Heavy Freezing Spray Warning 87, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST THU FEB 23 2012

.ANALYSIS AND UPPER LEVELS...
A BROAD TROUGH IS OVER THE MAINLAND OF ALASKA WITH A CLOSED LOW OVER
THE WESTERN ALEUTIANS THIS MORNING. THIS IS RESULTING IN SCATTERED TO
NUMEROUS SNOW SHOWERS OVER THE AREA. A DEEPER LOW IS IN THE BASE OF
THE TROUGH OVER THE NORTH PACIFIC SOUTH OF THE GULF OF ALASKA. A
STRONG FRONT IS PROGRESSING THROUGH THE CENTRAL ALEUTIANS THIS
AFTERNOON WITH GALE FORCE WINDS. THE JET SUPPORT WITH THIS FRONT IS
NOT THAT STRONG CURRENTLY. A SURFACE LOW IS ALSO PARKED OVER PRINCE
WILLIAM SOUND. AN AREA OF HIGH PRESSURE IS OVER THE EASTERN BERING.
FOR THE NEXT 24 HOURS...THIS PATTERN WILL SHIFT TO THE EAST WITH ONLY
THE PRINCE WILLIAM SOUND LOW REMAINING MOSTLY IN PLACE. AS A
RESULT...THE PRESSURE GRADIENT OVER PRINCE WILLIAM SOUND HAS CREATED
GUSTY WESTERLIES NEAR WHITTIER.

.MODEL DISCUSSION...
THE MODELS INITIALIZED OK THIS MORNING. SEEMS THE GFS AND ECMWF DID A
BETTER JOB WITH THE MOISTURE FIELD THAN OTHER MODELS. ECMWF HANDLED
THE VORTICITY PATTERN A BIT BETTER OVERALL. DESPITE THESE SMALL
DIFFERENCES...THE MODELS ARE IN GOOD AGREEMENT THROUGH AT LEAST THE
FIRST 96 HRS OF THE FORECAST. ONE MINOR DIFFERENCE IN SOLUTIONS IS IN
THE BRISTOL BAY AREA 00Z SATURDAY. THE ECMWF HAS A BIT MORE AMPLIFIED
SURFACE LOW. THIS WILL ONLY IMPACT MINOR WIND DIRECTION DIFFERENCE
EXTENDING INTO SATURDAY MORNING IN BRISTOL BAY. THE MAJOR PLAYER IS A
VERY LARGE LOW PRESSURE SYSTEM WRAPPING UP IN THE WESTERN NORTH
PACIFIC TOMORROW. THIS LOW TO MOVE SLOWLY INTO THE BERING SATURDAY
AND PROGRESS INTO THE EASTERN BERING SUNDAY AND FINALLY INTO THE GULF
EARLY NEXT WEEK. AN AREA OF HIGH PRESSURE WILL FOLLOW THE LOW ACROSS
THE BERING AHEAD OF ANOTHER LOW COMING AROUND THE KAMCHATKA PENINSULA
SUNDAY/MONDAY. AT THIS TIME...MODELS START TO DIVERGE A BIT DUE TO
JET POSITION DIFFERENCES. SINCE THE PATTERN IS QUITE PROGRESSIVE AT
THIS TIME...THE TIMING AND POSITIONS OF STORM SYSTEMS WILL BE
UNCERTAIN.

OVER THE GULF OF ALASKA...THE MODELS ARE IN VERY GOOD AGREEMENT
THROUGH TUESDAY. THE CURRENT WEAKER LOW IN PRINCE WILLIAM SOUND TO
LEAVE TOMORROW NIGHT WITH HIGH PRESSURE MOVING OVER THE AREA. THE
BERING LOW TO TRANSITION INTO THE AREA MONDAY.

.SHORT TERM FORECAST...
SOUTHCENTRAL...
AIR MASS UNSTABLE UNDER THE UPPER LEVEL TROUGH CREATING SCATTERED
SHOWERS. THE TROUGH AXIS TO SWING THROUGH LATER TONIGHT INCREASING
THE COVERAGE OF SHOWERS WITH SOME AREAS PICKING UP SOME MODERATE SNOW
AMOUNTS. THESE WILL LIKELY BE CONFINED TO THE HIGHER TERRAIN. THE LOW
IN PRINCE WILLIAM SOUND WILL REMAIN IN THE AREA THROUGH TOMORROW. AS
THE AREA OF HIGH PRESSURE OVER THE EASTERN BERING SWINGS INLAND
TONIGHT...THE PRESSURE GRADIENT OVER THE AREA TO INCREASE. AS A
RESULT...MODERATE WESTERLY GAP WINDS WILL BECOME STRONG TONIGHT. THE
LOW TO MOVE OUT TOMORROW NIGHT AND WINDS WILL DIMINISH. SKIES WILL BE
MOSTLY CLEAR TOMORROW AFTER THE PASSAGE OF THE TROUGH AXIS. SKIES
WILL REMAIN CLEAR WITH TEMPERATURES DIVING TOMORROW NIGHT WITH LESS
WIND AS WELL. EXPECT AREAS OF FOG TO DEVELOP IN A LOT OF AREAS. THE
LARGE LOW IN THE BERING TO BRING A FRONT INTO THE GULF SATURDAY AND
TO THE NORTHERN GULF COAST SATURDAY NIGHT. THIS WILL BRING GALE FORCE
WINDS TO THE GULF AND LOTS OF PRECIPITATION TO COASTAL AREAS.

SOUTHWEST...
TROUGH AXIS IS MOVING OVER THE AREA THIS AFTERNOON WITH SCATTERED TO
NUMEROUS SHOWERS. HIGH PRESSURE IS OVER THE EASTERN BERING WITH SOME
MODERATE WINDS ALONG THE COAST DUE TO THE GRADIENT. THIS TROUGH AXIS
WILL MOVE ACROSS THE MAINLAND TONIGHT AND SHOWERS WILL END FROM THE
WEST. TOMORROW IS A DAY OF INCREASING CLOUDS AND WINDS ALONG THE
COAST AS THE FRONT THAT IS CURRENTLY IN THE CENTRAL ALEUTIANS MAKES
ITS WAY TO THE COAST. THE FRONT WILL LOSE QUITE A BIT OF STEAM BEFORE
THEN AS THE JET SUPPORT IS WEAKENING FOR THE FRONT. EXPECT SOME SNOW
AND BLOWING SNOW ALONG THE COAST STARTING TOMORROW AFTERNOON BUT TO
NOT REACH BLIZZARD CONDITIONS. THE FRONT WILL WORK INLAND TOMORROW
NIGHT AS WINDS CONTINUE TO DECREASE. THE NEXT MASSIVE LOW WILL THEN
BECOME THE PLAYER SATURDAY AFTERNOON. WINDS WILL INCREASE THROUGH THE
AFTERNOON SATURDAY AND REACH GALE FORCE BY THE EVENING. RIGHT
NOW...WE ARE FAIRLY CERTAIN THIS LOW WILL BRING PRECIP AND WINDS TO
THE COAST SATURDAY EVENING. WE ARE NOT CERTAIN OF THE POSSIBILITY OF
BLIZZARD CONDITIONS AND WILL MONITOR THE SITUATION FOR POSSIBLE
ISSUANCE OF STATEMENTS FOR THIS SATURDAY NIGHT FRONT.

BERING SEA/ALEUTIANS...
STRONG LOW AND ASSOCIATED FRONT MOVING ACROSS THE WESTERN AND CENTRAL
BERING RESPECTIVELY. THE FRONT WILL OUTRACE ITS UPPER LEVEL SUPPORT
TONIGHT. HOWEVER...THERE IS ENOUGH ENERGY WITH IT FOR GALE FORCE
WINDS THIS AFTERNOON THROUGH TONIGHT. MOST OF THE PRECIPITATION ALONG
THE ALEUTIAN CHAIN HAS BEEN SNOW MIXED WITH RAIN. THEREFORE...WE HAVE
NOT HAD BLIZZARD CONDITIONS WITH THIS FRONT. WE DO EXPECT BLIZZARD
CONDITIONS FOR THE PRIBILOF ISLANDS TONIGHT AS THE FRONT REACHES
THERE BY MIDNIGHT. THE PARENT LOW FOR THIS FRONT TO DISSIPATE
TOMORROW AHEAD OF A RAPIDLY DEEPENING LOW IN THE NORTH PACIFIC. THIS
NEXT LOW WILL BE RATHER LARGE. IT IS ANTICIPATED TO MOVE INTO THE
BERING NEAR SHEMYA FRIDAY NIGHT AND SLOWLY PROGRESS ACROSS THE BERING
THIS WEEKEND. ITS ASSOCIATED FRONT WILL REMAIN MORE INTACT AS IT
MOVES THROUGH THE BERING. THEREFORE...WE CAN EXPECT SOME POSSIBLE
BLIZZARD CONDITIONS FOR THE PRIBILOFS AGAIN SATURDAY AFTERNOON.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...BLIZZARD WARNING ZONE 195
MARINE...STORM...175 176
         GALE...130 132 155 160 165 170 171 172 179 180 185
                411 412 413 414
         HEAVY FREEZING SPRAY...121 127 129 130
FIRE WEATHER...NONE

JN FEB 12