Brisk Wind Advisory 23, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
530 AM AKDT MON MAR 16 2015

.ANALYSIS AND UPPER LEVELS...

AN ACTIVE WEATHER PATTERN CONTINUES OVER SOUTHWEST AND SOUTH
CENTRAL ALASKA AS WE MOVE INTO THE FIRST HALF OF THE WEEK. THE
CORE OF A RATHER STRONG SEVERAL THOUSAND MILE LONG JET STREAM
REMAINS CENTERED BETWEEN 35N AND 40N WELL SOUTH OF THE ALEUTIANS
AND ALASKA PENINSULA. BITS OF ENERGY AND EDDIES PERIODICALLY
BREAK OFF OF THE DOWNSTREAM END OF THIS LARGE JET AND AND ARE
PULLED NORTH TOWARDS THE GULF OF ALASKA AND BERING BY THE LARGE
VERTICALLY STACK LOW CENTERED NEAR DUTCH HARBOR...EACH WAVE
BRINGING ANOTHER ROUND OF STORMY WEATHER.

CURRENTLY A FRONTAL SYSTEM STRETCHES ACROSS THE CENTRAL GULF OVER
THE KENAI PENINSULA AND PRINCE WILLIAM SOUND. A WAVE DEVELOPING
ALONG THE FRONT AT 55N 148W UNDER THE LEFT EXIT OF A SMALL JET
PUSHING INTO THE GULF OF ALASKA WILL CONTINUE TO LIFT NORTH TODAY
FURTHER STRENGTHENING THE FRONTAL SYSTEM AND TIGHTENING THE
SURFACE PRESSURE GRADIENT ACROSS THE NORTHERN GULF. A BIT FURTHER
TO THE WEST ANOTHER SHORTWAVE WITH ACCOMPANYING SOUTHERLY 500 MB
JET SUPPORT WILL LIFT NORTH TOWARD THE WESTERN ALASKA PENINSULA
TODAY AND TONIGHT.

&&

.MODEL DISCUSSION...

WHILE MODELS CONTINUE TO INITIALIZE SIMILARLY...THE VERY STRONG
JET STREAM AND THE LARGE ARRAY OF SMALL BUT FAST MOVING
FEATURES ARE ALLOWING SIGNIFICANT DIFFERENCES IN THE TIMING AND
TRACK OF INDIVIDUAL WAVES AND LOW PRESSURE SYSTEMS TO RAPIDLY
CREEP INTO THE VARIOUS MODEL SOLUTIONS FROM TUESDAY ONWARD.
CONFIDENCE IS HIGH THAT WE WILL REMAIN IN AN ACTIVE WEATHER
PATTERN WITH SOUTH TO SOUTHEAST FLOW BRINGING A WARMING TREND AS
WELL AS PERIODIC WET AND WINDY FRONTAL SYSTEMS LIFTING NORTH ACROSS
THE AREA. HOWEVER CONFIDENCE IN THE SPECIFIC TIMING AND DETAILS OF
EACH SYSTEM REMAINS RATHER LOW...ESPECIALLY FROM MIDWEEK ONWARD.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
AN UPPER LEVEL FRONT WILL SWEEP THROUGH SOUTH CENTRAL ALASKA
TODAY. THIS WILL BRING INCREASED CHANCES OF PRECIPITATION AND MUCH
WARMER TEMPERATURES. PRECIPITATION TYPE IS A DIFFICULT FORECAST
ISSUE IN THE TRANSITION FROM ARCTIC AIR TO A MORE "MARINE"
ENVIRONMENT. GENERALLY EXPECTING A MIX OF SNOW AND RAIN FOR INLAND
AREAS WITH MAINLY RAIN NEAR THE COAST. CONDITIONS WILL DRY OUT
LATE TONIGHT AND TUESDAY WHEN THE UPPER FRONT PUSHES INLAND AND
HIGH PRESSURE MOVES IN. ANOTHER LOW WILL ENTER THE GULF FROM THE
SOUTHEAST LATE TUESDAY AND LIKELY REACH THE GULF COAST AND KODIAK
TUESDAY NIGHT. THE NUMERICAL MODELS ARE IN FAIRLY POOR AGREEMENT
ON TIMING AND LOCATION OF THIS LOW...SO CONFIDENCE IN THIS PORTION
OF THE FORECAST IS RATHER LOW.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A SHORTWAVE MOVING OVER THE SOUTHWEST MAINLAND WILL BRING SNOWFALL
FROM NORTHERN BRISTOL BAY INTO THE KUSKOKWIM VALLEY THROUGH THIS
AFTERNOON. ANOTHER SHORTWAVE WILL THEN QUICKLY MOVE IN THIS
EVENING...BRINGING A SECOND ROUND OF SNOWFALL FROM WESTERN
BRISTOL BAY INTO THE KUSKOKWIM DELTA INTO TUESDAY. WINDS ALONG
COASTAL BRISTOL BAY WILL INCREASE TONIGHT AS ANOTHER LOW
APPROACHES THE AKPEN...BUT WIDESPREAD AREAS OF BLOWING SNOW
SHOULD NOT BE A PROBLEM AS WARM AIR ADVECTION WILL WARM MOST
AREAS RECEIVING SNOWFALL TO AROUND 30 DEGREES BY TUESDAY MORNING.
THESE WINDS ARE THEN EXPECTED TO DECREASE AGAIN LATE TUESDAY AS
CLEARING SKIES RETURN TO THE AREA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE FOCUS OVER THE BERING SEA CONTINUES TO CENTER AROUND THE
COMPLEX LOW CENTERED NEAR DUTCH HARBOR. WINDS AND SHOWERS IN THE
AREA WILL DIMINISH THROUGHOUT THE DAY TODAY...BUT ANOTHER LOW
CURRENTLY DEVELOPING TO THE SOUTH WILL BRING ACTIVE WEATHER BACK
TO THE AREA FOR THIS EVENING AND TUESDAY. THIS NEXT LOW WILL BRING
RAIN AND STRONG SOUTHERLY WINDS TO THE AKPEN BEGINNING THIS
EVENING...AND THEN HAS THE POTENTIAL TO BRING BLIZZARD CONDITIONS
BACK INTO THE PRIBILOF ISLANDS AS THE LOW MOVES INTO THE BERING ON
TUESDAY MORNING. AS A RESULT A BLIZZARD WATCH HAS BEEN ISSUED FOR
THE PRIBILOF ISLANDS. THE LIMITING FACTOR TO THIS BLIZZARD MAY BY
WITH HOW MUCH WARM AIR REACHES THE ISLANDS AS TEMPERATURES WILL BE
RISING BACK INTO UPPER 20S...BUT SNOWFALL RATES FROM THIS SYSTEM
LOOK TO BE ENOUGH TO AT LEAST BRING BRIEF PERIODS OF WHITE-OUT
CONDITIONS WITH STRONG NORTHEASTERLY WINDS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
MODELS ARE IN AGREEMENT THAT A BROADLY CYCLONIC JET WILL CURVE
THOUGH THE NORTH PACIFIC BETWEEN 30N AND 40N THIS WEEK. IT WILL
ALLOW AN UPPER LOW TO MOVE JUST SOUTH OF THE AKPEN AND REMAIN
ESSENTIALLY STATIONARY...WITH WAVES MOVING AROUND THE LOW AND
AFFECTING THE EASTERN GULF OF ALASKA. BEYOND THIS SYNOPTIC
PICTURE HOWEVER...THE MODELS RAPIDLY FALL INTO DISARRAY CONCERNING
THE ASSOCIATED SURFACE FEATURES...LOWERING FORECAST CONFIDENCE
UNTIL STEADIER MODEL TRENDS ARE PRODUCED.

THE WPC SOLUTION HEAVILY INCORPORATED THE EC ENSEMBLE WITH
SEVERAL OTHER COMPONENTS. THIS CONSOLIDATES A SURFACE LOW SOUTH OF
THE AKPEN TUE NIGHT THAT MOVES OVER THE EASTERN ALEUTIANS BY
THU..AND THEN DISSIPATES OVER THE EASTERN BERING ON SAT. LOWS AND
ASSOCIATED FRONTS MOVING AROUND THE UPPER LOW REACH THE NORTH GULF
COAST THU AND SAT. THE FORECAST MAINLY UTILIZED WPC IN THE LONG
TERM DUE TO THE STRUGGLING DETERMINISTIC MODELS...BUT ALSO
ENHANCED THE WIND FIELD AND OTHER FEATURES USING THE OPERATIONAL
EC, WHICH OFTEN RESEMBLED WPC GUIDANCE.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FOR SNOW 145. BLIZZARD WATCH 195.
MARINE...STORMS 119. GALES 120 125 129 130 131 132 139 150 155 165
170 173 174 175 176 177 179 180 351 412 413 414. HEAVY FREEZING
SPRAY 140 179 185 412 414.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...JR
SOUTHCENTRAL ALASKA...BL
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...TP

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE ANCHORAGE AK
221 PM AKDT MON MAR 16 2015

AKZ101-111-171030-
ANCHORAGE-MATANUSKA VALLEY-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA...PALMER...WASILLA...SUTTON...CHICKALOON
221 PM AKDT MON MAR 16 2015

...LOCALLY STRONG WINDS AND BLOWING DUST FROM ANCHORAGE TO THE
MATANUSKA VALLEY...

A POTENT STORM TRACKING UP COOK INLET IS PRODUCING LOCALLY STRONG
WIND GUSTS OF 25 TO 40 MPH FROM ANCHORAGE TO THE MATANUSKA VALLEY.
THE STRONGEST WINDS ARE BEING OBSERVED ALONG THE GLENN HIGHWAY
NORTH OF ANCHORAGE ON UP TO PALMER AND WASILLA. WITH LITTLE OR NO
SNOW ON THE GROUND DUST IS BEING BLOWN AROUND AND REDUCING
VISIBILITIES IN SOME AREAS. THE WORST CONDITIONS ARE ALONG THE
GLENN HIGHWAY NEAR THE KNIK RIVER WHERE VISIBILITIES ARE LESS
THAN 1 MILE. MEANWHILE...SNOW IS FALLING ALONG THE UPPER HILLSIDE
OF ANCHORAGE AND ALONG HIGHER ELEVATIONS OF THE CHUGACH MOUNTAINS
RESULTING IS SIMILARLY REDUCED VISIBILITIES. THESE CONDITIONS WILL
PERSIST THROUGH THE EVENING HOURS.

DRIVERS ON AREA ROADWAYS SHOULD EXERCISE CAUTION. STRONG GUSTY
WINDS CAN CAUSE A SUDDEN MOVEMENT OF VEHICLES. BLOWING DUST AT
LOWER ELEVATIONS AND BLOWING SNOW AT HIGHER ELEVATIONS WILL
PRODUCE LOCALIZED LOW VISIBILITIES.