Area Forecast Discussion - Southeastern
FXAK67 PAJK 031408
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
508 AM AKST TUE MAR 3 2015
.SHORT TERM...EARLY MORNING SATELLITE IMAGE SHOWS A WEAKENING COLD
FRONT OVER THE EASTERN GULF...SLOWLY APPROACHING THE PANHANDLE
COASTAL AREAS WITH LIGHT RAIN STARTED OVER YAKUTAT AREA. MID TO
HIGH LEVEL CLOUDS CONTINUE TO INCREASE ACROSS THE PANHANDLE UNDER
GENERALLY LIGHT AND VARIABLE WINDS. THE NORTHERN TIER OF THE
INCOMING FRONT BECAME OCCLUDED NEAR MIDDLETON ISLAND AND PRODUCED
SMALL CRAFT WINDS/SEAS FROM CAPE FAIRWEATHER TO CAPE SUCKLING.
WITH INCREASED CLOUD COVER...OVERNIGHT TEMPERATURES REMAIN IN THE
MID TO UPPER 30S ALONG THE NORTHEASTERN GULF COAST SOUTHEAST TO
THE SOUTHERN PANHANDLE. NORTHERNMOST ZONES AND THE EASTERN
PANHANDLE AREAS COOLED DOWN TO THE UPPER 20S TO THE LOWERS 30S.

MODELS REMAIN IN GENERAL AGREEMENT FOR THE HIGH PRESSURE IN
BRITISH COLUMBIA WEAKENS AND MOVES EAST BY TONIGHT AS THE WEAK
COLD FRONT OVER THE EASTERN GULF MOVES ONSHORE OVER THE PANHANDLE.
REFRESHED THE INHERITED FORECAST WITH THE NAM AND ECMWF FOR
PRESSURE AND WIND FIELDS. MADE A FEW FINE TUNES FOR POPS.QPF
FIELDS WITH THE SREF. GAVE HEAVIER WEIGHT FOR MOS TEMPERATURE
GUIDANCE FOR TONIGHT AND LOWERED OVERNIGHT LOWS SLIGHTLY BELOW
FREEZING FOR THE NORTHERN ONE THIRD OF THE PANHANDLE. 

AS THE HIGH IN BRITISH COLUMBIA WEAKENS AND MOVES EAST...RELAXED
PRESSURE GRADIENT WILL BECOME AN INCREASING SOUTHERLY GRADIENT
WITH THE INCOMING FRONTAL PASSAGE. HOWEVER...THE FRONT IS FAIRLY
WEEK AND CONTAINS LIMITED MOISTURE AS MODERATE UPPER LEVEL RIDGE
DOMINATING SOUTHEAST ALASKA. THE SMALL CRAFT LEVEL WINDS OVER THE
NORTHERN OUTSIDE WATERS WILL DIMINISH LATE THIS MORNING AS THE
FRONT MOVES ONSHORE. 

THE DOMINANT UPPER LEVEL RIDGE WILL WEAKEN A BIT THIS EVENING AND
SLIGHTLY DRIFT SOUTH BY LATE TONIGHT. AS A RESULT...THE
PRECIPITATION WILL SPREAD EAST TO SOUTHEAST WITH LIKELY POPS OVER
THE NORTHERN PANHANDLE. THE NORTHERN ONE THIRD OF THE PANHANDLE
WILL BECOME COLD ENOUGH FOR SNOW. ONCE AGAIN...THE LIMITED QPF
VALUES WILL KEEP SNOW FALL LESS THAN AN INCH. THE SOUTHERN TIER OF
THE INCOMING FRONT WILL DISORGANIZE BY THIS AFTERNOON AS IT ENTERS
THE MAIN PORTION OF THE UPPER RIDGE. EXPECT INCREASING MID TO HIGH
LEVEL CLOUDS THROUGH THE DAY...BUT NO RAINFALL OVER THE HORIZON.
.LONG TERM...ALMOST A WEEK OF DRY WEATHER WILL COME TO AN END BY
WEDNESDAY OVER THE NORTHERN PANHANDLE WITH WIDESPREAD GENERALLY
LIGHT RAINFALL. ONSHORE FLOW AND GENERAL HIGH POP/LOW QPF PATTERN WILL
BE IN PLACE WEDNESDAY INTO THE WEEKEND AS A SERIES OF FRONTAL
WAVES IMPACT THE AREA. AS CONTINENTAL AIR CONTINUES TO BE RESTRICTED
WELL TO THE NORTH DUE TO SOUTHWESTERLY FLOW ALOFT...APPEARS THAT
SNOW WILL NOT BE A FACTOR EXCEPT OVER THE HAINES/SKAGWAY AREAS AND
EVEN THERE EPISODES WILL LIKELY BE MIXED AND OF LITTLE
IMPACT...THROUGH ABOUT SAT. FOR WED ONLY UPDATES TO INHERITED DYNAMIC
FIELDS WERE NECESSARY AS THE ELONGATED NE-SW UPPER LOW MOVES
NORTHEASTWARD TOWARDS PANHANDLE...WITH A FEW WIND TWEAKS UPWARD
FOR CLARENCE STRAIT. THEN FOR THU THE NEW EC/NAM RUNS WERE
INTEGRATED. THE PATTERN SHOWS SLUGGISH PROGRESSION EASTWARD WITH
THE NAM A BIT STRONGER WITH THE ONSHORE FLOW AND RAIN AMOUNTS
MAXIMIZED OVER THE SOUTHERN HALF. TWEAKED OCEAN WINDS UP A BIT
WHILE THE INNER CHANNELS REMAIN TAME WITH RELATIVELY WEAK
GRADIENTS CONTINUING. ON FRI A BREAK IN PRECIP EARLY APPEARS
LIKELY BUT BRIEF WITH PANHANDLE RAIN RETURNING FOR THE AFTERNOON.
THE LAST FEW BLOCKS OF THE NAM BECAME AN OUTLIER AS FORECAST THEN
INTEGRATED NEW GFS FIELDS INTO THE MIX. WINDS WERE TWEAKED AGAIN
BUT LARGELY INHERITED WPC GRIDS WERE THEN UTILIZED. BY SAT AS
PRESSURE GRADIENTS RESPONDED TO UPPER TROUGHING BUILDING INTO THE
CENTRAL GULF AREA-WIDE MARINE WINDS INCREASE...AND BUMPED UP
SOUTHERLY WINDS IN THE NORTHERN HALF CHANNELS. UNSETTLED WEATHER
CONTINUES WITH A NEW LANDFALLING FRONT ON THE EC. ONLY THE SKAGWAY
AREA APPEARED TO HAVE ANY THREAT OF A MIX OF RAIN/SNOW AT THAT
POINT. THEN ON SUNDAY A COOLER AND STILL WET PATTERN CONTINUED
WITH ONSHORE FLOW AND WINDS CONTINUING TO INCREASE. ALL 3 MAJOR
MODELS ADVERTISE DEEP TROUGHING DIGGING INTO THE WEST/CENTRAL GULF
AT THIS POINT WITH COOLING LOW-LEVEL CONDITIONS BEGINNING OVER THE
NORTHERN PANHANDLE.

POP/THERMODYNAMIC UPDATES WERE MADE THROUGHOUT USING THE 00Z EC/GFS RUNS
AS AGREEMENT WAS STRONG THROUGH THE EXTENDED...ALONG WITH MOS
TEMPERATURES. WARMED NIGHTTIME TEMPERATURES IN GENERAL BY A COUPLE
DEGREES AND RAISED SNOW LEVELS A BIT OVER THE NORTH AS THERE IS
SIMPLY LITTLE SOURCE FOR COLD AIR IN THIS PATTERN THROUGH ABOUT SAT.

BROAD STRONG TROUGHING WITH AN INFLUX OF CONTINENTAL AIR AT LOW
LEVELS EARLY NEXT WEEK IS CONSISTENT WITH PREVIOUS EXTENDED
RUNS...THIS WILL NEED TO BE MONITORED ONCE WE GET INSIDE OF 4 OR 5
DAYS AS SIGNIFICANT SNOW COULD BE INVOLVED FOR AT LEAST THE
NORTHERN PANHANDLE. AT THIS POINT THE 3 MAJOR EXTENDED MODELS ARE
IN REMARKABLE AGREEMENT ON THIS. HELD OFF ON TAKING THE
TEMPERATURES DOWN MUCH ON MON/TUES UNTIL WE GET A FEW MORE MODEL
RUNS FOR THE PERIOD...CURRENT EC/GFS ARE ADVERTISING A BIG COOLDOWN.
MODEL CONFIDENCE WAS ABOVE AVERAGE THROUGH THE LONG TERM FOR A
CHANGE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ051-052. 

&&

$$

AHN/WESLEY

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