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FXAK67 PAJK 052346
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
346 PM AKDT TUE MAY 5 2015

.SHORT TERM...INVERTED TROUGH EXTENDING OVER THE PANHANDLE
WEAKENS THROUGH THE DAY AS A HIGH PRESSURE RIDGE OVER THE AK GULF
TRACKS EASTWARD. AFTERNOON SATELLITE IMAGERY SHOWING A FRONT IN
THE WESTERN GULF ASSOCIATED WITH A LOW OVER THE WESTERN TIP OF THE
ALEUTIANS SLOWING PROGRESSING EASTWARD. A HIGH CIRRUS CLOUD SHIELD
AHEAD OF THE FRONT IS RISING MOVE THE HIGH PRESSURE RIDGE WITH A
HIGH OPAQUE CLOUDS ADVANCING OVER THE PANHANDLE. WHILE THE REGION
WILL STAY DRY THROUGH WEDNESDAY THE HIGH CLOUD COVER LOOKS TO KEEP
OVER NIGHT LOWS A BIT WARMER AND TOMORROWS DAY TIMES HIGH JUST A
BIT COOLER. KEEPING ANY FROST OUT OF THE FORECAST FOR TONIGHT DUE
TO THE CLOUD COVER EVEN THROUGH WINDS ARE EXPECTED TO BE LIGHTER
TONIGHT DUE TO WEAKER PRESSURE GRADIENT. ONSHORE SEA BREEZE WILL
MOVE IN MOISTURE OVERLAND BUT UNLIKE LAST NIGHT THE INCREASED
CLOUD COVER SHOULD KEEP TEMPS ABOVE DEW POINT SO NOT EXPECTED ANY
FOG DEVELOPMENT. AFTERNOON SEA BREEZE HAS DEVELOPED AS THE
PREVIOUS NORTHERLY GRADIENT HAS DISSIPATED OR SHIFTED TO THE
SOUTH. MORE SEA BREEZE DEVELOPMENT FOR WEDNESDAY AFTERNOON BUT NOT
AS STRONG AS TODAY DUE TO THE LOWER DAY TIME HIGHS. WESTERLY TO
NORTHERLY WINDS OVER THE AK GULF WILL SHIFT TO THE SOUTH-
SOUTHEAST AS THE HIGH PRESSURE RIDGE MOVES INLAND AND THE FRONTAL
BOUNDARY ADVANCES INTO CENTRAL GULF. THE SOUTHEAST WINDS WILL
INCREASE TO 25 KT FOR OFFSHORE WATERS. INNER CHANNEL WINDS HAVE
SHIFTED OR WILL SHIFT TO THE SOUTH THROUGH WEDNESDAY MORNING. SOME
ENHANCED THERMAL WINDS FOR WEDNESDAY AFTERNOON INCREASING WINDS TO
THE 15 TO 20 KT RANGE.

MODELS IN GOOD AGREEMENT AND WERE STILL INLINE WITH PREVIOUS
FORECAST. NAM INITIALIZED WELL WITH GEM AS A CLOSE SOLUTION.
UPDATED GRIDS WITH A BLEND OT 12Z NAM/GEM ONLY SOME SMALL LOCAL
ADJUSTMENTS. FORECAST CONFIDENCE IS ABOVE AVERAGE.

.LONG TERM...A COMPLEX UPPER LOW STATIONED IN THE NORTH
PACIFIC...JUST SOUTH OF THE CENTRAL ALEUTIANS HOSTS SEVERAL SHORT-
WAVES ROTATING ABOUT IT. ONE SUCH FEATURE ROUNDING THE LOW`S BASE
NEAR 40 N 165 W THIS AFTERNOON WILL SWING NORTHEAST INTO THE
CENTRAL GULF BY LATE WEDNESDAY. THIS PERTURBATION WILL HERALD
WARMER MORE MOISTURE LADEN AIR AT MID AND UPPER LEVELS. THIS WILL
MEAN AN INCREASE IN CLOUD COVER WEDNESDAY NIGHT. THERE IS STILL
SOME UNCERTAINTY ON WHEN THE ADVANCING SHORT-WAVE BRINGS IN
DYNAMICS SUFFICIENT ENOUGH TO GENERATE A CHANCE OF RAIN FOR THE
NORTHEAST GULF, AND THEN THE INEVITABLE EXPANSION EASTWARD INTO
THE REST OF THE PANHANDLE. GFS HAS BEEN FASTEST WITH THE
PRECIPITATION. ECMWF AND NAM HAVE HELD BACK. AS THE GFS DEMANDED
THE LEAST CHANGE, ELECTED TO HOLD THE CURRENT FORECAST BUT
INCREASED THE CHANCE OF RAIN THURSDAY FOR YAKUTAT.

THE PARENT UPPER LOW MOVES INTO THE WESTERN GULF BY THURSDAY AND
BEGINS TO TAKE ON A NEGATIVE TILT. THIS WILL PERHAPS HELP SCATTER
SOME CLOUDS LATE WEDNESDAY BY DRAWING IN SOME DRIER AIR FROM THE
SOUTHEAST. HOWEVER, A STRONGER WAVE BEGINS TO PUSH NORTH INTO THE
EASTERN GULF THURSDAY NIGHT INTO FRIDAY. THIS WILL POTENTIALLY
SPREAD SOME LIGHT RAIN EASTWARD INTO THE GREATER PANHANDLE
THURSDAY NIGHT AND FRIDAY. CONFIDENCE GROWS FOR RAINFALL ACROSS
THE PANHANDLE FRIDAY NIGHT AS AN ASSOCIATED FRONT APPEARS TO MAKE
LANDFALL. IN ADDITION, WINDS LOOK TO REACH GALE FORCE WITH A
BARRIER JET OVER THE NORTHERN GULF AND RISE TO SOLID SMALL CRAFT
ADVISORY AHEAD OF THE FRONT TRAILING SOUTHEASTWARD ALONG THE COAST
ON FRIDAY. WINDS MAY BE UNDERREPRESENTED OVER THE PANHANDLE
FRIDAY NIGHT. AS BETTER GUIDANCE FOR ANY FORMATION OF A LOW LEVEL
JET COMES IN, WE WILL HAVE A BETTER IDEA ON HOW TO RAISE
WINDSPEEDS. BUT THE MARINE FORECAST HAS A DEFINITE TRANSITION TO
SOUTHERLY/EASTERLY EARLY IN THE LONG-RANGE PERIOD TO ACCOUNT FOR
THE APPROACH OF THESE GULF SYSTEMS.

AS SOME SORT OF LOW OVER THE GULF PERSISTS INTO THE WEEKEND, WE
CANNOT RULE OUT A CHANCE OF RAIN WITH MOSTLY CLOUDY SKIES FOR
MOTHER`S DAY WEEKEND. WE DID COOL HIGH TEMPERATURES BY TWO OR
THREE DEGREES TO TAKE INTO CONSIDERATION MORE CLOUD COVER THIS
WEEKEND. HOWEVER, THIS WORKS BOTH WAYS. GIVEN MORE CLOUD COVER,
THERE WILL BE NO THREAT OF FREEZING TEMPERATURES THIS WEEKEND TO
INTERRUPT ANY TRADITIONAL GARDENING PLANS.

ONLY MINOR TWEAKS TO INSIDE WINDS WEDNESDAY NIGHT INTO THURSDAY
NIGHT. USED ECMWF/GFS TO INCREASE GULF WINDS FRIDAY/FRIDAY NIGHT
AND ADOPTED WPC GUIDANCE FOR WEEKEND AND BEYOND TO TACKLE HIGH MODEL
SPREAD.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.

&&

$$

PRB/ADKINS

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