Gale Warning 197, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
115 PM AKDT THU AUG 21 2008

.SHORT TERM...EXTENSIVE LOW CLOUDS WITH AREAS OF FOG ACROSS THE
NORTHERN PANHANDLE DURING THE EARLY MORNING HOURS HAVE LIFTED A
LITTLE BY MID MORNING. A WEAK RIDGE OF HIGH PRESSURE ACROSS THE
SOUTHERN PANHANDLE HAD ALSO CAUSED PATCHY FOG ALONG THE IMMEDIATE
COAST BEFORE LIFTING BY MID MORNING. IN THE WAKE OF THE WEAKENING
RIDGE ACROSS THE LOCAL REGION...SOUTHEAST ALASKA HAS ENTERED INTO
A TRANSITION TIME FROM A COUPLE OF DAYS PLEASANT WEATHER TO A WET
PATTERN. WINDS ACROSS THE FORECAST AREA REMAIN RELATIVELY LIGHT.
SATELLITE LOOP SHOWS A WEAKENING SURFACE TROUGH SLOWLY DRIFTING
NORTHEAST ACROSS THE PANHANDLE AND PRE-FRONTAL BOUNDARY FORMING
AHEAD OF A DEVELOPING LOW IN THE NORTHEAST PACIFIC. THE PRE-
FRONTAL BOUNDARY LOOKS LIKE TO SPLIT AS IT APPROACHES TO CENTRAL
PANHANDLE COAST AS OF THIS WRITING.

LATEST MODELS ARE IN GOOD AGREEMENT WITH A BETTER INITIALIZATION
OF NAM FAMILY. PREFER TO SELECT THE NAM SOLUTION FOR THE SHORT
TERM FORECAST PACKAGE. WHILE THE WEAKENING RIDGE OF HIGH PRESSURE
REMAINING ACROSS THE SOUTHERN PANHANDLE THROUGH FRIDAY...A
DEVELOPING LOW IN THE NORTHEAST PACIFIC WILL ENTER THE SOUTH
EASTERN GULF ON FRIDAY MORNING AND DEEPEN. THIS LOW WILL CONTINUE
TO INTENSIFY SLIGHTLY AS IT DRIFTS NORTHWARD ACROSS THE EASTERN
GULF THROUGH LATE FRIDAY AFTERNOON. A LEADING EDGE OF FRONTAL
BOUNDARY ASSOCIATED WITH THE DEEPENING LOW WILL SWEEP ACROSS THE
EASTERN GULF AND SOUTHEAST ALASKA ON FRIDAY. AHEAD OF THE INCOMING
SYSTEM...THE MARINE STRATUS IS EXPECTED TO RETURN TO THE NORTHERN
PANHANDLE THIS EVENING THEN SPREAD SOUTHEAST ACROSS THE PANHANDLE
LATE TONIGHT...ALONG WITH THE INCREASING POPS.

IN BETWEEN THE REMAINING WEAK RIDGE OVER THE SOUTHERN PANHANDLE
AND THE INCOMING SYSTEM...PRESSURE GRADIENT WILL GRADUALLY
INCREASE LATE TONIGHT FROM THE SOUTHERN OUTSIDE WATERS TO MEET
SMALL CRAFT WINDS WITH BUILDING SEAS...AND SPREAD NORTH THROUGH
FRIDAY. INSIDE WATERS OPEN TO THE OCEAN WILL EXPERIENCE SMALL
CRAFT WINDS AS WELL WITH A SLIGHT BUILDING OF SEAS ON FRIDAY. WITH
ENHANCED MARINE LAYER OVER THE AREA THROUGH EARLY FRIDAY
MORNING...LIKELY TO CATEGORICAL POPS WILL BE THE FORECAST FOR THE
MOST ZONES ON FRIDAY. COASTAL ZONES WILL HAVE BREEZY TO WINDY
CONDITIONS ON FRIDAY. WILL NOT ISSUE A WIND ADVISORY FOR THE
CENTRAL AND SOUTHERN COASTAL ZONES WITH THE AFTERNOON PACKAGE BUT
NEED TO KEEP AN EYE ON FOR ANY POSSIBLE DEVELOPMENT.

.LONG TERM...UPPER LEVEL MODEL INITIALIZATION AND AGREEMENT LOOKS
GOOD THROUGH NEXT TUESDAY WITH GFS BUILDING A SLIGHTLY STRONGER
UPPER LEVEL RIDGE THAN ECMWF OVER THE EASTERN GULF. AFTER THIS
TIME FRAME...GFS TRACKS A SOMEWHAT DEEPER UPPER LOW EAST ALONG THE
NORTHERN GULF AND EFFECTIVELY DISPLACES THE RIDGE TO THE SOUTH BY
WEDNESDAY MORNING. BY NEXT WEEKEND...30 AUGUST...ECMWF BUILDS IN
A SIGNIFICANT UPPER RIDGE FROM THE SOUTHWEST THAT IS STRONGER AND
ABOUT 24 HOURS FASTER THAN GFS. AT THE SURFACE AT THE BEGINNING OF
THE LONG RANGE FORECAST PERIOD...BOTH GFS AND ECMWF ARE STILL
DEEPENING A SURFACE LOW IN THE EASTERN GULF. ECMWF HOWEVER...IS
MUCH MORE AGGRESSIVE IN DEEPENING THIS PARENT FEATURE AND
TRACKING IT NORTHWEST TO THE NORTHERN GULF BY SATURDAY MORNING.
GFS...ON THE OTHER HAND...INVESTS A LOT MORE ENERGY INTO A SECOND
LOW THAT FORMS ALONG THE FRONTAL BOUNDARY AND APPROACHES THE
SOUTHWEST PANHANDLE SATURDAY AFTERNOON. BASED ON JET STRENGTH AND
LOCATION BEING DEPICTED BY BOTH GFS AND ECMWF...PREFER THE GFS
SOLUTION FOR THE LONG RANGE FORECAST.

AS INDICATED IN THE SHORT RANGE DISCUSSION...A MOIST WEATHER
PATTERN HAS RESUMED OVER THE PANHANDLE WITH THE FIRST ROUND OF
WIDESPREAD RAIN COMING FROM A LOW THAT WILL BE WEST OF SITKA
FRIDAY EVENING. THE FRONT ASSOCIATED WITH THIS LOW WILL BECOME
DISORGANIZED ALONG THE OUTER COAST SO SOUTHWESTERN AND CENTRAL
PANHANDLE LOCATIONS MAY SEE A BREAK IN THE PRECIP LATE FRIDAY
NIGHT INTO SATURDAY MORNING. SOON THEREAFTER...ANOTHER LOW WILL
APPROACH THE COAST FROM THE SSW AND SPREAD MORE WIDESPREAD RAIN
FROM SOUTH TO NORTH SATURDAY THROUGH SUNDAY MORNING THAT WILL BE
MODERATE TO HEAVY AT TIMES ESPECIALLY OVER THE SOUTHERN HALF OF
THE PANHANDLE. AS THE HEAVIEST OF THE RAIN TRACKS NORTH ACROSS THE
PANHANDLE...RAIN RATES WILL DIMINISH BUT STILL EXPECT TO SEE
MODERATE RAIN OVER YAKUTAT THROUGH EARLY MONDAY MORNING. FOR
MONDAY...EXPECT WIDESPREAD SHOWER ACTIVITY AS A SURFACE TROUGH
PUSHES OVER THE TOP OF A WEAK RIDGE THAT SETS UP OVER THE
PANHANDLE. BY TUESDAY MORNING...THE RIDGE WILL DOMINATE PANHANDLE
WEATHER WITH ONSHORE FLOW...MARINE STRATUS...AND LIGHT RAIN.

BY MID WEEK NEXT WEEK...A FAIRLY DEEP SURFACE LOW WITH A WELL
ORGANIZED FRONT WILL APPROACH THE COAST AND DISPLACE THE RIDGE TO
THE EAST. MODEL DIFFERENCES ON THE TIMING...INTENSITY...AND TRACK
OF THIS LOW AND ITS ASSOCIATED FRONT MAKE THE SPECIFICS OF THIS
SYSTEM A LOW CONFIDENCE FORECAST. AT THIS POINT...IT IS SUFFICIENT
TO SAY THAT A WELL ORGANIZED DYNAMIC FRONT WILL IMPACT PANHANDLE
WEATHER IN THE LATTER HALF OF NEXT WEEK.

IN TERMS OF WIND...AM EXPECTING SMALL CRAFT CONDITIONS FRIDAY
NIGHT FROM CAPE DECISION NORTH TO YAKUTAT BAY WHICH SHOULD
MODERATE AS THE ASSOCIATED LOW WEST OF SITKA WEAKENS. EASTERLY
WINDS WILL INCREASE ON SATURDAY AS THE NEXT LOW APPROACHES FROM
THE SSW AND AM EXPECTING 25 TO AS MUCH AS 30 KTS IN THE SOUTHERN
COASTAL ZONES AND THE DIXON ENTRANCE. SHOULD ALSO SEE SMALL CRAFT
CONDITIONS BUILD NORTH OVER MOST OF THE INNER CHANNELS BY SATURDAY
AFTERNOON AND REMAIN FOR MUCH OF SUNDAY.

THE TEMPERATURE TREND IN THE EXTENDED RANGE FOR BOTH DAYTIME
HIGHS AND NIGHT TIME LOWS IS DOWN BY A DEGREE OR TWO AND IS
SEVERAL DEGREES BELOW NORMAL FOR THIS TIME OF YEAR.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ021-022-032>036-041>043-051.

&&

SJA/FRITSCH