Areal Flood Advisory 13, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
530 AM AKDT TUE SEP 20 2011

.ANALYSIS AND UPPER LEVELS...
THE BIG STORY CONTINUES TO BE THE LARGE LOW CENTERED NEAR KODIAK
ISLAND WITH A CENTRAL PRESSURE OF AROUND 967 MB. THIS LOW IS
ENCOMPASSING VIRTUALLY THE ENTIRE STATE...WITH THE WORST CONDITIONS
SOUTH AND EAST OF THE ALASKA RANGE. THE BARRIER JET THAT HAD FORMED
ALONG THE NORTH GULF COAST HAS DISSIPATED AND IS REPLACED BY
WIDESPREAD MODERATE SOUTHEAST WINDS. A SIGNIFICANT SHORTWAVE THAT
ROTATED AROUND THE MAIN LOW OVERNIGHT HAS MOVED ACROSS PRINCE WILLIAM
SOUND AND IS NOW OVER THE SUSITNA VALLEY. THIS IS THE SAME FEATURE
THAT BROUGHT MODERATE RAIN TO INLAND AREAS OF SOUTHCENTRAL INCLUDING
THE ANCHORAGE BOWL. BEHIND THIS SHORTWAVE AN AREA OF SIGNIFICANT
SURFACE PRESSURE RISES BROUGHT A BRIEF PERIOD OF VERY STRONG
SOUTHEAST WINDS INTO THE PRINCE WILLIAM SOUND VERY EARLY THIS
MORNING.

THE UPPER LEVEL PATTERN REMAINS A DEEPLY AMPLIFIED LONGWAVE TROUGH
OVER MAINLAND ALASKA. A 150 KT JET STREAM FLOWS OFF THE KAMCHATKA
PENINSULA DOWN INTO THE BASE OF THIS TROUGH NEAR 40N BEFORE MAKING A
SHARP LEFT/NORTHWARD TURN TOWARD THE ALASKA PANHANDLE. THIS AREA
WHERE THE JET STREAM RE-CURVES NORTHWARD WILL BE AN AREA OF FAVORED
DEVELOPMENT OF MORE LOWS FOR THE REST OF THE WEEK.

.MODEL DISCUSSION...
THE MODELS ARE STILL IN OVERALL VERY GOOD AGREEMENT ON THE
LARGE-SCALE PATTERN FOR THE NEXT WEEK. THIS WILL FEATURE THE LONGWAVE
TROUGH REMAINING CENTERED OVER WESTERN ALASKA AND REMAINING NEARLY
STATIONARY. A SERIES OF LOWS WILL DEVELOP OVER THE NORTHEAST PACIFIC
AND MOVE NORTHWARD TOWARD THE GULF OF ALASKA. UNLIKE THE CURRENT
STORM THAT IS WINDING DOWN TODAY...THE MODELS ARE IN GENERALLY GOOD
AGREEMENT THAT THE NEXT FEW LOWS WILL STAY PRIMARILY IN THE EASTERN
GULF...MEANING THE WORST WEATHER WILL BE LIMITED MAINLY TO THE
PANHANDLE. THE GFS WAS THE PREFERRED MODEL OVER THE BERING SEA AND
ALEUTIANS. OVER SOUTHCENTRAL ALASKA...THERE WAS NO SPECIFIC MODEL
PREFERENCE..AND A BLEND OF MODELS WAS USED FOR THE MORNING FORECAST.

.SHORT TERM FORECAST...
THE LOW NEAR KODIAK WILL CONTINUE TO WEAKEN TODAY AS IT DRIFTS
NORTHWESTWARD AND WEAKENS. WIDESPREAD SHOWERS TODAY IN MOST AREAS
WILL GRADUALLY BECOME MORE SCATTERED OVER INLAND LOCATIONS TONIGHT.
STRONG WINDS WILL ALSO BE GRADUALLY WEAKENING TODAY AS BROAD
SOUTHEAST FLOW CONTINUES ACROSS THE GULF. MOSTLY CLOUDY SKIES WITH
PERIODS OF RAIN OR SHOWERS WILL CONTINUE FOR MUCH OF THE
WEEK...ESPECIALLY ALONG THE COAST. A FAST-MOVING 970S LOW MOVES UP
INTO THE EASTERN GULF WEDNESDAY AND ANOTHER ON FRIDAY...WITH ONLY
SIGNIFICANT IMPACT TO SOUTHCENTRAL BEING WIDESPREAD RAIN GENERALLY
EAST OF CORDOVA.

OUT WEST...COOL AND GUSTY NORTHERLY FLOW CONTINUES ACROSS THE BERING
THROUGH THURSDAY. A WEAK LOW WILL AFFECT THE WESTERN ALEUTIANS ON
WEDNESDAY AND AGAIN ON FRIDAY...BRINGING A ROUND OF RAIN AND
RELATIVELY MODERATE WINDS.

.LONG TERM FORECAST...
COOL...CLOUDY...AND INTERMITTENTLY WET WEATHER TO CONTINUE FOR MUCH
OF THE WEEK ACROSS THE MAINLAND. THE BROAD LONGWAVE TROUGH
ENCOMPASSING THE REGION SHOWS FEW SIGNS OF SIGNIFICANT CHANGE THROUGH
AT LEAST THE MIDDLE OF NEXT WEEK. THE JET STREAM WILL REMAIN WELL
SOUTH OF MAINLAND ALASKA...KEEPING MOST OF THE VERY ACTIVE WEATHER
OVER THE PANHANDLE.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...SMALL STREAM FLOOD ADVISORY 125
MARINE...GALE 120 125 129 150 155 165 170 171 185
FIRE WEATHER...NONE

DIXON SEP 11