Heavy Freezing Spray Warning 47, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
422 PM AKDT SAT MAR 19 2016

.ANALYSIS AND UPPER LEVELS...
THE MAIN DRIVER TODAY IS THE UPPER LEVEL LOW THAT IS DROPPING FROM
THE INTERIOR TO SOUTHWEST ALASKA WHILE A WEAK SURFACE LOW HAS
FORMED IN PRINCE WILLIAM AND IS BACKING TOWARD COOK INLET. THE
JET IS ORIENTED FROM THE SOUTH SOUTHWEST TO NORTH NORTHEAST FROM
THE NORTH PACIFIC INTO PRINCE WILLIAM SOUND. THE LOW LEVEL FLOW IS
FROM THE SOUTH SOUTHEAST INTO PRINCE WILLIAM SOUND PUSHING IN WARM
AIR. A STATIONARY FRONT STRETCHES FROM THE PRINCE WILLIAM SOUND
LOW TO SOUTH OF KODIAK ISLAND TO A LOW OVER THE CENTRAL ALEUTIANS.
A LARGE VERTICALLY STACKED NEARLY STATIONARY LOW IS ABOUT 700 MILE
SOUTH OF KODIAK ISLAND

PRECIPITATION ASSOCIATED WITH THE LOW IN PRINCE WILLIAM SOUND IS
EVIDENT ON THE RADAR ACROSS THE SOUND AND HAS SPREAD ACROSS THE
CHUGACH MOUNTAINS TO THE ANCHORAGE AREA NORTH INTO THE SUSITNA
VALLEY AND COPER RIVER BASIN.

NORTHEAST OFFSHORE FLOW IS PREVAILING OVER THE SOUTHWEST MAINLAND
KEEPING CONDITIONS SUNNY AND DRY.

&&

.MODEL DISCUSSION...
OVERALL THE MODELS ARE IN GOOD SYNOPTIC LEVEL AGREEMENT. THE
ISSUES ARISE IN THE DETAILS. THE NAM AND CANADIAN ARE SLOWER TO
PUSH THE RAIN/SNOW LINE NORTH AND WEST AND DO NOT PUSH IT THROUGH
THE NORTHERN COOK INLET AND PALMER WASILLA AREA UNTIL TOMORROW
MORNING. HOWEVER THE MODELS ARE IN GOOD AGREEMENT WITH THE ONSET
OF THE STRONGER CROSS BARRIER DOWNSLOPE FLOW IN THE ANCHORAGE AREA
BY THIS EVENING. MODEL QPF VARIES CONSIDERABLY WITH THE HIGHER
RESOLUTION MODELS OF COURSE RESOLVING THIS WITH MORE DETAILS. THE
NAM WAS USED FOR THE FORECAST PACKAGE AS IT SEEMS TO BE BEST
CAPTURING THE DYNAMICS AND MESOSCALE COMPONENTS OF THE SYSTEM.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE HEAVY BANDED SNOWFALL WHICH SAT OVER THE ANCHORAGE AND
MATANUSKA VALLEY FOR MUCH OF THE DAY WILL SHIFT INTO THE SOUTHERN
SUSITNA VALLEY LATE THIS AFTERNOON THROUGH THIS EVENING THEN
SETTLE ALONG THE ALASKA RANGE LATER TONIGHT. THESE BANDS ARE
ASSOCIATED WITH STRONG ISENTROPIC LIFT WITH MUCH WARMER AIR FROM
THE GULF OF ALASKA RIDING UP AND OVER A DEEP ARCTIC AIR MASS OVER
SOUTHCENTRAL. ALSO OF NOTE...THE LOW LEVEL TEMPERATURES ARE IDEA
FOR DENDRITIC SNOW GROWTH WHICH IS LEADING TO LARGE SNOWFLAKES
AND SIGNIFICANT ACCUMULATION OF DRY SNOW. THE ANCHORAGE FORECAST
OFFICE MEASURED A 30 TO 1 RATIO OF SNOW TO LIQUID.

BACK BEHIND THESE FRONT BANDS OF SNOW IS THE WARM FRONT AND WARM
SECTOR PRECIP WHICH HAS BEEN SITTING OVER PRINCE WILLIAM SOUND.
AS AN UPPER LEVEL LOW OVER INTERIOR SOUTHWEST ALASKA CONTINUES TO
DROP SOUTHWESTWARD THIS PRECIP WILL BE ADVECTED NORTHWESTWARD
ACROSS THE KENAI PENINSULA...ANCHORAGE...AND THE MAT VALLEY
BRINGING ANOTHER ROUND OF SNOW THIS EVENING. TEMPERATURES WILL
GRADUALLY WARM LEADING TO SMALLER SNOWFLAKES. MORE IMPORTANTLY...
LOW LEVEL SOUTHEAST WINDS WILL INCREASE BY LATE THIS EVENING
LEADING TO DOWNSLOPE DRYING...BRINGING AN END TO THE SNOWFALL IN
THE LEE OF THE CHUGACH AND KENAI MOUNTAINS. MUCH WARMER AIR WILL
CONTINUE TO ADVECT NORTH AND WEST ACROSS THE REGION CHANGING ANY
REMAINING PRECIP TO RAIN ON SUNDAY.

A SERIES OF UPPER LEVEL WAVES WILL TRAVERSE THE REGION
SUNDAY...BUT WITH THE DEEP SOUTHEAST FLOW MOST OF THE PRECIP WILL
GET HUNG UP ALONG THE COAST OR UPSLOPE OF THE ALASKA RANGE. EXPECT
DRYING CONDITIONS OVER ALL OF SOUTHCENTRAL BY MONDAY AS AN UPPER
RIDGE BUILDS OVERHEAD. ACTIVE WEATHER WILL BE CONFINED TO THE
GULF AND KODIAK ISLAND AS THE UPPER LEVEL LOW SETTLES IN SOUTH OF
THE ALASKA PENINSULA. TEMPERATURES WILL REMAIN ON THE WARM
SIDE...WITH WIDESPREAD TEMPS IN THE 40S LIKELY...THOUGH THE NEW
SNOW COVER MAY HELP MODERATE THESE A BIT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
TEMPERATURES WILL CONTINUE TO BE ON A DOWNWARD TREND THIS EVENING
AS A COLD UPPER LEVEL LOW MOVES ACROSS THE SOUTHWEST MAINLAND. 850
MB TEMPERATURES HAVE ALREADY DROPPED NEARLY 5 DEGREES ACCORDING TO
THE PABE RAOB SOUNDINGS BETWEEN 12Z AND 00Z. THIS COLD AIR MASS
WILL OVERSPREAD SOUTHWEST ALASKA AND LEAD TO SOME OF THE COLDEST
TEMPERATURES OBSERVED IN QUITE SOME TIME. TEMPERATURES WILL BE 10
TO 15 DEGREES BELOW NORMAL TONIGHT BUT WILL BE SHORT LIVED AS AN
INVERTED TROUGH NOSES ACROSS SOUTHWEST ALASKA ON SUNDAY. WIND
CHILLS TONIGHT ACROSS THE KUSKOKWIM DELTA WILL RANGE FROM 15 BELOW
TO 25 BELOW AS A PERSISTENT NORTHERLY WIND OF 15 TO 25 MPH
GRADUALLY DIMINISHES OVERNIGHT. PRIOR TO THE WARM UP...THE
INVERTED SURFACE TROUGH WILL PUSH A FRONT ACROSS THE SOUTHWEST
MAINLAND WHICH WILL HELP GENERATE SNOW SHOWERS ACROSS THE BRISTOL
BAY AREA AND LOWER KUSKOKWIM VALLEY ON SUNDAY. SNOW ACCUMULATION
OF 3 TO 5 INCHES WILL BE SEEN EAST OF KING SALMON STARTING TONIGHT
AND LASTING THROUGH SUNDAY WHILE THE REST OF THE BRISTOL BAY AREA
AND LOWER KUSKOKWIM VALLEY SEEING AN INCH OR LESS OF ACCUMULATION.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A WEAK SURFACE TROUGH SOUTH OF ADAK WILL BRING SOME SNOW SHOWERS
TO THE CENTRAL ALEUTAINS THIS EVENING BEFORE DIVING SOUTH INTO THE
NORTH PACIFIC. HIGH PRESSURE QUICKLY BUILDS ACROSS THE WESTERN
HALF OF THE BERING SEA STARTING TONIGHT AND PERSISTS THROUGH
TUESDAY. SHOWER ACTIVITY WILL GRADUALLY INCREASE THROUGH SUNDAY
NIGHT ACROSS THE EASTERN HALF OF THE BERING SEA AS STRONG COLD AIR
ADVECTION (ASSOCIATED WITH THE UPPER LOW CURRENTLY OVER THE
SOUTHWEST MAINLAND) INCREASED LOW AND MID-LEVEL INSTABILITY. THE
BERING SIDE OF THE ALASKA PENINSULA WILL SEE MORE NUMEROUS SHOWERS
AS THE MOISTURE AND SHOWERS UPSLOPE ALONG THE MOUNTAINOUS TERRAIN.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
WET AND WARM WEATHER WILL CONTINUE ALONG THE GULF COAST INTO THE
MIDDLE OF NEXT WEEK AS AN UPPER LEVEL TROUGH CENTERED OVER THE
EASTERN BERING/ALEUTIANS BRINGS A SERIES OF NORTH PACIFIC LOWS
INTO THE GULF THROUGH WEDNESDAY. THESE SYSTEMS WILL HOWEVER
PRIMARILY IMPACT COASTAL AREAS AS RIDGING OVER THE INTERIOR WILL
HELP BRING MOSTLY CLOUDY SKIES...BUT OTHERWISE DRY CONDITIONS TO
MUCH OF SOUTHCENTRAL. THE BERING SEA ON THE OTHER HAND WILL ONCE
AGAIN BE UNDER PREVAILING NORTHWESTERLY FLOW AND COLD AIR
ADVECTION SHOWERS THROUGH MID WEEK. BY LATE NEXT WEEK MODEL
AGREEMENT BEGINS TO BREAK DOWN WITH THE EXACT DETAILS OF
INDIVIDUAL SYSTEMS...HOWEVER THEY ARE IN GENERALLY GOOD AGREEMENT
SYNOPTICALLY THAT AN UPPER LEVEL TROUGH WILL SET UP OVER THE
BERING WITH RIDGING OVER THE PANHANDLE. THIS IS A SIMILAR SYNOPTIC
PATTERN THAT THE STATE HAS BEEN UNDER FOR MUCH OF THE WINTER...SO
MOST AREAS SHOULD EXPECT ABOVE NORMAL TEMPERATURES WITH THE BEST
PRECIPITATION CHANCES EXPECTED FOR THE GULF COAST.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...SNOW ADVISORY 101 111 145.
MARINE...GALE WARNING 119 180.
 HEAVY FRZ SPRAY 160 179 180 185.

&&

SYNOPSIS AND MODEL DISCUSSION...SA
SOUTHCENTRAL ALASKA...SB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...DEK

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1032 PM AKDT SAT MAR 19 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0945 PM     SNOW             7 SE EAGLE RIVER        61.25N 149.42W
03/19/2016  M11.6 INCH                          AK   NWS EMPLOYEE

            NEW SNOWFALL THROUGH 945PM. STILL SNOWING LIGHTLY.

1000 PM     SNOW             6 SW ANCHORAGE          61.16N 149.99W
03/19/2016  M6.1 INCH                           AK   OFFICIAL NWS OBS

            OFFICIAL NWS OB - 6.1 INCHES MEASURED AT THE NWS OFFICE
            ON SAND LAKE RD. STILL SNOWING VERY LIGHTLY.

1023 PM     SNOW             SUTTON                  61.72N 148.88W
03/19/2016  M11.0 INCH                          AK   TRAINED SPOTTER

            MEASURED ON THE GLENN HIGHWAY NEXT TO THE ALPINE
            HISTORICAL PARK IN SUTTON. BEGAN SNOWING FRI NIGHT AND
            STILL SNOWING LIGHTLY AS OF SAT NIGHT.

&&

RDUELL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1102 PM AKDT SAT MAR 19 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1056 PM     SNOW             2 SE ANCHORAGE          61.19N 149.83W
03/19/2016  M8.0 INCH                           AK   PUBLIC

&&

RDUELL

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ANCHORAGE AK
1206 AM AKDT SUN MAR 20 2016

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

1203 AM     SNOW             SOLDOTNA                60.49N 151.06W
03/20/2016  E3.0 INCH                           AK   LAW ENFORCEMENT

1203 AM     SNOW             SEWARD                  60.11N 149.39W
03/20/2016  E4.0 INCH                           AK   LAW ENFORCEMENT

1203 AM     SNOW             HOMER                   59.64N 151.52W
03/20/2016  E0.3 INCH                           AK   LAW ENFORCEMENT

1203 AM     SNOW             VALDEZ                  61.08N 146.30W
03/20/2016  E36.0 INCH                          AK   LAW ENFORCEMENT

1203 AM     SNOW             PALMER                  61.60N 149.11W
03/20/2016  E9.0 INCH                           AK   LAW ENFORCEMENT

1203 AM     SNOW             WASILLA                 61.58N 149.46W
03/20/2016  E8.0 INCH                           AK   LAW ENFORCEMENT

&&

RDUELL