE NEAR THE
THRESHOLD FOR MIX PRECIP SO THIS WAS THE HARDEST PART OF THE
FORECAST. USED A BLEND OF THE GFS/EC THROUGH WED NIGHT THEN
REFRESHED THE FORECAST IN THE EXTENDED PORTION WITH THE NEW HPC
GUIDANCE.

AT THE START OF THE LONG TERM PERIOD DIGGING UPPER TROF WILL BE
DRIFTING INTO THE GULF THROUGH MON NIGHT. SHOWERS OVER THE
FORECAST AREA WILL BECOME SCATTERED LATE WITH AS A UPPER RIDGE
AHEAD OF THE TROF MOVES OVER SE AK. A SURFACE LOW WILL DEVELOP
FROM THE BASE OF THE UPPER TROF AND LIFT INTO THE NORTHERN GULF BY
TUE MORNING. PRECIP WILL START OUT AS SNOW NEAR PAYA WITH 1 TO 3
INCHES OF ACCUMULATIONS BUT AS THE WARM AIR LIFTS OVER THE AREA
AND MIXED TO THE SURFACE THE SNOW WILL CHANGE OVER TO RAIN BY THE
AFTERNOON. THE THREAT OF PRECIP OVER THE REST OF THE PANHANDLE
WILL INCREASE ALONG THE COAST BY THE AFTERNOON AND THEN INLAND TUE
NIGHT. FOR THE MOST PART THE P-TYPE WILL BE LIQUID BUT OVER THE
FAR NORTHERN AREAS THERE WILL BE AREAS OF RAIN AND SNOW. THE WINDS
WILL WILL BE STRONG OUT OF THE SOUTH TUE EVENING BUT AS THE FRONT
APPROACHES THE WINDS WILL BACK AROUND TO THE NORTH TUE AFTERNOON.

A THE UPPER LOW TRACKS EAST A STRONG LOW PRESSURE SYSTEM WILL DRIFT
NORTH TO BE NEAR HAIDA GWAII BY TUE NIGHT. IN DOING SO THE WINDS
OVER THE INNER CHANNELS WILL REMAIN FROM THE NORTH GENERALLY LESS
THAN 20 KT. THE PRECIP WILL TAPPER OFF OVER THE NORTHERN AREAS BUT
INCREASE OVER THE FAR SOUTHERN AREAS.

FOR THE REST OF THE WEEK...THE UPPER FLOW WILL BECOME MORE ZONAL
WITH ANOTHER LOW PRESSURE SYSTEM MOVING INTO THE GULF BY THURSDAY.
THIS SYSTEM WILL INCREASE WINDS OVER THE GULF TO MAX SMALL CRAFT
AND STRONG WINDS FROM THE SOUTH OF THE INNER CHANNELS. P-TYPE
AGAIN WILL BE TRICKY BUT THE THINKING IS THAT IT WILL START OUT AS
SNOW THEN MIX WITH RAIN WITH WAA. THIS ZONAL FLOW WILL PERSIST
INTO FRIDAY MORNING AS AFTER THAT THE MODELS ARE INDICATING THAT A
UPPER RIDGE WILL BUILD OVER THE GULF AND INCREASE THE OFFSHORE
FLOW OVER THE WEEKEND. THIS WILL DRY THE PANHANDLE OUT AND DROP
TEMPS WITH CAA FROM THE NW. THERE IS FAIR AGREEMENT WITH THIS
PATTERN AND AVERAGE FORECASTER CONFIDENCE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FREEZING RAIN ADVISORY UNTIL 4 PM AKST THIS AFTERNOON FOR AKZ019.
         STRONG WIND UNTIL 3 PM AKST THIS AFTERNOON FOR AKZ018.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-013-021-022-031>036-041>043-051-
     052.

&&

MM/ABJ