Gale Warning 184, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
327 PM AKDT SUN APR 24 2016

.SYNOPSIS...A WEATHER FRONT OVER THE INNER CHANNELS WILL DISSIPATE
SUNDAY NIGHT. LOW PRESSURE OVER THE CENTRAL GULF WILL WEAKEN TO A
TROUGH AND MOVE TO THE OUTER COAST LATE SUNDAY NIGHT. A GALE FORCE
WEATHER FRONT WILL MOVE INTO THE EASTERN GULF FROM THE SOUTHWEST ON
MONDAY.

&&

.SHORT TERM...A LARGE BUT RELATIVELY WEAK LOW DOMINATES THE GULF
OF ALASKA THIS AFTERNOON WITH A CIRCULATION ON SATELLITE IMAGERY
THAT EXTENDS FROM THE SOUTHERN OUTER COAST TO KODIAK ISLAND. A
WEAKENING SURFACE TROUGH IS ALSO EVIDENT IN IMAGERY. FARTHER
NORTH, MID LEVEL CLOUDS FROM A WEAKENING FRONT STREAM FROM EAST TO
WEST ACROSS THE NORTHERN PANHANDLE THIS AFTERNOON AND PERIODS OF
RAIN HAVE BEEN REPORTED IN SURFACE OBSERVATIONS THROUGHOUT THE
DAY. FARTHER SOUTH, A SURFACE RIDGE WILL PLAY INTO THE SHORT RANGE
FORECAST LATER. AS THE LOW AND DYING FRONT BECOME LESS AND LESS
OF AN ISSUE, A GALE FORCE LOW CURRENTLY SOUTH OF THE ALEUTIANS
WILL ROTATE A FRONT INTO THE CENTRAL GULF EARLY MONDAY WITH
CATEGORICAL POPS REACH THE CENTRAL AND NORTHERN OUTER COAST BY
MONDAY AFTERNOON. AS THE FRONT PROGRESSES EASTWARD, IT WILL
SHARPEN UP THE SURFACE RIDGE MENTIONED PREVIOUSLY WITH THE RIDGE
AXIS BECOMING ALIGNED WITH THE OUTER COASTLINE. IN FACT, RIDGE
AMPLIFICATION IS ALREADY IN PROGRESS AND A STIFF SOUTHERLY
PRESSURE GRADIENT HAS SET UP OVER THE FAR NORTHERN INNER CHANNELS.
NORTHERN LYNN CANAL IS SEEING SMALL CRAFT WINDS AND SKAGWAY IS
SEEING SOUTHERLY WINDS TO 20 MPH. SUSPECT THESE WINDS WILL RELAX A
LITTLE LATER THIS EVENING, BUT THEN PICK UP AGAIN TOMORROW.
ELSEWHERE, COASTAL WINDS ASSOCIATED WITH THE WEAKENING FRONT OVER
THE NORTHERN PANHANDLE CONTINUE OUT OF THE ESE AT 25 TO 30 KTS
OVER THE COASTAL MARINE ZONES NORTH OF CAPE DECISION. PRE-FRONTAL
WINDS ASSOCIATED WITH THE LOW NEAR THE ALEUTIANS WILL INCREASE TO
GALE FORCE OVER THE EASTERN GULF BY EARLY MONDAY MORNING AND THEN
PROGRESS TO THE COASTAL MARINE ZONES BY MONDAY EVENING. INNER
CHANNEL RESPONSE TO THIS FRONT WILL NOT OCCUR UNTIL EARLY IN THE
EXTENDED RANGE FORECAST.

UPDATED THE FORECAST USING A BLEND OF NAM, ECMWF, AND THE CANADIAN
NH MODELS FOR PRESSURE. WIND SPEEDS FROM GFS22. POP IS A BLEND OF
GFS40 AND SREF WITH GFS40 AND GFS22 USED TO DEVELOP QPF. TWEAKS TO
TEMPS BASED ON PERSISTENCE WITH CHANGES PRIMARILY TO MONDAY'S
HIGHS - LOWERED BY A FEW DEGREES. OVERALL FORECAST CONFIDENCE IS
AVERAGE.

.LONG TERM.../MONDAY NIGHT THROUGH SUNDAY/ NOT MUCH CHANGE IN THE
OVERALL PATTERN THROUGH THE NEXT SEVEN DAYS. A RATHER PERSISTENT
LONG WAVE UPPER TROUGH OVER THE BERING SEA, ANCHORED ON THE EAST
BY A SEMI- PERSISTENT UPPER LOW OVER THE SW GULF AND ALASKA
PENINSULA, WILL KEEP S TO SW FLOW GOING INTO THE GULF THROUGH THE
NEXT WEEK.

WITH THE OVERALL PATTERN NOT CHANGING ALL THAT MUCH, LONG RANGE
MODELS ARE IN RELATIVELY GOOD AGREEMENT WITH ANY LARGE
DISAGREEMENTS NOT SHOWING UP UNTIL NEXT WEEKEND. DECIDED TO USE
MAINLY NAM WITH SOME ECMWF OR GFS DEPENDING ON THE ELEMENT. THAT
BEING SAID, THE LONG RANGE FORECAST CAN BE SUMMED UP IN ONE WORD,
WET. BETWEEN MONDAY NIGHT AND SUN ABOUT 5 FRONTS OR SHORT WAVES
WILL BE MOVING THROUGH THE GULF AND PANHANDLE. THE FIRST, AND ONE
OF THE STRONGEST, COMES ON MON NIGHT INTO TUE WITH GALE FORCE
WINDS ACROSS THE GULF AND SOUTHERN PANHANDLE (STRONG WIND GUST
POSSIBLE FOR THE SOUTHERN PANHANDLE AS THIS FRONT MOVES THROUGH).
THE RAIN WILL SPREAD ACROSS THE AREA ON TUE AND PERSIST INTO EARLY
WED. WAVE NUMBER TWO, LIKELY THE SECOND WEAKEST OF THE SERIES,
APPROACHES THE PANHANDLE WED AFTERNOON SPREADING MORE WIND (SMALL
CRAFT WINDS FOR THE NORTHERN GULF) AND LIGHT RAIN BEFORE IT GETS
ABSORBED BY FRONT NUMBER THREE LATE WED NIGHT. SPEAKING OF FRONT
THREE, IT WILL ALSO SPREAD GALE FORCE WINDS ACROSS THE GULF WED
NIGHT WITH MORE RAIN FOR THE PANHANDLE WED NIGHT INTO THU. WAVE
FOUR SHOWS UP FRI EVENING AND WILL LIKELY BE THE WEAKEST OF THE
SERIES. LITTLE IN THE WAY OF WIND WITH THIS WAVE BUT SOME MORE
ORGANIZED BANDS OF RAIN SHOWERS ARE POSSIBLE WITH THIS WAVE.

FROM HERE, LONG RANGE SCENARIOS START TO DIVERGE DEPENDING ON THE
MODEL THROUGH THEY ARE MOSTLY FOCUSING ON THE SAME IDEA. JUST
DIFFERENT TIMING AND STRUCTURE. THE GENERAL IDEA IS FOR A BRIEF
DRY PERIOD ON SAT FOR THE PANHANDLE AS MORE EASTERLY FLOW TAKES
OVER. THE NEXT SYSTEM TAKES THE FORM OF YET ANOTHER GALE FORCE
LOW AND FRONT BY SAT NIGHT AND SUN. FORECAST CONFIDENCE IS NOT
THAT GREAT HOWEVER AS PREVIOUS RUNS HAD THE LOW MUCH FURTHER EAST
BUT THE GENERAL WESTWARD TREND SO FAR HAS BEEN CONSISTENT ACROSS
THE VARIOUS MODELS. DECIDED TO STICK WITH WPC EXTENDED GRIDS WITH
ITS USE OF ENSEMBLE MEANS TO CAPTURE THE EXTENDED FORECAST.

&&

.AVIATION...GENERALLY MARGINAL VMC WILL PREVAIL FOR THE SHORT TERM FORECAST
PERIOD THROUGH MONDAY AFTERNOON WITH CIGS BEING MORE OF AN ISSUE
THAN VSBY. WIDESPREAD LIGHT TURB BELOW THE FLIGHT LEVELS WITH 5000
FT WINDS SLOWLY PICKING UP OUT OF THE SOUTHEAST. WIND SHEAR NOT
AN ISSUE YEST, BUT MAY BECOME A CONCERN BY THIS TIME TOMORROW -
ESPECIALLY ON THE OUTER COAST AS THE FRONT BEGINS TO ROTATE NORTH
AND PROGRESS INLAND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
     SMALL CRAFT ADVISORY FOR PKZ012-041>043-051.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ022-053.
&&

FRITSCH/EAL

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