Gale Warning 383, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
140 PM AKDT TUE APR 7 2009

.ANALYSIS AND UPPER LEVELS...NEAR ZONAL FLOW EXISTS THIS MORNING
ACROSS THE NORTH PACIFIC WITH MANY LOWS EMBEDDED WITHIN THE
LONG-WAVE TROUGH TO THE NORTH. THE MAIN WEATHER PRODUCER AT THE
MOMENT IS NEARLY STATIONARY MATURE LOW OVER THE NORTHERN BERING.
A WEAK COLD FRONT ASSOCIATED WITH THIS LOW IS MOVING INLAND ACROSS
SOUTHWEST ALASKA...PRODUCING AREAS OF LIGHT SNOW. COLD ADVECTION
SOUTH OF THE LOW CENTER IS PRODUCING AN AREA OF SHOWERS OVER THE
NORTHERN BERING AS CLEARLY SEEN IN SATELLITE IMAGERY THIS MORNING.
THERE ARE NO OTHER MAJOR FEATURES TO SPEAK OF OVER THE BERING
REGION...ALTHOUGH CLOUD COVER IS EXTENSIVE. SOUTHCENTRAL ALASKA
IS UNDER THE INFLUENCE OF A SHORT-WAVE RIDGE THIS MORNING...WHICH
ALONG WITH LOW LEVEL OFFSHORE FLOW HAS RESULTED IN MOSTLY SUNNY
SKIES ACROSS THE REGION. A DEVELOPING LOW NEAR 44N 170E WILL BE
THE NEXT MAJOR STORM TO AFFECT THE FORECAST AREA.

.MODEL DISCUSSION...MODELS CONTINUE TO BE IN GOOD AGREEMENT WITH
HANDLING OF NEXT SYSTEM. THERE ARE MINOR DIFFERENCES IN POSITION
OF MAIN LOW AND TRIPLE POINT LOW THURSDAY NIGHT INTO FRIDAY..BUT
THESE DIFFERENCES HAVE LITTLE IMPACT ON THE FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...A WEAK UPPER LEVEL SHORT-WAVE JUST SOUTH OF
THE NORTHERN BERING LOW WILL AMPLIFY  TONIGHT A RIDGE BUILDS
UPSTREAM IN RESPONSE TO DEVELOPING PACIFIC LOW. THIS SHORT-WAVE
TROUGH WILL MOVE TO KODIAK ISLAND WEDNESDAY AND ACROSS SOUTHCENTRAL
WEDNESDAY NIGHT. THIS WILL PUSH REMNANT MOISTURE FROM SOUTHWEST
ALASKA FRONT ACROSS SOUTHCENTRAL AND THERE SHOULD BE JUST ENOUGH
LIFT WITH THE TROUGH TO PRODUCE A FEW SHOWERS. THE FRONT ASSOCIATED
WITH THE NEXT MAJOR STORM MOVING ALONG THE ALEUTIANS THIS WEEK WILL
REACH THE WESTERN GULF THURSDAY MORNING AND SPREAD TO SOUTHCENTRAL
THURSDAY NIGHT. FRONTAL ORIENTATION LOOKS FAVORABLE FOR DEVELOPMENT
OF A BARRIER JET ALONG THE NORTH GULF COAST...ALTHOUGH IT WILL BE
SHORT-LIVED AS UPPER LEVELS QUICKLY PUSH THE FRONT NORTHWARD WHERE
IT FALLS APART. STRONG SOUTHEAST FLOW WILL LIMIT PRECIPITATION ON
THE LEE SIDE OF MOUNTAINS. WITH DECENT DYNAMICS ALOFT DO EXPECT AT
LEAST A FEW SHOWERS IN MOST LOCATIONS. TEMPERATURES ALOFT WILL
REMAIN COLD ENOUGH TO PRODUCE SNOW MOST LOCATIONS...WITH RAIN MIXED
IN ALONG THE COAST DUE TO INFLUENCE OF WARMER GULF WATERS.

SOUTHWEST ALASKA...THERE IS NOT A WHOLE LOT OF PUSH BEHIND THE
COLD FRONT...SO IT WILL BE SLOW TO EXIT THE REGION. AREAS OF SNOW
WILL CONTINUE FROM BRISTOL BAY TO THE KUSKOKWIM VALLEY THROUGH
WEDNESDAY MORNING WITH REMNANTS OF THE FRONT HANGING UP IN THE
ALASKA RANGE BY THURSDAY AFTERNOON. MEANWHILE...NORTHERN BERING LOW
WILL SLOWLY TRACK TOWARD NORTON SOUND WHILE UPPER LEVEL SHORT-WAVE
AMPLIFIES AND SWINGS INTO SOUTHWEST ALASKA WEDNESDAY MORNING. THIS
WILL PRODUCE SNOW SHOWERS...ESPECIALLY ALONG THE KUSKOKWIM DELTA.
FRONT FROM THE NEXT STORM WILL MOVE INTO BRISTOL BAY THURSDAY...BUT
WONT MAKE IT ANY FURTHER NORTH THAN THAT AS TRIPLE POINT LOW FORMS
AND MOVES TO THE GULF. MOISTURE WILL HOWEVER SPREAD NORTH AND WEST
OF THE FRONT INTO THE REST OF SOUTHWEST ALASKA. MEANWHILE...A
SHORT-WAVE TROUGH WILL DROP SOUTHWARD OVER THE EASTERN BERING
BEHIND THE STORM BRINGING A SHOT OF COLD ADVECTION. THIS WILL
RESULT IN GUSTY WINDS ALONG THE SOUTHWEST COAST LATE THIS WEEK
WITH POTENTIAL FOR BLOWING SNOW.

BERING SEA ALEUTIANS...THE PACIFIC STORM WILL RAPIDLY DEEPEN UNDER
FAVORABLE UPPER LEVEL CONDITIONS (IN AN AREA OF STRONG UPPER
DIVERGENCE BETWEEN TWO JET STREAKS) AS IT TRACKS TO THE WESTERN
ALEUTIANS WEDNESDAY MORNING. THE LOW WILL THEN GRADUALLY WEAKEN
AS IT TRACKS EASTWARD WEDNESDAY AND THURSDAY. STORM FORCE WINDS
ARE EXPECTED ALONG THE BENT-BACK OCCLUSION WEDNESDAY AND WEDNESDAY
NIGHT...WHICH WILL AFFECT THE WESTERN ALEUTIAN MARINE AREAS. THE
AIR MASS OVER THE FAR WESTERN ALEUTIANS (INCLUDING SHEMYA) WILL
REMAIN COLD ENOUGH FOR SNOW...BUT INITIALLY EASTERLY FLOW SHOULD
HELP WARM SURFACE TEMPERATURE INTO THE MID 30S. AS FLOW BACKS TO
THE NORTH THERE MAY BE SOME COOLING OF THE SURFACE TEMPERATURE...BUT
EXPECT IT TO REMAIN NEAR FREEZING. THEREFORE...EXPECT LOW
VISIBILITIES IN SNOW AND BLOWING SNOW...BUT DONT EXPECT BLIZZARD
CRITERIA TO BE MET. COLD ADVECTION SNOW SHOWERS WILL KICK INTO GEAR
BEHIND THE STORM ACROSS THE BERING SEA AND ALEUTIANS THURSDAY AND
FRIDAY.

.LONG TERM FORECAST...LONG-WAVE PATTERN WILL REMAIN PROGRESSIVE
THROUGH THE EXTENDED FORECAST PERIOD. THIS WILL MAINTAIN THE GENERAL
WEST TO EAST STORM TRACK AND PROVIDE FOR CONTINUED COOL TEMPERATURES
ACROSS THE ALASKA REGION...ALTHOUGH THE LONGER DAYS ARE CERTAINLY
PROVIDING FOR MORE AFTERNOON HEATING FROM THE SUN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...175 176.
         GALE WARNING...150 155 165 170 171 172 179.
FIRE WEATHER...NONE.

SEB APR 09