Small Craft Advisory 319, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 AM ADT TUE APR 12 2005

.DISCUSSION...

.ANALYSIS...THE MAIN FEATURES OF THE NIGHT ARE A LARGE CLOSED LOW
CENTERED WEST OF BRITISH COLUMBIA NEAR 50N 134W...A SHORT-WAVE
RIDGE CENTERED ALONG A LINE FROM THE SOUTHERN AKPENN NORTHWESTWARD
TO SAINT MATTHEW ISLAND AND BACK WEST TO EASTERN SIBERIA...AND A
MORE TIGHTLY WOUND CLOSED LOW LOCATED BETWEEN KAMCHATKA AND THE
WESTERN ALEUTIANS. AS FAR AS SENSIBLE WEATHER...WEAK SHORT-WAVES
ARE ROTATING AROUND EASTERN CLOSED LOW WITH A WEAK SURFACE
REFLECTION OF ONE OF THESE LOCATED OVER THE NORTHERN GULF. NOT
MUCH IN THE WAY OF CLOUDS OR PRECIP WITH THIS LOW. MID TO HIGH
CLOUDS ARE MOVING FROM THE YUKON INTO THE COPPER RIVER BASIN AND
DISSIPATING AS THEY RUN INTO RIDGE BUILDING IN FROM THE EASTERN
BERING. ALASKA RANGE IS BLOCKING ANY LOW LEVEL MOISTURE AND PRECIP
THAT MAY BE ASSOCIATED WITH THESE UPPER LEVEL SHORT-WAVES. THE
SURFACE LOW OVER THE NORTHERN GULF IS PRODUCING A FAIRLY TIGHT
PRESSURE GRADIENT FROM KODIAK ISLAND INTO SOUTH CENTRAL ALASKA.
THIS IS COMBINING WITH WEAK COLD ADVECTION IN THE LOW LEVELS TO
PRODUCE LOCALLY GUSTY WINDS...ESPECIALLY FRO KODIAK ISLAND AND
VICINITY WHERE A WIND ADVISORY REMAINS IN EFFECT THROUGH TONIGHT.
THE TREND IS FOR DIMINISHING WINDS AS THE LOW OVER THE GULF WEAKENS.
BECAUSE OF THE WINDS TEMPERATURES OVER SOUTH CENTRAL REMAIN FAIRLY
MILD IN THE 30S AND 40S WITH SOME 20S INLAND. SOUTHWEST ALASKA IS
CALM AND CLEAR WITH TEMPS IN THE TEENS AND 20S. OUT WEST A FRONTAL
BOUNDARY EXTENDS FROM A LOW JUST EAST OF KAMCHATKA SOUTHEASTWARD
ACROSS THE CENTRAL ALEUTIANS. THIS IS PROGRESSING SLOWLY EASTWARD
WITH RAIN/SNOW AND SMALL CRAFT TO MINIMUM GALE WINDS. A WAVE FORMED
ALONG THE FRONT SOUTH OF ATKA LAST EVENING BUT HAS NOT DEVELOPED
ANY FURTHER. IF ANYTHING THE GRADIENT MAY BE A BIT TIGHTER THAN
THE MODELS INDICATE. ANOTHER FRONT FROM A LOW EAST OF THE SOUTHERN
TIP OF KAMCHATKA IS MOVING TOWARD THE WESTERN ALEUTIANS.

.MODEL ANALYSIS...GFS/NAM/UKMET IN GOOD AGREEMENT OVER MAINLAND
ALASKA BUT CONTINUE TO DIFFER ON EVOLUTION OF PATTERN OUT OVER THE
BERING SEA. NONE OF THE MODELS SHOW GOOD RUN TO RUN CONSISTENCY
ALTHOUGH THE GENERAL IDEA OF TRACKING MAIN UPPER LOW ACROSS BERING
THEN UNDERCUTTING RIDGE AND MOVING SOUTHEASTWARD INTO THE NORTH
PACIFIC LOOKS GOOD. SINCE NAM USUALLY DOES POORLY OUT WEST HAVE
DECIDED TO BASE THIS MORNINGS FORECASTS OFF OF THE GFS.

.SHORT-TERM FORECASTS...CLOSED LOW OFF OF BRITISH COLUMBIA AND ENERGY
ROTATING AROUND IT WILL BE HELD OFF TO THE EAST BY UPPER RIDGE OVER
EASTERN BERING/SOUTHWEST ALASKA THROUGH THE END OF THE WEEK. THE
ONLY IMPACT ON SOUTHCENTRAL WILL BE MID TO HIGH CLOUDS AND PERHAPS
A FEW SHOWERS ALONG THE ALASKA RANGE IN THE COPPER RIVER ZONE AND
ALONG THE NORTH GULF COAST NEAR CORDVOVA ON THURSDAY. OTHERWISE
EXPECT CONTINUED DRY AND MILD CONDITIONS ACROSS SOUTHCENTRAL AND
SOUTHWEST ALASKA FOR THE REST OF THE WEEK. FRONT MOVING THROUGH THE
CENTRAL ALEUTIANS WILL BECOME STATIONARY FROM JUST WEST OF COLD BAY
NORTHWEST TO THE PRIBILOFS TONIGHT AND WEAKEN WEDNESDAY. MEANWHILE
ANOTHER FRONT WITH SMALL CRAFT WINDS ALONG IT WILL MOVE ACROSS THE
WESTERN ALEUTIANS TODAY TO THE COLD BAY-PRIBILOFS LINE WEDNESDAY
NIGHT. THE MAIN UPPER LOW NEAR THE SOUTHERN TIP OF KAMCHATKA WILL
TRACK EAST ACROSS THE ALEUTIANS TODAY AND UNDERCUT THE UPPER RIDGE
WEDNESDAY NIGHT AND THURSDAY AS IT TRACKS TO THE NORTH PACIFIC. THE
RIDGE WILL PE PUSHED NORTHWARD ACROSS SOUTHWEST ALASKA WEDNESDAY
NIGHT AND THURSDAY. AS THE UPPER LOW CROSSES THE BERING ENERGY
ROTATING AROUND IT WILL FORM MULTIPLE SURFACE LOWS. THIS IS WHAT
THE MODELS ARE HAVING TROUBLE HANDLING. EXPECT CONTINUED WET
CONDITIONS ALONG THE ALEUTIAN CHAIN THROUGH THE END OF THE WEEK.

.EXTENDED FORECASTS...CONTINUE TO HAVE VERY LOW CONFIDENCE IN
MEDIUM RANGE FORECASTS WITH SEVERAL CUT-OFF LOWS AROUND THE NORTHERN
HEMISPHERE. THESE ARE NORMALLY NOT HANDLED WELL BY THE MODELS.
HAVING SAID THAT THE TREND FOR THIS PART OF THE WORLD HAS BEEN TO
INDICATE A CHANGE TO A MORE AMPLIFIED PATTERN LATE THIS WEEK INTO
NEXT WEEK WITH TROUGH OVER THE BERING AND RIDGE ALONG THE WEST COAST
OF U.S./CANADA. THIS WOULD RESULT IN AN INCREASE IN MOISTURE ACROSS
THE SOUTHERN MAINLAND OVER THE WEEKEND AND A CHANCE OF PRECIP THE
BEGINNING OF NEXT WEEK. THE BERING REGION AS USUAL WILL REMAIN WET
WITH OCCASIONAL GALES FORCE WINDS AS FRONTS MOVE THROUGH.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES AREAS 14 AND 15.
FIRE WEATHER...NONE.

SEB APR 05