Small Craft Advisory 241, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
248 PM AKDT MON APR 2 2012

.SHORT TERM...VERY WELL DEVELOPED MATURE LOW CURRENTLY LOCATED
OVER THE SOUTHEASTERN GULF WITH FOUR SEPARATE WRAPS VISIBLE IN
SATELLITE IMAGERY. A FEW OBSERVATIONS OF 50 KTS OR BETTER HAVE
BEEN REPORTED FROM STATIONS IN THE SOUTHEAST QUADRANT OF THIS
STORM BUT SO FAR NONE NOTED OVER SOUTHEAST ALASKA. THE FIRST BAND
WITH ASSOCIATED RAIN HAS MOVED THROUGH ALL BUT THE FAR NORTHERN
PANHANDLE WITH SUBSEQUENT BANDS AND THEIR RELATED SHOWER ACTIVITY
FORECAST TO CONTINUE TO MOVE ONSHORE THROUGH THE SHORT TERM
FORECAST PERIOD.

 VERY LITTLE CHANGE IN THE SYNOPTIC SITUATION THROUGH THE SHORT
TERM PERIOD AS THE LOW WILL BECOME QUASI-STATIONARY OVERNIGHT
TONIGHT AND SLOWLY WEAKEN THROUGH TUESDAY. PRECIPITATION
ASSOCIATED WITH THIS SYSTEM NOT MAKING IT VERY FAR INLAND WHICH
IS SURPRISING GIVEN THE LOW LEVEL JET STRENGTH, UPPER LEVEL
VORTICITY AND APPEARANCE OF THE SYSTEM IN SATELLITE IMAGERY. POP
AND QPF FIELDS FOR TONIGHT AND TOMORROW CONCENTRATE PRECIPITATION
OVER THE WESTERN HALF OF THE PANHANDLE SOUTH OF YAKUTAT. WARM
ADVECTION HAS OCCURRED AS EXPECTED, BUT DEW POINTS ARE LOW ENOUGH
THAT A MENTION OF SNOW MIXING IN WITH RAIN SHOWERS OVERNIGHT
SEEMED WARRANTED. NO ACCUMULATION EXPECTED ANYWHERE EXCEPT
POSSIBLY HYDER IN MISTY FJORDS. OVERNIGHT LOWS RANGING FROM THE
MID 20S VICINITY YAKUTAT, LOWER 30S OVER THE FAR NORTHERN INNER
CHANNELS,AND UPPER 30S OVER THE SOUTHERN PANHANDLE. HIGHS FOR
TOMORROW FROM THE MID 40S TO LOWERS 50S UNDER MOSTLY CLOUDY TO
CLOUDY SKIES AND SLOWLY DIMINISHING WINDS.

 GALES OVER THE COASTAL MARINE ZONES FROM CAPE SPENCER SOUTH FOR
TONIGHT...GRADUALLY DIMINISHING TO SMALL CRAFT INTENSITY ON THE
OUTSIDE LATE TOMORROW AFTERNOON. CARRIED A GALE IN CLARENCE
STRAIT AND THE DIXON ENTRANCE ALL THE WAY THROUGH TUESDAY
AFTERNOON. STRONG WIND HEADLINES CONTINUE TONIGHT FOR THE
SOUTHERN AND CENTRAL OUTER COAST AND FOR THIS EVENING FOR ZONE
28. HAVE ALSO HAD STRONG WINDS IN AND AROUND JUNEAU THROUGH THE
DAY. BELIEVE THESE ARE MORE RELATED TO GAP FLOW OUT OF INTERIOR
PASSES AND A WEAK MOUNTAIN WAVE OVER SHEEP MOUNTAIN. HAVE ALSO
EXTENDED STRONG WINDS IN THE JUNEAU PUBLIC ZONE FOR THE EARLY
EVENING BASED CURRENT OBSERVATIONS, HOWEVER THESE WIND GUSTS ARE
EXPECTED TO RELAX LATER TONIGHT.

 USED NAM FOR PRESSURE AND WIND BUT MODIFIED WIND SPEED UP TO BE
MORE IN LINE WITH GFS WIND SPEEDS. BLENDED GEM AND ECMWF FOR POP.
ADJUSTED TEMPS WITH BIAS CORRECTED NAM AND SREF. FORECAST
CONFIDENCE IS AVERAGE.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...THE LOW PRESSURE
SYSTEM IN THE SOUTHEAST GULF JUST WEST OF HAIDA GWAII WILL WEAKEN
TO AROUND 990 MB BY TUESDAY EVENING. THE LOW WILL DROP TO THE
SOUTH AND CONTINUE TO WEAKEN THROUGH WEDNESDAY. FOR THE SOUTHERN
PANHANDLE WINDS AND SHOWER ACTIVITY WILL DIMINISH WITH ONLY
ISOLATED SHOWERS REMAIN EARLY WEDNESDAY. MEANWHILE HIGH PRESSURE
RIDGE WILL MOVE OVER THE AK GULF AND WILL BE THE DOMINANT FEATURE
THROUGH THE WEEKEND AND POSSIBLY INTO EARLY NEXT WEEK. THIS WILL
MEAN WEAK WINDS, CLEAR SKIES AND DRY CONDITIONS FOR THE PANHANDLE.
EXCEPTION TO THE LIGHT WINDS WILL BE SEA BREEZE ACTIVITY IN THE
AFTERNOONS RESULTING FROM COOL WATER AND WARMING LAND INTERACTION.

WHILE MODELS ARE IN GOOD AGREEMENT THROUGH THE WEEK WITH RESPECT
TO OVERALL SYNOPTIC PATTERN. DO SEE SOME DIFFERENCES WITH LOCATION
OF THE RIDGE IN THE GULF BUT THESE RESULT IN ONLY MINOR CHANGES TO
THE FORECAST. BIGGEST ISSUE AMONG THE MODELS IS THE TIMING OF THE
RIDGE BREAK DOWN. BY LATE WEDNESDAY LOW PRESSURE SYSTEM MOVING
INTO THE BERING SEA WITH TROUGH EXTENDING DOWN INTO THE FAR
WESTERN GULF WAS SPLITTING WITH MAIN ENERGY MOVING SOUTH WITH
RESIDUAL SHORT WAVE TROUGH TRACKING EAST TOWARD THE AK PANHANDLE
BY THE WEEKEND. NEW RUNS STILL SHOW THE MAIN LOW MOVING SOUTHWARD
BUT THE NORTHERN SHORT WAVE NOW APPEARS TO BE BLOCKED BY THE AK
GULF HIGH PRESSURE AND INSTEAD OF MOVING TOWARD THE PANHANDLE
MOVING INTO THE AK INTERIOR. GFS KEEPS THE HIGH IN PLACE THROUGH
EARLY NEXT WEEK WHILE THE ECMWF DOES SHOWS A LOW MOVING IN FROM
THE BERING SEA LATE SUNDAY INTO MONDAY. GFS SHOWING MORE RUN TO
RUN CONSISTENCY COMPARED TO THE ECMWF BUT 12Z ECMWF WAS INDICATING
THE BLOCKING RIDGE REMAINING IN PLACE LONGER THAN THE 00Z ECMWF.
DUE TO SOME UNCERTAINTY HAVE KEPT CHANCE POPS IN THE
NORTHWESTERN GULF FOR MONDAY, BUT DID DROP POPS SLIGHTLY FOR THE
NORTHERN GULF.

MODELS WERE IN GOOD AGREEMENT AT THE START OF THE LONG TERM. GFS
WAS INITIALIZING WELL WHILE ECMWF LOOKING A BIT MORE OF AN OUTLIER
WITH THE POSITION OF THE LOW. INHERITED GRIDS WERE VERY CLOSE TO
THE 12Z GFS RUN SO ONLY MINOR TWEAKS WERE DONE. FOR THE REMAINDER
OF THE WEEK LITTLE CHANGE WAS MADE AS MODELS MATCHED UP AND
RESULTING WEATHER IS FAIRLY BENIGN. FORECAST CONFIDENCE IS ABOVE
AVERAGE THROUGH THE WEEK.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THROUGH TUESDAY MORNING FOR AKZ027.
         STRONG WIND FROM 7 PM AKDT THIS EVENING THROUGH TUESDAY MORNING
     FOR AKZ023.
         STRONG WIND UNTIL 10 PM AKDT THIS EVENING FOR AKZ028.
MARINE...GALE WARNING FOR PKZ022-033-035-036-041>043.
         SMALL CRAFT ADVISORY FOR PKZ011>013-021-031-032-034-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ052.

&&

FRITSCH/PRB