Area Forecast Discussion
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219
FXAK67 PAJK 071502
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
602 AM AKST SUN FEB 7 2016

.SHORT TERM...THE TRIPLE POINT FEATURE FROM A STRONG LOW ABOUT 300
NM SOUTH OF KODIAK ISLAND IS MOVING NORTH OVER THE SOUTHERN
PANHANDLE THIS MORNING. A STRONG 120 KT JET STREAM IS MOVING THE
DRY SLOT NORTHWARD OVER THE GULF OF ALASKA TO THE NORTHERN GULF THIS
MORNING. THE FRONT CONTINUES TO EXTEND SOUTH SOUTHWEST TO THE MID
TROPICS. STRONG MOISTURE INFLUX IN THE FLOW PATTERN IS BRINGING
VERY MOIST WARM AIR NORTHWARD TO THE SOUTHEAST GULF AND SOUTHERN
PANHANDLE THROUGH SUNDAY NIGHT.

A TRAILING LOW ON THE FRONTAL BAND IS MOVING NORTH TO THE
SOUTHEAST GULF THROUGH SUNDAY NIGHT AND THE WAVE IS MOVING ALONG
140 WEST AND THIS WILL PULL THE FRONT NORTH OF IT BACK TO THE
NORTHWEST ALLOWING THE MORE MOIST AIR BACK ACROSS THE SOUTHERN
PANHANDLE SUNDAY AND SUNDAY NIGHT. BETTER RAINFALL TOTALS WILL BE
THIS MORNING AND OVERNIGHT IN THE SOUTHERN PANHANDLE. COOLER AIR
TRAPPED NEAR HYDER THROUGH THIS EVENING BEFORE SUFFICIENT WARMING
ERODES IT WILL ALLOW HYDER TO PICK UP SEVERAL INCHES OF SNOW
TODAY AND EARLY THIS EVENING. HOWEVER AMOUNTS WILL BE BELOW
ADVISORY LEVELS.

WITH THE PRESENT WEATHER FRONT STILL MOVING ACROSS THE NORTHERN
PANHANDLE THERE ARE GALE FORCE WINDS OVER THE COASTAL AREAS AND A
FEW INNER CHANNELS OF THE PANHANDLE. OTHERWISE WINDS DIMINISHING
OVER THE GULF AND PANHANDLE TO SMALL CRAFT OR LESS. SEA STATE OVER
THE GULF OF ALASKA WILL BE INCREASING UP TO 15 - 20 FT DUE TO THE
SOUTHWEST TO WESTERLY SWELL MOVING IN. THE SWELL WILL LIKELY
ATTEMPT MOVE INTO THE SOME OF THE BAYS AND SOUNDS WITH THE PROPER
ORIENTATION FOR THE SWELLS.

MADE ONLY MINOR CHANGES AS THE PREVIOUS FORECAST HAD A GOOD HANDLE
ON THE FORECAST TRACK AND WHAT WAS GOING ON.

.LONG TERM...A ROCK SOLID RIDGE PARKED OVER THE WEST COAST AND A
DEEP MERIDIONAL TROUGH OVER THE PACIFIC ALONG 150 W TAKEN TOGETHER
CONTINUE TO FUNNEL A WARM, DEEP STREAM OF MOISTURE ACROSS THE
SOUTHERN PANHANDLE ON MONDAY. THIS WILL HAVE PRODUCED HEAVY
RAINFALL ACROSS THE SOUTHERN PANHANDLE SUNDAY AND SUNDAY NIGHT AND
THUS WILL PERSIST INTO MONDAY. HOWEVER AS A SHORT-WAVE OVER THE
AMERICAN MIDWEST SHARPENS SOUTHWARD, THE RIDGE WILL BUILD SLIGHTLY
NORTHWARD AND HENCE WILL BEGIN TO NUDGE THIS STREAM OF MOISTURE
NORTHWEST INTO THE CENTRAL PANHANDLE FOR MONDAY.
LIKEWISE...RAINFALL WILL INCREASE MONDAY AFTERNOON/EVENING FOR
JUNEAU...HAINES...AND SKAGWAY.

HELPING TO FOCUS THIS RAINFALL...WILL BE A SHORT-WAVE RIDING
NORTH WITHIN THE SOUTHERLY FLOW. MODELS HAVE DIFFERED ON
STRENGTH...BUT TRENDS ARE GOOD FOR SPINNING THIS INTO A BONAFIDE
QUICK-MOVING LOW. CURRENTLY WE ARE HOLDING THIS FEATURE BELOW
GALE-FORCE, BUT THE LATEST NAM IS STRONGER. THIS FEATURE WILL ALSO
SUPPORT WIDESPREAD SOUTHERLY WINDS THROUGH THE ENTIRE SYSTEM OF
INSIDE PASSAGES BY MONDAY NIGHT AS IT PASSES NORTHWARD. THIS
SHOULD EVEN INCLUDE LYNN CANAL AND SKAGWAY. 925 MB SOUTHERLY WINDS
ARE CONCERNING WITH THIS SYSTEM, AND SHOULD THEY MIX DOWN TO THE
SURFACE, OUR FORECAST WINDS ARE NO WHERE NEARLY THE STRENGTH THEY
NEED TO BE. WE HAVE ELEVATED WINDS ACROSS THE CENTRAL PANHANDLE TO
SMALL CRAFT, BUT WINDS THROUGH LYNN CANAL/GLACIER BAY NEED TO BE
INCREASED AS THIS LOW JUMPS INLAND. WARM AIR WILL ADVECT WITH THIS
SYSTEM IN EARNEST, AND MAY SUPPORT THE IDEA THAT WINDS AT THE
SURFACE WILL BE LIGHTER THAN 925 MB WINDS INDICATE AS MOMENTUM
WILL NOT TRANSFER TO THE SURFACE AS EFFICIENTLY AS WITHIN AN AREA
OF COLD AIR ADVECTION. THIS SURGE OF WARM AIR SHOULD TURN WINDS
SOUTHERLY AT HAINES AND SKAGWAY...ERASING ALL SNOW FROM THE
FORECAST. SNOW LEVELS WILL RISE TO 4000 FEET IN THE JUNEAU
VICINITY BY MONDAY EVENING. SNOW ACCUMULATION HAS BEEN HELD DOWN
MONDAY NIGHT NEAR WHITE PASS AS THERE IS A REAL THREAT THAT THE
PASS COULD SEE RAIN MIXED IN.

AS THIS SYSTEM PASSES AND THE RIDGE SHARPENS OVER THE
PANHANDLE...RAINFALL WILL DIMINISH TUESDAY BEFORE ANOTHER
DISTURBANCE APPROACHES THE PANHANDLE FROM THE SOUTH FOR TUESDAY
NIGHT. RATHER THAN A CONSISTENT JET OF WARM MOIST AIR AIMING
DIRECTLY AT THE PANHANDLE, A NEW PATTERN WILL EVOLVE BY TUESDAY
WITH A COMPLEX LOW CENTERED OVER THE SOUTHWEST GULF AND ROTATING
SHORT-WAVES PASSING COUNTER-CLOCKWISE OFFSHORE OF THE PANHANDLE...EACH
ONE OFFERING SHOTS OF RAIN AND KEEPING THE AIR MASS ACROSS
SOUTHEAST ALASKA VERY MILD FOR FEBRUARY. IN
ADDITION...PERIODICALLY THERE WILL BE WEAK CASES OF OUTFLOW WINDS
DURING DRIER PERIODS. ALTHOUGH RAIN DECORATES THE
FORECAST...AMOUNTS WILL GENERALLY BE ON THE LIGHTER SIDE IN
COMPARISON TO WHAT MOST OF US WILL EXPERIENCE IN THE NEXT COUPLE
OF DAYS. SNOW WILL BE GENERALLY CONFINED TO THE HIGHER ELEVATIONS.

WE USED ECMWF/NAM FOR MONDAY AND MONDAY NIGHT AND TRANSITIONED TO
A GEM/ECMWF BLEND FOR TUESDAY AND TUESDAY NIGHT. NO CHANGES
BEYOND. FORECAST CONFIDENCE AVERAGE FOR PERIOD.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 9 AM AKST THIS MORNING FOR AKZ027-028.
MARINE...GALE WARNING FOR PKZ022-033-035-036-041>043-051-052.
     SMALL CRAFT ADVISORY FOR PKZ021-031-032-034-053.
&&

$$

BEZENEK/JWA

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU



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