High Wind in Alaska, April 25, 2013

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT THU APR 25 2013

.ANALYSIS AND UPPER LEVELS...
TEXTBOOK REX BLOCK IN PLACE WITH A CLOSED HIGH PRESSURE ENCOMPASSING
THE BERING SEA AND CLOSED LOW TO THE SOUTH OVER THE NORTH CENTRAL
PACIFIC. THE WARM RIDGE OVER THE BERING ALONG WITH THE SPRAWLING
POLAR VORTEX CENTERED OVER THE CANADIAN ARCTIC HAS PROMOTED AN
UNSEASONABLY STRONG NORTHERLY JET OF 145KT OVER CENTRAL ALASKA. A
STRONG SHORTWAVE TROUGH IS EVIDENT ON SATELLITE...DIGGING INTO THE
GULF OF ALASKA PRESENTING VERY NOTICEABLE DRYING IN THE
MID-TROPOSPHERE. MOST AREAS ON THE BACKSIDE OF THE TROUGH ARE
CLEARING OUT QUICKLY LEAVING SOME MID-LEVEL CLOUDS. IN RESPONSE TO
THE TIGHTENING PRESSURE GRADIENT AND COLD AIR FILTERING IN FROM THE
NORTH...GUSTY NORTHERLY WINDS ARE BEGINNING TO TAKE SHAPE ACROSS THE
SOUTH CENTRAL IN GENERAL BUT ESPECIALLY IN OUTFLOW PRONE LOCATIONS ON
THE NORTH GULF COAST...SEWARD...WHITTIER...AND VALDEZ. THERE IS A
HIGH WIND WARNING OUT FOR VALDEZ AND THOMPSON PASS.

.MODEL DISCUSSION...
GUIDANCE REMAINS IN GREAT AGREEMENT WITH THE SYNOPTIC PATTERN THROUGH
THE SHORT TERM WITH THE REX BLOCK CREATING A VERY STABLE LONG-WAVE
PATTERN. FORECAST CONFIDENCE IS HIGH WITH THE MORNING PACKAGE.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...A GENERAL CLEARING AND DRYING WILL TAKE PLACE
TODAY WITH AN INCREASE IN NORTHERLY WINDS IN MOST LOCATIONS. THE
NORTHERLY JET STREAM AND COLD AIR RETURNING TO INLAND LOCATIONS HAS
TIGHTENED THE SURFACE PRESSURE GRADIENT ALONG THE NORTH GULF COAST.
STRONG DOWNWARD VERTICAL MOTION ON THE BACKSIDE OF THE TROUGH WILL
ACCELERATE AIR DOWN THE CHUGACH CREATING STRONG AND GUSTY WINDS FOR
MOST AREAS ALONG THE NORTH GULF COAST WITH THE STRONGEST BEING IN THE
VALDEZ AREA WHERE A HIGH WIND WARNING IS IN PLACE THROUGH THE
AFTERNOON. EXPECT THE NORTHERLY FLOW PATTERN TO CONTINUE THROUGH THE
WEEKEND WITH AN INCREASE IN HIGH CLOUDS FRIDAY AFTERNOON.

SOUTHWEST ALASKA...CLEAR DRY AND COLDER CONDITIONS WILL PREVAIL
THROUGH FRIDAY. SNOW SHOWERS WILL BECOME POSSIBLE FRIDAY AFTERNOON AS
ANOTHER DISTURBANCE DROPS SOUTHWARD IN THE NORTHERLY FLOW....MAINLY
ALONG THE ALASKA RANGE.

BERING SEA AND ALEUTIANS...HIGH PRESSURE WILL DOMINATE THE BERING IN
THE SHORT TERM. THE WESTERN BERING WILL REMAIN CONDUCIVE TO LOW
STRATUS AND FOG IN A BROAD EASTERLY FLOW. THE EASTERN BERING WILL SEE
PERIODS OF LOW CLOUDS AND FOG THIS MORNING BUT CHANCES WILL LESSEN AS
FLOW FROM THE MAINLAND TAKES HOLD AND MOVES A DRIER AIR MASS
OVERHEAD.

.LONG TERM FORECAST...
EXTENDED GUIDANCE CONTINUE TO SHOW A BREAKDOWN OF THE BLOCK WITH THE
HIGH RETROGRADING WESTWARD...WHICH WILL ALLOW FOR BOTH THE POLAR
VORTEX TO RETROGRADE WESTWARD AS WELL AND FOR THE REMNANTS OF THE
NORTH PACIFIC LOW TO DEVELOP INTO THE GULF. THE INTERACTION OF THESE
TWO SYSTEMS WILL BE THE FOCUS OF THE FORECAST NEXT WEEK BUT THE
DETAILS ARE STILL UNCLEAR AT THIS POINT. CONFIDENCE IS INCREASING IN
A SYSTEM IN THE GULF BY MIDWEEK. EXPECT A CONTINUATION OF BELOW
NORMAL TEMPERATURES.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 131
MARINE...GALE 127 130
FIRE WEATHER...NONE

MTL APR 13