Gale Warning 41, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
418 PM AKST SUN JAN 12 2014

.SHORT TERM...AFTERNOON SATELLITE LOOP REVEALS A WEAKENING LOW
IN THE NORTHERN GULF COAST WITH A COMPLEX FRONTAL PASSAGE
EXTENDING SOUTHEASTWARD ACROSS THE PANHANDLE. EAST OF THE LOW
CENTER...SNOW TAPER OFF OVER THE NORTHERNMOST AREAS. ALONG THE
FRONTAL BOUNDARY...A WEAKENING TRIPLE POINT PASSES OVER THE
SOUTHERN AREAS. TEMPERATURES WARM UP TO THE UPPER 30S TO THE
LOWER 40S ALONG THE COASTAL SECTIONS AND OVER THE SOUTHERN
PANHANDLE WITH RAIN. RELATIVELY COLD AIR ANCHORS OVER THE NORTH
CENTRAL PANHANDLE WITH DEW POINT TEMPERATURES STAY AROUND 32 FOR
CONTINUED SNOW. SNOW ACCUMULATIONS SO FAR REMAIN BELOW ADVISORY
LEVEL AND EXPECT SNOW WILL MIX WITH RAIN DURING THE AFTERNOON
INTO THE EVENING. ENHANCED ONSHORE FLOW BEHIND THE FRONTAL
PASSAGE KEEPS SMALL CRAFT TO GALE FORCE WINDS ACROSS THE OUTER
WATERS WITH ROUGH SEAS.

 MODELS REMAIN IN GENERAL AGREEMENT WITH THE WEAKENING LOW ALONG
THE NORTHERN GULF COAST MOVES OVER THE NORTHERN PANHANDLE TONIGHT
THEN DISSIPATES BY EARLY MONDAY MORNING. THEN A WEAK RIDGE OF
HIGH PRESSURE BUILDS OVER THE PANHANDLE MONDAY. THE
RIDGE...HOWEVER...WILL QUICKLY MOVE EAST INTO BRITISH COLUMBIA
MONDAY NIGHT AS A DEVELOPING LOW IN THE FAR WESTERN GULF PUSHES
ANOTHER FRONT INTO THE EASTERN GULF. REFRESHED THE INHERITED
FORECAST PACKAGE WITH THE ECMWF AND NAM...BUT CHANGES MADE WERE
VERY MINIMAL.

 THE ENHANCED ONSHORE FLOW BEHIND THE FRONT...COMBINED WITH A
LONG FETCH OF SOUTHWESTERLY SWELLS WILL MAINTAIN ROUGH SEAS
ACROSS THE GULF FOR UP TO 20 FT THROUGH TONIGHT. AS THE RIDGE
BUILDS OVER THE PANHANDLE...WINDS WILL SHIFT TO MORE SOUTHERLY
ACROSS THE INNER CHANNELS LATE TONIGHT INTO MONDAY. SOUTHERLY
PRESSURE GRADIENT WILL BECOME TIGHT BETWEEN THE RIDGE AND
RESIDUAL WEAK LOW TO THE NORTH. EXPECT SMALL CRAFT LEVEL
SOUTHERLY WINDS FOR THE NORTH- SOUTH ORIENTED INNER CHANNELS. THE
NORTHERNMOST AREAS WILL REMAIN BELOW FREEZING AND A SLIGHT
WARMING EXPECTED BY MONDAY AFTERNOON. RAIN WILL CONTINUE OVER THE
SOUTHERN PANHANDLE. SNOW MIXING WITH RAIN ACROSS THE CENTRAL
AREAS IN THE EVENING WILL BECOME SNOW AGAIN TONIGHT. AIR MASS
WILL BE GRADUALLY MODIFIED ON MONDAY AND EXPECT WARM ENOUGH
TEMPERATURES FOR RAIN OVER MUCH OF THE PANHANDLE...EXCEPT HAINES
AND SKAGWAY AREAS.

.LONG TERM...THE WORDS OF THE DAY...SIGNIFICANT FINE-TUNING OF THE
EXISTING FORECAST. OVERALL PATTERN HAS NOT CHANGED, BUT ADDED SOME
UMPH TO THE SYNOPTIC FLOW BASED ON LOCAL EFFECTS...NAMELY FOR
WIND.

SURGE OF TROPICAL MOISTURE...CURRENTLY TRAVELING NORTHEAST THROUGH
THE NORTH PACIFIC WILL MAKE A BEELINE FOR THE PANHANDLE FOR MONDAY
NIGHT INTO TUESDAY EVENING. THE RAIN WILL DEVELOP OVER THE
SOUTHERN PANHANDLE FIRST AND MOVE NORTHWARD RAPIDLY ACROSS THE
REST OF THE PANHANDLE. THE PRECIPITATION WILL FALL IN THE FORM OF
SNOW OVER THE LYNN CANAL AREA MONDAY NIGHT...AND TEMPERATURES WILL
REMAIN COLD ENOUGH THROUGH TUESDAY TO WARRANT THE ISSUANCE OF A
WINTER STORM WATCH. WHILE CURRENT FEELING IS THAT THIS IS A
MARGINAL EVENT, THE THREAT OF FREEZING RAIN MAY HAVE COLORED MY
OPINION ON WHETHER TO PULL THE TRIGGER. THE GREATEST THREAT OF
HEAVY SNOW WILL BE IN THE USUAL SUSPECTS OF WHITE PASS FOR
ELEVATION AND THE UPPER CHILKAT VALLEY WHERE THE COLD AIR TENDS TO
TAKE THE LONGEST TIME TO ERODE. IN ADDITION, MODELS NOT SUGGESTING
A SUPER-STRONG SURGE OF AIR MONDAY NIGHT THROUGH LYNN CANAL, SO
FEEL THAT THE STRENGTH OF THE SURGE WILL HAPPEN ALOFT...HENCE THE
USE OF THE TERM OVER-RUNNING EVENT. THE SNOW SHOULD MIX WITH RAIN
NEAR LYNN CANAL ON TUESDAY. A COMPANION COLD FRONT BEGINS TO PASS
EASTWARD THROUGH THE PANHANDLE CLOSELY ON TUESDAY AFTERNOON AND
THUS WILL HELP DRY THE ATMOSPHERE OUT. SNOW WILL THEN BEGIN TO
ABATE TUESDAY AFTERNOON AS THE TROPICAL MOISTURE ALOFT IS KICKED
TO THE EAST...THUS LIMITING THE QPF THEREAFTER.

THERE IS A CASE FOR YAKUTAT GETTING SOME FREEZING RAIN LATE MONDAY
NIGHT AND ADVISORY LEVEL SNOWFALL IS LIKELY AS THIS MOISTURE MOVES
NORTHWARD. HOWEVER, MOS GUIDANCE WINDS TRYING TO INDICATE SOME
SOUTHEAST TURN OF THE WINDS, AND THUS NOT AS CONFIDENT HERE...SO
NO WATCH ISSUED. TEMPERATURES MAY RISE A LITTLE IF ANY ONSHORE
FLOW MAKES ITS WAY DOWN TO THE SURFACE.

ALSO BUMPED UP WINDSPEEDS OVER THE LAND AREAS...ESPECIALLY THOSE
AFFECTED BY FRONTAL ACTIVITY. USING 75 PERCENT RULE OF 850 MB
WINDS FOR WARM AIR ADVECTION...THE POSSIBILITY OF STRONG WINDS
EXISTS FOR ZONE 27 AND 28 FOR LATE MONDAY NIGHT INTO TUESDAY
MORNING. IN ADDITION...AS THIS AFOREMENTIONED COLD FRONT PASSES
THROUGH THE NORTHERN PANHANDLE...A POST-FRONTAL RIDGE WILL
ACCELERATE WINDS THROUGH SKAGWAY...AND POSSIBLY HAINES. JUNEAU'S
WINDS WILL LIKELY BLOW 15 TO 25 MPH MONDAY NIGHT...AND POSSIBLY
EXTENDING INTO TUESDAY MORNING. YAKUTAT AND THE BAY WILL GET SOME
GOOD WINDS ON TUESDAY AFTERNOON INTO TUESDAY NIGHT WITH THE COLD
AIR ADVECTION FROM THE SOUTHWEST. AGAIN, NO REAL PATTERN CHANGE
ADVERTISED HERE...JUST FINE-TUNING DETAILS.

NO CHANGES TO EXTENDED PACKAGE...TIME LIMITED, BUT UNSETTLED AND
OVERALL WARM CONDITIONS LOOK TO CONTINUE THROUGH THE WEEKEND.
CONFIDENCE IN FORECAST GOOD FOR PATTERN...INCREASING FOR DETAILS,
BUT STAY TUNED, MORE FINE TUNINGS WILL BE MADE WITH MONDAY MORNING
PACKAGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ023.
         WINTER STORM WATCH FROM MONDAY EVENING THROUGH TUESDAY MORNING
     FOR AKZ018-019.
MARINE...GALE WARNING FOR PKZ042-043.
         SMALL CRAFT ADVISORY FOR PKZ012-013-021-022-031>036-041-051-052.

&&

AHN/JWA