Area Forecast Discussion - Southeastern
FXAK67 PAJK 121457
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
557 AM AKST FRI FEB 12 2016
.SHORT TERM...SATELLITE IMAGERY IS SHOWING A LOW THAT HAS MOVED
INTO THE CENTRAL GULF AS OF EARLY THIS MORNING. THE RELATED FRONT
IS CURRENTLY MOVING OVER THE PANHANDLE FROM SOUTH TO NORTH. A
TRANSITION FROM STRATIFORM TO CONVECTIVE PRECIPITATION WAS
OBSERVED OVERNIGHT IN WEATHER RADAR IMAGERY AND HAVE OPTED TO
START OUT THE SHORT TERM FORECAST WITH SHOWER TERMINOLOGY. WHILE
THE FRONT ITSELF WILL NOT STALL OVER SOUTHEAST ALASKA, SHOWERS
WILL REMAIN OVER THE FORECAST AREA FOR THE DURATION OF THE SHORT
TERM PERIOD AND BE AUGMENTED BY A SHORT WAVE THAT IS MOVING NORTH
PAST HAIDA GWAII THIS MORNING. SOME HEAVY PRECIPITATION WAS
REPORTED OVERNIGHT OVER THE SOUTHERN ZONES AND MORE HEAVY SHOWER
ACTIVITY IS EXPECTED LATER THIS AFTERNOON AND EVENING AROUND
YAKUTAT AND POINTS WEST. IN BETWEEN, LIGHT TO MODERATE PRECIP IS
EXPECTED. TEMPERATURES CONTINUE TO RUN WELL ABOVE NORMAL, SO
PRECIP FROM THIS SYSTEM WILL BE ALMOST ENTIRELY IN THE FORM OF
RAIN. POSSIBLE EXCEPTIONS ARE THE HIGHWAYS OUT OF HAINES AND
SKAGWAY AND HAINES ITSELF WHERE TEMPS AND DEWPOINTS ARE MARGINALLY
SUPPORTIVE OF SNOW THIS MORNING. 

GALE WARNINGS ISSUED FOR THE COASTAL MARINE ZONES FROM CAPE
EDGECUMBE NORTH THIS MORNING AS WELL AS OFFSHORE ZONE 310. ON THE
INSIDE, SMALL CRAFT SOUTHEASTERLIES IN CLARENCE STRAIT THIS
MORNING. MARGINAL SMALL CRAFT WINDS FOR CLARENCE STRAIT AND
FREDERICK SOUND SOUTH OF CAPE FANSHAW LATE TONIGHT AS WELL.
OTHERWISE, WINDS 20 KTS OR LESS ON THE INSIDE. CURRENT NORTHERLY WINDS
OVER THE NORTHERN INNER CHANNELS WILL SHIFT TO THE SOUTH AS THE
LOW PROGRESSES FARTHER NORTH AND THE PRESSURE GRADIENT REVERSES.
THE LOW ITSELF IS FAR ENOUGH OFFSHORE THAT HAZARDOUS WINDS ARE NOT
ANTICIPATED AT THE SURFACE OVER ANY OF THE PUBLIC ZONES. THERE
WERE SOME 35 TO 50 MPH WIND GUSTS IN AND AROUND DOWNTOWN JUNEAU
OVERNIGHT, BUT THE FRONT LOOKS LIKE IT HAS PASSED THROUGH AS OF
EARLY THIS MORNING, AS PRESSURES ARE RISING AT THE AIRPORT AND
WINDS AT THE JUNEAU TIDE GAUGE AND FEDERAL BUILDING HAVE
DIMINISHED. SIMILAR RELAXATION OF WIND AND WIND GUSTS OBSERVED AT
PETERSBURG, WRANGELL, AND KETCHIKAN AS THE FRONT PASSED THROUGH
AND PRESSURES BEGAN TO RISE.

USED A BLEND OF OF NAM AND GFS FOR UPDATES TO PRESSURE AND WIND.
POP AND QPF FROM GFS AND CANADIAN NH. MODEL GUIDANCE FOR
TEMPERATURES SIGNIFICANTLY COLDER THAN OBSERVED VALUES SO A
MODIFIED PERSISTENCE APPROACH WAS USED WITH TEMPS FROM THURSDAY
AND THURSDAY NIGHT USED AS A STARTING POINT, THEN MODIFIED A FEW
DEGREES COOLER BASED ON VERY WEAK COOL AIR ADVECTION FROM THE
SOUTH OF THE NEXT 24 HOURS. OVERALL FORECAST CONFIDENCE IS
AVERAGE.
.LONG TERM...OVERALL UPPER LEVEL PATTERN OF RIDGE OVER WESTERN
CANADA AND TROUGH OVER THE ALEUTIANS CONTINUES THROUGH MUCH OF
THE LONG RANGE PERIOD. AS A RESULT WE ARE STILL STUCK WITH S TO SW
FLOW AND FRONT AFTER FRONT BRINGING RAIN, WIND, AND WARMER
TEMPERATURES TO THE PANHANDLE. THERE ARE SOME CHANGES IN THE
WORKS HOWEVER AS A STRONGER SHORTWAVE TROUGH STARTS TO CUT INTO
THE WESTERN SIDE OF THE RIDGE MID NEXT WEEK ALLOWING SOME COOLER
AIR TO FILTER INTO THE AREA. THIS APPEARS TO BE SHORT LIVED AS THE
RIDGE POPS BACK UP NEXT WEEKEND.

AT THE SURFACE, WE AT LEAST HAVE TWO MORE FRONTS THAT COME THROUGH
THIS WEEKEND. ONE COMES SAT NIGHT WITH THE SECOND COMING SUN
NIGHT. MID RANGE MODELS ARE IN DECENT AGREEMENT ON THE TIMING OF
THE FEATURES BUT ARE HAVING TROUBLE WITH THE STRUCTURE OF THE
SECOND FEATURE. NAMELY THEY CAN NOT DECIDE IF THE FRONT WILL JUST
BE AN OPEN WAVE, OR WILL A CLOSED LOW FORM ON IT THAT WILL BE
AIMED AT THE CENTRAL PANHANDLE. GFS AND GEM FAVOR THE CLOSED LOW,
WHILE THE NAM IS WEAKER AND FARTHER SOUTH, AND THE ECMWF JUST
SHOWS AN OPEN WAVE. GFS AND GEM SEEMS TO FIT TOGETHER BETTER AND
HAD SOME ENSEMBLE SUPPORT SO WENT WITH THE CLOSED LOW APPROACH.

MODEL AGREEMENT BECOMES EVEN WORSE AS EARLY AS TUE AS THE NEXT
DISTURBANCE MOVES INTO THE SE GULF. AT THIS POINT MOST
OPERATIONAL MODELS ARE DEVELOPING A LOW JUST SOUTH OF THE GULF ON
MON AND BRINGING IT UP INTO THE SE GULF BY TUE. THE PROBLEMS COME
FROM WHERE IT EXACTLY GOES AND HOW STRONG IT IS. FOR TUE MORNING,
SOLUTIONS RANGE FROM A 1000 MB LOW NEAR DIXON ENTRANCE, A 989 MB
LOW IN THE SOUTHERN GULF OR A MORE TROUGH LIKE FEATURE ACROSS THE
NORTHERN GULF. ENSEMBLE SOLUTIONS DO NOT OFFER MUCH EXCEPT THAT
THEY POINT TOWARD SOME WEAK TROUGH LIKE FEATURE IN THE EASTERN
GULF AT THAT POINT. MODEL DISAGREEMENT ALSO CONTINUES INTO LATE
WEEK AS WELL. IN LIGHT OF THE RATHER POOR MODEL AGREEMENT ELECTED
TO DO FEW CHANGES FOR MON AND BEYOND TO AWAIT FOR FURTHER MODEL
RUNS TO FLESH THIS SYSTEM OUT.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ043-051-052. 
     SMALL CRAFT ADVISORY FOR PKZ022-031-034-036-041-042-053. 
&&

$$

FRITSCH/EAL

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