Blizzard and High Wind in Alaska, February 7, 2014

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
145 PM AKST THU FEB 6 2014

.ANALYSIS AND UPPER LEVELS...
AN UNUSUALLY STRONG UPPER HIGH CONTINUES TO DOMINATE WEATHER ACROSS
THE REGION. THE MUCH-ANTICIPATED UPPER SHORTWAVE HAS ROUNDED THE TOP
OF THIS HIGH AND IS NOW DROPPING SOUTHWARD THROUGH INTERIOR ALASKA. A
STRONG 150 KT JET BETWEEN THESE TWO FEATURES IS FUELING THE RAPID
AMPLIFICATION OF THE UPPER-LEVEL PATTERN ALONG WITH THE RESULTING
SURGE OF ARCTIC AIR CURRENTLY MOVING TOWARD SOUTHERN ALASKA. AT THE
SURFACE...PRESSURE GRADIENTS ARE CURRENTLY LIGHT ACROSS MOST OF THE
SOUTHERN MAINLAND. A TROUGH IN THE NORTHERN GULF CONTINUES TO PRODUCE
SOME GUSTY WINDS THROUGH THE FAVORED GAPS IN THE IMMEDIATE VICINITY
OF THE COAST. SOME SCATTERED AREAS OF LOW CLOUDS AND PATCHY FOG ARE
LINGERING AROUND COOK INLET AND THE SOUTHWEST MAINLAND BUT ARE
GRADUALLY DIMINISHING IN COVERAGE. OUT WEST...STRONG LOW-LEVEL
INVERSIONS ACROSS MUCH OF THE BERING SEA CONTINUE TO PRODUCE LIGHT
WINDS AND WIDESPREAD AREAS OF MARINE FOG AND STRATUS.

.MODEL DISCUSSION...
THE MODELS ARE IN EXCELLENT OVERALL AGREEMENT. THERE IS STILL A
PERSISTENT DISCREPANCY IN REGARDS TO THE TRACK OF THE SURFACE LOW
OVER THE WESTERN GULF AS IT WEAKENS AND MOVES TO THE SOUTHWEST DURING
THE DAY TOMORROW. THESE DIFFERENCES WILL HAVE FAIRLY MINOR IMPACTS ON
THE TIMING AND STRENGTH OF MANY OF THE GAP WINDS EXPECTED TO DEVELOP
TONIGHT AROUND THE AREA...BUT WILL MAKE A MUCH BIGGER DIFFERENCE FOR
KODIAK ISLAND. THE NAM TAKES THE LOW CENTER ACROSS KODIAK
ISLAND...WHICH WOULD DIMINISH THE WINDS AROUND THE TIME OF HEAVIEST
SNOWFALL. MEANWHILE THE GFS TAKES THE LOW WELL SOUTH OF THE ISLAND
AND WOULD KEEP BOTH WINDS AND HEAVY SNOW CONCURRENT FOR MUCH OF THE
DAY. THE ECMWF AND GEM BOTH SPLIT THE DIFFERENCE BETWEEN THE OTHER
TWO MODELS...AND REPRESENT A GOOD MIDDLE GROUND SOLUTION THAT IS ALSO
RELATIVELY CONSISTENT WITH THE INHERITED FORECAST.

.SHORT TERM FORECAST...
SOUTHCENTRAL...A DECEPTIVELY TRANQUIL DAY IS UNFOLDING ACROSS MUCH OF
SOUTHERN ALASKA. INCREASING MID AND HIGH-LEVEL CLOUDINESS ARE AN
EARLY INDICATION OF THE SIGNIFICANT WEATHER DESTINED TO IMPACT THE
AREA BEGINNING THIS EVENING. THERE IS NO SIGNIFICANT CHANGE TO THE
OVERALL FORECAST PHILOSOPHY TODAY. UPSTREAM SNOWFALL RATES ACROSS THE
INTERIOR HAVE BEEN IMPRESSIVE...WHICH RAISES CONFIDENCE IN SOME MINOR
ACCUMULATIONS THIS EVENING...MAINLY AROUND SOUTHERN PORTIONS OF THE
COPPER RIVER BASIN. MEANWHILE...WINDS WILL INCREASE DRAMATICALLY
ACROSS THE MATANUSKA VALLEY AND THROUGH THOMPSON PASS THIS EVENING AS
COLD AIR ADVECTION AND RAPID STORM INTENSIFICATION IN THE GULF KICK
INTO HIGH GEAR. SOON AFTER...ANCHORAGE AND THE WESTERN KENAI AS WELL
AS ALL FAVORED GAP WIND LOCATIONS WILL START TO SEE WINDS INCREASE
MARKEDLY. PRECIPITATION ASSOCIATED WITH THE NEW LOW WILL BE CONFINED
ALMOST ENTIRELY TO COASTAL AREAS...WITH THE EASTERN KENAI AND KODIAK
ISLAND BERING THE BRUNT OF THE SNOW. BLOWING SNOW ADVISORIES REMAIN
IN PLACE IN BOTH OF THESE AREAS.

SOUTHWEST...A SHIFT TO OVERALL OFFSHORE FLOW HAS COMMENCED...WHICH
WILL GRADUALLY ELIMINATE THE LOW CLOUDS AND FOG LOITERING ACROSS MUCH
OF THE AREA. THE MAIN IMPACT TO THE AREA FROM THE BIG STORM IN THE
GULF WILL BE A DRAMATIC INCREASE IN NORTHERLY WINDS TONIGHT AND
TOMORROW...WITH GUSTS LIKELY APPROACHING 60 MPH BY TOMORROW AFTERNOON
ALONG THE COAST. ACCOMPANYING THESE WINDS WILL BE A SIGNIFICANTLY
COLDER AIRMASS...WITH WIND CHILL VALUES WELL BELOW ZERO BY FRIDAY
AFTERNOON.

BERING SEA AND ALEUTIANS... HIGH PRESSURE REMAINS FIRMLY IN CONTROL
FOR THE NEXT SEVERAL DAYS...WHICH MEANS A CONTINUATION OF
UNSEASONABLY TRANQUIL WEATHER ACROSS THE BERING AND ALEUTIANS. THE
MOST ACTIVE WEATHER WILL BE FOUND OVER THE EASTERN BERING AND BRISTOL
BAY WHERE COLD AIR COMING OFF THE LAND WILL GENERATE SNOW SHOWERS AND
BLOWING SNOW ACROSS THE EASTERN ALEUTIANS ON FRIDAY AND FRIDAY NIGHT.

.LONG TERM FORECAST FROM PREVIOUS DISCUSSION...
THE EXTENDED FORECAST LOOKS TO BE DRIVEN BY THE CLOSED UPPER LOW
CURRENTLY DROPPING DOWN FROM THE ARCTIC. RIDGING WILL REMAIN OVER THE
WESTERN BERING WHILE THE REMNANTS OF THE CURRENT UPPER LOW WILL
GYRATE AROUND THE GULF. DETERMINISTIC GUIDANCE IS IN PRETTY GOOD
AGREEMENT WITH THE LONG-WAVE PATTERN WHICH WILL REMAIN CONDUCIVE FOR
BELOW NORMAL TEMPERATURES ACROSS THE MAINLAND ALONG WITH A
CONTINUATION OF DRY CONDITIONS. NORTH AMERICAN ENSEMBLE
GUIDANCE...GFS ENSEMBLES...AND EUROPEAN ENSEMBLE GUIDANCE ALL FAVOR
AN ARCTIC AIR DUMP INTO THE SOUTHWEST MAINLAND AND SUBSEQUENT
TROUGHING ALOFT...WHICH WOULD EVENTUALLY FAVOR THE RETURN OF
PRECIPITATION TO THE SOUTHCENTRAL BUT COLD AND DRY WILL PREVAIL FOR
THE TIME BEING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING 111
         WINTER WEATHER ADVISORY 125 171
MARINE...HEAVY FREEZING SPRAY 121 126 127 130 140 141 160 180 181 185
         STORM 119 120 127 130 131 138 139 180
         GALE 121 125 126 128 132 136 137 140 141 150 155 160 165 170
              171 172 173 174 175 176 179 181 185
FIRE WEATHER...RED FLAG WARNING 111 121

AMD FEB 14