Small Craft Advisory 393, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
332 PM AKDT WED JUL 4 2012

.SHORT TERM.../WEDNESDAY NIGHT AND THURSDAY/ EARLY AFTERNOON
SATELLITE LOOP SHOWS A RIDGE OF HIGH PRESSURE REMAINS ACROSS THE
EASTERN GULF AND SOUTHEAST ALASKA WITH A WEAK TROUGH OVER ALASKA
AND YUKON BORDER. THIS WEAK TROUGH PRODUCES INTERMITTENT LIGHT
RAIN ACROSS THE NORTHEASTERN GULF COAST. MOSTLY CLOUDY SKIES
PREVAIL ACROSS THE PANHANDLE AND OCCASIONAL SUNNY BREAKS OCCUR
DURING THE EARLY AFTERNOON. THE RIDGE MAINTAINS SOUTHERLY WINDS
15 TO 20 MPH NEAR SKAGWAY AND EAST-SOUTHEAST WIND 10 TO 15 MPH
NEAR HAINES. 20 TO 25 KNOTS WINDS BLOW OVER NORTHERN LYNN CANAL.
ELSEWHERE...WINDS ARE GENERALLY LIGHT AND VARIABLE.

MODELS REMAIN IN GOOD AGREEMENT WITH THE RIDGE OF HIGH PRESSURE
REMAINS OVER THE EASTERN GULF AND SOUTHEAST ALASKA THROUGH
THURSDAY. REFRESHED THE INHERITED FORECAST PACKAGE WITH THE NAM
FOR TONIGHT AND THURSDAY. A WEAK FRONTAL PASSAGE...ASSOCIATED WITH
AN INCOMING LOW OVER THE CENTRAL GULF...IS EXPECTED TO MOVE INTO
THE NORTHEASTERN GULF LATE THURSDAY. AHEAD OF THE FRONTAL
BOUNDARY...SOUTHEASTERLY WINDS WILL INCREASE TO MEET THE SMALL
CRAFT CRITERIA OVER THE NORTHERN OUTSIDE WATERS LATE TONIGHT AND
CONTINUE THROUGH THURSDAY. SOUTHERLY WINDS UP TO 20 MPH WILL
REVISIT THE NORTHERN INNER CHANNELS ON THURSDAY AFTERNOON.

UNDER MOSTLY CLOUDY SKIES SLIGHT CHANCE TO CHANCE POPS WILL
CONTINUE OVER THE NEXT 24 HOURS WITH BEST CHANCE ACROSS THE
NORTHEASTERN GULF COAST. EXPECTED RAIN WILL BE VERY LIGHT AND
INTERMITTENT WITH RAINFALL BELOW A QUARTER OF AN INCH. AN AREA OF
CATEGORICAL POP WILL MOVE INTO THE NORTHERN GULF LATE THURSDAY
NIGHT INTO EARLY FRIDAY MORNING. WITH LESS CLOUDS AND ABSENT OF
PRECIPITATION...PATCHY RADIATION FOG MAY OCCUR OVER THE SOUTHERN
AREAS LATE TONIGHT AND EARLY THURSDAY MORNING.

.HYDRO...SNOW MELT AND/OR RAINFALL ARE NO LONGER A FACTOR FOR
ANY HYDRO ISSUES ACROSS THE LOCAL REGION. HOWEVER...AS OF THIS
WEDNESDAY AFTERNOON...IT APPEARS THAT THE MENDENHALL RIVER IS
EXPERIENCING THE EARLY STAGES OF A GLACIER DAMMED LAKE RELEASE.
WATER HAS BEGUN RISING AND THE RATE OF RISE WILL LIKELY TO
INCREASE OVER THE NEXT 24 HOURS. IF THE CURRENT RATE OF RISE
CONTINUES OVERNIGHT TONIGHT...THE WATER LEVEL WILL EXCEED THE
ACTION STAGE DURING THE LATE THURSDAY AFTERNOON TIME FRAME AND BE
NEAR OR ABOVE FLOOD STAGE BY FRIDAY MORNING.

.LONG TERM...CHANGES ARE SMALL AND CONFIDENCE IS AVERAGE. THE
MODEL CONSENSUS IS GOOD, WITH ONE EXCEPTION FOR A LAND FALLING
FRONTAL WAVE NEAR CAPE CROSS SATURDAY AFTERNOON. AN INTERMEDIATE
SOLUTION WAS USED THAT DOES RESULT IN MINIMAL CHANGE TO THE
FORECASTS.

PLEASE NOTE THE FLOOD WATCH FOR MENDENHALL LAKE AND MENDENHALL
RIVER. THE STAGES OF MENDENHALL LAKE AND MENDENHALL RIVER ARE
RISING AND ARE CAUSED BY A GLACIER DAM RELEASE FROM THE VICINITY
OF SUICIDE BASIN. DATA ARE NOT AVAILABLE DIRECTLY FROM THE GLACIER
DAM SITE. THE FILLING OF THE SUICIDE BASIN GLACIER DAM WAS
CONFIRMED BY A CIVIL AIR PATROL FLIGHT ON JUNE 23. OVER THE LAST
TWO DAYS THE WATER LEVEL OF MENDENHALL LAKE HAS BEEN RISING WITH
THE SIGNATURE OF A GLACIER DAM RELEASE.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FLOOD WATCH FROM THURSDAY EVENING THROUGH FRIDAY AFTERNOON FOR
     AKZ025.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-051-052.

&&

AHN/JBT