Small Craft Advisory 370, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
259 PM AKDT MON JUN 6 2011

.SHORT TERM...THE DRYING TREND WILL CONTINUE FOR THE NEXT
24 HOURS. A STRONG RIDGE ALOFT AND SFC RIDGE EXTEND NNW INTO THE
GULF FM A PT 300 NM SW OF PAKT TO OVER PAMD. THIS RIDGE IS
DRIFTING CLOSER TO THE AS THE RESULT OF THE FRONT IN THE CENTRAL
GULF AS DISCUSSED IN THE LONG RANGE SECTION BELOW. A VORT MAX IS
MOVING SE AWAY FROM THE SOUTHERN PANHANDLE AT THIS TIME AND WAS
THE TRIGGER FOR THE SHOWERS THAT HAVE OCCURRED IN THE AOR LAST
NIGHT AND TODAY. AS THIS TROF PULLS FARTHER AWAY THE SHOWERS ARE
ENDING AND A LIMITED AMOUNT OF SFC DRYING IS TAKING PLACE DUE TO
THE LOSS OF CLOUD COVER. CHANGES ARE SMALL AND CONFIDENCE IS
AVERAGE.

 RADIATIVE FOG SHOULD OCCUR IN WIND SHELTERED AREAS TONIGHT.
BESIDES THE WIND LIMITING THE AREAL COVERAGE, THERE ARE OTHER
FACTORS IMPORTANT FOR FOG TONIGHT: FIRST THE LOSS OF CLOUD COVER
BEGINNING LATE TODAY WILL ONLY ALLOW LIMITED DRYING. SECOND,
THERE TENDS TO  BE SOME LIMIT TO HOW LOW THE VISIBILITIES BECOME
FOR EVENTS CLOSE TO THE SOLSTICE, I.E. NEAR THE MAX OF DAYLIGHT
LENGTH.

 SEA BREEZE ENHANCEMENT FOR SCA IN NRN LYNN CANAL AND FOR
CLARENCE STRAIT TUE AFTERNOON.

 &&

 .LONG TERM...PRETTY GOOD AGREEMENT IN PLACEMENT OF UPPER LEVEL
FEATURES THROUGH NEXT MONDAY AFTERNOON. MAIN FEATURES INCLUDE AN
UPPER RIDGE THAT WILL SAG TO THE SOUTH ON WEDNESDAY AS AN UPPER
TROUGH APPROACHES THE OUTER COAST BY THURSDAY MORNING. WEAK UPPER
LEVEL RIDGING WILL BUILD BACK IN OVER THE GULF FROM THE SOUTH AND
WEST ON FRIDAY AND MOVE EAST OVER THE PANHANDLE NEXT WEEKEND. A
SHORT WAVE WILL MOVE INTO THE NORTHERN GULF AND ATTEMPT TO
DISPLACE THE RIDGE ON SUNDAY. AT THE SURFACE, VERY GOOD
CONSISTENCY IN THE GFS BETWEEN THE 06Z AND 12Z MODEL RUNS. A
LITTLE BIT LESS SO IN ECMWF, PARTICULARLY IN THE SOUTH CENTRAL
GULF BY NEXT SUNDAY. RMOP VALUES START OUT QUITE HIGH, BUT THEN
FALL TO PREDICTABILITY PERCENTAGES OF LESS THAN 10 TO ONLY AS
MUCH AS 30 PERCENT. STANDARDIZED ANOMALIES FOR BOTH THE GEFS AND
THE ECMWF DO NOT REVEAL ANYTHING TREMENDOUSLY OUT OF THE
ORDINARY. SUM TOTAL IS AN AVERAGE CONFIDENCE FORECAST WITH NO
SIGNIFICANT OR SENSATIONAL WEATHER EXPECTED.

 MAIN FEATURE OF THE EXTENDED RANGE FORECAST IS A FRONT THAT WILL
EXTEND FROM THE KENAI PENINSULA SOUTH AND EAST INTO THE CENTRAL
GULF ON TUESDAY AFTERNOON. THE FRONT WILL BE PRESSING UP AGAINST
A SURFACE RIDGE SITUATED OVER THE EASTERN GULF AS IT TRACKS EAST
AND WEAKENING AS A RESULT. DO NOT BELIEVE IT WILL MAKE IT TO THE
OUTER COAST AS AN INTACT FEATURE BUT HAVE SOME POP IN THE GRIDS
TO REFLECT SPOTTY PRECIP THAT IS EXPECTED TO MAKE IT OVER THE TOP
OF THE RIDGE. PRESSURE PATTERN WILL RE-ORIENT AFTER THIS FRONT
AND A WEAK ONSHORE FLOW REGIME WILL CONTINUE TO PUSH MOIST LOW
LEVEL AIR INTO THE COAST, RESULTING IN MOSTLY CLOUDY TO CLOUDY
SKIES AND CHANCE OR SLIGHT CHANCE POPS OVER MUCH OF THE PANHANDLE
THROUGH FRIDAY NIGHT. PRESSURE PATTERN WILL RE-ORIENT ONCE AGAIN
BY NEXT WEEKEND, RESULTING IN A MORE NORTHWESTERLY LOW LEVEL FLOW
AND ALLOW FOR SOME PARTIAL CLEARING FOR LOCATIONS AWAY FROM THE
OUTER COAST. RESULTING DAYTIME HEATING COMBINED WITH A THERMAL
LOW OVER WESTERN CANADA WILL LIKELY PRODUCE SOME SHOWERS NEAR THE
COAST MOUNTAINS OVER THE SOUTHERN HALF OF THE PANHANDLE.

 HAVE A VERY CONSISTENT AFTERNOON SEA BREEZE THAT REACHES SMALL
CRAFT INTENSITY FOR NORTHERN LYNN CANAL WHICH SHOWS UP LATE IN
THE DAY AND DIMINISHES OVERNIGHT THROUGHOUT THE UPCOMING WEEK.
HAVE A SIMILAR BUT SLIGHTLY WEAKER WESTERLY WIND OVER CROSS SOUND
AND WESTERN PORTIONS OF ICY STRAIT. THIS MAY BE UNDERDONE AND
REQUIRE A FEW EXTRA KNOTS IN SUBSEQUENT FORECAST ISSUANCES.
ELSEWHERE, NOT A LOT OF WIND IN THE EXTENDED RANGE FORECAST.

 USED A BLEND OF GFS AND ECMWF THROUGH THURSDAY NIGHT, THEN AN
EC/GFS/HPC BLEND. FORECAST CONFIDENCE IS AVERAGE.

.AJK WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR
PKZ012-021-022-033-035-036-041-042. SMALL CRAFT ADVISORY DUE TO
SEAS FOR PKZ043-051.

&&

JBT/FRITSCH