Area Forecast Discussion
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FXAK67 PAJK 290032
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
332 PM AKST WED JAN 28 2015

.SHORT TERM...COLD AIR HAS REMAINED IN PLACE THROUGH THE DAY SUCH
THAT THOSE LOCATIONS WHICH WOKE UP TO SNOW THIS MORNING ARE STILL
SEEING SNOW. VERY LITTLE CHANGE TO TEMPERATURES EXPECTED
OVERNIGHT AND PLENTY OF MOISTURE STREAMING IN FROM THE SOUTH, SO
MORE SNOW IS FORECAST OVERNIGHT. HAVE ISSUED A WINTER STORM WARNING
FOR HAINES, AND HAVE WINTER WEATHER ADVISORIES FOR GUSTAVUS,
SKAGWAY, AND HAINES. A VERY MODEST INCREASE IN TEMPS OVERNIGHT IN
THE JUNEAU AREA IS POSSIBLE AND TEMPS ARE MOST LIKELY GOING TO
RISE ABOVE FREEZING TOMORROW, SO THAT ADVISORY WILL END FIRST AT
6AM.

SATELLITE IMAGERY IS SHOWING A FRONT ORIENTED NORTH-SOUTH AND
MOVING NNE OVER THE PANHANDLE. WATER VAPOR IMAGERY ALSO REVEALING
A BROAD AND SOLID CONNECTION TO LOW LATITUDE MOISTURE SOURCE. TPW
VALUES FAIRLY MODEST AT AROUND 1 INCH BUT WITH THE TRAINING MOTION
OVER SOUTHEAST ALASKA, THE NET EFFECT WILL BE MUCH MORE INTENSE.
RADAR DATA THROUGH THE DAY CONFIRMING THIS WITH UPWARDS OF 60 DBZ
TOTAL REFLECTIVITY BEING OBSERVED. 500MB DEFORMATION AND TEMPS
INDICATING AT LEAST ONE FRONTOGENETIC BAND IS MOVING NORTH ACROSS
THE PANHANDLE TODAY. ALL THIS ADDS UP TO A SIGNIFICANT INCREASE TO
THE SNOW TOTALS IN THE SHORT RANGE FORECAST ISSUED THIS AFTERNOON.

THINK THE RAIN-SNOW LINE WILL REMAIN SOMEWHERE BETWEEN ANGOON AND
ICY STRAIT FOR MOST OF THE NIGHT, SO HAVE RAIN FOR MOST OF THE
SOUTHERN PANHANDLE. RAIN HEAVY AT TIMES FOR THE FAR SOUTHERN
PORTION OF THE PANHANDLE. COORDINATED WITH ENVIRONMENT CANADA
REGARDING THE AREA AROUND HYDER AND STEWART WITH A RAIN-SNOW MIX
FOR BOTH TONIGHT AND TOMORROW MORNING. NOT ANTICIPATING MORE THAN
1 INCH THERE.

BLENDED NAM, GFS, AND GEM FOR UPDATES TO PRESSURE WITH THE GEM
BEING USED TO MORE CLEARLY CAPTURE A WAVE DEVELOPING INTO A SURFACE
LOW ALONG THE FRONTAL BOUNDARY. POP AND QPF PRIMARILY FROM NAM
WITH A LITTLE HELP FROM GFS. TEMPS PRIMARILY PER GFS MOS. OVERALL
FORECAST CONFIDENCE IS AVERAGE.

.LONG TERM...MODELS BEGINNING TO SHOW INCREASING THREAT FOR PRECIP
TO THE SRN AREA LATER THU NIGHT/FRI. GEM/EC/NAM ALL SHOW A LOW
MOVING NE TOWARD THE FAR SERN AREA...WITH SOME DIFFS IN EXACT
TRACK AND STRENGTH BETWEEN THE MODELS. USED BLEND OF THE 12Z GEM/EC/NAM
TO HANDLE THIS SYSTEM. POPS RAISED TO LIKELY BY EARLY FRI FOR THE
FAR SRN ZONES...WITH CHANCE POPS FOR THE S-CENTRAL AREA. ALSO
DRIED THINGS OUT SOME OVER THE NRN AREAS DUE TO THIS SYSTEM
TURNING FLOW OFFSHORE QUICKER. COLDER AIR SHOULD PUSH IN FROM THE
N ONCE SYSTEM MOVES OUT OF THE AREA FRI NIGHT AND SAT.

FOR THE WEEKEND AND BEYOND...ENDED UP MAINTAINING THE GEM/EC/NAM BLEND
THRU SAT...THEN WENT WITH LATEST WPC FROM SUN ONWARD. BLENDED WPC
WITH THE GEM/EC FOR SAT NIGHT. STRONG HIGH PRESSURE WILL BUILD
OVER INTERIOR AK AND NW CANADA. LOOKING LIKE A FRONT WILL TRY TO
MOVE NWD INTO THE AREA FOR THE SAT NIGHT-SUN PERIOD...BUT IT WILL
RUN INTO THE COLDER AND DRIER AIR MOVING SWD. THINK BEST THREAT
FOR PRECIP WILL BE OVER THE SRN HALF OF THE AREA WITH THIS SYSTEM.
LOOKS LIKE THE ARCTIC HIGH WILL FINALLY SLIDE OFF TO THE SE EARLY
NEXT WEEK WITH MORE SYSTEMS COMING TOWARD THE AREA FROM THE
SW...SO LOOKS LIKE INCREASING PRECIP THREAT AND MODERATION OF
TEMPS WILL OCCUR. SIGNIFICANT MODEL DIFFERENCES WHERE THE
SHORTWAVE ENERGY GOES HOWEVER...SO CONFIDENCE IN EXACT TIMING/TRACK
OF SYSTEMS NEXT WEEK IS BELOW AVERAGE.

&&

.AVIATION...MAIN IMPACTS TO AVIATION ACTIVITIES WILL BE REDUCED
VISIBILITIES IN SNOW. WIDESPREAD CEILINGS BELOW MOST PANHANDLE
MOUNTAINTOPS. AND ICING, MOSTLY RIME, HAS BEEN REPORTED BELOW FL100 IN
PIREPS TODAY. AM FULLY EXPECTING THOSE CONDITIONS TO CONTINUE
THROUGH TOMORROW AFTERNOON. SEE AAWU AIRMETS ZULU AND SIERRA AS
WELL AS THE APPLICABLE FA FOR ADDITIONAL INFORMATION.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY UNTIL 6 AM AKST THURSDAY FOR AKZ025.
         WINTER STORM WARNING UNTIL NOON AKST THURSDAY FOR AKZ019.
         WINTER WEATHER ADVISORY UNTIL NOON AKST THURSDAY FOR AKZ018-020.
         STRONG WIND UNTIL 4 PM AKST THIS AFTERNOON FOR AKZ018.
MARINE...GALE WARNING FOR PKZ022-036-041.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-031>035-042-043-051-052.

&&

$$

FRITSCH/RWT

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