Small Craft Advisory 191, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
501 AM AKST SUN MAR 1 2015

.ANALYSIS AND UPPER LEVELS...

THE WEST COAST NORTH AMERICAN UPPER RIDGE IS REDEVELOPING THIS
MORNING...EXTENDING FROM THE NORTH PACIFIC INTO THE GULF...AND
THEN ACROSS MAINLAND AK AND MOST OF THE BERING. A CUT-OFF LOW IS
SPINNING WELL SOUTH OF THE AKPEN...AND A SIGNIFICANT TROUGH
EXTENDS FROM SIBERIA ACROSS THE EXTREME WESTERN BERING. THESE LAST
TWO FEATURE WILL BE MAJOR PLAYERS INTO TUE. AT THE SURFACE...HIGH
PRESSURE IS TAKING UP RESIDENCE OVER MAINLAND AK WITH PLENTY OF
FOG DEVELOPING OVER SOUTHCENTRAL. A LOW WITH ASSOCIATED FRONTS IS
OVER THE EXTREME WESTERN BERING AND ALEUTIANS...BRINGING RAIN
NORTH INTO THE BERING WITH SMALL CRAFT WINDS. ANOTHER LOW IS WELL
SOUTH OF THE AKPEN WITH AN OCCLUDED FRONT APPROACHING THE EASTERN
ALEUTIANS WITH LOW CLOUDS AND RAIN.

&&

.MODEL DISCUSSION...

MODELS ARE IN AGREEMENT THAT THE LOW AND FRONTAL SYSTEM SOUTH OF
THE AKPEN WILL BE MERGING WITH THE WESTERN BERING SYSTEM THIS
EVENING. WHAT WILL SURVIVE FROM THIS MERGER WILL BE THE REMAINS OF
A WARM OCCLUDED FRONT THAT WILL AFFECT THE EASTERN
BERING...AKPEN AND BRISTOL BAY...AND GULF OF AK THROUGH MON...AND
THEN THE NORTHEASTERN GULF COAST INTO TUE. WHILE THIS IS
HAPPENING A BROAD TROUGH OF LOW PRESSURE PERSISTING OVER THE
BERING WILL DRIFT EAST OVER WESTERN AK ON TUE. THE NEXT FRONT TO
AFFECT THE WESTERN BERING WILL THEN ARRIVE MON NIGHT INTO TUE.
THE FORECAST UTILIZES PRIMARILY THE EC AND GFS SOLUTIONS INTO
TUE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
FOG AND STRATUS WHICH IS WIDESPREAD ACROSS ANCHORAGE AND THE
MAT-SU SHOULD BREAK UP BY MIDDAY TODAY WITH AN INCREASINGLY
POWERFUL SUN AS WE HEAD INTO THE FIRST DAY OF MARCH. THE FOG
APPEARS TOO EXTENSIVE AND TOO DEEP TO COMPLETELY BE ERODED...SO
EXPECT IT TO LINGER IN THE FAVORED AREAS (SUCH AS KNIK ARM).
LITTLE WILL CHANGE METEOROLOGICALLY TODAY WITH AN UPPER RIDGE
OVERHEAD...SO FOG MAY ATTEMPT TO MAKE A COME-BACK WHEN THE SUN
SETS EARLY THIS EVENING. HOWEVER...CLOUDS WILL BE ON THE INCREASE
TONIGHT AS THE RIDGE SLIDES BY AND DEVELOPMENT OF TURNAGAIN WINDS
WILL FOLLOW NOT TOO LONG BEHIND THAT. THUS...DO NOT EXPECT THE FOG
TONIGHT TO BE AS WIDESPREAD OR DENSE AS IT IS THIS MORNING.

AS THE RIDGE CONTINUES TO SLIDE EASTWARD MONDAY A FAIRLY STRONG
SHORT-WAVE WILL RIDE UP THE WEST SIDE RIGHT FOR SOUTHCENTRAL.
THE SURFACE LOW WILL BE QUITE WEAK...BUT WITH SUCH STRONG HIGH
PRESSURE OUT AHEAD OF IT STILL EXPECT GALE FORCE WINDS AS THE
FRONTAL SYSTEM LIFTS NORTHWARD ACROSS THE GULF. THE SYSTEM WILL
BRING WARMER ABOVE FREEZING AIR TO MUCH OF SOUTHCENTRAL...BUT THE
SYSTEM WILL OCCLUDE WELL TO THE SOUTH...SO IT WILL ONLY BE
MARGINALLY WARMER. THUS...STILL MAY SEE A FEW AREAS OF SNOW OR
RAIN/SNOW MIX AS PRECIPITATION ARRIVES LATE MONDAY THROUGH EARLY
TUESDAY. THERE WILL INITIALLY BE SOME STRONG CROSS-BARRIER FLOW
ACROSS THE KENAI AND CHUGACH MOUNTAINS WHICH WILL PRODUCE
DOWNSLOPE DRYING IN THE NORMAL PLACES. AS THE UPPER WAVE ARRIVES
EARLY TUESDAY THIS SHOULD WEAKEN AND VEER TOWARD THE SOUTH
ALLOWING SOME PRECIP TO MOVE INTO THESE AREAS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...

HIGH PRESSURE OVER SOUTHWEST ALASKA TODAY WILL BRING DRY CONDITIONS
TO THE REGION. A LOW PRESSURE SYSTEM PUSHING NORTH FROM THE
PACIFIC WILL BRING MOISTURE TO SOUTHERN BRISTOL BAY THAT WILL
SPREAD INLAND THROUGH MONDAY AND MONDAY NIGHT. THIS WILL BRING
WARMER TEMPERATURES AND RAIN AND SOME SNOW TO ALL OF SOUTHWEST
ALASKA...WITH FREEZING RAIN BECOMING A REAL CONCERN MONDAY
AFTERNOON INTO MONDAY NIGHT FOR THE KUSKOKWIM DELTA AND VALLEY.
THE CURRENT PLAN IS TO ISSUE A SPECIAL WEATHER STATEMENT WITH THE
MORNING FORECAST PACKAGE TO COVER THE POTENTIAL IMPACTS FROM THIS
UPCOMING WEATHER EVENT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
NEARLY STATIONARY WEATHER FRONT OVER THE CENTRAL BERING CONTINUES
TO WEAKEN THROUGH TODAY. MEANWHILE...LOW PRESSURE DEVELOPING SOUTH
OF THE CENTRAL AND EASTERN ALEUTIANS PUSHES RAIN OUT AHEAD OF THE
LOW TO IMPACT THE AKPEN THROUGH MONDAY...WITH RAIN DIMINISHING
ALONG THE EASTERN ALEUTIANS TONIGHT. MEANWHILE...ON THE NORTH AND
WEST SIDE OF THE LOW A DEFORMATION BAND OF RAIN AND SOME SNOW
DEVELOPS ACROSS THE CENTRAL ALEUTIANS NORTH THROUGH THE CENTRAL
BERING SEA.

THE NEXT WEATHER FRONT MOVES INTO THE WESTERN ALEUTIANS AND
SOUTHWESTERN BERING MONDAY NIGHT BRINGING A MIX OF RAIN AND SNOW
NEAR SHEMYA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...TUE THROUGH SAT)...
AS WE MOVE INTO TUESDAY...BOTH OF THE BIG WEATHER MAKERS
(PREVIOUSLY MENTIONED) ACROSS THE AREA WILL BE WEAKENING.
FIRST...THE FRONT ACROSS THE NORTHERN GULF WILL KEEP SOME SMALL
CRAFT WINDS IN THE BARRIER JET REGION. THE MID-LEVEL ENERGY
ASSOCIATED WITH THE FRONT WILL PUSH THROUGH COOK INLET. THIS
SHOULD BRING AN END TO ANY DOWNSLOPING WINDS AND PROVIDE ENOUGH
LIFT TO MAKE SURE EVERYONE GETS AT LEAST SOME PRECIPITATION. AND
PRECIPITATION TYPE WILL MOST LIKELY ONCE AGAIN BE A MIX ACROSS
MUCH OF SOUTH CENTRAL. STILL TOUGH TO SAY EXACTLY WHERE AND WHEN
THINGS MIGHT CHANGE FROM SNOW TO RAIN...BUT WITH AFTERNOON HIGHS
IN THE MID TO UPPER 30S FOR ANCHORAGE...A MIX LOOKS LIKELY.

OVER WESTERN HALF OF THE STATE...THE COLD FRONT WILL PUSH INLAND
FROM THE YK DELTA THROUGH THE KUSKOKWIM VALLEY ON TUESDAY. WHILE
NOT A TERRIBLY COLD AIR MASS BEHIND THE FRONT...IT WILL BE ENOUGH
TO CHANGE ANY RAIN OR MIXED PRECIPITATION BACK TO ALL SNOW.
PRECIPITATION WILL THEN COME TO AN END ENTIRELY THROUGH THE DAY
WEDNESDAY AS A SHORTWAVE RIDGE PASSES THROUGH THE AREA. ANOTHER
ROUTINE LOW PRESSURE CENTER AROUND 990 MB WILL SWEEP QUICKLY
ACROSS THE BERING SEA WED INTO THU. TEMPERATURES DO LOOK TO REMAIN
COLD ENOUGH AT THIS TIME TO SUPPORT ALL SNOW AS PRECIPITATION
REACHES THE COAST THU MORNING.

MOST OF THE ENERGY WITH THE UPPER LEVEL TROUGH PUSHING OVER THE
WESTERN HALF OF THE STATE TUE WILL BE PULLED NORTH TOWARD THE
ARCTIC COAST. HOWEVER...IT LOOKS LIKE THERE MIGHT BE JUST ENOUGH
LIFT LEFTOVER SOUTH OF THE AK RANGE TO CONTINUE TO "RING OUT"
LIGHT PRECIPITATION IN THAT REGION THROUGH MUCH OF THE WEEK. WITH
OVERNIGHT LOWS DROPPING BELOW FREEZING AND AFTERNOON HIGHS
CLIMBING WELL ABOVE FREEZING FOR MANY LOCATIONS...IT COULD MAKE
FOR MESSY PRECIPITATION TYPES FOR AN EXTENDED PERIOD.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...130 131 138 178 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...DS
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CC
LONG TERM...MO