Small Craft Advisory 416, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM AKDT WED MAY 20 2009

.MODEL DISCUSSION...MODEL INITIALIZATIONS REASONABLE. SYNOPTIC
PATTERNS SIMILAR THROUGH THE WEEKEND. MODELS TEND TO DIFFER ON THE
INTENSITY OF THE UPPER CENTER AND ASSOCIATED SURFACE CENTER MOVING
INTO THE GULF THU NIGHT. THE GFS IS THE MORE AGGRESSIVE...HOWEVER THE
LATEST ECMWF IS TRENDING TOWARD A DEEPER CENTER. OVERALL...WENT WITH
GFS PATTERN AND BLENDED PRESSURES WITH 12Z ECMWF TO MODERATE
PRESSURES OF GULF CENTER.

.UPPER LEVELS...
A WEAK BLOCKING PATTERN SETS UP OVER THE REGION THU AS THE LOW CENTER
CURRENTLY ALONG THE SW COAST MOVES TO THE GULF AND HIGH PRESSURE
BUILDS WEST OUT OF BRITISH COLUMBIA. CUT-OFF CENTER PERSISTS OVER THE
GULF THROUGH THE WEEKEND DURING WHICH IT INTENSIFIES THROUGH SAT THEN
SLOWLY WEAKENS. THE BERING SEA RIDGE IS FLATTENED AS SHORT WAVE MOVES
SE ACROSS THE CENTRAL BERING SEA THU NIGHT. RIDGE REBUILDS OVER THE
BERING SEA FRI/SAT.

.SHORT TERM FORECAST...
.EAST...PATTERN HAS SUMMER LOOK. THERMAL TROUGH OVER THE INTERIOR
INTENSIFIES INTO THE WEEKEND AND HIGH PRESSURE PERSISTS ALONG THE
NORTH GULF COAST. PRESSURE GRADIENTS LIKELY TO PRODUCE BRISK
MESOSCALE WINDS THROUGH THE COPPER RIVER BASIN AND SOUTHCENTRAL THU
AND FRI WITH INTENSIFICATION OF THE INTERIOR TROUGH DURING THE
AFTERNOON AND EVENING HOURS. RED FLAG CONDITIONS LIKELY IN ZONES 111
AND POSSIBLY 141 THU WITH GUSTLY WINDS AND AFTERNOON AND EVENING RH
BELOW 30 PERCENT. RED FLAG CONDITIONS ARE NOT EXPECTED IN THESE ZONES
WITH INTRUSION OF LOW LEVEL MOISTURE AND SLIGHTLY COOLER TEMPS FRI.
CONDITIONS BECOME MORE UNSTABLE THU AND FRI OVER THE COPPER RIVER
BASIN AND INTERIOR SOUTHCENRAL...SO PROB WILL SEE AFTERNOON AND
EVENING CONVECTION...ANY THUNDERSTORMS LIKELY TO BE UP ALONG THE
ALASKA RANGE AND OVER THE INTERIOR.

WEAK WAVE OVER THE SE GULF MOVES TO OVER KODIAK ISLAND THU NIGHT AND
WEAKENS. MOISTURE WITH ASSOCIATED WEAK FRONTAL ZONE BRINGS A CHANCE
OF RAIN/SHOWERS TO THE KENAI PEN AND PORTIONS OF THE NORTH GULF THU.

.SOUTHWEST MAINLAND...WEAK LOW ALONG THE DELTA COAST MOVES SOUTH OF
THE AK PEN TONIGHT. LIGHT RAIN/SNOW SHOWERS WITH STRATUS LIKELY
THROUGH TONIGHT ALONG THE COASTS. STRATUS SHOULD BE BREAKING OVER
BRISTOL BAY ON THU/FRI WITH ONSET OF SYNOPTIC SCALE OFFSHORE FLOW.
CONDITIONS WILL BECOME MORE UNSTABLE OVER THE KUSKOKWIM VALLEY THU
AND FRI WITH STRENGTHENING INTERIOR THERMAL TROUGH. GENERAL
AFTERNOON/EVENING SHOWERS ARE EXPECTED THU...MAY SEE THUNDERSTORMS
FRI AFTERNOON AND EVENING.

.BERING SEA/ALEUTIANS/AK PEN...BERING SEA RIDGE FLATTENS AS WEAKENING
FRONT SHIFTS EAST AND A OPEN WAVE MOVES TO NEAR THE EASTERN ALEUTIANS
THU AFTERNOON. RIDGE REBUILDS OVER THE BERING SEA FRI AND SAT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...RED FLAG WARNINGS 111 AND 141.

RMC MAY 09