Gale Warning 179, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
300 PM AKST TUE FEB 10 2009

.ANALYSIS AND UPPER LEVELS...
A CONCENTRIC COLD CORE UPPER LEVEL LOW REMAINS IN PLACE OVER NORTHERN
ALASKA. TWO TROUGHS EXTEND SOUTH FROM THE MAIN LOW...ONE IS MOVING
EAST OF ALASKA AND A SECOND IS MOVING ACROSS THE CENTRAL BERING SEA.
BETWEEN THESE TWO TROUGHS IS A SHORT WAVE RIDGE WHERE FAIR CONDITIONS
CAN BE FOUND OVER MUCH OF SOUTHCENTRAL AND SOUTHWEST ALASKA.

AT THE SURFACE...HIGH PRESSURE PERSISTS OVER THE MAINLAND CENTERED
OVER THE KOYUKUK RIVER VALLEY WHICH IS WHERE THE COLDEST TEMPERATURES
IN THE STATE CAN BE FOUND. TO THE WEST...AN OCCLUDED FRONT IS
APPROACHING BRISTOL BAY AND THE KUSKOKWIM DELTA. A 970 MB LOW
NORTHWEST OF SHEMYA IS WEAKENING AS IT DRIFTS NORTHWESTERN INTO THE
CENTRAL BERING. THE NEXT MAJOR SYSTEM CAN BE SEEN ON SATELLITE OVER
THE NORTH PACIFIC AS IT RAPIDLY GAINS STRENGTH THIS EVENING.

.MODEL DISCUSSION...
MODELS SEEM TO BE GETTING A BETTER HANDLE ON THE PROGRESSION OF THE
DEVELOPING NORTH PACIFIC LOWS AS CONSISTENCY FROM RUN TO RUN IS
IMPROVING. THE INHERITED FORECAST IN THE SHORT AND MID TERM IS
REPRESENTATIVE OF THE LATEST MODEL RUNS SO ONLY MINOR CHANGES WERE
NECESSARY. IN THE MID TO LONG RANGE...THE ECMWF SEEMS TO BE THE
OUTLIER WITH THE LATEST DEVELOPING LOW MOVING OUT OF THE NORTH
PACIFIC.

.SHORT TERM FORECAST...

SOUTHCENTRAL...
FAIR WEATHER OVER SOUTHCENTRAL EARLY THIS AFTERNOON WITH MOSTLY SUNNY
SKIES PREVAILING. THE EXCEPTION IS ALONG COOK INLET WHERE SOME LOW
STRATUS AND FOG ARE LURKING JUST OFF THE COAST. NORTHERLY WINDS OVER
THE INLET WILL INCREASE AS A RESULT OF THE DEVELOPING LOW SOUTH OF
KODIAK WHICH WILL HELP ERODE ANY STRATUS THAT REMAINS THIS EVENING.

A SHORT WAVE THAT IS CLEARLY VISIBLE ON THE WATER VAPOR IMAGERY WILL
TRIGGER THE AFOREMENTIONED SURFACE LOW TO DEVELOP OVERNIGHT. THERE IS
SOME UNCERTAINTY AS TO HOW FAR NORTH THE MOISTURE FROM THIS SYSTEM
WILL REACH AS THE LOW IS PROGGED TO SHEAR APART AND WEAKEN IN THE
EASTERN GULF BY WEDNESDAY NIGHT. THE 18Z RUN OF THE GFS AND NAM ARE
NOW BRINGING MORE MOISTURE INTO SOUTHCENTRAL. WE WILL STILL BE GOING
WITH A CHANCE OF SNOW TOMORROW EVENING FOR ANCHORAGE UP TO THE
SUSITNA VALLEY BUT CHANCES ARE GOOD THAT SOME LIGHT SNOW WILL FALL
FOR A PERIOD TOMORROW AS A DEFORMATION ZONE SETS UP OVER THE REGION.
MOST OF THE SNOW WILL FALL ALONG THE COAST AND THE SOUTHERN SUSITNA
VALLEY WHERE ISENTROPIC LIFT WILL BE MAXIMIZED.

THERE IS A POSSIBILITY AS WELL THAT KODIAK CITY COULD SEE BLOWING
SNOW AS THE NORTHERLY FLOW ON THE BACKSIDE OF THE LOW WRAPS MOISTURE
AND COLD AIR AROUND. WILL MENTION AREAS OF BLOWING SNOW FOR THIS ZONE
AS NOT CONFIDENT ENOUGH AT THIS POINT TO MENTION BLIZZARD CONDITIONS.
SOUTHCENTRAL WILL SEE A BREAK IN THE WEATHER BRIEFLY BEFORE THE NEXT
FRONTAL BOUNDARY MOVES INTO THE NORTHERN GULF ON FRIDAY BRINGING RAIN
AND SNOW TO THE COAST AND SNOW LIKELY OVER THE INTERIOR.

SOUTHWEST ALASKA...
BETHEL RADAR IS PICKING UP THE MOISTURE ASSOCIATED WITH THE WEAKENING
FRONT OVER THE EASTERN BERING SEA. LIGHT SNOW AND BLOWING SNOW IS
LIKELY ALONG THE COAST BUT THE FRONT IS WEAKENING AS THE ENERGY GETS
DISPLACED TO THE GULF. SNOW WILL SPREAD INLAND AND MAKE IT ALL THE
WAY UP TO THE UPPER KUSKOKWIM OVERNIGHT BUT SNOW TOTALS WILL REMAIN
LIGHT ACROSS THE AREA. INFRARED AND VISIBLE SATELLITE DEPICTING THE
PRECIPITATION BEHIND THE FRONT IS CONVECTIVE. SHOWERS WILL MOVE
INLAND OVERNIGHT AND GRADUALLY DIMINISH IN COVERAGE BY WEDNESDAY.

UNSETTLED WEATHER WILL CONTINUE AS ANOTHER OCCLUDED FRONT APPROACHES
THE COAST THURSDAY. MUCH MORE MOISTURE IS ASSOCIATED WITH THIS
SYSTEM...SO THERE WILL BE THE POSSIBILITY OF A BLIZZARD ALONG THE
COAST AS WELL AS MUCH STRONGER WINDS THROUGH THE GAPS ACROSS THE
INTERIOR.

BERING SEA/ALEUTIANS...
AS PREVIOUSLY MENTIONED...THE POST FRONTAL AIRMASS IS CONVECTIVE SO
SHOWERS WILL PERSIST THROUGH TONIGHT. A NORTH PACIFIC LOW WILL DEEPEN
RAPIDLY TO 970 MB LATE WEDNESDAY NIGHT AND MOVE INTO THE WESTERN
BERING SEA AS A 962 MB LOW THURSDAY. THIS SYSTEM WILL BEGIN TO WRAP
SOME ARCTIC AIR DOWN ON THE BACKSIDE WHICH WILL EVENTUALLY MAKE IT TO
THE MAINLAND OVER THE WEEKEND. IN THE MEAN TIME...THERE IS THE
POTENTIAL FOR HIGH WIND WARNINGS ALONG THE FRONT THURSDAY AND THEN
BLIZZARDS ACROSS THE BACKSIDE OF THE LOW ON FRIDAY.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...STORM WARNING...172 175 176 411
         GALE WARNING...132 165 170 171 185 352 412 413 414
         HEAVY FREEZING SPRAY WARNING...129 130 140
FIRE WEATHER...NONE.

AB FEB 09