Gale Warning 658, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT MON OCT 19 2015

.ANALYSIS AND UPPER LEVELS...
THE DOMINATE FEATURE FOR THE REGION THIS MORNING IS THE DEEPENING
TROUGH CENTERED OVER THE CENTRAL CENTRAL ALEUTIANS ALONG 170W. AS
WITH YESTERDAY...TWO CLOSED LOWS REMAIN EMBEDDED WITHIN THE TROUGH
WITH A VERTICALLY STACKED LOW NEAR NUNIVAK ISLAND AND A
DEVELOPING SOUTH OF DUTCH HARBOR. WHILE MOST OF THE POLAR JET
REMAINS DISPLACED TO BELOW 40N...THE TROUGH IS DIGGING DEEP ENOUGH
TO SHIFT THE JET NORTHWARD INTO THE NORTHEASTERN PACIFIC ALONG THE
EASTWARD SIDE OF THE TROUGH. THE JET IS WELL DEVELOPED WITH A
140KT JET MAXIMUM IN THE ASCENDING BRANCH. MULTIPLE SHORTWAVES ARE
ROTATING AROUND THE LOW NEAR NUNIVAK ISLAND...BRINGING SHOWERS TO
SOUTHWEST ALASKA AND THE CENTRAL BERING SEA. ELSEWHERE...A
WEAKENING TROUGH OVER THE NORTHERN GULF IS ROTATING NORTHEASTWARD
INTO SOUTHCENTRAL AND SOUTHEAST ALASKA PRODUCING WIDESPREAD
RAINFALL ALONG THE GULF COAST NORTHWARD INTO THE SUSITNA VALLEY.
A RIDGE IS MOVING INTO THE WESTERN BERING SEA AHEAD OF A SHORTWAVE
TROUGH MOVING THROUGH THE KAMCHATKA PENINSULA.

AT THE SURFACE...THE MAIN FEATURE ON THE WEATHER CHART THIS
MORNING IS THE RAPIDLY DEVELOPING 978 MB LOW SOUTH OF THE ALASKA
PENINSULA. THIS HAS EXCELLENT JET SUPPORT WHILE IT DEVELOPS IN
THE FRONT LEFT EXIT REGION OF THE ASCENDING BRANCH OF THE POLAR
JET. THIS FEATURE WILL BE THE MAIN WEATHER MAKER FOR THE FORECAST
AREA THROUGH THE SHORT TERM. A WEAKENING SURFACE LOW NEAR NUNIVAK
ISLAND WILL CONTINUE TO DRIFT TO THE NORTHWEST. FINALLY...A LOW IS
DEVELOPING JUST OFF THE KAMCHATKA COAST ALONG A FRONTAL BOUNDARY.

&&

.MODEL DISCUSSION...
MODELS CONTINUE TO BE IN GOOD OVERALL AGREEMENT IN THE SYNOPTIC
PATTERN AND WITH THE DEVELOPMENT OF THE LOW SOUTH OF THE ALASKA
PENINSULA. THE CANADIAN MODEL IS THE OUTLIER IN THIS PACKAGE WITH
A FASTER AND FURTHER WEST TRACK. THE GFS CONTINUES TO HAVE GOOD
RUN TO RUN CONSISTENCY...THUS IT WAS USED FOR THIS FORECAST
PACKAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

TODAY WILL BE THE DAY BETWEEN WEATHER SYSTEMS FOR MOST OF
SOUTHCENTRAL ALASKA. THE UPPER LEVEL DISTURBANCE THAT HAS BEEN
MOVING OVER THE AREA FROM SOUTH TO NORTH IS BRINGING SOME RAIN
SHOWERS TO THE SUSITNA VALLEY THIS MORNING BUT WILL MOVE NORTH OF
THE ARE BY THE AFTERNOON. THE BIGGEST UNCERTAINTY WITH THE WEATHER
TODAY IS WHETHER THERE WILL BE SIGNIFICANT AREAS OF FOG TO
DEVELOP...ESPECIALLY AROUND THE COOK INLET REGION. IT REMAINS VERY
MOIST IN THE LOWER LEVELS AFTER THE PERSISTENT RAINFALL BUT THERE
MAY BE ENOUGH MIXING WITH THE SOUTH TO SOUTHEAST WINDS TO KEEP
MUCH FOG FROM DEVELOPING. THE NEXT SYSTEM WILL MOVE INTO KODIAK
FROM THE SOUTH THIS AFTERNOON AND BRING SOME GALE AND EVEN STORM
FORCE WINDS TO THE MARINE AREAS AROUND THE GULF. THIS SYSTEM WILL
BRING WIDESPREAD RAINFALL TO COASTAL AREAS BUT MOST OF THE INLAND
AREAS WILL ONLY SEE CHANCE OF RAIN AS THERE SHOULD BE A BIT OF
DOWNSLOPING ACROSS THE CHUGACH AND KENAI MOUNTAINS WITH THIS SYSTEM.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK SURFACE LOW JUST SOUTH OF NUNIVAK ISLAND WILL DISSIPATE BY
TUESDAY. THIS SYNOPTIC FEATURE WILL CONTINUE TO PRODUCE A SHOWERY
WEATHER REGIME ACROSS THE SOUTHWEST. THE ALASKA PENINSULA WILL
HAVE A WEATHER FRONT TRACKING INTO THE AREA BY LATE MONDAY EVENING
ASSOCIATED WITH A STORM FORCE LOW TRACKING JUST SOUTH OF THE
EASTERN ALEUTIANS. THIS WILL BRING STRONG EASTERLY GALE FORCE
WINDS TO THE BRISTOL BAY REGION ACCOMPANIED BY WIDESPREAD RAIN
BEFORE TAPERING OFF BY TUESDAY AFTERNOON.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
AN UPPER LEVEL TROUGH IN THE CENTRAL TO NORTHERN BERING SEA WILL
BRING SCATTERED SHOWERS THROUGH TUESDAY. THE EASTERN ALEUTIANS
WILL HAVE A STORM FORCE NORTH PACIFIC LOW TRACKING NEAR 52N 159W
BY MONDAY AFTERNOON. THIS WILL INCREASE THE PRESSURE GRADIENTS
RESULTING IN STORM FORCE WINDS EXTENDING ALONG THE EASTERN
ALEUTIANS ON THE PACIFIC SIDE THROUGH LATE MONDAY AFTERNOON BEFORE
DIMINISHING AS THE LOW TRACKS FARTHER EASTWARD. ON MONDAY
AFTERNOON...THE WESTERN ALEUTIANS WILL HAVE A FAST MOVING LOW
PUSHING A FRONT ACROSS THE WESTERN AND CENTRAL ALEUTIANS. THIS
SYSTEM WILL BRING WIDESPREAD RAIN WITH SMALL CRAFT SOUTHWESTERLY
WINDS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE PATTERN LOOKS TO BE ACTIVE FOR THE SECOND HALF OF THE WEEK AND
MOVING INTO THE WEEKEND. TUESDAY NIGHT THERE IS GOOD AGREEMENT ON
A LOW MOVING INTO THE GULF FROM THE SOUTHWEST BRINGING WARM AIR
TO THE SOUTHCENTRAL AND RAIN ALONG THE NORTH GULF COAST. THIS
SYSTEM WILL PUSH OFF TO THE EAST AND THEN THE MODELS BECOME MORE
CHAOTIC. SOMETIME ON WEDNESDAY ANOTHER LOW WILL APPROACH THE
WESTERN ALEUTIANS BUT THERE IS DISCREPANCY ON WHERE THE LOW WILL
SETUP OR IF AND WHERE A TRIPLE POINT LOW WILL DEVELOP RESULTING IN
LOWER CONFIDENCE. BECAUSE OF THE VARIATION IN DETERMINISTIC
SOLUTIONS A COMBINATION OF ENSEMBLES WAS USED...PRIMARILY THE EC
ENSEMBLE AND THE NAEFS. THIS NEW SOLUTION BRINGS AN ELONGATED LOW
INTO THE WESTERN ALEUTIANS THURSDAY EVENING AND THEN TRACKS IT
OVER THE ALASKA PENINSULA FRIDAY NIGHT AND INTO THE GULF SATURDAY
NIGHT INTO SUNDAY. WITH THIS MORE SOUTHERLY TRACK THE MAJORITY OF
THE RAIN WILL BE ALONG THE ALEUTIANS AND EVENTUALLY THE NORTH GULF
COAST.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 119 120 130 131 136 137 138 160 165 172.
         STORMS 132 150 155.

&&

SYNOPSIS AND MODEL DISCUSSION...RF
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...DK