Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 031227
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
427 AM AKDT MON AUG 3 2015

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL RIDGE OVER THE WESTERN BERING SEA HAS PINCHED OFF
INTO A HIGH CENTERED NEAR THE FAR EASTERN RUSSIA/NORTHWEST BERING
SEA COASTLINE...WITH ASSOCIATED RIDGING EXTENDING EAST INTO THE
INTERIOR OF THE WESTERN ALASKA MAINLAND. THE CLOCKWISE FLOW AROUND
THIS RIDGE PERSISTS OVER THE SOUTHERN MAINLAND...WITH CYCLONIC
COUNTER-CLOCKWISE FLOW BECOMING THE RULE OVER THE CENTRAL AND
EASTERN BERING AROUND AN ORGANIZED LOW CENTERED ABOUT 200 MILES
SOUTH OF THE SOUTHERN ALASKA PENINSULA.

&&

.MODEL DISCUSSION...
MODELS CONTINUE TO DO WELL WITH THE SYNOPTIC PATTERN THROUGH EARLY
THIS WEEK. THE DISCREPANCY IN POSITION AND MOVEMENT OF THE LOW
SOUTH OF THE ALASKA PENINSULA AND MOVING TOWARD THE SOUTHERN GULF
HAS LARGELY BEEN RESOLVED. HOWEVER...SIGNIFICANT DISCREPANCIES
BEGIN TO ARISE MID-WEEK AS THE GFS AND NAM ESPECIALLY ARE NOW
DEPICTING AN UPPER LEVEL LOW DROPPING SOUTH FROM THE ARCTIC
SOUTH TO THE WEST OF THE ALASKA RANGE TOWARD THE WESTERN GULF TO
MERGE WITH THE CURRENT LOW SOUTH OF THE ALASKA PENINSULA.

SUCH A SOLUTION AS DEPICTED BY THE GFS AND NAM WOULD SUGGEST THE
NEED FOR MUCH HIGHER PRECIPITATION POTENTIAL ALONG THE ALASKA
RANGE TUESDAY INTO WEDNESDAY AND FOR INLAND AREAS OF SOUTHCENTRAL
ESPECIALLY WEDNESDAY AND THURSDAY. THIS MORNING`S FORECAST PACKAGE
BEGINS TO GIVE SOME CREDENCE TO THESE NEW SOLUTIONS...WHILE ALSO
ALLOWING MORE TIME FOR MODEL DISCREPANCIES TO WORK THEMSELVES OUT.

IT IS IMPORTANT TO NOTE THAT THE EUROPEAN MODEL...A VERY GOOD
MODEL...KEEPS THE TROUGH/LOW TO THE NORTH OVER THE INTERIOR ALONG
WITH THE HIGHER PRECIPITATION CHANCES MID-WEEK.

&&

.FIRE WEATHER...

THE SHORTWAVES OVER SOUTHCENTRAL HAVE ASSISTED IN KEEPING THE
HUMIDITY FAIRLY HIGH IN SPITE OF WARM TEMPERATURES. THIS WILL
REMAIN THE SITUATION WHERE THERE WILL BE A GOOD STRETCH OF WARM
TEMPERATURES THROUGH THE FIRST HALF OF THE WEEK OVER SOUTHCENTRAL.
HOWEVER THE DEWPOINTS WILL REMAIN FAIRLY HIGH OVER THE REGION
WHICH WILL PREVENT THE MINIMUM RELATIVE HUMIDITY TO DROP TOO LOW.
IN ADDITION THE OVERNIGHT RECOVERY WILL REMAIN EXCELLENT WITH THE
LONGER NIGHTS IN AUGUST AS COMPARED WITH THE WARM STRETCHES THAT
OCCURRED IN JUNE.

IN SOUTHWEST ALASKA PLENTY OF MOIST MARINE AIR WILL KEEP RELATIVE
HUMIDITY VALUES ON THE HIGH SIDE SO NO REAL FIRE WEATHER CONCERNS
WEST OF THE ALASKA RANGE.

FOR MID-WEEK...IF THE GFS SOLUTION PANS OUT VERY WARM TEMPERATURES
MAY COINCIDE WITH DRY CONDITIONS WEDNESDAY IN THE COPPER RIVER
BASIN...POSSIBLY RESULTING IN MINIMUM AFTERNOON HUMIDITY VALUES
DROPPING INTO THE MID-20S ALONG WITH THE DEVELOPMENT OF A SOUTH
BREEZE OF 10 TO 15 MPH. THIS WOULD CAUSE SOME FIRE WEATHER
CONCERNS IF IT PANS OUT...BUT FOR RIGHT NOW IS CONSIDERED A LOW-
CONFIDENCE SOLUTION AT THIS TIME.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE RIDGE OF HIGH PRESSURE CENTERED OVER SOUTHWEST ALASKA WILL
DRIFT EAST THROUGH TUESDAY NIGHT. THE RIDGE WILL BE CENTERED OVER
SOUTH CENTRAL ALASKA LATE TONIGHT AND THEN SLIDE INTO CANADA LATER
TUESDAY. THE LOW SOUTH OF THE ALASKA PENINSULA WILL MOVE NORTHEAST
TO JUST SOUTH OF KODIAK ISLAND BY LATE TUESDAY NIGHT. CONDITIONS
WILL REMAIN DRY ACROSS THE MAINLAND INTO TUESDAY AFTERNOON AS THE
RIDGE SUPPRESSES ALL SHOWER ACTIVITY. AS THE RIDGE SLIDES EAST
LATER TUESDAY SOME SHOWERS COULD POP UP OVER THE MOUNTAINS
SURROUNDING THE SUSITNA RIVER VALLEY. A THUNDERSTORM OR TWO IS
EVEN POSSIBLE OVER THE TALKEETNA MOUNTAINS. A FRONT ASSOCIATED
WITH THE LOW MENTIONED ABOVE WILL BRING THE LIKELIHOOD OF RAIN
INTO KODIAK ISLAND ON TUESDAY...WITH SHOWERS EXPECTED TUESDAY
NIGHT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE WARMING AND DRYING TREND OVER THE SOUTHWEST MAINLAND WILL
CONTINUE AS HIGH PRESSURE ALOFT CONTINUES TO BUILD IN OVER THE
SOUTHWEST MAINLAND...AND OFFSHORE FLOW GRADUALLY INCREASES THROUGH
TUESDAY. PORTIONS OF THE ALASKA PENINSULA WILL BE THE EXCEPTION
TO THE DRYING TREND TONIGHT INTO TUESDAY...WHERE RAIN CHANCES
WILL INCREASE IN ASSOCIATION WITH A SLOW MOVING PACIFIC LOW
TRACKING TOWARD KODIAK ISLAND. ENOUGH INSTABILITY WILL BUILD
TUESDAY AFTERNOON AND EVENING FOR A SLIGHT CHANCE OF ISOLATED
THUNDERSTORMS ALONG AND NEAR THE ALASKA RANGE...BUT THE REMAINDER
OF THE REGION WILL REMAIN STABLE AND DRY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
HIGH PRESSURE OVER THE BERING SEA WILL KEEP MARINE STRATUS AND
AREAS OF PATCHY FOG OVER THE ENTIRE BERING AND ALEUTIAN CHAIN
THROUGH THE PERIOD. A SLOW MOVING NORTH PACIFIC LOW WILL CONTINUE
TO BRING LIGHT RAIN TO THE EASTERN ALEUTIANS THROUGH TUESDAY
MORNING...AS WELL AS GALE FORCE EASTERLY WINDS. WINDS WILL SHIFT
TO NORTHERLY OVER THE EASTERN ALEUTIANS TUESDAY AFTERNOON AS THE
LOW TRACKS INTO THE SOUTHWEST GULF...KEEPING GUSTY GAP WINDS OVER
THE EASTERN ALEUTIANS THROUGH WEDNESDAY. FURTHER WEST...A STALLED
FRONT OVER THE WESTERN ALEUTIANS WILL CONTINUE TO PRODUCE GUSTY
WINDS OVER THE AREA THROUGH WEDNESDAY.

&&

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

TUESDAY NIGHT A STACKED LOW PRESSURE SYSTEM WILL BE TRACKING EAST
FROM NEAR SAND POINT TO THE SOUTHERN GULF THROUGH THE END OF THE
WEEK. GUSTY SMALL CRAFT WINDS AND RAIN ARE EXPECTED AROUND THE CORE
OF THE LOW AS IT MAINTAINS STRENGTH ON ITS PATH TO THE EASTERN
GULF. ALSO...GUSTY GRADIENT WINDS INCREASE ACROSS THE COPPER
RIVER VALLEY AND THROUGH CHANNELED TERRAIN OF TURNAGAIN ARM ON
WEDNESDAY INTO THURSDAY AS THE GULF LOW TIGHTENS THE SURFACE
GRADIENT ALONG THE COAST. OTHERWISE...DRY CONDITIONS ARE EXPECTED
ACROSS THE SOUTHERN MAINLAND AND THE BERING WHILE UNDER THE
INFLUENCE OF RIDGING.

FOR THE SECOND HALF OF THE WORK WEEK...TWO UPPER LEVEL LOWS MOVE
ACTIVE WEATHER TOWARD THE FORECAST AREA WITH A PROGRESSIVE WEATHER
PATTERN PERSISTING INTO THE WEEKEND. THE FIRST SYSTEM THAT DRIVES
WEATHER TO THE SOUTHERN MAINLAND...DIGS FROM THE NORTHWEST ON WEDNESDAY
NIGHT. THE SOUTHWARD EXTENT OF THIS SYSTEM REMAINS UNRESOLVED...BUT
IT BRINGS THE NEXT POTENTIAL FOR RAIN ALONG THE ALASKA RANGE AND
SOUTHCENTRAL ON THURSDAY. THE OTHER SYSTEM MOVES UP FROM THE
NORTH PACIFIC TO THE WESTERN ALEUTIANS WEDNESDAY NIGHT INTO
THURSDAY MORNING. THIS STORM SYSTEM IS EXPECTED TO BRING A FRONT
WITH POSSIBLE GALE FORCE WINDS AND RAIN. THE FRONT PUSHES INTO THE
CENTRAL BERING AND EASTERN ALEUTIANS BY FRIDAY. THIS SYSTEM IS
PROJECTED TO PICK UP ITS PACE INTO SATURDAY WITH THE FRONT
SPREADING RAIN INTO THE SOUTHWEST. MODELS ARE NOT IN GOOD
AGREEMENT ON BOTH OF THESE NEXT SYSTEMS...THEREFORE A CONSERVATIVE
BLEND OF THE EC AND GFS WAS UTILIZED TO UPDATE THE LONG RANGE
FORECAST.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES...155.
FIRE WEATHER...NONE.

&&

$$

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



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