Gale Warning 178, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
453 PM AKDT TUE MAR 10 2015

.SHORT TERM...REMNANT SNOW SHOWER ACTIVITY IS ON THE DOWNTURN
THROUGHOUT...MEANWHILE WINDS ARE RAPIDLY INCREASING OVER THE NORTH
AS CONTINENTAL HIGH BUILDS IN FROM THE NORTH. WE DON'T GET THE
FULL FLEDGED IMPACT OF THE HIGH AS IT IS TRANSIENT AND MOVES
SOUTHEAST...WHILE NEW LOW ALREADY BEGINS TO MOVE IN FROM THE SOUTH
EARLY WED. HOWEVER NORTHERN LYNN IS ALREADY MARGINALLY GALE WITH
GUSTS TO 45 KT AND THIS IS EXPECTED TO CONTINUE THROUGH TOMORROW
WITH SOME FREEZING SPRAY EXPECTED WITH THE COLD TEMPS. SOUTHERN
LYNN IS EXPECTED TO GET INTO GALE STRENGTH BY 15Z...AND EASTERN
REACHES OF STEPHENS BY 18Z...MEANWHILE SCA WINDS WORK THEIR WAY
SOUTHWARD THROUGH THE PANHANDLE OVERNIGHT. AT 15Z SKAGWAY IS
ANTICIPATED TO BEGIN STRONG WINDS. PART OF THE CAUSE OF SOUTHERN
CHANNELS STRONG WINDS IS THE TIGHTENING GRADIENT LATE TONIGHT AND
TOMORROW AS NEW LOW BUILDS INTO THE SOUTHERN PANHANDLE. UTILIZED
MOSTLY INHERITED DYNAMIC FIELDS FOR THE FORECAST WITH UPDATED
WINDS BOOK-ENDED 00Z TONIGHT AND 03Z THURS AS THERE WERE MINOR
MODEL CHANGES...CHOSE AN EC/NAM COMBO FOR THIS ALONG WITH LOCAL
CHANNEL TWEAKS FOR THE MORE SIGNIFICANT WIND PERIODS.

SECOND PRIMARY CHALLENGE IS PRECIP TYPE AS PRECIP MOVES IN FROM
THE SOUTH ON WED. BEGINNING DURING THE 12-15Z PERIOD. NEW MODELS (ALSO
CHOSE EC/NAM ALONG WITH INHERITED GRIDS FOR THERMODYNAMIC
UPDATES) ARE A FEW HOURS FASTER WITH RAIN ONSET AND PREDICT UP TO
ABOUT 0.75" LIQUID IN SOME AREAS OF THE SOUTH THROUGH 03Z THU.
INITIAL PRECIP TYPE COULD BE BRIEFLY SNOW OVER HYDER AREA AND MORE
SIGNIFICANT FROM JUNEAU NORTHWARD TOMORROW NIGHT. APPEARS MOST
LIKELY THAT THE RAIN/SNOW LINE WILL BE JUST SOUTH OF OR IN THE
VICINITY OF THE JUNEAU AREA AT THE ONSET OF PRECIP DURING THE 21Z
WED -- 03Z THU PERIOD. WITH DIURNAL A SIGNIFICANT PERIOD OF SNOW
IS POSSIBLE DURING THE EARLY PORTION OF THE PRECIP OVERNIGHT
THU AS SLIGHT DIURNAL COOLING MAY BE A FACTOR...WITH THE TYPE ISSUE EVEN
MORE CRITICAL LATER ON FOR THE HAINES/SKAGWAY COOLER ZONES...THIS
GOES INTO THE LONG TERM PERIOD OF THE FORECAST.

.LONG TERM...NORTHERLY OUTFLOW WINDS WILL CONTINUE WEDNESDAY
NIGHT AS A LOW/ASSOC WARM FRONT APPROACHES FROM THE SOUTH. THE
LOW CENTER WILL MOVE NORTH ACROSS THE EASTERN GULF THROUGH
THURSDAY...BUT PRECIP WITH IT...AS DISCUSSED ABOVE...WILL ALREADY
BE OCCURRING OVER THE SOUTHERN PANHANDLE WITH THE WARM FRONT THEN
SPREAD NORTH TO BE OVER JUNEAU WEDNESDAY NIGHT...INTO HAINES BY
EARLY THURSDAY MORNING AND TO YAKUTAT MID DAY. THINK THAT
TEMPERATURES WILL BE COLD ENOUGH FOR PRECIP TO START AS SNOW FROM
AROUND TENAKEE NORTHWARD WED NIGHT. TIMING OF WHEN IT STARTS A
LITTLE UNCERTAIN AS THE ECMWF IS THE FASTEST /STARTING IN JUNEAU
BY LATE AFTERNOON/ AND THE NAM IS THE SLOWEST /STARTING IN JUNEAU
CLOSER TO 9PM/ WITH THE GFS BEING IN BETWEEN...BUT CLOSER TO THE
NAM. TEMPERATURES WILL WARM QUICKLY ONCE THE FRONT MOVES THROUGH
AND CAUSES WINDS TO SHIFT FROM NORTHERLY TO SOUTHERLY. THIS SHOULD
OCCUR IN JUNEAU BY THURSDAY AFTERNOON AND IN HAINES LATE AFTERNOON
OR EVENING. AGAIN THE TIMING OF THIS SHIFT/WARMING AND CHANGE OVER
TO RAIN IS A LITTLE UNCERTAIN. THUS SNOWFALL AMOUNTS ARE TRICKY.
HAVE GONE WITH 2-5 INCHES IN JUNEAU WEDNESDAY NIGHT AND UP TO
ANOTHER 2 INCHES THURS MORNING BEFORE THE CHANGE OVER. BECAUSE THE
CHANGE OVER IS LATER IN HAINES HAVE HIGHER SNOWFALL AMOUNTS AND
WILL NEED TO CONSIDER A WATCH/WARNING FOR THAT AREA.

MANY PLACES WILL SEE GUSTY WINDS AS THE LOW PASSES ON THURSDAY.
HAVE SUSTAINED 40KT WIND OVER THE OUTSIDE WATERS. UPPER LEVEL
FLOW BECOMES STRONGER OUT OF THE SW/ONSHORE THURSDAY INTO FRIDAY
AS A TROUGH DIGS INTO THE GULF. SURFACE WINDS OVER THE GULF WILL
SHIFT TO THE W-SW AND CAA WILL SPREAD ACROSS THE GULF AFTER THE
LOW MOVES INLAND AND TRANSITION THINGS BACK TO CONVECTIVE
SHOWERS. TEMPERATURES AT 850MB WILL FALL AND BE COLD ENOUGH FOR
THEM TO BE SNOW SHOWERS...WITH HIGHLY VARIABLE AMOUNTS.

UPPER LEVEL FLOW WILL WEAKEN THROUGH THE WEEKEND WITH THE TROUGH
FLATTENING AS IT MOVES THROUGH. THEN A RIDGE WILL BUILD OVER THE
EASTERN GULF SUNDAY AND OVER THE PANHANDLE MONDAY. THIS SHOULD
ALLOW FOR MORE BREAKS BETWEEN SHOWERS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM WEDNESDAY MORNING THROUGH WEDNESDAY EVENING FOR
     AKZ018.
MARINE...GALE WARNING FOR PKZ012-013-031.
         SMALL CRAFT ADVISORY FOR PKZ011-021-022-032>036-041>043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051.

&&

WESLEY/FERRIN

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