Area Forecast Discussion
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FXAK67 PAJK 311325
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
525 AM AKDT FRI OCT 31 2014

.SHORT TERM...SEVERAL UPPER VORT LOBES ARE FORECAST TO CONSOLIDATE
INTO A CLOSED LOW OVER THE BERING SEA DURING THE NEXT 24
HRS...WHILE A LEAD IMPULSE MOVES E ACROSS THE GULF. AS THIS TAKES
PLACE...SURFACE LOW PRESSURE WILL GRADUALLY DEEPEN INVOF BRISTOL
BAY...AND ASSOCIATED FRONTAL BOUNDARY MOVES RAPIDLY EWD ACROSS THE
GULF FRI NIGHT BEFORE ENTERING THE PANHANDLE SAT MORNING. IN THE
MEANTIME...A WEAK TROUGH CURRENTLY LOCATED OVER THE ERN GULF WILL
CONTINUE TO SUPPORT SHOWERS OVER SERN AK AS IT PROGRESSES INTO WRN
B.C. BY THIS EVENING. DESPITE THE PRESENCE OF COLD AIR
ALOFT...STEEP MIDLEVEL LAPSE RATES...AND WEAK CAPE...THE LACK OF
STRONG FORCING FOR ASCENT AND RELATIVELY COOL WATER TEMPERATURES
SHOULD PRECLUDE OFFSHORE THUNDERSTORM DEVELOPMENT TODAY.
STRENGTHENING LOW-LEVEL WAA OCCURRING INVOF THE APPROACHING GULF
FRONT WILL THEN YIELD MODERATE STRATIFORM RAINFALL OVER THE
PANHANDLE TONIGHT.

WINDS WILL BE THE PRIMARY HAZARD DURING THE SHORT TERM PERIOD.
ENHANCED LEE TROUGHING/PRESSURE GRADIENT WILL PERSIST OVER LYNN
CANAL DUE TO 30 KT MIDLEVEL SWLYS SPREADING ACROSS THE
AREA...RESULTING IN A PROLONGED PERIOD OF SMALL CRAFT WINDS. OVER
THE OUTSIDE WATERS...50 KT SELY LLJ WILL MATERIALIZE BY TONIGHT
AND AID IN GALE FORCE WINDS BY 09Z SAT. SLY LLJ WILL THEN SPREAD
INLAND BY 12Z SAT...YIELDING GALE FORCE WINDS FOR CLARENCE
STRAIT...AND HIGH END SMALL CRAFT SPEEDS OVER STEPHENS PASSAGE.
ENELY GAP WINDS MAY STRENGTHEN TO GALE OVER CROSS SOUND AS WELL.
ATTM...LOW-LEVEL STABILITY IS EXPECTED TO BE LARGE ENOUGH AHEAD
OF THE APPROACHING FRONT TO PRECLUDE STRONG WINDS FOR COASTAL
LAND AREAS AS WELL AS KETCHIKAN...BUT THIS WILL NEED TO BE RE-
EVALUATED DURING THE DAY SHIFT. IN ADDITION...WINDS MAY BECOME
GUSTY LATE TONIGHT FOR DOWNTOWN JUNEAU AND S DOUGLAS AS LLJ
SPREADS NWD INTO THE AREA.

BLENDED 00Z NAM/ECMWF WITH INHERITED PRESSURE GRIDS IN ORDER TO ADD
RESOLUTION TO THE FRONT APPROACHING THE AREA TONIGHT. POP GRIDS
WERE REFRESHED WITH GFS/ECMWF BLEND...AND HI-RES ARW/NMM WERE
COMBINED WITH COARSER RES GUIDANCE FOR QPF. FORECAST CONFIDENCE IS
ABOVE AVERAGE.

.LONG TERM...CUTOFF LOW OVER BRISTOL BAY WILL MAKE VERY LITTLE
PROGRESS EASTWARD THROUGH THE WEEKEND. A WESTERLY JET OF 135 KT
AT 300 MB AT THE BASE OF THE TROUGH SPANNING THE BAROCLINIC ZONE
WILL SUPPORT A HARDY SHORTWAVE AS IT RACES EAST ACROSS THE GULF OF
ALASKA SATURDAY. THE ASSOCIATED FRONT DISCUSSED IN THE SHORT-TERM
WILL PUSH INTO THE PANHANDLE SATURDAY MORNING AND WEAKEN, BUT
SLOWLY. THE SHORTWAVE PUSHING THE FRONT WILL LEAD A MODIFIED COLD
AIR MASS INTO SOUTHEAST ALASKA LATE IN THE WEEKEND WHICH WILL
DESTABILIZE THE ATMOSPHERE ENOUGH TO BEGIN CHANGING THE RAIN TO
SHOWERS OVER THE PANHANDLE BY SATURDAY NIGHT. IN ADDITION,
UNDERNEATH THE SHORTWAVE AS IT PASSES THROUGH THERE IS A SLIGHT
CHANCE OF THUNDER OVER EASTERN GULF WATERS. JUDGING BY PRESSURE
GRADIENTS ACROSS SOUTHEAST ALASKA SATURDAY, WINDS OVER THE
PANHANDLE SHOULD BEGIN EASING AS THE FRONT SLIDES INLAND. HOWEVER,
GIVEN SOME WEAK COLD AIR ADVECTION SATURDAY MORNING AND THE
INDICATED LOW LEVEL JET PERSISTING, BREEZY CONDITIONS WILL STILL
BE LIKELY ACROSS MUCH OF THE INTERIOR INSIDE PASSAGES IN THE
LEAST.

SOME SUBTLE DIFFERENCES IN WAVE ACTIVITY BEYOND SATURDAY AS MODELS
ARE STRUGGLING TO IDENTIFY FEATURES ROTATING AROUND THE BRISTOL
BAY LOW. THE POSITION OF THE LOW THOUGH ENSURES MOIST SOUTHWEST
FLOW WILL KEEP SHOWERS IN THE FORECAST THROUGH THE REST OF THE
WEEKEND. DEPENDING ON TIMING OF WAVE ASSOCIATED FRONTAL FEATURES,
WIND FORECASTS ARE VERY GENERAL DURING THIS PERIOD, AND MAY BE
NUDGED UP IN THE FUTURE AS WAVE RESOLUTION IMPROVES.

WELL TO OUR WEST THIS WEEKEND A STRONGER WAVE OVER KAMCHATKA LOOKS
LIKELY TO UNDERCUT A WESTERN BERING SEA RIDGE AND PUSH THE BRISTOL
BAY LOW INTO THE WESTERN GULF OF ALASKA BY EARLY NEXT WEEK. THIS
SUBTLE SHIFT OF POSITION WILL CAUSE ROTATING SHORTWAVES TO SPAWN
LOWS/FRONTS SOUTH OF THE PANHANDLE INSTEAD OF OVER THE CENTRAL
PANHANDLE. THIS COULD POTENTIALLY ALLOW THE NORTHERN PANHANDLE TO
EXPERIENCE A BRIEF BREAK POSSIBLY MONDAY, BUT UNCERTAINTY IS STILL
HIGH AND WILL LARGELY DEPEND ON HOW MUCH OFFSHORE COMPONENT THE
UPPER LEVEL FLOW WILL ENCOMPASS. HOWEVER, THIS POTENTIAL BREAK
WILL BE EVER SO BRIEF AS THE FLOW PUSH THE FEATURE NORTHWARD
MONDAY NIGHT/TUESDAY. THE SOUTHERN PANHANDLE WILL RECEIVE NO SUCH
REPRIEVE. WITH THE UPPER LEVEL LOW PERSISTING OVER THE WESTERN
GULF...RAIN AND PERIODS OF WIND WILL CONTINUE TO BE A FIXTURE OVER
THE FORECAST.

FINALLY...SNOW WILL LIKELY REMAIN CONFINED TO WHITE PASS DURING
THE NEXT WEEK. SOME SIGNS THAT SOME COLDER AIR MAY SLIDE SOUTH
BY TUESDAY AS GRADIENTS TURN NORTHERLY, BUT WITH OVERALL MIDLEVEL
FLOW VERY SOUTHERLY, THICKNESSES WILL REMAIN GREAT ENOUGH TO KEEP
SNOW MOSTLY OUT OF THE FORECAST AT SEA LEVEL.

INCREASED WINDS SATURDAY WITH HELP FROM NAM/ECWMF. MADE FEW
CHANGES BEYOND AS GENERAL FORECAST BASED OFF ECMWF AND WPC HOLDS
FAIRLY SOLID. FORECAST CONFIDENCE ABOVE AVERAGE...ESPECIALLY FOR
OVERALL WET PATTERN.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ022-036-041>043-051-052.
         SMALL CRAFT ADVISORY FOR PKZ012-013-021-031>035.

&&

$$

GARNER/ADKINS

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