Areal Flood Warning 23, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
430 AM AKDT MON MAY 9 2011

.MODEL DISCUSSION...

SYNOPTICALLY THE MODELS ARE IN GOOD AGREEMENT. THERE ARE SOME SUBTLE
DIFFERENCES IN THE TRACK OF LOW PRESSURE THAT DEVELOPS ALONG A WEAK
FRONTAL BOUNDARY IN THE CENTRAL GULF LATER TODAY AS AN UPPER LEVEL
LOW MOVES EAST ACROSS THE ALASKA PENINSULA FROM THE EASTERN BERING
SEA. A NAM/GFS BLEND WAS PREFERRED IN THE EAST WITH THE GFS PREFERRED
OUT WEST.

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL PARENT LOW IS PROGRESSING EAST ACROSS THE ALASKA
PENINSULA HEADED TOWARDS THE WESTERN GULF OF ALASKA THIS MORNING.
SEVERAL DISTURBANCES ARE ROTATING AROUND THIS FEATURE AS IT TRACKS
WEST. THE MOST POTENT OF THESE IS DIRECTLY SOUTH OF THE UPPER LOW IN
THE NORTH PACIFIC AND IS TRACKING NORTH AND EAST TOWARDS THE CENTRAL
GULF. THIS FEATURE WILL INDUCE WEAK CYCLOGENESIS (DEVELOPING LOW
PRESSURE) OVER THE CENTRAL GULF THIS AFTERNOON WITH FURTHER
STRENGTHENING OVERNIGHT TONIGHT IN THE EAST-CENTRAL GULF BEFORE
APPROACHING NORTHERLY FLOW OVER THE STATE PUSHES THE LOW COMPLEX
SOUTH INTO THE NORTHEAST PACIFIC BY TUESDAY NIGHT. AS CYCLOGENESIS
TAKES PLACE TONIGHT IN THE GULF...NORTHERLY WINDS WILL BEGIN
INCREASING AS THE PRESSURE GRADIENT INCREASES ALONG THE GULF
COAST...AND WITH THE ARRIVAL OF A NORTHERLY JET STREAK ON TUESDAY
WINDS WILL INCREASE ACROSS THE SUSITNA VALLEY AND WESTERN KENAI
PENINSULA.

OUT TOWARDS THE BERING...HIGH PRESSURE ALOFT WILL MOVE RAPIDLY EAST
ACROSS THE WESTERN AND CENTRAL BERING THROUGH TUESDAY...THEN STALL
OVER THE EASTERN BERING AND FAR WESTERN ALASKA MIDWEEK. A SERIES OF
FRONTS WILL TRACK ACROSS THE WESTERN BERING ON THE UPSTREAM SIDE OF
THE HIGH PRESSURE AND BRING A RETURN TO UNSETTLED WEATHER ALONG WITH
SOME STRONGER WINDS.

.SHORT TERM FORECAST...

SOUTH AND EAST OF THE ALASKA RANGE...

FRONTAL BOUNDARY WILL MOVE NORTH TOWARDS THE GULF COAST TODAY...THEN
RETREAT SOUTH ON THE BACK SIDE OF THE LOW AS THE PARENT SYSTEM TRACKS
INTO THE EASTERN GULF. WETTEST CONDITIONS WILL GENERALLY BE IN
WESTERN PRINCE WILLIAM SOUND AND THE KENAI PENINSULA...WITH ISOLATED
TO SCATTERED SHOWERS FARTHER INLAND AND OVER HIGHER TERRAIN TOWARDS
THE INTERIOR THROUGH THIS EVENING. CYCLOGENESIS IN THE CENTRAL GULF
TONIGHT WILL HELP INCREASE THE PRESSURE GRADIENT OVER THE REGION AND
HELP INDUCE STRENGTHENING NORTHERLY FLOW BY MIDDAY
TUESDAY...ESPECIALLY OVER THE WESTERN SUSITNA VALLEY AND COOK INLET
REGION. AN APPROACHING JET STREAK FROM THE NORTH AND WEST ON
WEDNESDAY MAY STRENGTHEN NORTHERLY WINDS A LITTLE FURTHER. THE BIG
CONCERN WITH WINDS WILL BE FIRE WEATHER CONDITIONS...WITH INCREASING
WINDS AND DRY NORTHERLY FLOW RED FLAG CONDITIONS ARE A CONSIDERATION
FOR THE WESTERN KENAI PENINSULA. WILL CONTINUE TO MONITOR LATEST
FORECASTS...BUT FOR NOW LOOKS LIKE SEVERAL DAYS OF SHOWERS MAY
PROVIDE ENOUGH INCIPIENT MOISTURE TO KEEP RELATIVE HUMIDITIES JUST
HIGH ENOUGH TO PRECLUDE ISSUING A FIRE WEATHER WATCH OR RED FLAG
WARNING. OTHERWISE...MUCH DRIER CONDITIONS EXPECTED THROUGH LATE WEEK
AFTER THIS CURRENT SYSTEM MOVES OUT OF MOST AREAS TONIGHT.

SOUTHWEST ALASKA...

RAIN SHOWERS WILL SLOWLY DECREASE IN COVERAGE THROUGH THIS EVENING IN
BRISTOL BAY ZONE...WITH A GENERAL CLEARING AND WARMING TREND AS THE
SUN SHOULD MAKE A RETURN TO THE SKIES MOST AREAS FOR MOST AREAS
THROUGH MIDWEEK.

BERING SEA/ALEUTIANS...

GUSTY NORTHWESTERLY WINDS AND RAIN AND SNOW SHOWERS WILL AFFECT THE
ALASKA PENINSULA AND DUTCH HARBOR AREAS THROUGH THIS AFTERNOON AND
THEN CONDITIONS GRADUALLY IMPROVE AS HIGH PRESSURE MOVES EAST ACROSS
THE AREA. THE STRENGTH OF THE HIGH PRESSURE RIDGE ALOFT ALONG WITH
THE COLD SEA SURFACE TEMPERATURES WILL LIKELY KEEP LOW STRATUS OVER
MUCH OF THE AREA. A LARGE COMPLEX LOW PRESSURE SYSTEM BETWEEN THE
WESTERN ALEUTIANS AND THE KAMCHATKA PENINSULA WILL ROTATE
DISTURBANCES NORTH AND EAST ACROSS THE REGION TONIGHT THROUGH
MIDWEEK...BRINGING AN INCREASE IN WINDS TO GALE FORCE AS WELL AS
PERIODS OF RAIN.

.LONG TERM FORECAST...

THE EXTENDED PERIOD LOOKS TO BE DOMINATED BY LOW PRESSURE SYSTEMS AND
ASSOCIATED UNSETTLED WEATHER OVER THE BERING REGION GRADUALLY PUSHING
EASTWARD HIGH PRESSURE WITH ASSOCIATED TRANQUIL WEATHER OVER THE GULF
AND SOUTHCENTRAL REGIONS. CURRENT MODEL TRENDS CONTINUALLY SUGGEST A
SLOWER PROGRESSION OF THESE DISTURBANCES EAST INTO THE GULF WITH EACH
NEW SET OF MODEL RUNS...YIELDING LOW TO MEDIUM CONFIDENCE IN THE
FORECAST BEYOND THIS WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD WARNING...152
MARINE...GALES...150 170 175 176
FIRE WEATHER...NONE.

29 MAY 11