Small Craft Advisory 573, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
345 PM AKDT WED SEP 3 2014

.SHORT TERM...AFTERNOON SATELLITE IMAGE REVEALS A DISSIPATING
FRONTAL BOUNDARY ALONG THE NORTHERN GULF COAST MOVING EASTWARD
ACROSS THE NORTHERN PANHANDLE WITH LINGERING LIGHT SHOWERS.
PERSISTING HIGH PRESSURE IN THE EASTERN PACIFIC CONTINUES PULLING
A LARGE MOISTURE PLUME FROM THE SUB-TROPICAL REGION INTO THE GULF
OF ALASKA. AN OCCLUDED FRONTAL PASSAGE FORMING SOUTH OF KODIAK
ISLAND SLOWLY DRIFTING EASTWARD INTO THE CENTRAL GULF. A RIDGE OF
HIGH PRESSURE ACROSS SOUTHEAST ALASKA SLOWLY DRIFTING EAST TO
SOUTHEAST WITH SOUTHERLY PRESSURE GRADIENT TIGHT ENOUGH TO PRODUCE
NEAR SMALL CRAFT WINDS OVER NORTHERN LYNN CANAL AND CROSS SOUND.
SHOWERS GRADUALLY TAPERING OFF ACROSS THE PANHANDLE WITH DAYTIME
TEMPERATURES RANGING FROM THE MID TO UPPER 50S OVER THE NORTHERN
AREAS TO THE UPPER 50S TO THE LOWER 60S ACROSS THE SOUTHERN ZONES.

MODELS REMAIN IN FAIR AGREEMENT THROUGH THURSDAY WITH THE RIDGE
OF HIGH PRESSURE OVER SOUTHEAST ALASKA CONTINUES TO MOVE
SOUTHEASTWARD AS THE WARM OCCLUSION MOVES INTO THE EASTERN GULF.
REFRESHED THE INHERITED FORECAST PACKAGE WITH THE NAM12 TO MAKE A
FEW ADJUSTMENTS FOR THE INTENSITY AND TIMING OF THE INCOMING
FRONTAL PASSAGE. THE NAM12 WAS INITIALIZED WELL AND HAS SHOWN A
GOOD CONSISTENCY OVER THE PAST SEVERAL MODEL RUNS.

SCATTERED SHOWERS WILL CONTINUE TO DIMINISH ACROSS THE PANHANDLE
THIS EVENING...THEN EXPECT CHANCE OF RAIN LATER TONIGHT. THE
SOUTHWESTERN CORNER OF THE PANHANDLE WILL SEE AN INCREASING POPS
EARLY THURSDAY MORNING AS THE LEADING EDGE OF THE INCOMING FRONT
NOSING THE RAIN BAND SOUTHEASTWARD TO TOUCH THE SOUTHWESTERN
PANHANDLE. CONTINUED GLOOMY SKIES WITH TAPERING OFF PRECIPITATION
WILL LEAD AREAS OF FOG FORM ACROSS MUCH OF THE PANHANDLE AND INNER
CHANNELS DURING THE LATE NIGHT AND EARLY MORNING HOURS. NOT MUCH
DIURNAL TEMPERATURES FLUCTUATIONS ARE EXPECTED WITH OVERNIGHT LOWS
IN THE MID TO UPPER 40S ACROSS THE NORTHERN PANHANDLE TO THE UPPER
40S TO THE LOWER 50S OVER THE SOUTHERN AREAS. THURSDAY HIGHS WILL
BE MOSTLY IN THE MID TO UPPER 50S...EXCEPT AROUND 60 OVER THE
SOUTHERNMOST PANHANDLE. CHANCE POPS WILL PREVAIL UNTIL THE WELL
ORGANIZED FRONTAL PASSAGE IN THE EASTERN GULF ON THURSDAY MOVES
ONSHORE OVER THE PANHANDLE BY THURSDAY NIGHT.

.LONG TERM...OVERALL SYNOPTIC PATTERN REMAINS UNCHANGED FROM
PREVIOUS THINKING. A COUPLE OF FRONTS AFFECT THE PANHANDLE OVER
THE WEEKEND WITH A BRIEF PERIOD OF DRIER WEATHER EARLY NEXT WEEK
BEFORE ANOTHER FRONT MOVES BACK INTO THE AREA MID WEEK. THE
GENERAL THEME WILL BE CLOUDY AND WET WEATHER FOR MUCH OF THE
NORTHERN HALF OF THE AREA WITH DRIER CONDITIONS OVER THE SOUTH.

WARM FRONTAL FEATURE MOVES CONTINUES TO PUSH NORTHEAST INTO THE
PANHANDLE THURSDAY EVENING WITH RAIN OVERSPREADING MUCH OF THE
AREA. HEAVIEST RAIN WILL BE FOCUSED IN THE YAKUTAT AREA WITH A
LONG FETCH OF SOUTHWEST FLOW AND SOME TROPICAL MOISTURE AIMED AT
THE NORTHERN GULF COAST. THIS FRONT WILL DRIFT INLAND ON FRIDAY
AFTERNOON WITH RIDGE BUILDING IN BEHIND IT. THE TRAILING SURFACE
FRONTAL BOUNDARY WILL BE RIGHT ON ITS HEELS MOVING INTO THE
PANHANDLE WITH ANOTHER ROUND OF HEAVIER RAINFALL THROUGH THE DAY
ON SATURDAY. RAIN CHANCES REMAIN ON THE HIGH SIDE OVER THE WEEKEND
AS A PIECE OF NORTHERN STREAM ENERGY SWINGS DOWN FROM THE
NORTHWEST. AS THIS SYSTEM PULLS TO THE SOUTHEAST SUNDAY NIGHT RAIN
CHANCES WILL DIMINISH AND HIGH PRESSURE WILL BUILD INTO THE AREA
FROM THE NORTH.

MAIN CHANGES TO THE FORECAST WERE TO INCREASE WINDS ACROSS THE
CENTRAL AND NORTHERN PANHANDLE THURSDAY NIGHT THROUGH FRIDAY
NIGHT. SHARPENING SURFACE RIDGE BOTH ON THURSDAY NIGHT AND THROUGH
THE DAY FRIDAY WILL RESULT IN WIDESPREAD SMALL CRAFT WINDS ACROSS
THE CENTRAL AND NORTHERN INNER CHANNELS. THERE IS A POTENTIAL FOR
NORTHERN LYNN CANAL TO REACH GALE FORCE ON FRIDAY
AFTERNOON/EVENING. LAND WINDS WILL ALSO BECOME GUSTY DURING THIS
TIME FRAME ESPECIALLY LATER ON FRIDAY WITH THE SKAGWAY AREA
POTENTIALLY REACHING THE STRONG WIND CRITERIA OF GUSTS TO 40 MPH.
THESE WINDS WILL SLOWLY DIMINISH OVER THE WEEKEND WITH NORTHERLIES
DEVELOPING OVER THE FAR NORTHERN INNER CHANNELS LATE SUNDAY INTO
MONDAY. MODELS CONTINUE TO STRUGGLE WITH THE PATTERN AFTER EARLY
WEEK AS ECMWF IS FASTER AND BRINGS A FRONT BACK INTO THE AREA ON
TUESDAY. GFS IS SLOWER WITH THE FRONT HOLDING OFF UNTIL WEDNESDAY.

USED A BLEND OF THE 12Z NAM/ECMWF THROUGH 84 HOURS THEN
TRANSITIONED TO MAINLY THE LATEST WPC GUIDANCE. CONFIDENCE IS
AVERAGE THROUGH MUCH OF THE WEEKEND BEFORE DECREASING INTO EARLY
NEXT WEEK AS MODEL SOLUTIONS DIVERGE ON TIMING OF THE NEXT FRONTAL
FEATURE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-051-052.

&&

AHN/TPS

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