Weather Service Report


648 
FXAK67 PAJK 271314
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
514 AM AKDT FRI MAR 27 2015

.SHORT TERM...SOUTHERLY WINDS OVER NORTHERN LYNN CANAL AND
SKAGWAY HAVE ONCE AGAIN BEEN PERSISTENTLY STRONGER THAN
ANTICIPATED AND THIS WILL LIKELY CONTINUE THROUGH MORNING...THUS
WE BUMPED UP ZONE 12 TO SCA. BRIEF RAIN SHOWERS HAVE BEEN
SCATTERED AROUND THE REGION OVERNIGHT ESPECIALLY IN THE YAKUTAT
AND JUNEAU AREAS. THEY OWE THEIR EXISTENCE TO UPRIGHT INSTABILITY
WITH VERY COLD TEMPS ALOFT...-30 TO -32C AT 500MB. THESE WILL
LIKELY PERIODICALLY DEVELOP AND DISSIPATE OVER THE NEXT 12 HOURS
OR SO OVER MAINLY THE NORTHERN PANHANDLE. KLAWOCK AREA HAS BEEN
DOWN TO 1 MILE IN FOG BUT OTHERWISE MID-LEVEL CLOUDS APPEAR TO
HAVE PREVENTED SIGNIFICANT FOG FORMATION OVERNIGHT.

ON THE LARGE SCALE...AS UPPER LOW SPINS AROUND THE ALEUTIANS
THROUGH FRI NIGHT...A STRONG LOBE ON ITS SOUTHEASTERN QUADRANT
ENTERS THE WESTERN GULF. THIS SPINS UP A 975-980ISH LOW WHICH
MIGRATES INTO THE CENTRAL GULF. STRONG SOUTHEAST WINDS DEVELOP
OVER THE EASTERN GULF IN RESPONSE...CAUSING GALES ON THE ADJACENT
SOUTHERN OFFSHORE ZONES BY SAT MORNING AND VARIOUS SCA-LEVEL
WINDS IN THE SOUTHERN CHANNELS AS WELL AS CROSS SOUND. PRECIP
SHIELD ASSOCIATED WITH THE FRONT JUST REACHES THE FRINGE OF THE
SOUTHERN PANHANDLE COAST BY 15Z SAT AS SOUTHEASTERLY WINDS WITH
GUSTS INCREASING OVER EXPOSED LAND AREAS. MEANWHILE SHOWERY SCENARIO
CONTINUES THROUGH EARLY TONIGHT OVER THE CENTRAL AND NORTHERN
PANHANDLE PRIOR TO APPROACH OF THE NEW LOW...PRIMARILY DUE TO
CONTINUED ONSHORE FLOW. SHOWERS WILL BE LIGHT WITH THE EXCEPTION
OF SOME TEMPORARILY MODERATE RATES THIS AFTERNOON. BRIEF PERIODS
OF MIXED PRECIP ARE POSSIBLE TONIGHT OVER THE HAINES AND SKAGWAY
AREA BUT ANY SNOW AMOUNTS WILL BE VERY SMALL. AS SKIES PARTIALLY
CLEAR OVER THE CENTRAL AND SOUTHERN PANHANDLE TONIGHT A PERIOD OF
PATCHY FOG IS LIKELY PRIOR TO WINDS AND MID-LEVEL CLOUDS
INCREASING OVER MOST AREAS BY SATURDAY MORNING. INCLUDED PATCHY
FOG FOR THE 03-15Z PERIOD OVER MANY SECTIONS OF THE SOUTH AND
CENTRAL.

USING PRIMARILY NAM AND EC MODEL UPDATES...TWEAKED THE WINDS
ASSOCIATED WITH THE STRENGTHENING GRADIENT ASSOCIATED WITH THE
APPROACHING FRONT FRI NIGHT. WENT SLIGHTLY STRONGER WITH WINDS OVER
WATER AND ALSO OVER SOME OF THE SOUTHERN CHANNELS WITH FAVORABLE
ORIENTATION AND/OR OCEAN CONNECTIONS. THUS AT THE 15Z HANDOFF ON
SAT WINDS WILL BE ON THE INCREASE IN THESE AREAS AND SPREADING TO
THE NORTHEAST IN CHANNELS WITH FAVORABLE ORIENTATION TO THE
PRESSURE GRADIENT. ALSO UPDATED THERMODYNAMIC FIELDS WITH THE NEW
MODEL RUNS. LOCAL QPF AMOUNTS IN SHOWERS TODAY COULD REACH A THIRD
TO A HALF INCH IN LOCAL AREAS OVER THE NORTH WITH THE POSSIBILITY OF
SLIGHTLY HIGHER AMOUNTS IN THE YAKUTAT REGION.

.LONG TERM...UPPER LOW AND ASSOCIATED SURFACE CYCLONE IS FORECAST
TO MOVE NWD INTO THE SWRN GULF DURING SAT. AS THIS TAKES PLACE...A
GALE FORCE FRONT WILL PROGRESS ENE ACROSS THE ERN GULF BY MIDDAY
SAT...AND THEN ONSHORE OVER THE SRN PANHANDLE SAT
AFTERNOON/EVENING. GUSTS WILL APPROACH STRONG WIND CRITERIA /40
MPH/ FOR AKZ023...AKZ027...AND AKZ028 /SITKA TO HYDABURG TO
KETCHIKAN/ WITH THE FRONTAL PASSAGE...AND SLY GALE FORCE WINDS
WILL BE PROBABLE OVER CLARENCE STRAIT AS 50 KT PRE-FRONTAL LLJ
OVERSPREADS THE REGION. IN ADDITION...MODERATE TO HEAVY RAIN RATES
ARE ANTICIPATED ALONG/AHEAD OF THE FRONT...PARTICULARLY THE SRN
PANHANDLE WHERE MOISTURE FLUX WILL BE STRONGEST.

AFTER SAT...MODEL GUIDANCE REMAINS IN GENERAL AGREEMENT WITH THE
EVOLUTION OF LARGE-SCALE FEATURES THROUGH EARLY NEXT WEEK...SHOWING
A WEAK TROUGH PERSISTING OVER THE WRN GULF...AND A RIDGE OVER NWRN
CANADA. HOWEVER...DIFFERENCES EXIST WITH A SHORTWAVE MOVING NE
TOWARD THE SRN PANHANDLE MON AFTERNOON. THE ECMWF AND GEM DEVELOP
A STRONG SURFACE CYCLONE WITH THIS WAVE...WHILE THE 00Z GFS IS
LACKING SUCH DEVELOPMENT. ATTM...DID NOT LEAN TOWARD ANY ONE
PARTICULAR SOLUTION MON AFTERNOON THROUGH THE REMAINDER OF THE
LONG TERM DUE TO THE RAPID INCREASE IN SHORTWAVE MODEL SPREAD.
HOWEVER...THE GENERAL PATTERN WILL SUPPORT A PROLONGED PERIOD OF
WET RAINY WEATHER.

INHERITED PRESSURE GRIDS WERE LEFT UNTOUCHED...AND FEATURE SMALL
CRAFT TO GALE FORCE WINDS DURING THE WEEKEND...AND GENERALLY WEAK
WINDS THEREAFTER /THOUGH THIS COULD CHANGE GOING INTO EARLY NEXT
WEEK IF THE ECMWF AND GEM SOLUTIONS PROVE CORRECT/. POP AND QPF
WERE REFRESHED WITH A BLEND OF THE 00Z GFS/ECMWF WITH INHERITED
GRIDS.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ041>043. 
         SMALL CRAFT ADVISORY FOR PKZ022-033-035-036-051-052. 

&&

$$

WESLEY/GARNER

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