Small Craft Advisory 319, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
347 PM AKDT SAT APR 9 2016

.SHORT TERM...AN OCCLUDED FRONT WILL MOVE SLOWLY E INTO THE
CENTRAL GULF TONIGHT...THEN INTO THE EASTERN GULF SUN. A HIGH
PRESSURE RIDGE WILL HOLD OVER THE MAIN PART OF SE AK THROUGH SUN.
USED A BLEND OF THE 12Z GFS AND NAM...MAINLY FOR ITS HANDLING OF
THE FRONT...WHICH THE MODELS WERE SLIGHTLY FASTER MOVING IN OVER
THE NORTHERN GULF.

MAIN FORECAST CONCERNS WILL BE PRECIP POTENTIAL...CLOUD
COVER...AND WINDS. RIGHT NOW...PRECIP IS MAINLY OVER THE CENTRAL
GULF N TO NEAR PAYA. AS THE FRONT MOVES SLOWLY E...EXPECT THE
PRECIP BAND TO SHIFT WITH IT. LOOKS LIKE SOME OF THE FRONTAL
PRECIP WILL REACH THE N-CENTRAL OUTER COAST LATE TONIGHT...THEN
TRY TO SPREAD SLOWLY INLAND OVER THE NORTHERN PANHANDLE SUN. IT IS
TRICKY AS TO WHETHER THIS PRECIP WILL REACH THE PAJN AREA...SO
WENT WITH MIDDLE GROUND POPS FOR THE AFTERNOON. SOME OTHER PRECIP
MAY BE CAUSED BY A SMALL WARM FRONTAL TYPE BAND MOVING NNE ACROSS
THE AREA TONIGHT...BUT AM EXPECTING NO MORE THAN SPRINKLES OR VERY
LIGHT RAIN AS THE BAND MOVES ACROSS THE AREA. FINALLY...THERE ARE
SPOTTY SHALLOW SHOWERS OVER THE E-CENTRAL GULF. SOME OF THESE MAY
CLIP THE OUTER COAST TONIGHT. FOR SIMPLICITY...USED STRATIFORM
TERMINOLOGY TO HANDLE ALL THE PRE-FRONTAL PRECIP.

CLOUDS WITH THE OCCLUDED FRONT EXTEND INTO THE EASTERN GULF. THERE
ARE ALSO A DECK OF STRATOCU CLOUDS AS FAR E AS CHATHAM STRAIT AND
SCATTERED SHALLOW CUMULUS OVER THE S-CENTRAL AREA AND NEAR PAJN.
THINK THE STRATOCU DECK WILL PUSH SLOWLY INLAND TONIGHT AFTER
DIURNAL COOLING HAS STARTED. THERE WILL ALSO BE A BAND OF CLOUDS
WITH THE SMALL WARM FRONT MOVING NNE ACROSS MOST OF THE AREA
TONIGHT AND SUN MORNING. LOOKS LIKE THE FAR SE PART OF THE AREA
WILL SEE THE LEAST CLOUD COVER THROUGH SUN. AFTER WARM FRONTAL
CLOUDS PASS THROUGH THE WESTERN PART OF THE SOUTHERN
PANHANDLE TONIGHT...SKIES SHOULD BECOME PARTLY CLOUDY AGAIN SUN
MORNING.

STRONGEST WINDS ARE AHEAD OF THE OCCLUDED FRONT...WITH 30-35 KT
E-SE WINDS. OVER THE CENTRAL GULF N TO MARINE ZONE 52. THIS BAND
OF WIND WILL SLOWLY PUSH E WITH THE FRONT BUT IT WILL WEAKEN AS
THE FRONT DOES. SHOULD BE BELOW SCA LEVEL WINDS AHEAD OF THE FRONT
SUN AFTERNOON. WINDS ELSEWHERE WILL BE DOMINATED BY LOCAL
EFFECTS...WITH A TENDENCY TOWARD NW WINDS OVER THE SOUTHERN AREA
DUE TO A WEAK INVERTED TROF EXTENDING N INTO THAT AREA. AS FRONT
AND SUPPORTING UPPER TROF MOVE CLOSER SUN...WILL LIKELY SEE MORE
S-SE WINDS OVER THE NORTHERN AREAS WITH UP TO 20 KT OVER THE FAR
N. OTHERWISE WINDS WILL GENERALLY BE LESS THAN 15 KT.

OTHERWISE...SEAS WILL GRADUALLY BUILD AS SWELLS GENERATED BY THE
OCCLUDED FRONT MOVE INTO THE EASTERN GULF. WILL HAVE ALL GULF
COASTAL WATERS REACH SCA LEVEL (8 FT+) SEAS BY LATE SUN MORNING.

.LONG TERM...SUN NIGHT THE FRONT DISCUSSED ABOVE MOVES INTO THE
PANHANDLE AS THE UPPER LEVEL RIDGE AXIS PASSES TO THE EAST. BUT
THE FRONT WILL BE WEAKENING AS IT MOVES INTO THE RIDGE WITH RAIN
BECOMING SCATTERED/INTERMITTENT. THE FRONTAL TROUGH AT THE MID
LEVELS WITH A PEAK IN VORTICITY PASSES 6-12Z SUN NIGHT...SO
WHATEVER SHOWERS MOVE THROUGH EXPECT THEM TO PEAK DURING THAT
TIME AS WELL.

SWLY ONSHORE FLOW WILL KEEP SCATTERED SHOWERS AROUND ON MONDAY.
THEN FLOW BACKS S TO SE AS AN UPPER LEVEL AND SURFACE LOW TRACKS
SE ACROSS THE SOUTHERN GULF MONDAY NIGHT. THE FRONT ASSOC WITH
THIS LOW WILL CAUSE RAIN TO MOVE INTO THE SOUTHERN OUTER COAST
MONDAY NIGHT THEN SPREAD N ACROSS THE PANHANDLE TUESDAY.
HOWEVER...THE LOW BEING TO THE SOUTH WILL INCREASE OFFSHORE FLOW
FOR THE NORTHERN HALF OF THE PANHANDLE TUESDAY. THIS WILL LIMIT
RAINFALL AMOUNTS OVER THAT AREA.

MODELS DIVERGE MID WEEK ON HOW THE LOW DISSIPATES AND WHETHER IT
CAUSES ANOTHER ROUND OF PRECIP FOR THURS NIGHT/FRIDAY. THE NEXT
BIG LOW/FRONT LOOKS TO MOVE UP FROM THE SOUTH OVER NEXT WEEKEND.
ALL IN ALL AN ACTIVE WEEK OF WEATHER...BUT IT DOES LOOK LIKE THERE
WILL BE BREAKS BETWEEN EACH SYSTEM. FORECAST CONFIDENCE ON TIMING
OF RAIN IS SLIGHTLY BELOW NORMAL DO TO MODEL SPREAD. USED A BLEND
OF THE GFS AND ECMWF THROUGH THE MID RANGE THEN TRENDED TOWARD WPC
GUIDANCE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ052.
     SMALL CRAFT ADVISORY FOR PKZ043-051.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042-053.
&&

RWT/FERRIN

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