Small Craft Advisory 739, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
222 PM AKST THU NOV 17 2011

.SHORT TERM...AT 1800 UTC A WEAKENING LOW PRESSURE CENTER WAS
LOCATED JUST WEST OF CAPE ST JAMES WHILE HIGH PRESSURE CONTINUED
TO BUILD OVER NORTHWEST CANADA AND SOUTHEAST ALASKA. THE LATEST
SATELLITE IMAGERY SHOWS A FEW CONVECTIVE BANDS WERE SPIRALING
AROUND THE LOW AND REACHING THE EXTREME SOUTHERN PANHANDLE.
SURFACE OBSERVATIONS IN THIS AREA REPORTED BRIEF FLURRIES DURING
THIS TIME...BUT THESE SHOULD END BY EARLY TONIGHT AS THE LOW
MOVES FURTHER SOUTHEASTWARD. MODELS ARE IN FAIRLY GOOD AGREEMENT
WITH THE GENERAL SYNOPTIC TREND BUT THERE ARE SUBTLE DIFFERENCES
IN THEIR HANDLING OF WEAK CIRCULATIONS EMBEDDED IN THE INVERTED
OFFSHORE TROUGH.

 THE STRONG PRESSURE GRADIENT ACROSS SOUTHEAST ALASKA BETWEEN THE
HIGH CENTER TO THE NORTH AND THE LOW TO THE SOUTH WILL RELAX A
BIT THROUGH FRIDAY AS THE LOW MOVES SOUTHWARD...BUT AN INVERTED
TROUGH WILL PERSIST OFFSHORE SO ANY SIGNIFICANT DECREASE IN WINDS
WILL BE SLOW...ESPECIALLY IN NORTHERN SECTIONS. MOUNTAIN WAVE
CONDITIONS IMPROVE AGAIN EARLY THURSDAY NIGHT WHICH WILL CAUSE
SOME WIND GUSTS TO 40 KTS IN DOWNTOWN JUNEAU AND DOUGLAS.

 AS ARCTIC AIR CONTINUES TO SETTLE INTO THE PANHANDLE AND SKIES
CLEAR TEMPERATURES WILL BE COLDER TONIGHT THAN LAST NIGHT
REACHING SINGLE DIGITS IN SOME NORTHERN WIND SHELTERED LOCATIONS.

.LONG TERM...ARCTIC HIGH WILL REMAIN JUST N AND E OF THE AREA THRU
SUN NIGHT...THEN MOVE SLOWLY OFF TO THE E EARLY NEXT WEEK. ARCTIC
FRONT WILL REMAIN OVER THE ERN GULF WITH ONE OR MORE MINOR LOWS
MOVING SE ALONG IT FRI NIGHT INTO SAT NIGHT. ARCTIC FRONT WILL
RETREAT NWD STARTING SUN AS A COMPLEX LOW AND FRONTAL SYSTEM MOVE
INTO THE SRN AND ERN GULF. LOOKS LIKE THE FIRST LOW WILL MOVE NWD
TO THE FAR E-CNTRL GULF MON THEN DISSIPATE AS IT RUNS FURTHER N INTO
THE ARCTIC AIRMASS MON NIGHT. ANOTHER LOW SHOULD MOVE INTO THE ERN
GULF LATE MON NIGHT AND TUE...AND THIS LOW WILL HELP WIPE OUT THE
ARCTIC AIRMASS OVER ALL BUT THE FAR NRN AREA BY LATE TUE AFTERNOON.
STILL SOME MODEL TIMING ISSUES ON THE COMPLEX SYSTEM...SO LATEST
HPC WAS USED FOR THE 12Z MON PERIOD ON OUT. BEFORE THEN...USED
GFS/NAM BLEND FROM 00Z SAT TO 12Z SUN...THEN GFS FOR 12Z SUN TO
06Z MON.

LOOKS LIKE THE COLDEST AIR WILL BE OVER THE AREA LATE FRI INTO
EARLY SUN. WILL HAVE TO WATCH FOR POTENTIAL PRECIP ALONG THE COAST
FROM THE LOWS RUNNING SE ALONG THE ARCTIC FRONT DURING THIS TIME.
ALSO WILL HAVE STRONG OUTFLOWS GOING ON DURING THIS PERIOD...SO
LATER SHIFTS WILL LIKELY NEED SOME WIND HEADLINES.

TEMPS WILL BEGIN TO MODERATE FROM THE S SUN INTO EARLY NEXT WEEK.
PRECIP IS EXPECTED TO MOVE INTO THE SRN AREA AHEAD OF THE FIRST
LOW AND FRONT BY SUN EVENING...THEN SPREAD N TO THE CENTRAL AREA MON.
MAY HAVE SOME DOWNSLOPE GOING ON ALONG THE COAST MTNS N OF
FREDERICK SOUND SO POPS WILL BE A LITTLE LOWER THERE THAN FURTHER
W MON. MAY SEE A MINOR BREAK IN PRECIP ESPECIALLY N MON NIGHT AFTER
FIRST LOW TROFS OUT OVER THE NE GULF AND SECOND LOW MOVES INTO THE
SE GULF. HOWEVER LOOKS LIKE SOME OVERRUNNING WILL CONTINUE OVER
THE NRN THIRD OF THE AREA SO WILL KEEP HIGHER POPS GOING MON NIGHT
OVER THE N. MORE WIDESPREAD PRECIP IS EXPECTED TUE AND THE
N-CENTRAL AREA SHOULD WARM UP ABOVE FREEZING BY LATE TUE AFTERNOON.

LATER IN THE WEEK SOME COOLER AIR WILL LIKELY MOVE IN FROM THE W
BUT INTENSITY OF THE COLD AIR IS IN QUESTION DUE TO HOW FAST NEXT
SYSTEM MOVES INTO THE AREA. AT THE LEAST WILL HAVE AN ANCHOR LOW
OVER THE NRN GULF WITH COLD AIR FLOWING OUT TO THE W AND S OF THE
LOW AND INTO SE AK UNTIL ANOTHER SYSTEM PINCHES OFF THIS COLD FLOW.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 9 PM AKST THIS EVENING FOR AKZ022-025.
         STRONG WIND THROUGH LATE TONIGHT FOR AKZ018-019.
         STRONG WIND UNTIL MIDNIGHT AKST TONIGHT FOR AKZ017.
MARINE...GALE WARNING FOR PKZ011>013-022-031-051-053.
         SMALL CRAFT ADVISORY FOR PKZ021-032>036-041>043.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ052.

&&

CFD/RWT