Small Craft Advisory 259, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
511 AM AKDT MON MAR 23 2015

.ANALYSIS AND UPPER LEVELS...
HIGH PRESSURE HAS BUILT IN OVER THE SOUTHCENTRAL LEADING TO
CLEAR SKIES IN THE AREA. OUT WEST TROUGHING THAT EXTENDS FROM THE
ALEUTIANS INTO THE NORTH PACIFIC IS ALLOWING FOR WEAK WAVES TO
MOVE ACROSS THE ALEUTIANS AND SOUTHWEST BRINGING SHOWERS TO THESE
AREAS. THIS TROUGHING IS ALSO BRINGING WARMER AIR TO THE SOUTHERN
MAINLAND.

&&

.MODEL DISCUSSION...
THE MODELS IN THE SHORT TERM ARE IN GOOD AGREEMENT BUT ISSUES
ARISE IN THE MID TERM WHEN THE NEXT SYSTEM COMES UP FROM THE NORTH
PACIFIC. THEY ALL WANT TO SPLIT THE LOW SOUTH OF THE ALASKA
PENINSULA BUT THERE ARE DIFFERENCES IN WHICH LOW KEEPS THE
MAJORITY OF THE ENERGY. THE EC AND GEM KEEP THE LOW NEAR THE
ALASKA PENINSULA STRONGER WHILE THE NAM AND GFS HAVE THE LOW
APPROACHING THE KENAI PENINSULA AS THE STRONGER OF THE TWO.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (MONDAY THROUGH TUESDAY
NIGHT)...
A STRONG UPPER LEVEL CUT-OFF HIGH CENTERED OVER THE
KENAI PENINSULA WILL REMAIN NEARLY STATIONARY THROUGH TONIGHT.
CLEAR SKIES HAVE ALLOWED TEMPERATURES TO DROP BELOW FREEZING
ACROSS MOST OF THE REGION...BUT EXPECT GOOD RECOVERY UNDER SUNNY
SKIES. WATER VAPOR IMAGERY SHOWS AN AREA OF STRONGER SUBSIDENCE
AND DRIER AIR ROTATING WESTWARD ACROSS THE GULF. THIS WILL ROTATE
NORTHWARD ON THE WEST SIDE OF THE HIGH UP TO SOUTHCENTRAL TONIGHT
AND ALLOW FOR EVEN MORE EFFECTIVE RADIATIONAL COOLING. THUS...HAVE
LOWERED FORECAST MINIMUM TEMPERATURES.

ALTHOUGH A STRONG UPPER LEVEL RIDGE IS OFTEN CONDUCIVE TO FOG
FORMATION IT DOES NOT LOOK LIKE THAT WILL BE MUCH OF AN ISSUE IN
THIS CASE. A LOOK AT THE ANCHORAGE SOUNDING FROM YESTERDAY
AFTERNOON SHOWS LOW LEVEL INSTABILITY WITH A WILL MIXED BOUNDARY
LAYER. THIS MEANS IT TAKES QUITE A WHILE TO FORM A STEEP SURFACE-
BASED INVERSION OVERNIGHT AND CHANCES OF CAUSING SATURATION AND
FORMATION OF FOG ARE SMALL. IF ANY FOG DOES FORM IT WOULD LIKELY
OCCUR AROUND SUNRISE AND BE VERY LOCALIZED IN NATURE. WITH
SURFACE TEMPERATURES EXPECTED TO FALL EVEN FARTHER EARLY TOMORROW
MORNING THINK THERE MIGHT BE A BETTER CHANCE OF SEEING SOME PATCHY
FOG.

MEANWHILE KODIAK ISLAND IS RIGHT BETWEEN THE UPPER RIDGE AND A
WEAK STORM SYSTEM OVER THE PACIFIC. THIS SYSTEM WILL SLOWLY LIFT
NORTHWESTWARD AROUND THE PERIPHERY OF THE HIGH WHICH WILL BRING
SOME STEADY LIGHT RAIN TO KODIAK TONIGHT INTO TUESDAY. A MORE
SIGNIFICANT CHANGE WILL FOLLOW AS AN AMPLIFYING TROUGH OVER THE
NORTH CENTRAL PACIFIC CAUSES DEVELOPMENT OF A DEEP LOW AND PUSHES
A FRONTAL SYSTEM NORTHWARD ACROSS THE GULF TUESDAY NIGHT. THIS
WILL BRING MUCH STRONGER WINDS AND MODERATE TO HEAVY RAIN. AS THIS
SYSTEM APPROACHES THE RIDGE OVER SOUTHCENTRAL WILL BEGIN TO EXIT
TO THE NORTHEAST OPENING THE DOOR FOR INCREASING CLOUDS TUESDAY
NIGHT...AND ULTIMATELY LEADING TO A RETURN TO MORE ACTIVE WEATHER.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
HIGH CIRRUS WILL CONTINUE TO STREAM ACROSS THE WESTERN MAINLAND
TODAY AS THE EAST BEGINS TO CLEAR OUT UNDER THE BUILDING RIDGE
ALOFT. TEMPERATURES ALONG THE KUSKOKWIM DELTA WILL VARY GREATLY
BETWEEN THE COAST AND INLAND WHILE COLDER AIR STREAMS DOWN FROM
THE NORTH ALONG THE COAST...BUT INLAND AREAS WILL SEE SIGNIFICANT
MODIFICATION FROM SUNSHINE. THE NEXT CHANCE FOR RAIN WILL COME
LATE TONIGHT INTO TUESDAY AS A DISTURBANCE PUSHES INTO BRISTOL
BAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A LOW LEVEL TROUGH/FRONTAL BOUNDARY WILL CONTINUE TO WORK WESTWARD
THROUGH THE BERING TODAY...IMPACTING THE EASTERN ALEUTIANS AND THE
PRIBILOF ISLANDS. THE EASTERN CHAIN AND ALASKA PENINSULA WILL SEE
SCATTERED RAIN SHOWERS WITH THIS SYSTEM. THE PRIBILOF ISLANDS
WILL SEE SNOW DEVELOPING ALONG THIS LOW LEVEL FEATURE WITH A GOOD
CHANCE FOR ACCUMULATING SNOW FROM LATE AFTERNOON INTO THE EVENING
HOURS. WINDS APPROACHING 20-30 MPH WILL REMAIN CONDUCIVE FOR AREAS
OF BLOWING SNOW BUT WARM SURFACE TEMPERATURES WILL MITIGATE THE
THREAT SOMEWHAT. THE FRONT STALLS IN PLACE ON TUESDAY KEEPING SNOW
SHOWERS IN THE FORECAST ON TUESDAY.

&&

.LONG TERM FORECAST (WEDNESDAY THROUGH SUNDAY)...

MODEL AGREEMENT REMAINS VERY GOOD WITH THE PROGRESSION OF
THE WEAKENING STORM FORCE FRONT OVER THE NORTHERN GULF ON
WEDNESDAY. RAIN AND GUSTY WINDS WILL ACCOMPANY THIS FRONT ON
WEDNESDAY OVER THE GULF COAST BEFORE DISSIPATING OVER THE NORTH
GULF COAST ON THURSDAY MORNING. ITS ASSOCIATED LOW WILL SLOWLY
MOVE INTO THE GULF FOR ON THURSDAY...PROVIDING FOR MOIST SOUTHERLY
FLOW OVER THE GULF CONTINUED RAIN THROUGH THE WORK WEEK. INLAND
AREAS FROM THE NORTHERN KENAI PENINSULA NORTHWARD WILL SEE
INCREASING CHANCES OF RAIN FROM THIS SYSTEM ON THURSDAY AND FRIDAY
AS DOWNSLOPING FROM THE FRONT DIMINISHES...HOWEVER IT STILL
APPEARS THAT THE BULK OF THE PRECIPITATION WILL FALL OVER THE GULF
COAST WITH SCATTERED SHOWERS EXPECTED INLAND. OUT
WEST...PERSISTENT NORTHERLY FLOW OVER THE BERING WILL CONTINUE FOR
THE THROUGH THE WORK WEEK A CHANCE OF RAIN AND SNOW RETURNING TO
THE SOUTHWEST ON WEDNESDAY AS AN UPPER LEVEL TROUGH DEVELOPS
OVERHEAD.

THE NEXT SYSTEM DEVELOPS AS A WAVE OF ENERGY ROUNDS THE BASE OF
THE UPPER TROUGH OVER THE BERING/NORTH PACIFIC ON FRIDAY CUTTING
OFF A NEW LOW CENTER JUST SOUTH OF KODIAK ISLAND. THERE STILL IS
UNCERTAINTY ON THE TRACK AND STRENGTH OF THIS SYSTEM INTO THIS
WEEKEND...BUT THERE IS GOOD AGREEMENT THAT A STATIONARY UPPER
LEVEL TROUGH WILL DEVELOP OVER THE AREA EARLY ON SATURDAY. THIS
WILL KEEP STORMY WEATHER IN THE FORECAST FROM THE EASTERN BERING
INTO THE SOUTHERN MAINLAND AND GULF THROUGH SUNDAY...WITH NO SIGNS
OF RIDGING RETURNING TO THE MAINLAND BEFORE NEXT WEEK.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 131 132 138 150
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...DK
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...ML
LONG TERM...DEK/KH