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000
FXAK67 PAJK 070128
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
428 PM AKST FRI DEC 6 2013

.SHORT TERM...THE SURFACE PRESSURE PATTERN OVER THE PANHANDLE IS
VERY WEAK...TO THE POINT THAT DETERMINING A WIND DIRECTION IS
DIFFICULT. MID AND UPPER LEVEL FLOW REMAINS NORTHERLY WITH HIGH
PRESSURE OVER OVER THE GULF SO HAVE USED THAT ALONG WITH
STREAMLINES TO ADJUST WIND DIRECTIONS FOR THIS PACKAGE...ALTHOUGH
OVERALL WINDS WILL BE LIGHT. ONE EXCEPTION TO THIS IS THE HYDER
AND MISTY FJORDS AREA WHERE A NELY OUTFLOW WIND CONTINUES TONIGHT
AS THE STRONG SURFACE HIGH PRESSURE IN B.C. IS CAUSING A PRESSURE
GRADIENT THERE.

 MID AND HIGH CLOUDS ARE MOVING IN FROM THE NORTH AND CAUSE MAKE
FOR MOSTLY CLOUDY SKIES OVERNIGHT. DESPITE THE CLOUD COVER THE
LIGHTER WINDS TONIGHT AND SNOW COVERED GROUND WILL STILL ALLOW
FOR RADIATIONAL COOLING TONIGHT AND MAKE FOR ANOTHER COLD MORNING
SIMILAR TO THE PAST SEVERAL DAYS. TEMPERATURES AT 850MB WILL BE
WARMING THROUGH THE SHORT TERM PERIOD AND CONTINUE THE INVERSION
THAT HAS BEEN GOING. WITH LITTLE WIND THERE WON`T BE MUCH
OPPORTUNITY FOR THESE WARMER TEMPERATURES TO MIX DOWN...HOWEVER
STILL HAVE HIGHS TOMORROW REACHING THE LOWER 30S TO NEAR 40 ALOFT
ALONG THE OUTER COAST. CONFIDENCE IN THE INNER VALLEYS GETTING
THAT WARM IS LOW AFTER MINS IN THE TEENS TO SINGLE DIGITS AGAIN.

 SOME MODELS ARE INDICATING A SLIGHT CHANCE OF PRECIP TONIGHT AND
TOMORROW. THIS IS MAINLY LIMITED TO THE COASTAL AREAS AROUND
YAKUTAT AND SITKA AS WELL AS NORTH OF WHITE PASS. HAVE CLOUDS
MOVING INTO THESE AREAS BUT DID NOT INCLUDE MUCH POPS IN THE
FORECAST AS THERE IS NOT A LOT OF FORCING TO CAUSE PRECIP.
THINKING THAT IF ANYTHING DID FALL OUT IT WOULD EVAPORATE BEFORE
HITTING THE GROUND.

 USED MAINLY THE NAM12 FOR UPDATES TODAY. MAIN ADJUSTMENTS WERE
TO DECREASE POPS AND WIND SPEEDS.

 &&

.LONG TERM...MAIN FORECAST CHALLENGE IN THE EXTENDED RANGE
FORECAST COMES FAIRLY EARLY. AT ISSUE IS THE INTERSECTION OF WARM
AIR ALOFT MOVING IN FROM THE WEST, VERY LITTLE WIND AND BELOW
FREEZING TEMPS AT THE SURFACE AND POP VALUES GREATER THAN 15
PERCENT AND A VERY STABLE LOW LEVEL AIRMASS. SUM TOTAL OF THIS IS
THE THREAT OF FREEZING DRIZZLE. ANOTHER QUESTION IS WHETHER OR NOT
ANY SUPERCOOLED LIQUID WATER ALOFT WILL EVAPORATE AS VIRGA BEFORE
REACHING THE SURFACE. THIS SCENARIO WOULD BE MORE OF A CONCERN FOR
AIRCRAFT FLYING APPROACHES THROUGH THE WARMER AIR ALOFT, THEN ICING
UP AS THEY ENTER THE COLDER NEAR SURFACE AIR. BUFKIT DRAWN UPON
HEAVILY FOR THE AFTERNOON EXTENDED RANGE FORECAST AND MAIN FOCUS
WAS ON SUNDAY NIGHT. HAVE ONE MORE DAY TO LOOK AT THIS DEVELOPING
SITUATION SO HAVE OPTED TO NOT INCLUDE REFERENCES TO FREEZING
RAIN IN THE AFTERNOON FORECAST FOR FEAR OF RAISING PUBLIC CONCERNS
THAT WE IN SOUTHEAST ALASKA ARE ABOUT TO EXPERIENCE WHAT ANCHORAGE
JUST WENT THROUGH.

APART FROM THE POTENTIAL FOR FREEZING RAIN SUNDAY NIGHT, THE LONG
RANGE FORECAST REMAINS FAIRLY QUIET UNTIL LATE TUESDAY NIGHT OR
WEDNESDAY, WHEN THE NEXT WELL ORGANIZED FRONT ARRIVES FROM THE
WEST ALONG THE OUTER COAST. THIS SYSTEM WILL HAVE A TRAJECTORY
THAT MORE OFTEN THAN NOT RESULTS IN RAIN RATHER THAN SNOW FOR
SOUTHEAST ALASKA. THE LOW ASSOCIATED WITH THIS FRONT WILL PUSH FAR
ENOUGH TO THE EAST TO RESULT IN WIDESPREAD SMALL CRAFT WINDS OVER
THE COASTAL MARINE ZONES AND GALE FORCE WINDS OVER OFFSHORE MARINE
ZONE 310. RESULTING OFFSHORE PRESSURE GRADIENT WILL GENERATE SMALL
CRAFT WINDS OVER MOST OF THE INNER CHANNELS AS WELL AS GALES OVER
NORTHERN LYNN CANAL ON WEDNESDAY.

USED A BLEND OF NAM AND ECMWF FOR PRESSURE AND WIND THROUGH MONDAY
NIGHT WIT WPC THEREAFTER. POP AND QPF FROM GEM, GFS, AND ECMWF.
USED SOME NAM AS WELL THROUGH SUNDAY NIGHT. TEMPS AND RELATIVE
HUMIDITY PRIMARILY FROM GFS. FORECAST CONFIDENCE IS AVERAGE TO
BELOW AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.

&&

$$

FERRIN/FRITSCH