Small Craft Advisory 493, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
305 PM AKDT FRI AUG 26 2011

.SHORT TERM... LOW PRESSURE IN THE CENTRAL GULF HAS CAUSED
SHOWERS ACROSS MUCH OF THE PANHANDLE TODAY. SHOWERS ARE EXPECTED
TO CONTINUE THROUGH THE EVENING...SOME SHOWERS MAY BECOME
MODERATE TO HEAVY ALONG WITH SOME GUSTY WINDS. THE LOW WILL
SLOWLY MOVE OFF TO THE NW AND FILL TONIGHT ALLOWING FOR SHOWER
ACTIVITY TO LIFT NORTH AS WELL AND WINDS IN THE OFFSHORE WATERS
TO SLOWLY DECREASE. SOUTHERN AREAS WILL SEE SOME BREAKS IN THE
CLOUDS THROUGH THE EVENING...LEADING TO ADDITIONAL RADIATIONAL
COOLING OVERNIGHT AND THE POTENTIAL FOR FOG EARLY SATURDAY
MORNING. SATURDAY LOOKS TO BE A TRANSITIONAL DAY BEFORE THE NEXT
LOW PRESSURE SYSTEM ENTERS THE GULF. AREAS WITH THE GREATEST
CHANCE OF SHOWERS IS TO THE NORTH WHERE THE REMNANT TROUGH WITH
STILL BE LIFTING NORTH. OTHERWISE SHOWERS SHOULD BE SCATTERED TO
ISOLATED WITH MOSTLY CLOUDY SKIES. BY AFTERNOON THE NEXT LOW
PRESSURE SYSTEM MOVING INTO THE GULF WILL START TO INCREASE WINDS
ONCE AGAIN IN THE OFFSHORE AREA...AS A RESULT SEAS WILL NOT HAVE
MUCH OF A CHANCE TO DECREASE. THE INCREASING PRESSURE GRADIENT
WILL ALSO INCREASE THE EASTERLY WINDS THROUGH CROSS SOUND TO
SMALL CRAFT LEVEL BY LATE AFTERNOON.

MODELS WERE IN GOOD AGREEMENT WITH THE LOW IN THE GULF. THE 00Z
ECMWF HAD THE BEST INITIALIZATION OF PRESSURE OVER THE PANHANDLE
SO INCORPORATED THAT WITH THE MESO-SCALE NAM12. THE NAM WAS ALSO
USED FOR POPS AS IT HAS HAD A GOOD REPRESENTATION FOR WHERE PRECIP
IS FALLING.

&&

.LONG TERM...NEXT OCCLUDED FRONT MOVES ONSHORE SOUTHEAST ALASKA
SATURDAY NIGHT AND THEN STALLS AND WEAKENS ON SUNDAY. UPPER LOW
MOVES ACROSS SOUTHEAST ALASKA MONDAY. A WEAK SURFACE RIDGE BUILDS
NORTH THOUGH THE PANHANDLE MONDAY NIGHT AND TUESDAY AND THEN
SHIFTS EAST OF THE AREA BY WEDNESDAY AFTERNOON. FLAT WESTERLY FLOW
PERSISTS ALOFT. ANOTHER SYSTEM MOVES TO THE EASTERN GULF WEDNESDAY
AFTERNOON AND THEN DISSIPATES OVER THE PANHANDLE WED NIGHT AND
THURSDAY.

LIGHT TO MODERATE RAIN SPREADS ACROSS THE AREA SATURDAY NIGHT
WITH A WET DAY EXPECTED ACROSS THE REGION ON SUNDAY. UPPER LOW
OVER GULF MOVES ESE ACROSS THE PANHANDLE MONDAY. RAIN DECREASES
FROM THE NW STARTING SUNDAY NIGHT AND SHOULD BE DONE OVER ALL
AREAS BY TUESDAY MORNING. WILL KEEP TUE-TUE NIGHT DRY AS WEAK
RIDGE BUILDS IN. MAINLY DRY ACROSS THE INNER CHANNELS WEDNESDAY
BUT APPROACHING FRONT WILL BRING A CHANCE OF RAIN TO THE COAST BY
THE AFTERNOON. BY WEDNESDAY NIGHT LIGHT-MODERATE RAINS SPREADS
BACK OVER ALL PANHANDLE.

EXPECTING MIN GALES IN THE COASTAL WATERS SATURDAY NIGHT AHEAD OF
FRONT. THIS WAKENS TO SMCR SUNDAY AND FALLS BELOW SMCR LEVELS
SUNDAY NIGHT. MODELS HAVE A SLIGHT DIFFERENCE IN TRACK OF LOW
ACROSS PANHANDLE WHICH WILL AFFECT WIND DIRECTIONS BUT GENERALLY
EXPECT A WEAK SHIFT TO THE NORTHWEST MONDAY AND TUESDAY. WILL KEEP
A 6-8 FOOT SW SWELL IN EASTERN GULF THROUGH MONDAY. THE FRONT
MOVING ONSHORE WEDNESDAY NIGHT HAS A BETTER SIGNATURE ALOFT THAN
AT THE SURFACE AND WILL ONLY SEE MIN SMCR IN EASTERN GULF AHEAD OF
FRONT AND LESS THAN SMCR FOR INNER CHANNELS.

MODELS IN OK AGREEMENT THROUGH THE LONG TERM. HAVE BETTER
AGREEMENT WITH SYNOPTIC PICTURE BUT DIFFERENCES WITH POSITION OF
LOW CENTERS WILL HAVE IMPACTS ON SENSIBLE WEATHER FOR THE
PANHANDLE. CONFIDENCE IS LOWER TODAY FOR TUE-WED PERIOD. WILL
CONTINUE DRY TREND BUT 12Z EC HINTING AT A WEAK TROUGH PUSHING
ACROSS THE AREA WITH SPOTTY LIGHT RAIN FOR CONTINUITY. OTHERWISE
NAM12 USED FOR PRESSURE AND WINDS THROUGH 72 HOURS THEN USED A
GFS/EC BLEND WHILE TRYING TO MAINTAIN A DEEPER LOW CENTER AND
SLIGHTLY STRONGER RIDGE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ022-041>043-051-052.

&&

HANNON/MM