Small Craft Advisory 549, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM ADT SUN JUN 24 2007

.ANALYSIS...
A BROAD AREA OF LOW PRESSURE EXTENDS FROM THE NORTHERN BERING ACROSS
SOUTHWEST ALASKA INTO THE SOUTHERN GULF OF ALASKA. SHOWERS ARE
PRESENT FROM PRINCE WILLIAM SOUND WEST THROUGH THE EASTERN BERING. A
FRONT IS MOVING ACROSS THE WESTERN ALEUTIANS AS WELL WITH PLENTY OF
PRECIP. HIGH PRESSURE IS OVER THE EASTERN GULF AND CENTRAL BERING
SEA. WIND SPEEDS CLOSE TO THE AREAS OF LOW PRESSURE ARE NEAR SMALL
CRAFT LEVELS.

.MODEL DISCUSSION...
12Z MODELS IN GOOD AGREEMENT THROUGH THE FIRST 72 HOURS.
THEN...THERE EXISTS ONE UNCERTAINTY THAT HAS AN EFFECT FROM WEDNESDAY
ONWARD. THE UNCERTAINTY ARISES FROM A SHORT WAVE THAT WILL TRAVERSE
THE BERING WEDNESDAY. DEPENDING ON THE PATH AND INTENSITY...IT WILL
CHANGE THE PROGRESSION OF THE CHUKCHI SEA UPPER LOW LATER IN THE
WEEK. THIS COULD MEAN THE DIFFERENCE BETWEEN TROUGH OVER THE INTERIOR
FRIDAY REMAINING THROUGH THE WEEKEND OR A RIDGE BUILDING OVER THE
AREA. RIGHT NOW SOME OF THE GFS ENSEMBLES AND EURO MODELS POINT
TOWARD RIDGE. A FEW MEMBERS AND THE OPERATIONAL GFS POINT TOWARD
TROUGH. THEREFORE...HAVE LEANED TOWARD THE NEWER GFS SOLUTION SINCE
THINKING IS THE WAVE WILL STAY TO THE SOUTH AND DROP INTO THE GULF
THURSDAY INTO FRIDAY ALLOWING FOR THE TROUGH TO DIG OVER THE
INTERIOR.

.UPPER LEVELS...
TROUGH OVER THE WESTERN PORTION OF THE STATE WITH TWO LOW CENTERS IN
SOUTHWEST ALASKA THIS MORNING. ONE TO PUSH NORTH TOMORROW TO THE
CHUKCHI SEA WITH THE OTHER DEVELOPING INTO A CLOSED LOW OVER THE GULF
MONDAY. IN THE MEANTIME...A LOW REMAINS OVER THE KAMCHATKA PENINSULA.
THE RIDGE OVER THE CENTRAL BERING TO PUSH TO THE EASTERN BERING
TUESDAY AS WELL.  A SHORT WAVE TO COME OUT OF THE NORTH PACIFIC TO
CROSS THE CENTRAL ALEUTIANS TUESDAY EVENING. THIS IS THE FEATURE TO
CREATE ALL THE UNCERTAINTY. A TROUGH REMAINS OVER THE INTERIOR...BUT
HIGH PRESSURE IS OVER EASTERN ALASKA.

.SHORT TERM FORECAST...
ALEUTIANS...
FRONT ACROSS THE WESTERN ALEUTIANS TO MOVE INTO THE CENTRAL ALEUTIANS
MONDAY THEN SPLIT. ANOTHER LOW TO DRIVE OUT OF THE SOUTHWEST
ASSOCIATED WITH AN UPPER LEVEL WAVE AND WORK TO ADAK TUESDAY. PRECIP
AND WINDS SHOULD PICK UP WITH THIS SYSTEM. THE LOW WILL WORK ACROSS
THE BERING KNOCKING DOWN THE HIGH PRESSURE WEDNESDAY. THE LOW WILL
EVENTUALLY DROP INTO THE GULF THURSDAY NIGHT. BEHIND THE
SYSTEM...HIGH PRESSURE TO RE-AMPLIFY OVER THE WESTERN BERING.

SOUTHWEST ALASKA...
UPPER LEVEL LOW AND BROAD SURFACE LOW SITUATED OVER THE AREA WITH
WIDESPREAD PRECIP. A SHORT WAVE WITH A WEAK SURFACE LOW MOVING SOUTH
OVER THE EASTERN BERING TO DISSIPATE TONIGHT. SOME INSTABILITY IN THE
CLEARING OVER THE KUSKOKWIM DELTA AND CONVERGENCE FROM THE WEAK LOW
IN THE BERING. THE LOW COMPLEX TO LIFT NORTH TOMORROW AFTERNOON.
ENOUGH INSTABILITY WITH THE LOW TO SPARK CONVECTION ONCE AGAIN
MONDAY. SOME DRYING TO OCCUR BEHIND THE SYSTEM FOR TUESDAY.
HOWEVER...THERE WILL BE SOME RESIDUAL MOISTURE FOR INLAND CONVECTION
OVER THE HIGHER TERRAIN. HIGH PRESSURE MOVES TO THE COAST THOUGH.
HIGH PRESSURE MOVES OVER THE ENTIRE AREA WEDNESDAY WITH ISOLATED
CONVECTION EXPECTED. THE LOW FROM THE BERING MOVES ACROSS THE AKPEN
THURSDAY FOR SOME SHOWERS STARTING WEDNESDAY NIGHT ALONG THE COAST
AND SOME INCREASE IN WIND.

SOUTH CENTRAL ALASKA...
UPPER LOW OVER BRISTOL BAY WITH SOUTHERLY FLOW OVER SOUTH CENTRAL
PROVIDING PLENTY OF PRECIPITATION TO THE AREA EXCEPT THE COPPER RIVER
BASIN. THE UPPER LOW DROPS INTO THE GULF TONIGHT...BUT PRECIP TO
CONTINUE OVER THE SAME AREAS. THE CURRENT RIDGE OF HIGH PRESSURE
ALONG THE NORTHERN GULF COAST TO INTENSIFY TONIGHT AS THE LOW DROPS
INTO THE GULF. AS THIS HAPPENS...EASTERLY WINDS TO INCREASE THROUGH
WEST TO EAST GAPS. IN ADDITION...SOME DRYING TO OCCUR FROM THE EAST
TONIGHT AND THROUGH TOMORROW AS THE HIGH CENTER MOVES OVER THE KENAI
MONDAY NIGHT. THERMAL RIDGE THEN ALLOWED TO EXTEND FURTHER WEST OVER
THE INTERIOR WITH A LOW NOW IN THE SOUTHERN GULF. EXPECT INSTABILITY
AND TEMPERATURE TO RISE MONDAY THROUGH WEDNESDAY.

THE COPPER RIVER BASIN REACHED RED FLAG CRITERIA YESTERDAY
AFTERNOON/EVENING AND IS EXPECTED THE SAME THIS AND MONDAY
AFTERNOON/EVENING. WINDS TO BE SLIGHTLY STRONGER TODAY. CONDITIONS TO
BE A BIT MORE MARGINAL TOMORROW. HUMIDITIES NOT EXPECTED TO INCREASE
DURING THIS PERIOD.

.LONG TERM FORECAST...
FROM THE UNCERTAINTY DECISION DISCUSSED EARLIER...THERE SHOULD BE A
COOLER AND UNSETTLED AIR MASS OVER THE MAINLAND. SHOWERS WILL
DOMINATE THE GULF. A FRONT TO PUSH ACROSS THE WESTERN AND CENTRAL
BERING SATURDAY INTO SUNDAY. HIGH PRESSURE WILL SHIFT FROM THE
WESTERN BERING TO THE EASTERN BERING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...DENSE FOG ADVISORY ZONE 131
MARINE...NONE
FIRE WEATHER...RED FLAG WARNING THROUGH MON EVENING ZONE 141

JN JUN 07