Gale Warning 735, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
600 AM AKDT FRI OCT 14 2011

.ANALYSIS AND UPPER LEVELS...

AN ACTIVE PATTERN DOMINATES THE ALASKA FORECAST AREA THIS MORNING WITH
AN UPPER LEVEL TROUGH COVERING THE BERING AND AN UPPER LEVEL RIDGE
ENCOMPASSING THE NORTH PACIFIC. A 130 KT JET THAT LIES SOUTH OF THE
ALEUTIANS...ALONG THE BOUNDARY OF THESE TWO FEATURES...IS SUPPORTING A
SURFACE LOW OVER BRISTOL BAY. ALTHOUGH THIS SURFACE LOW IS APPROACHING
OCCLUSION...THE ASSOCIATED UPPER LEVEL LOW PRESSURE SYSTEM REMAINS
RELATIVELY WEAK AND WILL RAPIDLY DISSIPATE INTO A TROUGH BY LATE
MORNING. TO THE EAST OF THIS LOW...AN IMPRESSIVE RIDGE IS BUILDING DUE
TO AMPLE LATENT HEAT RELEASE AND MID LEVEL MOISTURE SUPPORT. THIS
MOISTURE WILL CONTINUE TO FUEL THE DEVELOPMENT OF THE SURFACE LOW AND
SUPPORT PRECIPITATION ACROSS MUCH OF THE FORECAST AREA AS THIS SYSTEM
MOVES EAST TODAY.

.MODEL DISCUSSION...MODELS ARE IN RELATIVELY GOOD AGREEMENT IN THE SHORT
TERM ON BOTH THE TIMING AND INTENSITY OF THE LOW PRESSURE SYSTEM AS IT
MOVES FROM THE BERING INTO THE GULF. MODELS BEGIN TO DIVERGE
SUBSTANTIALLY BY MONDAY...WITH THE NAM BEING THE OUTLIER. AS A
RESULT...THE GFS WAS THE FAVORED MODEL BY THE END OF THE SHORT TERM.
MODELS ARE IN ABOUT AVERAGE AGREEMENT IN THE LONG TERM AND HPC GUIDANCE
WAS RELIED UPON.

.SHORT TERM FORECAST...

SOUTHCENTRAL...THE APPROACH OF A LOW PRESSURE SYSTEM AND FRONT TOWARDS
THE SOUTHCENTRAL REGION TODAY HAS ALREADY CAUSED GUSTY WINDS THROUGH
CHANNELED TERRAIN THIS MORNING AS THE PRESSURE GRADIENT INCREASES ACROSS
THE REGION.  IN ADDITION...CONDITIONS ALOFT ARE GOOD FOR SUPPORTING
MOUNTAIN WAVES...ESPECIALLY NEAR ANCHORAGE. THE SOUNDING THIS MORNING
SHOWS AN INVERSION JUST AT MOUNTAIN HEIGHT. WINDS ARE PERPENDICULAR TO
THE MOUNTAIN THROUGH ABOUT 5000 FT...BUT BECOME PARALLEL TO THE
ANCHORAGE CHUGACH ALOFT. THESE CONDITIONS ARE IDEAL FOR THE FORMATION
AND TRAPPING OF MOUNTAIN WAVES.  AS A RESULT...SPURIOUS GUSTS HAVE
OCCURRED ACROSS THE HIGHER TERRAIN OF ANCHORAGE IN ADDITION TO THE GAP
FLOW THROUGH TURNAGAIN ARM THIS MORNING. SO FAR...WIND GUSTS HAVE
ALREADY REACHED OVER 75 MPH AT MCHUGH CREEK THIS MORNING WITH UNOFFICIAL
REPORTS OF GUSTS TO 70 MPH ALONG HIGHER ELEVATIONS. STRONG WIND GUSTS
ARE EXPETED TO CONTINUE INTO TONIGHT UNTIL THE FRONT MOVES ONSHORE AND
WEAKENS ALONG THE EAST GULF COAST.

WHILE DOWNSLOPING IS GENERALLY LIMITING PRECIPITATION ACROSS MUCH OF
SOUTHCENTRAL RIGHT NOW...RAIN WILL BEGIN TO FILL IN BY THIS EVENING AS
MOUNTAIN PERPENDICULAR WINDS WEAKENS SUBSTANTIALLY. WITH COLD AIR
POOLING IN INTERIOR VALLEYS...A RAIN SNOW MIXTURE IS POSSIBLE WITH THIS
SYSTEM.  SNOW HAS ALREADY STARTED TO FALL AT TALKEETNA THIS
MORNING...AND A FEW INCHES OF SNOW ARE POSSIBLE WEST OF THE PARKS
HIGHWAY TODAY.

.SOUTHWEST ALASKA...A LOW PRESSURE SYSTEM AND ITS ASSOCIATED FRONT IS
BRINGING GUSTS TO OVER 60 MPH TO THE ALASKA PENINSULA THIS MORNING.
STRONG DOWNWARD VERTICAL MOTION BEHIND THIS FRONT WILL BRING GUSTY
WESTERLY WINDS ACROSS MUCH OF THE REGION TODAY...ALTHOUGH WINDS ARE
EXPECTED TO BE MUCH WEAKER BY AFTERNOON. HIGH PRESSURE WILL BUILD IN
BEHIND THIS SYSTEM AND BRING GENERALLY QUIET CONDITIONS SATURDAY.  A
WEAK WAVE COULD TOUCH OFF SOME SHOWERS LATE SUNDAY ALONG THE COAST WITH
NO STRONG WINDS EXPECTED.

BERING SEA/ALEUTIANS...CONDITIONS WILL CONTINUE TO BECOME CALMER ACROSS
THE BERING THE NEXT FEW DAYS AS THE BRISTOL BAY LOW MOVES INLAND. WHILE
A LOW PRESSURE SYSTEM WILL APPROACH SHEMYA BY THIS AFTERNOON...MODELS
INDICATE THAT THE BULK OF THE WINDS WILL REMAIN SOUTH OF THE ISLAND AND
ONLY GALES ARE EXPECTED. THIS LOW WILL SKIRT SOUTH OF THE ALEUTIANS
SATURDAY AND RELATIVELY QUIET CONDITIONS WILL OCCUR ACROSS THE BERING
OVER THE WEEKEND.

.LONG TERM FORECAST...A DYNAMIC PATTERN WILL PERSIST ACROSS THE BERING
AND MAINLAND ALASKA FOR THE NEXT WEEK WITH A SERIES OF LOWS MOVING
ACROSS THE REGION. WITH THE JET STREAM LOCATED JUST SOUTH OF THE
ALEUTIANS...LOW PRESSURE SYSTEMS WILL CONTINUE TO DEVELOP AND MOVE
RAPIDLY ACROSS THE BERING INTO THE GULF.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING... 101
MARINE...GALES...120 125 129 130 132 150 155 160 165 170 171 180
FIRE WEATHER...NONE.

OCT 11
ELN