Heavy Freezing Spray Warning 3, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
421 PM AKST MON JAN 18 2016

.ANALYSIS AND UPPER LEVELS...
THERE IS A LOW PRESSURE SYSTEM IN THE NORTHERN GULF WITH THE
SURFACE CENTER JUST TO THE SOUTHWEST OF MONTAGUE ISLAND. THIS
SYSTEM IS BRINGING RAIN AND SNOW TO THE SOUTH CENTRAL COAST. SOME
PRECIPITATION IS JUST BEGINNING TO WORK ITS WAY FURTHER
INLAND...BUT IN GENERAL THE INLAND AREAS REMAIN FAIRLY DRY. THERE
IS ANOTHER LOW PRESSURE SYSTEM OVER THE CENTRAL AND WESTERN
ALEUTIANS WITH THE CENTER ABOUT 100 MILES WEST OF ADAK. A DECENT
AMOUNT OF COLD AIR AND CONVECTIVE SHOWERS ARE PUSHING SOUTHWARD
ON THE BACK (WEST) SIDE OF THIS LOW. A LARGE BUT WEAK UPPER LOW IS
LOCATED WELL TO THE SOUTH OF THE ALASKA PENINSULA AND KODIAK
ISLAND. EASTERLY FLOW ALOFT CONTINUES OVER SOUTHERN ALASKA WITH
THE MAIN UPPER LOW TO THE SOUTH AND HIGH PRESSURE OVER CENTRAL
ALASKA.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT TODAY. THERE
ARE A FEW MINOR DIFFERENCES IN HOW THEY HANDLE THE LOW IN THE
GULF THIS EVENING...THEN LARGER DIFFERENCES IN HOW THEY HANDLE THE
NEXT LOW FOR TUESDAY NIGHT. FOR THE FIRST LOW THE DIFFERENCES ARE
SMALL ENOUGH TO NOT IMPACT THE FORECAST TOO MUCH. FOR THAT SECOND
LOW...THE NAM AND ECMWF ARE FASTER AND A LITTLE FURTHER SOUTH WITH
THE LOW CENTER. THE CANADIAN GEM IS FURTHER NORTH AND
SLOWER...ESPECIALLY THE REGIONAL GEM.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
BROAD OFFSHORE FLOW WITH GUSTY GAP DRIVEN WINDS CONTINUE TO
DOMINATE THE AREAS SURROUNDING THE NORTHERN GULF COAST AND PRINCE
WILLIAM SOUND...AS A WEAKENING LOW PRESSURE SYSTEM TRACKS
WESTWARD OVER THE KENAI PENINSULA TONIGHT. GUSTY WINDS WHICH HAVE
INCREASED OVER THE FAVORED AREAS TODAY (INCLUDING THE MATANUSKA
VALLEY...THOMPSON PASS...AND ALONG TURNAGAIN ARM) WILL BEGIN TO
DIMINISH AS THE SYSTEM WEAKENS AND CONTINUES TO TRACK WESTWARD
OVER THE KENAI PENINSULA TONIGHT. RAIN AND SNOW ASSOCIATED WITH
THIS SYSTEM OVER THE EASTERN KENAI PENINSULA AND AREAS AROUND
PRINCE WILLIAM SOUND WILL CONTINUE THROUGH TOMORROW MORNING...
BEFORE TAPERING OFF TOMORROW AFTERNOON. PRECIPITATION ON THE LEE
SIDE OF THE CHUGACH AND KENAI MOUNTAINS WILL REMAIN MORE SCATTERED
AND LIMITED IN PRECIPITATION AMOUNTS...AS CROSS BARRIER FLOW
INCREASES TONIGHT. IT LOOKS LIKE THE BEST CHANCE FOR ANY SHOWERS
TO SPILL-OVER WOULD BE ALONG THE WESTERN KENAI AND THE
ANCHORAGE/MATANUSKA VALLEY THIS EVENING WHILE THE DOWNSLOPING IS
WEAK. HOWEVER...LITTLE TO NO ACCUMULATION IS EXPECTED OVER THESE
AREAS.

BY TUESDAY AFTERNOON...ANOTHER LOW FOLLOWING A VERY SIMILAR TRACK
TO THE SYSTEM MENTIONED ABOVE...STARTS TO TRACK THROUGH THE
NORTHERN GULF. THIS SYSTEM LOOKS ALMOST LIKE A CARBON-COPY OF THE
SYSTEM MENTIONED ABOVE...ONLY SLIGHTLY WEAKER. THIS MEANS GUSTY
WINDS INLAND WITH MORE PRECIPITATION FOR COASTAL AREAS...AND
TEMPERATURES SHOULD REMAIN AT OR BELOW FREEZING FOR INLAND
LOCATIONS TO START THE WEEK.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...

NORTHEASTERLY FLOW WILL CONTINUE ACROSS SOUTHWEST ALASKA FOR THE
NEXT SEVERAL DAYS AS AN EXPANSIVE AREA OF LOW PRESSURE REMAINS
WELL ENTRENCHED OVER THE NORTH PACIFIC/GULF OF ALASKA. THIS WILL
LEAD TO MAINLY DRY CONDITIONS THROUGH THE FIRST HALF OF THE WEEK
WITH EXCEPTION TO TONIGHT AND TUESDAY NIGHT WHEN A SERIES OF UPPER
LEVEL DISTURBANCES PUSH ACROSS THE AREA. WHILE THE LOW LEVELS ARE
RELATIVELY DRY...THERE IS AMPLE MOISTURE ALOFT WHICH WILL BE
UTILIZED BY THE UPPER LEVEL DISTURBANCES IN THE COMING DAYS. THIS
MOISTURE WILL BLEED ACROSS THE ALASKA AND ALEUTIAN RANGES AND
ALLOW PRECIPITATION TO "SPILL OVER" THE MOUNTAINS AND SCATTERED
SNOW SHOWERS (RAIN SHOWERS SOUTH OF KING SALMON TUESDAY AFTERNOON).
TEMPERATURES THE NEXT SEVERAL NIGHTS SHOULD BE A TOUCH COOLER THAN
THOSE OBSERVED LAST NIGHT WITH GENERALLY LESS CLOUD COVER.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

THE BERING SEA WILL REMAIN UNDER NORTHEASTERLY FLOW WHICH SHOULD
ALLOW THE SHOWERY WEATHER REGIME TO CONTINUE. SHOWERS WILL BE
QUITE SCATTERED AS THEY WILL LARGELY BE REGULATED BY FRAGMENTS OF
UPPER LEVEL ENERGY TRAVERSING THE UPPER LEVEL LONGWAVE PATTERN.
THE NORTHEASTERLY FLOW WILL BRING COOLER TEMPERATURES TO THE
BERING SEA OVER THE NEXT SEVERAL DAYS WITH SNOW BEING THE MAIN
PRECIPITATION TYPE...EXCEPT OVER THE EASTERN ALEUTIANS AND ALASKA
PENINSULA WHERE RAIN WILL BE MORE LIKELY TONIGHT AND TUESDAY
MORNING BEFORE ENOUGH COLD AIR MODIFIES THE AIR MASS TO SUPPORT
SNOW. THE AREA OF LOW PRESSURE JUST TO THE NORTHWEST OF ADAK WILL
CONTINUE TO DROP SOUTH INTO THE NORTH PACIFIC TONIGHT AND A SMALL
SWATH OF GALE FORCE WINDS WILL BE OBSERVED IN CLOSE PROXIMITY TO
THE LOW CENTER. FOLLOWING THIS LOW...A RELATIVELY QUIET PERIOD OF
WEATHER WILL BE OBSERVED THROUGH WEDNESDAY MORNING.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

A QUIET WEATHER PATTERN WILL BE IN PLACE OVER THE REGION WEDNESDAY
INTO WEDNESDAY NIGHT...THEN BEGIN TO BECOME INFLUENCED BY TWO LOW
PRESSURE SYSTEMS. THE FIRST ONE WILL BE FROM THE NORTHEAST
PACIFIC THAT MOVES TOWARD THE GULF OF ALASKA THURSDAY AND SLOWLY
WEAKENS FRIDAY INTO EARLY SATURDAY BEFORE DISSIPATING. IT WILL
BECOME ABSORBED INTO THE BROAD CYCLONIC CIRCULATION FROM THE
OTHER LOW WHICH MOVES SLOWLY EAST ALONG THE ALEUTIAN CHAIN FROM
THURSDAY THROUGH SATURDAY. MODELS THEN SUGGEST ONE OR TWO
STRENGTHENING TRIPLE POINT LOWS MAY DEVELOP OVER THE NORTHEAST
PACIFIC AND MOVE NORTH TOWARD SOUTHERN ALASKA AND/OR THE SOUTHEAST
BERING SUNDAY THROUGH MONDAY...BUT CONFIDENCE IN THIS IS FAIRLY
LOW AT THIS TIME.

THE MAIN IMPACTS WITH THIS PATTERN WILL BE A FAIRLY QUIET WEATHER
REGIME FOR MUCH OF THE REGION THE LATER PART OF THIS WEEK INTO
THE WEEKEND. THERE WILL BE LITTLE SIGNIFICANT CHANGE IN
TEMPERATURES...WITH NEAR NORMAL TO SLIGHTLY ABOVE NORMAL
TEMPERATURES OVER MUCH OF THE REGION...AND PRECIPITATION CHANCES
REMAINING NEAR NORMAL TO ABOVE NORMAL. STRONGER WINDS TO GALE-
FORCE WILL BE CONFINED TO STRONGER EMBEDDED LOWS WITHIN THE BROAD
CYCLONIC PATTERN.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119 120.
		 HEAVY FREEZING SPRAY 160 180-185.

&&

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