Small Craft Advisory 38, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
348 PM AKST TUE JAN 11 2011

.SHORT TERM...UPPER LEVEL TROF WILL SLOWLY DIG SWWD OVER THE
AREA THRU WED. ARCTIC HIGH PRESSURE WILL SLOWLY BUILD OVER NW
CANADA THRU WED. USED 12Z NAM FOR TONIGHT AND WED...MAINLY FOR
ITS BETTER HANDLING OF THE PRES GRADIENT ALONG THE MOUNTAINS.

MAIN FORECAST ISSUES WILL BE WINDS AND TEMPS. THE MOST CONCERN
WIND WISE WILL BE IN THE JUNEAU AREA...WHERE A TAKU WIND IS
EXPECTED TO DEVELOP TONIGHT...AND CONTINUE INTO WED. THE ONE
ELEMENT THAT THE MODELS HAVE HAD A HARD TIME WITH IS THE CRITICAL
LEVEL...AS THEY HAVE MADE MINOR SHIFTS IN THE UPPER LEVEL TROF
AXIS WITH EACH RUN. USING A CONSENSUS APPROACH ON THIS WOULD YIELD
AN EXCELLENT CRITICAL LEVEL FROM 12Z TONIGHT TO 00Z THU. EXPECT
THE HIGHEST WINDS TO OCCUR DURING THIS TIME...WITH 70+ KT GUSTS
LIKELY. BEFORE CRITICAL LEVEL SETS UP...STRONG COLD ADVECTION WILL
HELP TO MIX DOWN SOME OF THE MOMENTUM AND GUSTS TO 55 KT ARE
POSSIBLE BEFORE THE MAIN TAKU EVENT STARTS UP LATE TONIGHT.
ELSEWHERE...OUTFLOWS AND SOME COLD ADVECTION MIX DOWN WILL BE MAIN
WIND CONCERNS. ATTM...HAVE DECIDED TO STICK WITH CURRENT PUBLIC
WIND HEADLINES EXCEPT EXTEND OUT ZONE 26 UNTIL 4 PM WED. FOR
MARINE AREAS...STRONGEST WINDS WILL BE OUT OF INTERIOR PASSES AND
THRU LYNN CANAL. WILL SEE STORM FORCE WINDS IN LYNN CANAL BY LATE
TONIGHT. WILL HAVE SCA TO GALE FORCE WINDS IN MOST OTHER AREAS
ESPECIALLY LATE TONIGHT AND WED.

AS FOR TEMPS...COLD ADVECTION WILL INCREASE TONIGHT AND CONTINUE
THRU WED. MOS HAS BEEN TOO COLD OF LATE AND DID SLOW DOWN TEMP
DROP OFF TONIGHT A BIT FROM MOS GUIDANCE GIVEN DECENT WINDS WILL
BE SOMEWHAT WIDESPREAD. HOWEVER...TEMPS WILL LIKELY CONTINUE
FALLING SLOWLY THRU THE DAY WED...ESPECIALLY OVER THE N...AND WENT
NEAR MOS GUIDANCE BY 00Z THU MOST AREAS. ALL AREAS WILL BE BELOW
AVERAGE TEMP WISE BY LATE WED AFTERNOON...BY AS MUCH AS 15
DEGREES. GIVEN THE WIND EXPECTED AND THE FALLING TEMPS...WIND
CHILLS WILL BE A PROBLEM ESPECIALLY UP N. HAVE KEPT PAHN AND PAGY
ZONES AS WINTER WX ADVYS TO TAKE INTO ACCOUNT ADVY LEVEL WIND
CHILLS LATE TONIGHT AND WED AT HIGHER ELEVATIONS OF THOSE AREAS.
EVEN AT SEA LEVEL WIND CHILLS WILL LIKELY BE ZERO TO 15 BELOW BY
WED AFTERNOON OVER THE N. WILL HAVE FREEZING SPRAY DEVELOP OVER
THE NRN CHANNELS TONIGHT...AND REACH CENTRAL AREAS WED ONCE AIR
TEMPS OVER WATER GET COLD ENOUGH.

OTHERWISE...CLOUD COVER MAY BE A BIT TRICKY TO FORECAST
ESPECIALLY WED AS MODELS DIFFER ON STRENGTH OF A MID LEVEL VORT
MAX OVER THE SE GULF. THE GFS IS STRONGEST AND DEVELOPS MID-LEVEL
CLOUDS OVER THE SOUTHERN HALF OF THE AREA BY LATE WED
MORNING...WHILE OTHERS ARE WEAKER WITH THE VORT...AND DIFFER ON
CLOUD FORMATION JUST E OF IT OVER THE SRN AREA WED. WENT WITH A
BLENDED FORECAST WHICH BRINGS MOSTLY CLOUDY TO THE SRN AREA WED
AFTERNOON...WHILE THE N STAYS PARTLY CLOUDY TO MOSTLY CLEAR. THE
COLD AIR FLOWING OUT OVER THE GULF WILL DEVELOP CLOUD AND SNOW
SHOWER BANDS IN THE CONVERGENCE ZONES BETWEEN OUTFLOW AREAS ONCE
COLD ENOUGH AIR MOVES OUT THERE...WHICH LOOKS LIKELY TO OCCUR WED.
BASICALLY STUCK WITH PREVIOUS POP FORECAST TO HANDLE THIS.

&&

.LONG TERM...HIGH PRESSURE CONTINUES TO BE THE MAIN ISSUE FOR THE
FORECAST AREA. THE CONTINUED WIND AND COLD WILL PERSIST INTO
THURSDAY WITH COLDER TEMPERATURES OVER THE NORTHERN PORTION OF THE
PANHANDLE OCCURRING THURSDAY NIGHT INTO FRIDAY MORNING. SUB ZERO
TEMPERATURES OVER THE NORTHERN THIRD AND SPOTTY AREAS INTO THE
NORTH CENTRAL PANHANDLE. THE WINDS WILL ALSO HAVE VERY COLD WIND
CHILLS AROUND AS WELL.

SOUTHERN STREAM JET STREAM FROM THE PACIFIC AIMED AT THE BRITISH
COLUMBIA COAST THROUGH THE END OF THE WEEK IS TRYING TO DRIFT
NORTHWARD TO WHERE BY FRIDAY WITH THE NEXT SHORT WAVE INBOUND THAT
THERE IS AT LEAST A CHANCE OF SNOW ACROSS THE SOUTHERN. THERE IS
UNCERTAINTY ABOUT THIS SYSTEM AS ONE OF THE EARLY RUNS HAD THE
WAVE A LITTLE FURTHER NORTH THAT WAS SHOWING A POTENTIAL FOR A
SIGNIFICANT SNOWFALL THERE FOR FRIDAY.

LATER PORTIONS OF THE FORECAST PERIOD WAS ADJUSTED TO THE HPC
SOLUTION...AND A CHANCE OF SNOW ACROSS SOUTHERN HALF OF THE
PANANDLE FOR THE LAST COUPLE OF DAYS. FORECAST INTO THE EARLY
WEEKEND WAS ADJUSTED WITH AN INFLUENCE OF THE NAM AND ECMWF
SOLUTIONS.

CONFIDENCE IS ROUGHLY AVERAGE THROUGH THE TIME RANGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WIND ADVISORY UNTIL 4 PM AKST WEDNESDAY FOR AKZ026.
         HIGH WIND WARNING UNTIL 3 AM AKST THURSDAY FOR AKZ025.
         WIND ADVISORY UNTIL 3 AM AKST THURSDAY FOR AKZ017-022-029.
         WIND ADVISORY UNTIL 3 AM AKST THURSDAY FOR AKZ020.
         WINTER WEATHER ADVISORY UNTIL 4 PM AKST THURSDAY FOR AKZ018-019.
MARINE...HEAVY FREEZING SPRAY WARNING FOR PKZ011.
         HEAVY FREEZING SPRAY WARNING FOR PKZ013.
         HEAVY FREEZING SPRAY WARNING FOR PKZ012.
         STORM WARNING FOR PKZ012.
         GALE WARNING FOR PKZ011-013-021-022-031-035-043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ032>034-036-041-042.

&&

RWT/BEZENEK