Home > Products > Valid Products > AFD

000
FXAK68 PAFC 011226
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
426 AM AKDT SAT AUG 1 2015

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL RIDGING CONTINUES TO BUILD FROM THE SOUTHWESTERN
BERING NORTHEAST INTO THE SOUTHERN INTERIOR OF THE ALASKA
MAINLAND...WITH A NARROW YET WEAK UPPER LEVEL TROUGH SITUATED FROM
AN UPPER LEVEL LOW CENTER NEAR YAKUTAT WEST-SOUTHWEST THROUGH THE
SOUTHERN GULF TO JUST SOUTH OF THE ALASKA PENINSULA AND EASTERN
ALEUTIANS. BETWEEN THE RIDGE TO THE NORTH AND THE TROUGH TO THE
SOUTH...AN UNSTABLE ATMOSPHERE REMAINS FROM THE CENTRAL ALASKA
PENINSULA TO NEAR KODIAK ISLAND TO THE COASTAL MOUNTAINS OF THE
SOUTHERN MAINLAND NORTH AND EAST TO THE SOUTHERN COPPER RIVER
BASIN. TO THE NORTH OF THIS LINE...CONDITIONS CONTINUE TO STEADILY
STABILIZE AS MID-LEVEL TEMPERATURES WARM.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD ENOUGH AGREEMENT TO GIVE A HIGH AMOUNT OF
CONFIDENCE IN THE FORECAST WELL INTO THE EARLY PART OF NEXT WEEK.
THE MAIN AREA OF DISAGREEMENT IN THE LAST 24 HOURS HAD BEEN
CENTERED ON A STACKED LOW PRESSURE SYSTEM THAT DEVELOPS SUNDAY IN
THE NORTH PACIFIC ABOUT 350 MILES SOUTHEAST OF DUTCH
HARBOR. THE GFS AND EUROPEAN (EC) MODELS HAVE COME INTO GOOD
AGREEMENT WITH THE PLACEMENT AND EVOLUTION OF THIS
FEATURE...DEVELOPING THE LOW INTO A LOW-END NEAR-GALE FORCE LOW
THAT MEANDERS NORTH TOWARD THE ALASKA PENINSULA MONDAY AND TUESDAY BEFORE
SLIDING SLOWLY EAST THE MIDDLE PART OF NEXT WEEK TOWARD THE FAR
SOUTHWEST GULF OF ALASKA. THE PLACES THIS WILL IMPACT THE MOST
WILL BE THE ALASKA PENINSULA (AND POSSIBLY THE EASTERN ALEUTIANS)
ON MONDAY INTO TUESDAY AND THEN THE GULF OF ALASKA REGION TOWARD
WEDNESDAY AND THURSDAY. INLAND AREAS WILL NOT BE IMPACTED AS MUCH
DUE TO THE TRACK REMAINING IN THE FAR SOUTHERN PART OF THE
FORECAST AREA REGARDLESS OF THE TIMING. HIGH PRESSURE WITH ABOVE
NORMAL TEMPERATURES AND LITTLE IF ANY SHOWER ACTIVITY CAN BE
EXPECTED ESPECIALLY FOR INLAND AREAS.

&&

.FIRE WEATHER...
THE EARLY PART OF NEXT WEEK WILL SEE SOME WARMER TEMPERATURES AND
LOWER RH VALUES IN CONJUNCTION WITH THE UPPER LEVEL HIGH PRESSURE
OVER SOUTHERN ALASKA. HOWEVER THESE RH VALUES ARE NOT EXPECTED TO
BE UNUSUAL LOW WITH LOWEST VALUES IN THE MID TO UPPER 20S IN
INTERIOR PARTS OF SOUTHCENTRAL ALASKA. HUMIDITY WILL BE HIGHER
WEST OF THE ALASKA RANGE AS LOW LEVEL MOISTURE OFF BRISTOL BAY
WILL MAKE IT INLAND.

&&

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

THE BUILDING RIDGE INTO THE MAINLAND FROM THE BERING SEA WILL
CONTINUE THE TREND FOR WARMER AND DRIER CONDITIONS AS WE MOVE
THROUGH THIS WEEKEND INTO EARLY NEXT WEEK. AN UPPER LEVEL
SHORTWAVE MOVING AHEAD OF THE RIDGE AXIS WILL PROVIDE ENOUGH
INSTABILITY FOR SOME CONVECTIVE POTENTIAL MAINLY ALONG THE CHUGACH
MOUNTAINS IN THE SOUTHERN COPPER RIVER BASIN AND ALONG THE
TALKEETNA MOUNTAINS. THE OFFSHORE FLOW WILL NOT BE AS SIGNIFICANT
TODAY ALLOWING FOR THE SEA BREEZE TO DEVELOP IN COASTAL LOCATIONS.
THIS WILL SUPPRESS HIGH TEMPERATURES FOR COASTAL LOCATIONS BELOW
YESTERDAY`S VERY WARM READINGS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE CONTINUES TO BUILD IN OVER THE BERING WITH THE
ASSOCIATED RIDGE TRACKING OVER THE SOUTHWEST. THIS WILL CONTINUE
TO CLEAR OUT THE SKIES OVER THE AREA...WITH THE EXCEPTION OF
AFTERNOON WITH SOME RESIDUAL INSTABILITY AND UNSTABLE CONDITIONS
ALONG THE AKPEN. THIS ALONG WITH DAYTIME HEATING WILL RESULT IN
CONVECTION OVER THE ALASKA PENINSULA THIS AFTERNOON. OTHERWISE,
WARMER AIR ALOFT WILL BECOME MORE ABUNDANT OVER MUCH OF THE
SOUTHWEST MAINLAND THROUGH THE WEEKEND...STABILIZING THE
ATMOSPHERE AND CLEARING OUT MUCH OF THE CLOUD COVER. WITH THE HIGH
IN PLACE FOG DEVELOPMENT IS LIKELY...ESPECIALLY ALONG THE COAST.
WITH WESTERLY/ONSHORE FLOW OFF THE BERING NEAR THE KUSKOKWIM DELTA
FOG WILL LIKELY BE ADVECTED INLAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
WITH HIGH PRESSURE OVER THE BERING SEA...STRATUS AND FOG WILL
REMAIN ABUNDANT THROUGH THE WEEKEND. FURTHER WEST...A WEAK TROUGH
WILL MOVE IN NEAR THE WESTERN ALEUTIANS AND STALL OUT SATURDAY
BRINGING IN SOME LIGHTER RAIN TO THE ISLANDS. THEN ON SUNDAY
EVENING A NORTH PACIFIC LOW WILL APPROACH THE ALASKA PENINSULA
BRINGING SOME MORE STEADY RAIN TO THE AREA.

&&

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

GENERALLY PLEASANT CONDITIONS MARKED BY ABUNDANT SUNSHINE AND
WARMER TEMPERATURES WILL SETTLE OVER THE REGION THROUGH THE MIDDLE
OF NEXT WEEK AS HIGH PRESSURE REMAINS OVER THE BERING SEA AND
EXTENDS EASTWARD OVER THE MAINLAND. AS MENTIONED IN THE MODEL
DISCUSSION SECTION...A CUTOFF LOW DEVELOPS OVER THE NORTH PACIFIC
TO THE SOUTH OF THE ALASKA PENINSULA SUNDAY IN RESPONSE TO THE
BUILDING RIDGE OVER THE BERING. THE AREAS IMPACTED WILL BE MAINLY
CONFINED TO THE AKPEN/EASTERN ALEUTIANS BEFORE BEGINNING TO
APPROACH THE WESTERN GULF OF ALASKA REGION BY WEDNESDAY.

&&


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

&&

$$

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





000
FXAK68 PAFC 011226
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
426 AM AKDT SAT AUG 1 2015

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL RIDGING CONTINUES TO BUILD FROM THE SOUTHWESTERN
BERING NORTHEAST INTO THE SOUTHERN INTERIOR OF THE ALASKA
MAINLAND...WITH A NARROW YET WEAK UPPER LEVEL TROUGH SITUATED FROM
AN UPPER LEVEL LOW CENTER NEAR YAKUTAT WEST-SOUTHWEST THROUGH THE
SOUTHERN GULF TO JUST SOUTH OF THE ALASKA PENINSULA AND EASTERN
ALEUTIANS. BETWEEN THE RIDGE TO THE NORTH AND THE TROUGH TO THE
SOUTH...AN UNSTABLE ATMOSPHERE REMAINS FROM THE CENTRAL ALASKA
PENINSULA TO NEAR KODIAK ISLAND TO THE COASTAL MOUNTAINS OF THE
SOUTHERN MAINLAND NORTH AND EAST TO THE SOUTHERN COPPER RIVER
BASIN. TO THE NORTH OF THIS LINE...CONDITIONS CONTINUE TO STEADILY
STABILIZE AS MID-LEVEL TEMPERATURES WARM.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD ENOUGH AGREEMENT TO GIVE A HIGH AMOUNT OF
CONFIDENCE IN THE FORECAST WELL INTO THE EARLY PART OF NEXT WEEK.
THE MAIN AREA OF DISAGREEMENT IN THE LAST 24 HOURS HAD BEEN
CENTERED ON A STACKED LOW PRESSURE SYSTEM THAT DEVELOPS SUNDAY IN
THE NORTH PACIFIC ABOUT 350 MILES SOUTHEAST OF DUTCH
HARBOR. THE GFS AND EUROPEAN (EC) MODELS HAVE COME INTO GOOD
AGREEMENT WITH THE PLACEMENT AND EVOLUTION OF THIS
FEATURE...DEVELOPING THE LOW INTO A LOW-END NEAR-GALE FORCE LOW
THAT MEANDERS NORTH TOWARD THE ALASKA PENINSULA MONDAY AND TUESDAY BEFORE
SLIDING SLOWLY EAST THE MIDDLE PART OF NEXT WEEK TOWARD THE FAR
SOUTHWEST GULF OF ALASKA. THE PLACES THIS WILL IMPACT THE MOST
WILL BE THE ALASKA PENINSULA (AND POSSIBLY THE EASTERN ALEUTIANS)
ON MONDAY INTO TUESDAY AND THEN THE GULF OF ALASKA REGION TOWARD
WEDNESDAY AND THURSDAY. INLAND AREAS WILL NOT BE IMPACTED AS MUCH
DUE TO THE TRACK REMAINING IN THE FAR SOUTHERN PART OF THE
FORECAST AREA REGARDLESS OF THE TIMING. HIGH PRESSURE WITH ABOVE
NORMAL TEMPERATURES AND LITTLE IF ANY SHOWER ACTIVITY CAN BE
EXPECTED ESPECIALLY FOR INLAND AREAS.

&&

.FIRE WEATHER...
THE EARLY PART OF NEXT WEEK WILL SEE SOME WARMER TEMPERATURES AND
LOWER RH VALUES IN CONJUNCTION WITH THE UPPER LEVEL HIGH PRESSURE
OVER SOUTHERN ALASKA. HOWEVER THESE RH VALUES ARE NOT EXPECTED TO
BE UNUSUAL LOW WITH LOWEST VALUES IN THE MID TO UPPER 20S IN
INTERIOR PARTS OF SOUTHCENTRAL ALASKA. HUMIDITY WILL BE HIGHER
WEST OF THE ALASKA RANGE AS LOW LEVEL MOISTURE OFF BRISTOL BAY
WILL MAKE IT INLAND.

&&

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

THE BUILDING RIDGE INTO THE MAINLAND FROM THE BERING SEA WILL
CONTINUE THE TREND FOR WARMER AND DRIER CONDITIONS AS WE MOVE
THROUGH THIS WEEKEND INTO EARLY NEXT WEEK. AN UPPER LEVEL
SHORTWAVE MOVING AHEAD OF THE RIDGE AXIS WILL PROVIDE ENOUGH
INSTABILITY FOR SOME CONVECTIVE POTENTIAL MAINLY ALONG THE CHUGACH
MOUNTAINS IN THE SOUTHERN COPPER RIVER BASIN AND ALONG THE
TALKEETNA MOUNTAINS. THE OFFSHORE FLOW WILL NOT BE AS SIGNIFICANT
TODAY ALLOWING FOR THE SEA BREEZE TO DEVELOP IN COASTAL LOCATIONS.
THIS WILL SUPPRESS HIGH TEMPERATURES FOR COASTAL LOCATIONS BELOW
YESTERDAY`S VERY WARM READINGS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE CONTINUES TO BUILD IN OVER THE BERING WITH THE
ASSOCIATED RIDGE TRACKING OVER THE SOUTHWEST. THIS WILL CONTINUE
TO CLEAR OUT THE SKIES OVER THE AREA...WITH THE EXCEPTION OF
AFTERNOON WITH SOME RESIDUAL INSTABILITY AND UNSTABLE CONDITIONS
ALONG THE AKPEN. THIS ALONG WITH DAYTIME HEATING WILL RESULT IN
CONVECTION OVER THE ALASKA PENINSULA THIS AFTERNOON. OTHERWISE,
WARMER AIR ALOFT WILL BECOME MORE ABUNDANT OVER MUCH OF THE
SOUTHWEST MAINLAND THROUGH THE WEEKEND...STABILIZING THE
ATMOSPHERE AND CLEARING OUT MUCH OF THE CLOUD COVER. WITH THE HIGH
IN PLACE FOG DEVELOPMENT IS LIKELY...ESPECIALLY ALONG THE COAST.
WITH WESTERLY/ONSHORE FLOW OFF THE BERING NEAR THE KUSKOKWIM DELTA
FOG WILL LIKELY BE ADVECTED INLAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
WITH HIGH PRESSURE OVER THE BERING SEA...STRATUS AND FOG WILL
REMAIN ABUNDANT THROUGH THE WEEKEND. FURTHER WEST...A WEAK TROUGH
WILL MOVE IN NEAR THE WESTERN ALEUTIANS AND STALL OUT SATURDAY
BRINGING IN SOME LIGHTER RAIN TO THE ISLANDS. THEN ON SUNDAY
EVENING A NORTH PACIFIC LOW WILL APPROACH THE ALASKA PENINSULA
BRINGING SOME MORE STEADY RAIN TO THE AREA.

&&

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

GENERALLY PLEASANT CONDITIONS MARKED BY ABUNDANT SUNSHINE AND
WARMER TEMPERATURES WILL SETTLE OVER THE REGION THROUGH THE MIDDLE
OF NEXT WEEK AS HIGH PRESSURE REMAINS OVER THE BERING SEA AND
EXTENDS EASTWARD OVER THE MAINLAND. AS MENTIONED IN THE MODEL
DISCUSSION SECTION...A CUTOFF LOW DEVELOPS OVER THE NORTH PACIFIC
TO THE SOUTH OF THE ALASKA PENINSULA SUNDAY IN RESPONSE TO THE
BUILDING RIDGE OVER THE BERING. THE AREAS IMPACTED WILL BE MAINLY
CONFINED TO THE AKPEN/EASTERN ALEUTIANS BEFORE BEGINNING TO
APPROACH THE WESTERN GULF OF ALASKA REGION BY WEDNESDAY.

&&


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

&&

$$

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




000
FXAK68 PAFC 011226
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
426 AM AKDT SAT AUG 1 2015

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL RIDGING CONTINUES TO BUILD FROM THE SOUTHWESTERN
BERING NORTHEAST INTO THE SOUTHERN INTERIOR OF THE ALASKA
MAINLAND...WITH A NARROW YET WEAK UPPER LEVEL TROUGH SITUATED FROM
AN UPPER LEVEL LOW CENTER NEAR YAKUTAT WEST-SOUTHWEST THROUGH THE
SOUTHERN GULF TO JUST SOUTH OF THE ALASKA PENINSULA AND EASTERN
ALEUTIANS. BETWEEN THE RIDGE TO THE NORTH AND THE TROUGH TO THE
SOUTH...AN UNSTABLE ATMOSPHERE REMAINS FROM THE CENTRAL ALASKA
PENINSULA TO NEAR KODIAK ISLAND TO THE COASTAL MOUNTAINS OF THE
SOUTHERN MAINLAND NORTH AND EAST TO THE SOUTHERN COPPER RIVER
BASIN. TO THE NORTH OF THIS LINE...CONDITIONS CONTINUE TO STEADILY
STABILIZE AS MID-LEVEL TEMPERATURES WARM.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD ENOUGH AGREEMENT TO GIVE A HIGH AMOUNT OF
CONFIDENCE IN THE FORECAST WELL INTO THE EARLY PART OF NEXT WEEK.
THE MAIN AREA OF DISAGREEMENT IN THE LAST 24 HOURS HAD BEEN
CENTERED ON A STACKED LOW PRESSURE SYSTEM THAT DEVELOPS SUNDAY IN
THE NORTH PACIFIC ABOUT 350 MILES SOUTHEAST OF DUTCH
HARBOR. THE GFS AND EUROPEAN (EC) MODELS HAVE COME INTO GOOD
AGREEMENT WITH THE PLACEMENT AND EVOLUTION OF THIS
FEATURE...DEVELOPING THE LOW INTO A LOW-END NEAR-GALE FORCE LOW
THAT MEANDERS NORTH TOWARD THE ALASKA PENINSULA MONDAY AND TUESDAY BEFORE
SLIDING SLOWLY EAST THE MIDDLE PART OF NEXT WEEK TOWARD THE FAR
SOUTHWEST GULF OF ALASKA. THE PLACES THIS WILL IMPACT THE MOST
WILL BE THE ALASKA PENINSULA (AND POSSIBLY THE EASTERN ALEUTIANS)
ON MONDAY INTO TUESDAY AND THEN THE GULF OF ALASKA REGION TOWARD
WEDNESDAY AND THURSDAY. INLAND AREAS WILL NOT BE IMPACTED AS MUCH
DUE TO THE TRACK REMAINING IN THE FAR SOUTHERN PART OF THE
FORECAST AREA REGARDLESS OF THE TIMING. HIGH PRESSURE WITH ABOVE
NORMAL TEMPERATURES AND LITTLE IF ANY SHOWER ACTIVITY CAN BE
EXPECTED ESPECIALLY FOR INLAND AREAS.

&&

.FIRE WEATHER...
THE EARLY PART OF NEXT WEEK WILL SEE SOME WARMER TEMPERATURES AND
LOWER RH VALUES IN CONJUNCTION WITH THE UPPER LEVEL HIGH PRESSURE
OVER SOUTHERN ALASKA. HOWEVER THESE RH VALUES ARE NOT EXPECTED TO
BE UNUSUAL LOW WITH LOWEST VALUES IN THE MID TO UPPER 20S IN
INTERIOR PARTS OF SOUTHCENTRAL ALASKA. HUMIDITY WILL BE HIGHER
WEST OF THE ALASKA RANGE AS LOW LEVEL MOISTURE OFF BRISTOL BAY
WILL MAKE IT INLAND.

&&

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

THE BUILDING RIDGE INTO THE MAINLAND FROM THE BERING SEA WILL
CONTINUE THE TREND FOR WARMER AND DRIER CONDITIONS AS WE MOVE
THROUGH THIS WEEKEND INTO EARLY NEXT WEEK. AN UPPER LEVEL
SHORTWAVE MOVING AHEAD OF THE RIDGE AXIS WILL PROVIDE ENOUGH
INSTABILITY FOR SOME CONVECTIVE POTENTIAL MAINLY ALONG THE CHUGACH
MOUNTAINS IN THE SOUTHERN COPPER RIVER BASIN AND ALONG THE
TALKEETNA MOUNTAINS. THE OFFSHORE FLOW WILL NOT BE AS SIGNIFICANT
TODAY ALLOWING FOR THE SEA BREEZE TO DEVELOP IN COASTAL LOCATIONS.
THIS WILL SUPPRESS HIGH TEMPERATURES FOR COASTAL LOCATIONS BELOW
YESTERDAY`S VERY WARM READINGS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE CONTINUES TO BUILD IN OVER THE BERING WITH THE
ASSOCIATED RIDGE TRACKING OVER THE SOUTHWEST. THIS WILL CONTINUE
TO CLEAR OUT THE SKIES OVER THE AREA...WITH THE EXCEPTION OF
AFTERNOON WITH SOME RESIDUAL INSTABILITY AND UNSTABLE CONDITIONS
ALONG THE AKPEN. THIS ALONG WITH DAYTIME HEATING WILL RESULT IN
CONVECTION OVER THE ALASKA PENINSULA THIS AFTERNOON. OTHERWISE,
WARMER AIR ALOFT WILL BECOME MORE ABUNDANT OVER MUCH OF THE
SOUTHWEST MAINLAND THROUGH THE WEEKEND...STABILIZING THE
ATMOSPHERE AND CLEARING OUT MUCH OF THE CLOUD COVER. WITH THE HIGH
IN PLACE FOG DEVELOPMENT IS LIKELY...ESPECIALLY ALONG THE COAST.
WITH WESTERLY/ONSHORE FLOW OFF THE BERING NEAR THE KUSKOKWIM DELTA
FOG WILL LIKELY BE ADVECTED INLAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
WITH HIGH PRESSURE OVER THE BERING SEA...STRATUS AND FOG WILL
REMAIN ABUNDANT THROUGH THE WEEKEND. FURTHER WEST...A WEAK TROUGH
WILL MOVE IN NEAR THE WESTERN ALEUTIANS AND STALL OUT SATURDAY
BRINGING IN SOME LIGHTER RAIN TO THE ISLANDS. THEN ON SUNDAY
EVENING A NORTH PACIFIC LOW WILL APPROACH THE ALASKA PENINSULA
BRINGING SOME MORE STEADY RAIN TO THE AREA.

&&

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

GENERALLY PLEASANT CONDITIONS MARKED BY ABUNDANT SUNSHINE AND
WARMER TEMPERATURES WILL SETTLE OVER THE REGION THROUGH THE MIDDLE
OF NEXT WEEK AS HIGH PRESSURE REMAINS OVER THE BERING SEA AND
EXTENDS EASTWARD OVER THE MAINLAND. AS MENTIONED IN THE MODEL
DISCUSSION SECTION...A CUTOFF LOW DEVELOPS OVER THE NORTH PACIFIC
TO THE SOUTH OF THE ALASKA PENINSULA SUNDAY IN RESPONSE TO THE
BUILDING RIDGE OVER THE BERING. THE AREAS IMPACTED WILL BE MAINLY
CONFINED TO THE AKPEN/EASTERN ALEUTIANS BEFORE BEGINNING TO
APPROACH THE WESTERN GULF OF ALASKA REGION BY WEDNESDAY.

&&


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

&&

$$

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




000
FXAK68 PAFC 011226
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
426 AM AKDT SAT AUG 1 2015

.ANALYSIS AND UPPER LEVELS...
UPPER LEVEL RIDGING CONTINUES TO BUILD FROM THE SOUTHWESTERN
BERING NORTHEAST INTO THE SOUTHERN INTERIOR OF THE ALASKA
MAINLAND...WITH A NARROW YET WEAK UPPER LEVEL TROUGH SITUATED FROM
AN UPPER LEVEL LOW CENTER NEAR YAKUTAT WEST-SOUTHWEST THROUGH THE
SOUTHERN GULF TO JUST SOUTH OF THE ALASKA PENINSULA AND EASTERN
ALEUTIANS. BETWEEN THE RIDGE TO THE NORTH AND THE TROUGH TO THE
SOUTH...AN UNSTABLE ATMOSPHERE REMAINS FROM THE CENTRAL ALASKA
PENINSULA TO NEAR KODIAK ISLAND TO THE COASTAL MOUNTAINS OF THE
SOUTHERN MAINLAND NORTH AND EAST TO THE SOUTHERN COPPER RIVER
BASIN. TO THE NORTH OF THIS LINE...CONDITIONS CONTINUE TO STEADILY
STABILIZE AS MID-LEVEL TEMPERATURES WARM.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD ENOUGH AGREEMENT TO GIVE A HIGH AMOUNT OF
CONFIDENCE IN THE FORECAST WELL INTO THE EARLY PART OF NEXT WEEK.
THE MAIN AREA OF DISAGREEMENT IN THE LAST 24 HOURS HAD BEEN
CENTERED ON A STACKED LOW PRESSURE SYSTEM THAT DEVELOPS SUNDAY IN
THE NORTH PACIFIC ABOUT 350 MILES SOUTHEAST OF DUTCH
HARBOR. THE GFS AND EUROPEAN (EC) MODELS HAVE COME INTO GOOD
AGREEMENT WITH THE PLACEMENT AND EVOLUTION OF THIS
FEATURE...DEVELOPING THE LOW INTO A LOW-END NEAR-GALE FORCE LOW
THAT MEANDERS NORTH TOWARD THE ALASKA PENINSULA MONDAY AND TUESDAY BEFORE
SLIDING SLOWLY EAST THE MIDDLE PART OF NEXT WEEK TOWARD THE FAR
SOUTHWEST GULF OF ALASKA. THE PLACES THIS WILL IMPACT THE MOST
WILL BE THE ALASKA PENINSULA (AND POSSIBLY THE EASTERN ALEUTIANS)
ON MONDAY INTO TUESDAY AND THEN THE GULF OF ALASKA REGION TOWARD
WEDNESDAY AND THURSDAY. INLAND AREAS WILL NOT BE IMPACTED AS MUCH
DUE TO THE TRACK REMAINING IN THE FAR SOUTHERN PART OF THE
FORECAST AREA REGARDLESS OF THE TIMING. HIGH PRESSURE WITH ABOVE
NORMAL TEMPERATURES AND LITTLE IF ANY SHOWER ACTIVITY CAN BE
EXPECTED ESPECIALLY FOR INLAND AREAS.

&&

.FIRE WEATHER...
THE EARLY PART OF NEXT WEEK WILL SEE SOME WARMER TEMPERATURES AND
LOWER RH VALUES IN CONJUNCTION WITH THE UPPER LEVEL HIGH PRESSURE
OVER SOUTHERN ALASKA. HOWEVER THESE RH VALUES ARE NOT EXPECTED TO
BE UNUSUAL LOW WITH LOWEST VALUES IN THE MID TO UPPER 20S IN
INTERIOR PARTS OF SOUTHCENTRAL ALASKA. HUMIDITY WILL BE HIGHER
WEST OF THE ALASKA RANGE AS LOW LEVEL MOISTURE OFF BRISTOL BAY
WILL MAKE IT INLAND.

&&

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

THE BUILDING RIDGE INTO THE MAINLAND FROM THE BERING SEA WILL
CONTINUE THE TREND FOR WARMER AND DRIER CONDITIONS AS WE MOVE
THROUGH THIS WEEKEND INTO EARLY NEXT WEEK. AN UPPER LEVEL
SHORTWAVE MOVING AHEAD OF THE RIDGE AXIS WILL PROVIDE ENOUGH
INSTABILITY FOR SOME CONVECTIVE POTENTIAL MAINLY ALONG THE CHUGACH
MOUNTAINS IN THE SOUTHERN COPPER RIVER BASIN AND ALONG THE
TALKEETNA MOUNTAINS. THE OFFSHORE FLOW WILL NOT BE AS SIGNIFICANT
TODAY ALLOWING FOR THE SEA BREEZE TO DEVELOP IN COASTAL LOCATIONS.
THIS WILL SUPPRESS HIGH TEMPERATURES FOR COASTAL LOCATIONS BELOW
YESTERDAY`S VERY WARM READINGS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE CONTINUES TO BUILD IN OVER THE BERING WITH THE
ASSOCIATED RIDGE TRACKING OVER THE SOUTHWEST. THIS WILL CONTINUE
TO CLEAR OUT THE SKIES OVER THE AREA...WITH THE EXCEPTION OF
AFTERNOON WITH SOME RESIDUAL INSTABILITY AND UNSTABLE CONDITIONS
ALONG THE AKPEN. THIS ALONG WITH DAYTIME HEATING WILL RESULT IN
CONVECTION OVER THE ALASKA PENINSULA THIS AFTERNOON. OTHERWISE,
WARMER AIR ALOFT WILL BECOME MORE ABUNDANT OVER MUCH OF THE
SOUTHWEST MAINLAND THROUGH THE WEEKEND...STABILIZING THE
ATMOSPHERE AND CLEARING OUT MUCH OF THE CLOUD COVER. WITH THE HIGH
IN PLACE FOG DEVELOPMENT IS LIKELY...ESPECIALLY ALONG THE COAST.
WITH WESTERLY/ONSHORE FLOW OFF THE BERING NEAR THE KUSKOKWIM DELTA
FOG WILL LIKELY BE ADVECTED INLAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
WITH HIGH PRESSURE OVER THE BERING SEA...STRATUS AND FOG WILL
REMAIN ABUNDANT THROUGH THE WEEKEND. FURTHER WEST...A WEAK TROUGH
WILL MOVE IN NEAR THE WESTERN ALEUTIANS AND STALL OUT SATURDAY
BRINGING IN SOME LIGHTER RAIN TO THE ISLANDS. THEN ON SUNDAY
EVENING A NORTH PACIFIC LOW WILL APPROACH THE ALASKA PENINSULA
BRINGING SOME MORE STEADY RAIN TO THE AREA.

&&

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

GENERALLY PLEASANT CONDITIONS MARKED BY ABUNDANT SUNSHINE AND
WARMER TEMPERATURES WILL SETTLE OVER THE REGION THROUGH THE MIDDLE
OF NEXT WEEK AS HIGH PRESSURE REMAINS OVER THE BERING SEA AND
EXTENDS EASTWARD OVER THE MAINLAND. AS MENTIONED IN THE MODEL
DISCUSSION SECTION...A CUTOFF LOW DEVELOPS OVER THE NORTH PACIFIC
TO THE SOUTH OF THE ALASKA PENINSULA SUNDAY IN RESPONSE TO THE
BUILDING RIDGE OVER THE BERING. THE AREAS IMPACTED WILL BE MAINLY
CONFINED TO THE AKPEN/EASTERN ALEUTIANS BEFORE BEGINNING TO
APPROACH THE WESTERN GULF OF ALASKA REGION BY WEDNESDAY.

&&


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

&&

$$

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





000
FXAK68 PAFC 010036
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
436 PM AKDT FRI JUL 31 2015

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN SHOWS THE UPPER LEVEL RIDGE OVER THE
BERING SEA AND BUILDING OVER THE INTERIOR OF THE STATE. THE MAIN
UPPER LEVEL LOW IS NOW SOUTH OF THE MAINLAND IN THE GULF OF
ALASKA. THE RIDGE WILL BUILD IN OVER THE MAINLAND PART OF THE
STATE OVER THE COURSE OF THE WEEKEND. THE ATMOSPHERE OVER
SOUTHCENTRAL ALASKA AND NEAR THE BRISTOL BAY REGION WILL BE
UNSTABLE THIS AFTERNOON AND EVENING.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD ENOUGH AGREEMENT TO GIVE A HIGH AMOUNT OF
CONFIDENCE IN THE FORECAST THROUGH THE WEEKEND OVER MOST OF THE
AREA. THE MOST SIGNIFICANT DIFFERENCE IN MODELS IS SOUTH OF
ALASKA PENINSULA AND KODIAK ISLAND SUNDAY INTO TUESDAY WHERE
THERE IS A BIT OF DISAGREEMENT BETWEEN MODELS AS TO HOW FAST A
LOW FROM THE NORTH PACIFIC WILL TRACK TOWARD THE GULF. THE GFS
WAS A BIT OF AN OUTLIER FROM THE 12Z SUITE OF MODELS HAVING A
SOLUTION MUCH FASTER THAN THE ECMWF NAM OR GEM. HOWEVER THE 18Z
NAM JUMPED FORWARD TOWARD THE FASTER GFS SOLUTION. IT WILL BE
INTERESTING TO SEE IF THE MODELS START TO SHIFT TOWARD THIS FASTER
SOLUTION OR HOLD FARTHER BACK. THE PLACES THIS WILL IMPACT THE
MOST WILL BE THE ALASKA PENINSULA ON MONDAY AND THEN THE GULF OF
ALASKA REGION BY LATE TUESDAY. INLAND AREAS WILL NOT BE IMPACTED
AS MUCH DUE TO THE TRACK REMAINING IN THE FAR SOUTHERN PART OF
THE FORECAST AREA REGARDLESS OF THE TIMING.

&&

.FIRE WEATHER...
THE EARLY PART OF NEXT WEEK WILL SEE SOME WARMER TEMPERATURES AND
LOWER RH VALUES IN CONJUNCTION WITH THE UPPER LEVEL HIGH PRESSURE
OVER SOUTHERN ALASKA. HOWEVER THESE RH VALUES ARE NOT EXPECTED TO
BE UNUSUALLY LOW WITH LOWEST VALUES IN THE MID TO UPPER 20S IN
INTERIOR PARTS OF SOUTHCENTRAL ALASKA. HUMIDITY WILL BE HIGHER
WEST OF THE ALASKA RANGE AS LOW LEVEL MOISTURE OFF BRISTOL BAY
HEADS INLAND.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
CONDITIONS OVER SOUTHCENTRAL ALASKA WILL CONTINUE TO DRY OUT AND
WARM UP AS THE RIDGE BEGINS TO SETTLE IN OVER THE AREA THROUGH
SUNDAY. THE BEST CHANCES FOR SHOWERS WILL BE THIS EVENING AS THERE
WILL BE ENOUGH WIDESPREAD MOISTURE AND INSTABILITY TO GENERATE
SHOWERS AND ISOLATED THUNDERSTORMS...MAINLY OVER THE SUSITNA
VALLEY AND THE COPPER RIVER BASIN. ALTHOUGH CONDITIONS ARE
EXPECTED TO STABILIZE AS THE RIDGE BUILDS IN ON SATURDAY...AN
UPPER LEVEL SHORTWAVE MOVING AHEAD OF THE RIDGE AXIS WILL PROVIDE
ENOUGH INSTABILITY FOR SOME CONVECTIVE POTENTIAL...MAINLY ALONG
MOUNTAIN AREAS WHERE THERE WILL BE SUFFICIENT MOISTURE FOR
SHOWERS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...
HIGH PRESSURE IS BUILDING IN OVER THE BERING WITH ASSOCIATED
RIDGING MOVING IN OVER THE SOUTHWEST. THIS IS CLEARING OUT THE
SKIES IN THE AREA BUT FOR THIS EVENING THE UPPER LEVELS WILL
REMAIN COLD ENOUGH FOR UNSTABLE CONDITIONS TO CONTINUE AROUND
BRISTOL BAY. THIS WILL RESULT IN THUNDERSTORM DEVELOPMENT IN
THE BRISTOL BAY AREA THAT WILL EXTEND UP INTO THE ALASKA RANGE.
OVERNIGHT THE RIDGING WILL BUILD IN MORE BRINGING IN MORE WARM
AIR ALOFT WHICH WILL PROVIDE A MORE STABLE ATMOSPHERE AND
SUBSEQUENTLY LESS CLOUD COVER. WITH THE HIGH IN PLACE FOG
DEVELOPMENT IS LIKELY...ESPECIALLY ALONG THE COAST. WITH WESTERLY
FLOW OFF THE BERING NEAR THE KUSKOKWIM DELTA FOG WILL LIKELY BE
ADVECTED INLAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
WITH HIGH PRESSURE OVER THE BERING STRATUS AND FOG WILL REMAIN
ABUNDANT THROUGH THE WEEKEND. WAY OUT WEST NEAR THE WESTERN
ALEUTIANS A WEAK TROUGH WILL MOVE IN AND STALL OUT THERE SATURDAY
BRINGING IN SOME LIGHTER RAIN TO THE ISLANDS. THEN ON SUNDAY
EVENING A NORTH PACIFIC LOW WILL APPROACH THE ALASKA PENINSULA
BRINGING SOME MORE STEADY RAIN TO THE AREA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
GENERALLY PLEASANT CONDITIONS MARKED BY ABUNDANT SUNSHINE AND
WARMER TEMPERATURES WILL SETTLE OVER THE REGION THROUGH THE MIDDLE
OF NEXT WEEK AS HIGH PRESSURE REMAINS OVER THE BERING SEA AND
EXTENDS EASTWARD OVER THE MAINLAND. A SLIGHT COMPLICATING FACTOR
WILL BE THE EVOLUTION OF A CUTOFF LOW THAT DEVELOPS OVER THE NORTH
PACIFIC THIS WEEKEND IN RESPONSE TO THE BUILDING RIDGE OVER THE
BERING. MODEL SPREAD HAS INCREASED OVER THE PAST 24 HOURS WITH
RESPECT TO THIS FEATURE...WITH THE 12Z GFS AND 18Z NAM DEPICTING A
DRAMATIC EASTWARD SHIFT THAT WOULD BRING THE LOW AND AN ASSOCIATED
FRONT MUCH CLOSER TO THE WESTERN GULF AND THUS INCREASE
PRECIPITATION CHANCES OVER KODIAK ISLAND BY EARLY NEXT WEEK. THE
EC/GEM KEEP THE LOW FARTHER TO THE WEST WITH IMPACTS MAINLY
CONFINED TO THE AKPEN/EASTERN ALEUTIANS BEFORE BEGINNING TO
APPROACH THE BRISTOL BAY REGION BY WEDNESDAY. PREFERRED TO STAY
CLOSER TO THE WESTERN SOLUTION FOR NOW AS IT HAS BEEN THE MOST
CONSISTENT OVER THE PAST FEW DAYS. REGARDLESS...THE BULK OF THE
IMPACTS FROM THIS SYSTEM ARE EXPECTED TO REMAIN SOUTH OF THE
MAINLAND THROUGH MIDWEEK BEFORE PRECIPITATION CHANCES BEGIN TO
INCREASE AS HIGH PRESSURE GRADUALLY WEAKENS.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...RF
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...CB





000
FXAK68 PAFC 311312
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
512 AM AKDT FRI JUL 31 2015

.ANALYSIS AND UPPER LEVELS...

VERY FEW CHANGES HAVE OCCURRED FROM YESTERDAY AS THE STAGNANT
WEATHER PATTERN HAS PERSISTED. AN UPPER LOW OVER THE SOUTHWESTERN
GULF IS NOW BEGINNING TO CUT OFF AS A RIDGE OVER THE WESTERN
BERING AND EASTERN RUSSIA SHIFTS EASTWARD DUE TO SUBSIDENCE.
BETWEEN THESE FEATURES...THE JET STREAM IS FLOWING GENERALLY ALONG
THE 170W MERIDIAN THROUGH THE BERING INTO THE NORTH PACIFIC. A
STATIONARY VERTICALLY STACKED LOW PERSISTS SOUTH OF THE WESTERN
ALEUTIANS...CUT OFF SOUTH OF THE WESTERN BERING RIDGE. THAT LOW
REMAINS THE STRONGEST SURFACE FEATURE TO AFFECT THE ANCHORAGE
OFFICE AREA OF RESPONSIBILITY. WATER VAPOR IMAGERY INDICATES MUCH
DRIER MID- LEVEL AIR MOVING SOUTH TOWARD SOUTHERN ALASKA FROM THE
WESTERN AND CENTRAL INTERIOR.

&&

.MODEL DISCUSSION...

THE MODELS REMAIN IN EXCELLENT AGREEMENT ON THE LARGE SCALE
PATTERN EVOLUTION GOING INTO THE WEEKEND. THE LACK
OF DEFINABLE SURFACE FEATURES NEAR MAINLAND ALASKA MEANS THAT
SMALL UPPER LEVEL DISTURBANCES INTERACTING WITH THE TERRAIN AND
LOCALIZED CONVERGENCE BOUNDARIES WILL REMAIN THE DRIVING FACTORS
FOR PRECIPITATION THROUGH FRIDAY. AS AN UPPER LEVEL RIDGE BUILDS
EAST INTO MAINLAND ALASKA...WARMING TEMPERATURES IN THE UPPER
LEVELS BY SATURDAY WILL DIMINISH THE INSTABILITY THAT HAS
SUPPORTED DIURNAL SHOWER AND THUNDERSTORM DEVELOPMENT. CONFIDENCE
IS HIGH ON THE OVERALL PATTERN AND MODERATE ON THE TIMING AND
LOCATION OF ANY SHOWERS AND ISOLATED THUNDERSTORMS THROUGH
SATURDAY.

&&

.FIRE WEATHER...

A MOIST WEATHER PATTERN HAS PERSISTED FOR THE PAST WEEK AND
BROUGHT PERIODIC SHOWERS TO MUCH OF SOUTHERN ALASKA. A WARMER AND
DRIER PATTERN IS EXPECTED WITH LESS IN THE WAY OF CLOUD COVER BY
THE WEEKEND...WITH HUMIDITY LEVELS DROPPING BELOW 30 PERCENT THIS
WEEKEND IMMEDIATELY DOWNSTREAM OF THE ALASKA RANGE IN THE SUSITNA
VALLEY AND COPPER RIVER BASIN. THE WET THUNDERSTORM POTENTIAL
REMAINS THROUGH TODAY ESPECIALLY FROM THE TALKEETNA MOUNTAINS
SOUTH TO THE CHUGACH RANGE...AFTER WHICH WARMING TEMPERATURES
ALOFT WILL CAP POTENTIAL CONVECTION AND SIGNIFICANTLY REDUCE THE
THREAT FOR THUNDERSTORMS. THE LACK OF ANY STRONG SURFACE FEATURES
THROUGH THE WEEKEND WILL KEEP WINDS IN MOST AREAS LIGHT.

&&

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

DOWNSLOPE DRYING WILL CLEAR SKIES OUT FROM THE SUSITNA VALLEY
DOWN THROUGH THE COOK INLET REGION...INCLUDING OUTFLOW AREAS ALONG
THE NORTH GULF COAST SUCH AS WHITTIER AND SEWARD. HOWEVER...LOW-
LEVEL MOISTURE WILL BE MUCH SLOWER TO RETREAT FROM THE MOUNTAINS.
WITH SUFFICIENT LOW-LEVEL MOISTURE AND MODERATE TO STRONG DRYING
A FEW THOUSAND FEET ABOVE...INSTABILITY WILL GREATLY INCREASE FROM
THE TALKEETNA MOUNTAINS SOUTH TO THE CHUGACH AND KENAI MOUNTAIN
RANGES. HOWEVER...GIVEN STORM MOTIONS LIKELY TO STAY NORTH OR EVEN
NORTH- NORTHWEST...THE GREATEST IMPACT ON POPULATED AREAS WILL
LIKELY BE THE GLENN HIGHWAY CORRIDOR FROM PALMER TO EUREKA...WHICH
WILL LIE IN THE CROSSHAIRS OF THUNDERSTORM ACTIVITY THAT WILL MOVE
OFF OF THE TALKEETNA MOUNTAINS. THESE STORMS WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY RAINS...SMALL HAIL...AND GUSTY WINDS
WITH THEM.

INCREASING STABILITY AND WARMING TEMPERATURES ALOFT WILL LARGELY
CAP CONVECTIVE ACTIVITY FOR SATURDAY...WITH THE POSSIBLE EXCEPTION
BEING AREAS ALONG THE EASTERN CHUGACH RANGE FROM THE RICHARDSON
HIGHWAY EAST AND SOUTH OF THE EDGERTON HIGHWAY...WHERE ISOLATED
THUNDERSTORMS WILL BE STILL POSSIBLE.

A MID LEVEL RIDGE WILL THEN BUILD INTO THE AREA BY SATURDAY
MORNING...ALLOWING FOR WARMER AND DRIER CONDITIONS TO SPREAD INTO
THE AREA AND PERSIST INTO EARLY NEXT WEEK.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...FRI AND
SAT)...ANOTHER ROUND OF CONVECTION IS IN STORE FOR TODAY...BUT IT
SHOULD BE SLIGHTLY MORE CONSOLIDATED FURTHER SOUTH THAN DAYS PAST.
THE RIDGE FROM THE BERING WILL CONTINUE TO BUILD IN OVER THE NEXT
FEW DAYS. HOWEVER...ON THE LEADING EDGE OF THAT RIDGE...IN A
CORRIDOR FROM KING SALMON TO THE ALEUTIAN RANGE...THERE WILL STILL
BE ENOUGH INSTABILITY THIS AFTERNOON TO MAKE FOR SOME
THUNDERSTORMS. WHILE THEY WILL NOT BE TERRIBLY WIDESPREAD...THOSE
THAT DO FORM WILL HAVE A RATHER UNSTABLE ENVIRONMENT TO TAKE
ADVANTAGE OF WHICH COULD RESULT IN SOME HEAVY DOWNPOURS...GUSTY
WINDS...AND SMALL HAIL. NORTHWEST TO NORTHEAST FLOW WILL PUSH THE
STORMS THROUGH THE ALASKA PENINSULA AND INTO THE GULF OF ALASKA
DURING THE OVERNIGHT HOURS.

SATURDAY WE WILL START TO SEE THE RIDGE BUILDING IN A BIT
STRONGER. THIS SHOULD HELP TO CAP ANY THUNDERSTORMS FROM
DEVELOPING. ALTHOUGH A VERY WEAK UPPER LEVEL WAVE WILL CLIMB OVER
THE TOP OF THE RIDGE AND COULD TRIGGER A FEW SHOWERS LATE IN THE
DAY...ESPECIALLY OVER THE KUSKOKWIM DELTA. OTHERWISE...A WARMING
AND DRYING TREND WILL START TO ESTABLISH ITSELF THROUGH THE
WEEKEND AND PERSIST INTO EARLY NEXT WEEK.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2...FRI AND
SAT)...HIGH PRESSURE WILL REMAIN FIRMLY IN CONTROL OF THE AREA
FOR THE NEXT SEVERAL DAYS. WITH ABUNDANT LOW LEVEL MOISTURE...THIS
MEANS LOW STRATUS AND FOG WILL LIKELY BECOME MORE OF AN ISSUE EACH
DAY. IT WILL ALSO KEEP WINDS LIGHT FOR MOST OF THE BERING SEA. THE
EXCEPTION TO THESE CONDITIONS WILL BE THE CENTRAL TO WESTERN
ALEUTIANS. ONE WEAK AREA OF LOW PRESSURE WILL DRIFT SOUTHWARD AWAY
FROM THE AREA TODAY...BUT IT WILL MAKE FOR ENOUGH GRADIENT WITH
THE HIGH TO THE NORTH TO KEEP SOME MODEST EASTERLY WINDS IN THE
FORECAST. A NEW LOW WILL FORM ALONG AN OLD BOUNDARY SOUTH OF DUTCH
HARBOR SATURDAY INTO SUNDAY WHICH WILL REINFORCE THESE EASTERLY
WINDS. MODELS ARE STILL STRUGGLING WITH THE DETAILS OF THIS
SYSTEM...SO OPTED TO HOLD AT SMALL CRAFT SPEEDS FOR NOW.

&&

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

THE 12Z DETERMINISTIC AND ENSEMBLE GUIDANCE ARE FINALLY IN GOOD
AGREEMENT WITH THE PROGRESSION OF THE SYNOPTIC PATTERN THROUGH THE
MAJORITY OF THE EXTENDED PERIOD. AN UPPER LEVEL TROUGH SOUTH OF
THE ALEUTIANS ISLANDS AND EXTENDING TO THE ALASKA PANHANDLE WILL
BEGIN PINCHING OFF FROM THE MEAN FLOW AS HIGH PRESSURE OVER THE
BERING SEA AND NORTH PACIFIC BUILD AND CUT OFF AN UPPER LEVEL LOW
SOUTH OF THE EASTERN ALEUTIANS ON SUNDAY. THIS LOW LOOKS AS IF IT
WILL STAY NEARLY STATIONARY WHILE TRACKING SLIGHTLY NORTH DURING
THE WEEK AS BUILDING HIGH PRESSURE TRAPS THE LOW IN THE NORTH
PACIFIC/BERING SEA. TWO OTHER UPPER LOWS (ONE LOCATED OVER THE
KAMCHATKA PENINSULA AND THE OTHER OVER THE ALASKA PANHANDLE) WILL
ACT AS ANCHORS IN THE LONGWAVE PATTERN AND PREVENT THE BREAKDOWN
OF THE RIDGES WHICH WOULD LEAD TO A MORE PROGRESSIVE UPPER LEVEL
PATTERN AND A PATTERN CHANGE. WHAT THIS MEANS FOR ALASKA IS THAT
SOUTHCENTRAL ALASKA WILL LIKELY REMAIN ON THE DRY SIDE WITH PLENTY
OF BREAKS IN CLOUD COVER AS HIGH PRESSURE REMAINS IN FULL CONTROL
OF THE WEATHER. HOWEVER...SOUTHWEST ALASKA AND THE BERING SEA
COULD SEE A BIT CLOUDIER AND WETTER WEATHER DEPENDING ON THE EXACT
TRACK AND EXTENT OF THE UPPER LEVEL LOW AND ITS ASSOCIATED SFC FEATURE.

&&


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

&&

$$

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




000
FXAK68 PAFC 311312
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
512 AM AKDT FRI JUL 31 2015

.ANALYSIS AND UPPER LEVELS...

VERY FEW CHANGES HAVE OCCURRED FROM YESTERDAY AS THE STAGNANT
WEATHER PATTERN HAS PERSISTED. AN UPPER LOW OVER THE SOUTHWESTERN
GULF IS NOW BEGINNING TO CUT OFF AS A RIDGE OVER THE WESTERN
BERING AND EASTERN RUSSIA SHIFTS EASTWARD DUE TO SUBSIDENCE.
BETWEEN THESE FEATURES...THE JET STREAM IS FLOWING GENERALLY ALONG
THE 170W MERIDIAN THROUGH THE BERING INTO THE NORTH PACIFIC. A
STATIONARY VERTICALLY STACKED LOW PERSISTS SOUTH OF THE WESTERN
ALEUTIANS...CUT OFF SOUTH OF THE WESTERN BERING RIDGE. THAT LOW
REMAINS THE STRONGEST SURFACE FEATURE TO AFFECT THE ANCHORAGE
OFFICE AREA OF RESPONSIBILITY. WATER VAPOR IMAGERY INDICATES MUCH
DRIER MID- LEVEL AIR MOVING SOUTH TOWARD SOUTHERN ALASKA FROM THE
WESTERN AND CENTRAL INTERIOR.

&&

.MODEL DISCUSSION...

THE MODELS REMAIN IN EXCELLENT AGREEMENT ON THE LARGE SCALE
PATTERN EVOLUTION GOING INTO THE WEEKEND. THE LACK
OF DEFINABLE SURFACE FEATURES NEAR MAINLAND ALASKA MEANS THAT
SMALL UPPER LEVEL DISTURBANCES INTERACTING WITH THE TERRAIN AND
LOCALIZED CONVERGENCE BOUNDARIES WILL REMAIN THE DRIVING FACTORS
FOR PRECIPITATION THROUGH FRIDAY. AS AN UPPER LEVEL RIDGE BUILDS
EAST INTO MAINLAND ALASKA...WARMING TEMPERATURES IN THE UPPER
LEVELS BY SATURDAY WILL DIMINISH THE INSTABILITY THAT HAS
SUPPORTED DIURNAL SHOWER AND THUNDERSTORM DEVELOPMENT. CONFIDENCE
IS HIGH ON THE OVERALL PATTERN AND MODERATE ON THE TIMING AND
LOCATION OF ANY SHOWERS AND ISOLATED THUNDERSTORMS THROUGH
SATURDAY.

&&

.FIRE WEATHER...

A MOIST WEATHER PATTERN HAS PERSISTED FOR THE PAST WEEK AND
BROUGHT PERIODIC SHOWERS TO MUCH OF SOUTHERN ALASKA. A WARMER AND
DRIER PATTERN IS EXPECTED WITH LESS IN THE WAY OF CLOUD COVER BY
THE WEEKEND...WITH HUMIDITY LEVELS DROPPING BELOW 30 PERCENT THIS
WEEKEND IMMEDIATELY DOWNSTREAM OF THE ALASKA RANGE IN THE SUSITNA
VALLEY AND COPPER RIVER BASIN. THE WET THUNDERSTORM POTENTIAL
REMAINS THROUGH TODAY ESPECIALLY FROM THE TALKEETNA MOUNTAINS
SOUTH TO THE CHUGACH RANGE...AFTER WHICH WARMING TEMPERATURES
ALOFT WILL CAP POTENTIAL CONVECTION AND SIGNIFICANTLY REDUCE THE
THREAT FOR THUNDERSTORMS. THE LACK OF ANY STRONG SURFACE FEATURES
THROUGH THE WEEKEND WILL KEEP WINDS IN MOST AREAS LIGHT.

&&

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

DOWNSLOPE DRYING WILL CLEAR SKIES OUT FROM THE SUSITNA VALLEY
DOWN THROUGH THE COOK INLET REGION...INCLUDING OUTFLOW AREAS ALONG
THE NORTH GULF COAST SUCH AS WHITTIER AND SEWARD. HOWEVER...LOW-
LEVEL MOISTURE WILL BE MUCH SLOWER TO RETREAT FROM THE MOUNTAINS.
WITH SUFFICIENT LOW-LEVEL MOISTURE AND MODERATE TO STRONG DRYING
A FEW THOUSAND FEET ABOVE...INSTABILITY WILL GREATLY INCREASE FROM
THE TALKEETNA MOUNTAINS SOUTH TO THE CHUGACH AND KENAI MOUNTAIN
RANGES. HOWEVER...GIVEN STORM MOTIONS LIKELY TO STAY NORTH OR EVEN
NORTH- NORTHWEST...THE GREATEST IMPACT ON POPULATED AREAS WILL
LIKELY BE THE GLENN HIGHWAY CORRIDOR FROM PALMER TO EUREKA...WHICH
WILL LIE IN THE CROSSHAIRS OF THUNDERSTORM ACTIVITY THAT WILL MOVE
OFF OF THE TALKEETNA MOUNTAINS. THESE STORMS WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY RAINS...SMALL HAIL...AND GUSTY WINDS
WITH THEM.

INCREASING STABILITY AND WARMING TEMPERATURES ALOFT WILL LARGELY
CAP CONVECTIVE ACTIVITY FOR SATURDAY...WITH THE POSSIBLE EXCEPTION
BEING AREAS ALONG THE EASTERN CHUGACH RANGE FROM THE RICHARDSON
HIGHWAY EAST AND SOUTH OF THE EDGERTON HIGHWAY...WHERE ISOLATED
THUNDERSTORMS WILL BE STILL POSSIBLE.

A MID LEVEL RIDGE WILL THEN BUILD INTO THE AREA BY SATURDAY
MORNING...ALLOWING FOR WARMER AND DRIER CONDITIONS TO SPREAD INTO
THE AREA AND PERSIST INTO EARLY NEXT WEEK.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...FRI AND
SAT)...ANOTHER ROUND OF CONVECTION IS IN STORE FOR TODAY...BUT IT
SHOULD BE SLIGHTLY MORE CONSOLIDATED FURTHER SOUTH THAN DAYS PAST.
THE RIDGE FROM THE BERING WILL CONTINUE TO BUILD IN OVER THE NEXT
FEW DAYS. HOWEVER...ON THE LEADING EDGE OF THAT RIDGE...IN A
CORRIDOR FROM KING SALMON TO THE ALEUTIAN RANGE...THERE WILL STILL
BE ENOUGH INSTABILITY THIS AFTERNOON TO MAKE FOR SOME
THUNDERSTORMS. WHILE THEY WILL NOT BE TERRIBLY WIDESPREAD...THOSE
THAT DO FORM WILL HAVE A RATHER UNSTABLE ENVIRONMENT TO TAKE
ADVANTAGE OF WHICH COULD RESULT IN SOME HEAVY DOWNPOURS...GUSTY
WINDS...AND SMALL HAIL. NORTHWEST TO NORTHEAST FLOW WILL PUSH THE
STORMS THROUGH THE ALASKA PENINSULA AND INTO THE GULF OF ALASKA
DURING THE OVERNIGHT HOURS.

SATURDAY WE WILL START TO SEE THE RIDGE BUILDING IN A BIT
STRONGER. THIS SHOULD HELP TO CAP ANY THUNDERSTORMS FROM
DEVELOPING. ALTHOUGH A VERY WEAK UPPER LEVEL WAVE WILL CLIMB OVER
THE TOP OF THE RIDGE AND COULD TRIGGER A FEW SHOWERS LATE IN THE
DAY...ESPECIALLY OVER THE KUSKOKWIM DELTA. OTHERWISE...A WARMING
AND DRYING TREND WILL START TO ESTABLISH ITSELF THROUGH THE
WEEKEND AND PERSIST INTO EARLY NEXT WEEK.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2...FRI AND
SAT)...HIGH PRESSURE WILL REMAIN FIRMLY IN CONTROL OF THE AREA
FOR THE NEXT SEVERAL DAYS. WITH ABUNDANT LOW LEVEL MOISTURE...THIS
MEANS LOW STRATUS AND FOG WILL LIKELY BECOME MORE OF AN ISSUE EACH
DAY. IT WILL ALSO KEEP WINDS LIGHT FOR MOST OF THE BERING SEA. THE
EXCEPTION TO THESE CONDITIONS WILL BE THE CENTRAL TO WESTERN
ALEUTIANS. ONE WEAK AREA OF LOW PRESSURE WILL DRIFT SOUTHWARD AWAY
FROM THE AREA TODAY...BUT IT WILL MAKE FOR ENOUGH GRADIENT WITH
THE HIGH TO THE NORTH TO KEEP SOME MODEST EASTERLY WINDS IN THE
FORECAST. A NEW LOW WILL FORM ALONG AN OLD BOUNDARY SOUTH OF DUTCH
HARBOR SATURDAY INTO SUNDAY WHICH WILL REINFORCE THESE EASTERLY
WINDS. MODELS ARE STILL STRUGGLING WITH THE DETAILS OF THIS
SYSTEM...SO OPTED TO HOLD AT SMALL CRAFT SPEEDS FOR NOW.

&&

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

THE 12Z DETERMINISTIC AND ENSEMBLE GUIDANCE ARE FINALLY IN GOOD
AGREEMENT WITH THE PROGRESSION OF THE SYNOPTIC PATTERN THROUGH THE
MAJORITY OF THE EXTENDED PERIOD. AN UPPER LEVEL TROUGH SOUTH OF
THE ALEUTIANS ISLANDS AND EXTENDING TO THE ALASKA PANHANDLE WILL
BEGIN PINCHING OFF FROM THE MEAN FLOW AS HIGH PRESSURE OVER THE
BERING SEA AND NORTH PACIFIC BUILD AND CUT OFF AN UPPER LEVEL LOW
SOUTH OF THE EASTERN ALEUTIANS ON SUNDAY. THIS LOW LOOKS AS IF IT
WILL STAY NEARLY STATIONARY WHILE TRACKING SLIGHTLY NORTH DURING
THE WEEK AS BUILDING HIGH PRESSURE TRAPS THE LOW IN THE NORTH
PACIFIC/BERING SEA. TWO OTHER UPPER LOWS (ONE LOCATED OVER THE
KAMCHATKA PENINSULA AND THE OTHER OVER THE ALASKA PANHANDLE) WILL
ACT AS ANCHORS IN THE LONGWAVE PATTERN AND PREVENT THE BREAKDOWN
OF THE RIDGES WHICH WOULD LEAD TO A MORE PROGRESSIVE UPPER LEVEL
PATTERN AND A PATTERN CHANGE. WHAT THIS MEANS FOR ALASKA IS THAT
SOUTHCENTRAL ALASKA WILL LIKELY REMAIN ON THE DRY SIDE WITH PLENTY
OF BREAKS IN CLOUD COVER AS HIGH PRESSURE REMAINS IN FULL CONTROL
OF THE WEATHER. HOWEVER...SOUTHWEST ALASKA AND THE BERING SEA
COULD SEE A BIT CLOUDIER AND WETTER WEATHER DEPENDING ON THE EXACT
TRACK AND EXTENT OF THE UPPER LEVEL LOW AND ITS ASSOCIATED SFC FEATURE.

&&


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

&&

$$

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





000
FXAK68 PAFC 310025
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
425 PM AKDT THU JUL 30 2015

.ANALYSIS AND UPPER LEVELS...
VERY FEW CHANGES HAVE OCCURRED FROM YESTERDAY AS THE STAGNANT
WEATHER PATTERN HAS PERSISTED. AN UPPER LOW OVER THE SOUTHWESTERN
GULF IS NOW BEGINNING TO CUT OFF AS A RIDGE OVER THE WESTERN
BERING AND EASTERN RUSSIA SHIFTS EASTWARD DUE TO SUBSIDENCE.
BETWEEN THESE FEATURES...THE JET STREAM IS FLOWING GENERALLY ALONG
THE 170W MERIDIAN THROUGH THE BERING INTO THE NORTH PACIFIC. A
STATIONARY VERTICALLY STACKED LOW PERSISTS SOUTH OF THE WESTERN
ALEUTIANS...CUT OFF SOUTH OF THE WESTERN BERING RIDGE. THAT LOW
REMAINS THE STRONGEST SURFACE FEATURE TO AFFECT THE AOR. OVER THE
BERING...VISIBLE SATELLITE IS SHOWING LOW STRATUS COVERING NEARLY
ALL OF THE SEA AND IS EXPECTED TO PERSIST FOR THE NEXT SEVERAL
DAYS.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN EXCELLENT AGREEMENT ON THE LARGE SCALE
PATTERN EVOLUTION GOING INTO THE WEEKEND. THE LACK OF DEFINABLE
SURFACE FEATURES NEAR MAINLAND ALASKA MEANS THAT SMALL UPPER LEVEL
DISTURBANCES INTERACTING WITH THE TERRAIN WILL REMAIN THE DRIVING
FACTORS FOR PRECIPITATION THROUGH FRIDAY. AS AN UPPER LEVEL RIDGE
BUILDS EAST INTO MAINLAND ALASKA...WARMING TEMPERATURES IN THE
UPPER LEVELS BY SATURDAY WILL DIMINISH THE INSTABILITY THAT HAS
SUPPORTED SPORADIC PERIODIC SHOWER AND THUNDERSTORM DEVELOPMENT.
AS HAS BEEN THE CASE FOR MUCH OF THE PAST WEEK...CONFIDENCE IS
HIGH ON THE OVERALL PATTERN BUT REMAINS LOWER THAN NORMAL ON THE
TIMING AND LOCATION OF ANY SHOWERS AND ISOLATED THUNDERSTORMS.

&&

.FIRE WEATHER...
A MOIST WEATHER PATTERN HAS PERSISTED FOR THE PAST WEEK AND
BROUGHT PERIODIC SHOWERS TO MUCH OF SOUTHERN ALASKA. A WARMER AND
MODESTLY DRIER PATTERN IS EXPECTED WITH LESS IN THE WAY OF CLOUD
COVER BY THE WEEKEND...THOUGH RELATIVE HUMIDITY WILL REMAIN ABOVE
CRITICAL LEVELS DESPITE DEVELOPING WEAK OFFSHORE FLOW. THE WET
THUNDERSTORM POTENTIAL REMAINS THROUGH FRIDAY...AFTER WHICH
WARMING TEMPERATURES ALOFT WILL CAP POTENTIAL CONVECTION AND
SIGNIFICANTLY REDUCE THE THREAT FOR THUNDERSTORMS. THE LACK OF ANY
STRONG SURFACE FEATURES THROUGH THE WEEKEND WILL KEEP WINDS IN
MOST AREAS LIGHT.


&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH LIKE THE LAST TWO DAYS...THE FOCUS TODAY CENTERED AROUND
DIURNAL THUNDERSTORM DEVELOPMENT. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP AGAIN THIS EVENING ALONG THE HIGHER ELEVATIONS
AROUND SOUTHCENTRAL AS THE THERMAL TROUGH PERSISTS UNDER A
DEVELOPING MID LEVEL RIDGE. ONE NOTABLE CHANGE WITH THE AFTERNOON
PACKAGE TODAY WAS TO BRING ISOLATED THUNDERSTORMS TO THE AREAS OF
CHUGACH MOUNTAINS NEAR THE ANCHORAGE BOWL AND MATANUSKA VALLEY AS
INCREASED DAYTIME HEATING FROM CLEARING SKIES THIS AFTERNOON
SHOULD SUPPLY ENOUGH INSTABILITY FOR A FEW STRIKES. THESE
THUNDERSTORMS AGAIN ARE EXPECTED TO HAVE LITTLE IF ANY MOTION AS
WINDS ALOFT REMAIN WEAK...SO ANY DEVELOPMENT WILL BE CONFINED TO
THE MOUNTAINS. THE ATMOSPHERE IS ALSO MOISTURE LADEN (AS WAS
INDICATED WITH PRECIPITABLE WATER VALUES OF 0.75 INCHES)...SO ANY
SHOWERS OR THUNDERSTORMS THIS EVENING HAVE THE POTENTIAL TO
PRODUCE MODERATE TO HEAVY RAINFALL AT TIMES. WITH LITTLE CHANGE IN
THE OVERALL PATTERN OR LOCATION OF THE THERMAL TROUGH ON
FRIDAY...DIURNAL CONVECTION IS EXPECTED AGAIN IN THESE SAME AREAS.
A WEAK LOW THAT WILL DEVELOP NEAR PRINCE WILLIAM SOUND WILL THEN
BRING GUSTY OUTFLOW WINDS TO THE NORTH GULF COAST FROM FRIDAY TO
SATURDAY MORNING...WITH THE STRONGEST WINDS EXPECTED NEAR WHITTIER
WITH GUSTS TO 30 MPH ON FRIDAY AFTERNOON.

A MID LEVEL RIDGE WILL THEN BUILD INTO THE AREA BY SATURDAY
MORNING...ALLOWING FOR WARMER AND DRIER CONDITIONS TO SPREAD INTO
THE AREA FOR THE WEEKEND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...
AFTERNOON AND EVENING SHOWERS ARE EXPECTED ACROSS MUCH OF SOUTHWEST
ALASKA FROM THE KILBUCK MOUNTAINS AND EAST. THERE IS ALSO ENOUGH
INSTABILITY FOR THUNDERSTORM DEVELOPMENT ALONG THE ALASKA RANGE.
OVERNIGHT SHOWERS WILL DIE DOWN BUT WILL COME BACK FRIDAY
AFTERNOON. HOWEVER...AS THE UPPER LEVELS WARM FROM THE NORTHWEST
THE AREA WILL BECOME MORE STABLE PUSHING THE MAJORITY OF THE
SHOWERS TO THE BRISTOL BAY AND ALASKA RANGE AREAS. THESE AREAS
WILL ALSO BE THE LOCATION OF THE BEST OPPORTUNITY FOR
THUNDERSTORMS. AS THE UPPER LEVELS CONTINUE TO WARM INTO THE
WEEKEND THE THREAT OF SHOWERS AND THUNDERSTORMS WILL FADE AWAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
WITH ABUNDANT MOISTURE AND HIGH PRESSURE BUILDING IN...FOG AND
STRATUS WILL BE THE NORM FOR THE BERING AND ALEUTIANS INTO THE
WEEKEND. FOR THE CENTRAL AND WESTERN ALEUTIANS A WEAK LOW SOUTH
OF THE ISLANDS WILL BRING IN SOME LIGHT RAIN INTO THE WEEKEND IN
ADDITION TO THE FOG AND STRATUS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE 12Z DETERMINISTIC AND ENSEMBLE GUIDANCE ARE FINALLY IN GOOD
AGREEMENT WITH THE PROGRESSION OF THE SYNOPTIC PATTERN THROUGH THE
MAJORITY OF THE EXTENDED PERIOD. AN UPPER LEVEL TROUGH SOUTH OF
THE ALEUTIANS ISLANDS AND EXTENDING TO THE ALASKA PANHANDLE WILL
BEGIN PINCHING OFF FROM THE MEAN FLOW AS HIGH PRESSURE OVER THE
BERING SEA AND NORTH PACIFIC BUILD AND CUT OFF AN UPPER LEVEL LOW
SOUTH OF THE EASTERN ALEUTIANS ON SUNDAY. THIS LOW LOOKS AS IF IT
WILL STAY NEARLY STATIONARY WHILE TRACKING SLIGHTLY NORTH DURING
THE WEEK AS BUILDING HIGH PRESSURE TRAPS THE LOW IN THE NORTH
PACIFIC/BERING SEA. TWO OTHER UPPER LOWS (ONE LOCATED OVER THE
KAMCHATKA PENINSULA AND THE OTHER OVER THE ALASKA PANHANDLE) WILL
ACT AS ANCHORS IN THE LONGWAVE PATTERN AND PREVENT THE BREAKDOWN
OF THE RIDGES WHICH WOULD LEAD TO A MORE PROGRESSIVE UPPER LEVEL
PATTERN AND A PATTERN CHANGE. WHAT THIS MEANS FOR ALASKA IS THAT
SOUTHCENTRAL ALASKA WILL LIKELY REMAIN ON THE DRY SIDE WITH PLENTY
OF BREAKS IN CLOUD COVER AS HIGH PRESSURE REMAINS IN FULL CONTROL
OF THE WEATHER. HOWEVER...SOUTHWEST ALASKA AND THE BERING SEA
COULD SEE A BIT CLOUDIER AND WETTER WEATHER DEPENDING ON THE EXACT
TRACK AND EXTENT OF THE UPPER LEVEL LOW AND ITS ASSOCIATED SFC
FEATURE.

&&


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

&&

$$

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




000
FXAK68 PAFC 310025
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
425 PM AKDT THU JUL 30 2015

.ANALYSIS AND UPPER LEVELS...
VERY FEW CHANGES HAVE OCCURRED FROM YESTERDAY AS THE STAGNANT
WEATHER PATTERN HAS PERSISTED. AN UPPER LOW OVER THE SOUTHWESTERN
GULF IS NOW BEGINNING TO CUT OFF AS A RIDGE OVER THE WESTERN
BERING AND EASTERN RUSSIA SHIFTS EASTWARD DUE TO SUBSIDENCE.
BETWEEN THESE FEATURES...THE JET STREAM IS FLOWING GENERALLY ALONG
THE 170W MERIDIAN THROUGH THE BERING INTO THE NORTH PACIFIC. A
STATIONARY VERTICALLY STACKED LOW PERSISTS SOUTH OF THE WESTERN
ALEUTIANS...CUT OFF SOUTH OF THE WESTERN BERING RIDGE. THAT LOW
REMAINS THE STRONGEST SURFACE FEATURE TO AFFECT THE AOR. OVER THE
BERING...VISIBLE SATELLITE IS SHOWING LOW STRATUS COVERING NEARLY
ALL OF THE SEA AND IS EXPECTED TO PERSIST FOR THE NEXT SEVERAL
DAYS.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN EXCELLENT AGREEMENT ON THE LARGE SCALE
PATTERN EVOLUTION GOING INTO THE WEEKEND. THE LACK OF DEFINABLE
SURFACE FEATURES NEAR MAINLAND ALASKA MEANS THAT SMALL UPPER LEVEL
DISTURBANCES INTERACTING WITH THE TERRAIN WILL REMAIN THE DRIVING
FACTORS FOR PRECIPITATION THROUGH FRIDAY. AS AN UPPER LEVEL RIDGE
BUILDS EAST INTO MAINLAND ALASKA...WARMING TEMPERATURES IN THE
UPPER LEVELS BY SATURDAY WILL DIMINISH THE INSTABILITY THAT HAS
SUPPORTED SPORADIC PERIODIC SHOWER AND THUNDERSTORM DEVELOPMENT.
AS HAS BEEN THE CASE FOR MUCH OF THE PAST WEEK...CONFIDENCE IS
HIGH ON THE OVERALL PATTERN BUT REMAINS LOWER THAN NORMAL ON THE
TIMING AND LOCATION OF ANY SHOWERS AND ISOLATED THUNDERSTORMS.

&&

.FIRE WEATHER...
A MOIST WEATHER PATTERN HAS PERSISTED FOR THE PAST WEEK AND
BROUGHT PERIODIC SHOWERS TO MUCH OF SOUTHERN ALASKA. A WARMER AND
MODESTLY DRIER PATTERN IS EXPECTED WITH LESS IN THE WAY OF CLOUD
COVER BY THE WEEKEND...THOUGH RELATIVE HUMIDITY WILL REMAIN ABOVE
CRITICAL LEVELS DESPITE DEVELOPING WEAK OFFSHORE FLOW. THE WET
THUNDERSTORM POTENTIAL REMAINS THROUGH FRIDAY...AFTER WHICH
WARMING TEMPERATURES ALOFT WILL CAP POTENTIAL CONVECTION AND
SIGNIFICANTLY REDUCE THE THREAT FOR THUNDERSTORMS. THE LACK OF ANY
STRONG SURFACE FEATURES THROUGH THE WEEKEND WILL KEEP WINDS IN
MOST AREAS LIGHT.


&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH LIKE THE LAST TWO DAYS...THE FOCUS TODAY CENTERED AROUND
DIURNAL THUNDERSTORM DEVELOPMENT. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP AGAIN THIS EVENING ALONG THE HIGHER ELEVATIONS
AROUND SOUTHCENTRAL AS THE THERMAL TROUGH PERSISTS UNDER A
DEVELOPING MID LEVEL RIDGE. ONE NOTABLE CHANGE WITH THE AFTERNOON
PACKAGE TODAY WAS TO BRING ISOLATED THUNDERSTORMS TO THE AREAS OF
CHUGACH MOUNTAINS NEAR THE ANCHORAGE BOWL AND MATANUSKA VALLEY AS
INCREASED DAYTIME HEATING FROM CLEARING SKIES THIS AFTERNOON
SHOULD SUPPLY ENOUGH INSTABILITY FOR A FEW STRIKES. THESE
THUNDERSTORMS AGAIN ARE EXPECTED TO HAVE LITTLE IF ANY MOTION AS
WINDS ALOFT REMAIN WEAK...SO ANY DEVELOPMENT WILL BE CONFINED TO
THE MOUNTAINS. THE ATMOSPHERE IS ALSO MOISTURE LADEN (AS WAS
INDICATED WITH PRECIPITABLE WATER VALUES OF 0.75 INCHES)...SO ANY
SHOWERS OR THUNDERSTORMS THIS EVENING HAVE THE POTENTIAL TO
PRODUCE MODERATE TO HEAVY RAINFALL AT TIMES. WITH LITTLE CHANGE IN
THE OVERALL PATTERN OR LOCATION OF THE THERMAL TROUGH ON
FRIDAY...DIURNAL CONVECTION IS EXPECTED AGAIN IN THESE SAME AREAS.
A WEAK LOW THAT WILL DEVELOP NEAR PRINCE WILLIAM SOUND WILL THEN
BRING GUSTY OUTFLOW WINDS TO THE NORTH GULF COAST FROM FRIDAY TO
SATURDAY MORNING...WITH THE STRONGEST WINDS EXPECTED NEAR WHITTIER
WITH GUSTS TO 30 MPH ON FRIDAY AFTERNOON.

A MID LEVEL RIDGE WILL THEN BUILD INTO THE AREA BY SATURDAY
MORNING...ALLOWING FOR WARMER AND DRIER CONDITIONS TO SPREAD INTO
THE AREA FOR THE WEEKEND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...
AFTERNOON AND EVENING SHOWERS ARE EXPECTED ACROSS MUCH OF SOUTHWEST
ALASKA FROM THE KILBUCK MOUNTAINS AND EAST. THERE IS ALSO ENOUGH
INSTABILITY FOR THUNDERSTORM DEVELOPMENT ALONG THE ALASKA RANGE.
OVERNIGHT SHOWERS WILL DIE DOWN BUT WILL COME BACK FRIDAY
AFTERNOON. HOWEVER...AS THE UPPER LEVELS WARM FROM THE NORTHWEST
THE AREA WILL BECOME MORE STABLE PUSHING THE MAJORITY OF THE
SHOWERS TO THE BRISTOL BAY AND ALASKA RANGE AREAS. THESE AREAS
WILL ALSO BE THE LOCATION OF THE BEST OPPORTUNITY FOR
THUNDERSTORMS. AS THE UPPER LEVELS CONTINUE TO WARM INTO THE
WEEKEND THE THREAT OF SHOWERS AND THUNDERSTORMS WILL FADE AWAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
WITH ABUNDANT MOISTURE AND HIGH PRESSURE BUILDING IN...FOG AND
STRATUS WILL BE THE NORM FOR THE BERING AND ALEUTIANS INTO THE
WEEKEND. FOR THE CENTRAL AND WESTERN ALEUTIANS A WEAK LOW SOUTH
OF THE ISLANDS WILL BRING IN SOME LIGHT RAIN INTO THE WEEKEND IN
ADDITION TO THE FOG AND STRATUS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE 12Z DETERMINISTIC AND ENSEMBLE GUIDANCE ARE FINALLY IN GOOD
AGREEMENT WITH THE PROGRESSION OF THE SYNOPTIC PATTERN THROUGH THE
MAJORITY OF THE EXTENDED PERIOD. AN UPPER LEVEL TROUGH SOUTH OF
THE ALEUTIANS ISLANDS AND EXTENDING TO THE ALASKA PANHANDLE WILL
BEGIN PINCHING OFF FROM THE MEAN FLOW AS HIGH PRESSURE OVER THE
BERING SEA AND NORTH PACIFIC BUILD AND CUT OFF AN UPPER LEVEL LOW
SOUTH OF THE EASTERN ALEUTIANS ON SUNDAY. THIS LOW LOOKS AS IF IT
WILL STAY NEARLY STATIONARY WHILE TRACKING SLIGHTLY NORTH DURING
THE WEEK AS BUILDING HIGH PRESSURE TRAPS THE LOW IN THE NORTH
PACIFIC/BERING SEA. TWO OTHER UPPER LOWS (ONE LOCATED OVER THE
KAMCHATKA PENINSULA AND THE OTHER OVER THE ALASKA PANHANDLE) WILL
ACT AS ANCHORS IN THE LONGWAVE PATTERN AND PREVENT THE BREAKDOWN
OF THE RIDGES WHICH WOULD LEAD TO A MORE PROGRESSIVE UPPER LEVEL
PATTERN AND A PATTERN CHANGE. WHAT THIS MEANS FOR ALASKA IS THAT
SOUTHCENTRAL ALASKA WILL LIKELY REMAIN ON THE DRY SIDE WITH PLENTY
OF BREAKS IN CLOUD COVER AS HIGH PRESSURE REMAINS IN FULL CONTROL
OF THE WEATHER. HOWEVER...SOUTHWEST ALASKA AND THE BERING SEA
COULD SEE A BIT CLOUDIER AND WETTER WEATHER DEPENDING ON THE EXACT
TRACK AND EXTENT OF THE UPPER LEVEL LOW AND ITS ASSOCIATED SFC
FEATURE.

&&


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

&&

$$

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





000
FXAK68 PAFC 310025
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
425 PM AKDT THU JUL 30 2015

.ANALYSIS AND UPPER LEVELS...
VERY FEW CHANGES HAVE OCCURRED FROM YESTERDAY AS THE STAGNANT
WEATHER PATTERN HAS PERSISTED. AN UPPER LOW OVER THE SOUTHWESTERN
GULF IS NOW BEGINNING TO CUT OFF AS A RIDGE OVER THE WESTERN
BERING AND EASTERN RUSSIA SHIFTS EASTWARD DUE TO SUBSIDENCE.
BETWEEN THESE FEATURES...THE JET STREAM IS FLOWING GENERALLY ALONG
THE 170W MERIDIAN THROUGH THE BERING INTO THE NORTH PACIFIC. A
STATIONARY VERTICALLY STACKED LOW PERSISTS SOUTH OF THE WESTERN
ALEUTIANS...CUT OFF SOUTH OF THE WESTERN BERING RIDGE. THAT LOW
REMAINS THE STRONGEST SURFACE FEATURE TO AFFECT THE AOR. OVER THE
BERING...VISIBLE SATELLITE IS SHOWING LOW STRATUS COVERING NEARLY
ALL OF THE SEA AND IS EXPECTED TO PERSIST FOR THE NEXT SEVERAL
DAYS.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN EXCELLENT AGREEMENT ON THE LARGE SCALE
PATTERN EVOLUTION GOING INTO THE WEEKEND. THE LACK OF DEFINABLE
SURFACE FEATURES NEAR MAINLAND ALASKA MEANS THAT SMALL UPPER LEVEL
DISTURBANCES INTERACTING WITH THE TERRAIN WILL REMAIN THE DRIVING
FACTORS FOR PRECIPITATION THROUGH FRIDAY. AS AN UPPER LEVEL RIDGE
BUILDS EAST INTO MAINLAND ALASKA...WARMING TEMPERATURES IN THE
UPPER LEVELS BY SATURDAY WILL DIMINISH THE INSTABILITY THAT HAS
SUPPORTED SPORADIC PERIODIC SHOWER AND THUNDERSTORM DEVELOPMENT.
AS HAS BEEN THE CASE FOR MUCH OF THE PAST WEEK...CONFIDENCE IS
HIGH ON THE OVERALL PATTERN BUT REMAINS LOWER THAN NORMAL ON THE
TIMING AND LOCATION OF ANY SHOWERS AND ISOLATED THUNDERSTORMS.

&&

.FIRE WEATHER...
A MOIST WEATHER PATTERN HAS PERSISTED FOR THE PAST WEEK AND
BROUGHT PERIODIC SHOWERS TO MUCH OF SOUTHERN ALASKA. A WARMER AND
MODESTLY DRIER PATTERN IS EXPECTED WITH LESS IN THE WAY OF CLOUD
COVER BY THE WEEKEND...THOUGH RELATIVE HUMIDITY WILL REMAIN ABOVE
CRITICAL LEVELS DESPITE DEVELOPING WEAK OFFSHORE FLOW. THE WET
THUNDERSTORM POTENTIAL REMAINS THROUGH FRIDAY...AFTER WHICH
WARMING TEMPERATURES ALOFT WILL CAP POTENTIAL CONVECTION AND
SIGNIFICANTLY REDUCE THE THREAT FOR THUNDERSTORMS. THE LACK OF ANY
STRONG SURFACE FEATURES THROUGH THE WEEKEND WILL KEEP WINDS IN
MOST AREAS LIGHT.


&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH LIKE THE LAST TWO DAYS...THE FOCUS TODAY CENTERED AROUND
DIURNAL THUNDERSTORM DEVELOPMENT. SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP AGAIN THIS EVENING ALONG THE HIGHER ELEVATIONS
AROUND SOUTHCENTRAL AS THE THERMAL TROUGH PERSISTS UNDER A
DEVELOPING MID LEVEL RIDGE. ONE NOTABLE CHANGE WITH THE AFTERNOON
PACKAGE TODAY WAS TO BRING ISOLATED THUNDERSTORMS TO THE AREAS OF
CHUGACH MOUNTAINS NEAR THE ANCHORAGE BOWL AND MATANUSKA VALLEY AS
INCREASED DAYTIME HEATING FROM CLEARING SKIES THIS AFTERNOON
SHOULD SUPPLY ENOUGH INSTABILITY FOR A FEW STRIKES. THESE
THUNDERSTORMS AGAIN ARE EXPECTED TO HAVE LITTLE IF ANY MOTION AS
WINDS ALOFT REMAIN WEAK...SO ANY DEVELOPMENT WILL BE CONFINED TO
THE MOUNTAINS. THE ATMOSPHERE IS ALSO MOISTURE LADEN (AS WAS
INDICATED WITH PRECIPITABLE WATER VALUES OF 0.75 INCHES)...SO ANY
SHOWERS OR THUNDERSTORMS THIS EVENING HAVE THE POTENTIAL TO
PRODUCE MODERATE TO HEAVY RAINFALL AT TIMES. WITH LITTLE CHANGE IN
THE OVERALL PATTERN OR LOCATION OF THE THERMAL TROUGH ON
FRIDAY...DIURNAL CONVECTION IS EXPECTED AGAIN IN THESE SAME AREAS.
A WEAK LOW THAT WILL DEVELOP NEAR PRINCE WILLIAM SOUND WILL THEN
BRING GUSTY OUTFLOW WINDS TO THE NORTH GULF COAST FROM FRIDAY TO
SATURDAY MORNING...WITH THE STRONGEST WINDS EXPECTED NEAR WHITTIER
WITH GUSTS TO 30 MPH ON FRIDAY AFTERNOON.

A MID LEVEL RIDGE WILL THEN BUILD INTO THE AREA BY SATURDAY
MORNING...ALLOWING FOR WARMER AND DRIER CONDITIONS TO SPREAD INTO
THE AREA FOR THE WEEKEND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA...
AFTERNOON AND EVENING SHOWERS ARE EXPECTED ACROSS MUCH OF SOUTHWEST
ALASKA FROM THE KILBUCK MOUNTAINS AND EAST. THERE IS ALSO ENOUGH
INSTABILITY FOR THUNDERSTORM DEVELOPMENT ALONG THE ALASKA RANGE.
OVERNIGHT SHOWERS WILL DIE DOWN BUT WILL COME BACK FRIDAY
AFTERNOON. HOWEVER...AS THE UPPER LEVELS WARM FROM THE NORTHWEST
THE AREA WILL BECOME MORE STABLE PUSHING THE MAJORITY OF THE
SHOWERS TO THE BRISTOL BAY AND ALASKA RANGE AREAS. THESE AREAS
WILL ALSO BE THE LOCATION OF THE BEST OPPORTUNITY FOR
THUNDERSTORMS. AS THE UPPER LEVELS CONTINUE TO WARM INTO THE
WEEKEND THE THREAT OF SHOWERS AND THUNDERSTORMS WILL FADE AWAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS...
WITH ABUNDANT MOISTURE AND HIGH PRESSURE BUILDING IN...FOG AND
STRATUS WILL BE THE NORM FOR THE BERING AND ALEUTIANS INTO THE
WEEKEND. FOR THE CENTRAL AND WESTERN ALEUTIANS A WEAK LOW SOUTH
OF THE ISLANDS WILL BRING IN SOME LIGHT RAIN INTO THE WEEKEND IN
ADDITION TO THE FOG AND STRATUS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
THE 12Z DETERMINISTIC AND ENSEMBLE GUIDANCE ARE FINALLY IN GOOD
AGREEMENT WITH THE PROGRESSION OF THE SYNOPTIC PATTERN THROUGH THE
MAJORITY OF THE EXTENDED PERIOD. AN UPPER LEVEL TROUGH SOUTH OF
THE ALEUTIANS ISLANDS AND EXTENDING TO THE ALASKA PANHANDLE WILL
BEGIN PINCHING OFF FROM THE MEAN FLOW AS HIGH PRESSURE OVER THE
BERING SEA AND NORTH PACIFIC BUILD AND CUT OFF AN UPPER LEVEL LOW
SOUTH OF THE EASTERN ALEUTIANS ON SUNDAY. THIS LOW LOOKS AS IF IT
WILL STAY NEARLY STATIONARY WHILE TRACKING SLIGHTLY NORTH DURING
THE WEEK AS BUILDING HIGH PRESSURE TRAPS THE LOW IN THE NORTH
PACIFIC/BERING SEA. TWO OTHER UPPER LOWS (ONE LOCATED OVER THE
KAMCHATKA PENINSULA AND THE OTHER OVER THE ALASKA PANHANDLE) WILL
ACT AS ANCHORS IN THE LONGWAVE PATTERN AND PREVENT THE BREAKDOWN
OF THE RIDGES WHICH WOULD LEAD TO A MORE PROGRESSIVE UPPER LEVEL
PATTERN AND A PATTERN CHANGE. WHAT THIS MEANS FOR ALASKA IS THAT
SOUTHCENTRAL ALASKA WILL LIKELY REMAIN ON THE DRY SIDE WITH PLENTY
OF BREAKS IN CLOUD COVER AS HIGH PRESSURE REMAINS IN FULL CONTROL
OF THE WEATHER. HOWEVER...SOUTHWEST ALASKA AND THE BERING SEA
COULD SEE A BIT CLOUDIER AND WETTER WEATHER DEPENDING ON THE EXACT
TRACK AND EXTENT OF THE UPPER LEVEL LOW AND ITS ASSOCIATED SFC
FEATURE.

&&


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

&&

$$

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




000
FXAK68 PAFC 301253
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
453 AM AKDT THU JUL 30 2015

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL TROUGH AXIS RESIDES FROM THE NORTHWEST TERRITORIES
THROUGH THE YUKON THROUGH THE SOUTHERN GULF TO THE SOUTHEASTERN
BERING. ANOTHER STACKED LOW RESIDES ABOUT 250 MILES SOUTHEAST OF
SHEMYA. AN UPPER LEVEL HIGH RESIDES OVER THE FAR WESTERN
BERING...WITH SUBTLE RIDGING FROM NEAR THE BERING STRAIT EXTENDING
SOUTH AND EAST AND NOSING INTO THE UPPER COOK INLET REGION.

THERE IS VERY LITTLE CHANGE IN THE GEOPOTENTIAL HEIGHT FIELD BETWEEN
THE UPPER LEVEL TROUGH AND EMBEDDED LOWS AND THE UPPER LEVEL
RIDGING...AN INDICATION THAT VERY WEAK FLOW EXISTS ACROSS THE
REGION. THE SURFACE PATTERN IS NOT MUCH DIFFERENT...WITH A WEAK
THERMAL TROUGH OVER THE SOUTHERN INTERIOR OF ALASKA WITH A WEAK
SURFACE RIDGE OVER THE NORTH GULF COAST.

&&

.MODEL DISCUSSION...

OVER THE NEXT DAY OR TWO THE STAGNANT SLOW-CHANGING WEATHER
PATTERN CONTINUES TO AID THE MODELS` EXCELLENT AGREEMENT IN
SHOWING A LACK OF ANY STRONG FEATURES. THEREFORE ONCE AGAIN THE
PRIMARY DRIVERS OF THE WEATHER ARE MUCH SMALLER TRANSIENT FEATURES
THAT ARE GENERALLY NOT WELL RESOLVED BY THE MODELS. BECAUSE OF
THEIR BETTER RESOLUTION AND LESS SMOOTHING...THE LOCAL MODELS WERE
PREFERRED FOR THIS FORECAST PACKAGE. LOCAL CONVERGENCE ZONES IN
OTHERWISE VERY SLOW MOVING FLOW WILL CONTINUE TO PRODUCE SHOWER
ACTIVITY...WITH A FEW THUNDERSTORMS ALONG THE MOUNTAINS IN THE
MOIST ENVIRONMENT. CONFIDENCE REMAINS LOWER THAN NORMAL CONCERNING
THE TIMING OF THESE SHOWERS AND THUNDERSTORMS OVER MOST OF
SOUTHERN ALASKA.

THE MODELS CONTINUE TO AGREE THAT THE TROUGH WILL GRADUALLY BREAK
DOWN OVER MAINLAND ALASKA...LEAVING A CUTOFF LOW OVER THE GULF AND
THE WESTERN BERING RIDGE SPREADING EASTWARD TO REPLACE THE
TROUGH. INITIALLY THE HEIGHT RISES WILL BE DUE TO SUBSIDENCE AND
THE UPPER LOW OVER THE SOUTHWESTERN GULF CUTTING OFF FROM THE COLD
POOL OF AIR ALONG THE ARCTIC COAST...AND NOT SIGNIFICANT WARMING
OF THE UPPER LEVELS UNTIL THE WEEKEND. THIS PATTERN WILL HELP
PROLONG THE INSTABILITY NEEDED FOR THUNDERSTORM DEVELOPMENT NEAR
THE MOUNTAINS AND LOCAL CONVERGENCE ZONES FOR THE REMAINDER OF THE
WORKWEEK.

&&

.FIRE WEATHER...

THE DEEP...MOIST...NEARLY STAGNANT AIR MASS IN PLACE CONTINUES TO
KEEP FIRE WEATHER CONCERNS MINIMAL FOR MOST OF SOUTHERN ALASKA
WITH CONTINUED HIGH RELATIVE HUMIDITY...LIGHT WINDS...AND
EXTENSIVE CLOUD COVER. WET THUNDERSTORMS REMAIN A POSSIBILITY
NEAR THE MOUNTAINS AS THE ATMOSPHERE REMAINS MOIST AND UNSTABLE. A
WARMING AND DRYING TREND REMAINS IN THE FORECAST OVER THE COMING
DAYS WITH THE BUILDING UPPER LEVEL RIDGE INTO SOUTHERN ALASKA.
RELATIVE HUMIDITIES THOUGH SHOULD REMAIN ALMOST ENTIRELY ABOVE 30
PERCENT EVEN WITH OFFSHORE FLOW. WARMING IN THE UPPER LEVELS BY
THE WEEKEND WILL INCREASE STABILITY AND HELP CAP POTENTIAL
CONVECTION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH OF SOUTHCENTRAL WILL HAVE PERSISTENT CLOUDY AND SHOWERY
WEATHER TODAY AS WEAK SYNOPTIC FORCING WILL PREVENT ANY
SIGNIFICANT CHANGE IN THE WEATHER. THE ATMOSPHERE REMAINS VERY
MOIST HOWEVER...SO ANY SHOWERS THAT DO FORM HAVE THE POTENTIAL TO
PRODUCE BRIEF PERIODS OF MODERATE TO HEAVY RAIN. AFTERNOON/EVENING
THUNDERSTORMS WILL OCCUR ONCE AGAIN MAINLY OVER THE TALKEETNA
MOUNTAINS...ALASKA RANGE AND THE WESTERN KENAI PENINSULA TODAY...HOWEVER
WITH WEAK WINDS ALOFT THERE SHOULD BE LITTLE IF ANY MOVEMENT OF THESE
SHOWERS. WINDS WILL REMAIN LIGHT IN MOST AREAS.

BY FRIDAY...RIDGING ALOFT BUILDING IN FROM THE WEST WILL BEGIN TO
STRENGTHEN AND BRING WARMER AND DRIER CONDITIONS TO MOST AREAS.
THUNDERSTORM ACTIVITY SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
CLOSER TO THE GULF COAST WHERE THE BEST COMBINATION OF LOW-LEVEL
MOISTURE...MID-LEVEL DRYING...AND A MID-LEVEL DISTURBANCE WILL BE
LOCATED. INCREASING OFFSHORE FLOW IN THE LOWER LEVELS WILL LIKELY
MEAN NORTH GULF COAST LOCATIONS SUCH AS SEWARD COULD SEE
TEMPERATURES CLIMB INTO THE 70S FOR HIGHS.

CONVECTION SHOULD BE GREATLY LIMITED FOR SATURDAY TO LOCATIONS
TOWARD THE FAR SOUTHEASTERN COPPER RIVER BASIN AND THE FAR EASTERN
CHUGACH RANGE.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK THERMAL TROUGH ACROSS THE INTERIOR WITH AN AXIS EXTENDING
INTO THE SOUTHWEST...WILL REMAIN A FOCUS FOR AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS TO DEVELOP THROUGH THIS EVENING. CONDITIONS
WILL BECOME MORE STABLE FROM NORTH TO SOUTH FRIDAY...WITH GREATEST
INSTABILITY AND POTENTIAL FOR SHOWERS AND STORMS TO BE LOCATED
TOWARD THE BRISTOL BAY COAST AND NORTHERN ALASKA PENINSULA...FIRST
IN THE AFTERNOON WITH INTERACTION OF LOCALIZED CONVERGENCE
BOUNDARIES (SEA-BREEZE)...AND LATER WELL INTO THE OVERNIGHT WITH
A MID-LEVEL DISTURBANCE APPROACHING FROM THE NORTH.

 &&

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

RIDGING BUILDS INTO THE CENTRAL BERING THROUGH FRIDAY NIGHT WITH
A WEAKENING UPPER LOW ALONG THE WESTERN AND CENTRAL ALEUTIANS.
THIS IS A RELATIVELY BENIGN SURFACE PATTERN WITH SMALL CRAFT WINDS
CONFINED TO THE WESTERN HALF OF THE ALEUTIANS. CLOUDY CONDITIONS
WILL ENCOMPASS THE BERING WITH WEAK EMBEDDED SHORTWAVES PRODUCING
OCCASIONAL SHOWERS. AREAS OF DENSE FOG IS EXPECTED TO FORM TODAY
INTO FRIDAY AS STABLE CONDITIONS SETTLE ACROSS THE CENTRAL
BERING.


&&

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

AN UPPER LEVEL RIDGE WILL OVERSPREAD THE MAJORITY OF THE STATE
THROUGH THE WEEKEND. WHILE THIS RIDGE BUILDS ACROSS THE STATE...A
PORTION OF THE LONGWAVE TROUGH THAT HAS BEEN CREATING THE SHOWERY
WEATHER ACROSS THE STATE WILL GET CUT OFF AS RIDGING BUILDS ACROSS
THE NORTH PACIFIC. THIS WILL CREATE A CUT OFF LOW SOUTH OF THE
EASTERN ALEUTIANS THAT IS EXPECTED TO DEVELOP ON SATURDAY AS A
SHORTWAVE INTERACTS WITH MULTIPLE FRAGMENTS OF ENERGY ASSOCIATED
WITH THE UPPER LEVEL TROUGH THAT IS GETTING CUT OFF. THE
DETERMINISTIC AND ENSEMBLE MEMBERS HAVE THE DEVELOPMENT OF THIS
LOW PROGGED FAIRLY WELL AS IT DEVELOPS SOUTH OF THE EASTERN
ALEUTIANS SATURDAY. MODELS THEN BEGIN TO STRUGGLE WITH THE
PLACEMENT OF THIS UPPER LEVEL FEATURE AND AN ASSOCIATED SURFACE
LOW THAT DEVELOPS IN RESPONSE TO MID AND UPPER LEVEL CYCLOGENESIS.
THE REASON FOR THE DIFFICULTY IN TIMING AND PLACEMENT IS BECAUSE
STEERING CURRENTS CAN BE QUITE DIFFICULT TO DETERMINE WHEN A LOW
IS NO LONGER LOCATED IN A TROUGH BUT RATHER STUCK BETWEEN TWO
UPPER LEVEL RIDGES. IN SHORT...DEPENDING ON HOW THE LONGWAVE
TROUGH (ROSSBY WAVE) OVER RUSSIA DEVELOPS IN RESPONSE TO A
DEEPENING AREA OF LOW PRESSURE WILL INFLUENCE THE WESTERN RIDGE
OVER THE BERING SEA AND HOW IT WILL FORCE THE AREA OF LOW PRESSURE
IN THE NORTH PACIFIC EAST INTO THE GULF OF ALASKA OR POSSIBLY EVEN
INTO THE ALASKA MAINLAND. WHAT THIS MEANS FOR ALASKA IS THAT A
PERIOD OF WARMER TEMPERATURES...DRIER CONDITIONS AND LESS CLOUDY
SKIES WILL LIKELY BE OBSERVED THROUGH THE WEEKEND AND INTO THE
BEGINNING OF NEXT WEEK. DEPENDING ON THE TRACK OF THE UPPER LEVEL
AND SURFACE LOWS...RAIN CHANCES MAY SNEAK BACK IN TOWARD THE
MIDDLE OF NEXT WEEK BUT CONFIDENCE IS NOT HIGH WITH MORE THAN
SCATTERED SHOWERS AT THIS TIME.

&&




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

&&

$$

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





000
FXAK68 PAFC 301253
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
453 AM AKDT THU JUL 30 2015

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL TROUGH AXIS RESIDES FROM THE NORTHWEST TERRITORIES
THROUGH THE YUKON THROUGH THE SOUTHERN GULF TO THE SOUTHEASTERN
BERING. ANOTHER STACKED LOW RESIDES ABOUT 250 MILES SOUTHEAST OF
SHEMYA. AN UPPER LEVEL HIGH RESIDES OVER THE FAR WESTERN
BERING...WITH SUBTLE RIDGING FROM NEAR THE BERING STRAIT EXTENDING
SOUTH AND EAST AND NOSING INTO THE UPPER COOK INLET REGION.

THERE IS VERY LITTLE CHANGE IN THE GEOPOTENTIAL HEIGHT FIELD BETWEEN
THE UPPER LEVEL TROUGH AND EMBEDDED LOWS AND THE UPPER LEVEL
RIDGING...AN INDICATION THAT VERY WEAK FLOW EXISTS ACROSS THE
REGION. THE SURFACE PATTERN IS NOT MUCH DIFFERENT...WITH A WEAK
THERMAL TROUGH OVER THE SOUTHERN INTERIOR OF ALASKA WITH A WEAK
SURFACE RIDGE OVER THE NORTH GULF COAST.

&&

.MODEL DISCUSSION...

OVER THE NEXT DAY OR TWO THE STAGNANT SLOW-CHANGING WEATHER
PATTERN CONTINUES TO AID THE MODELS` EXCELLENT AGREEMENT IN
SHOWING A LACK OF ANY STRONG FEATURES. THEREFORE ONCE AGAIN THE
PRIMARY DRIVERS OF THE WEATHER ARE MUCH SMALLER TRANSIENT FEATURES
THAT ARE GENERALLY NOT WELL RESOLVED BY THE MODELS. BECAUSE OF
THEIR BETTER RESOLUTION AND LESS SMOOTHING...THE LOCAL MODELS WERE
PREFERRED FOR THIS FORECAST PACKAGE. LOCAL CONVERGENCE ZONES IN
OTHERWISE VERY SLOW MOVING FLOW WILL CONTINUE TO PRODUCE SHOWER
ACTIVITY...WITH A FEW THUNDERSTORMS ALONG THE MOUNTAINS IN THE
MOIST ENVIRONMENT. CONFIDENCE REMAINS LOWER THAN NORMAL CONCERNING
THE TIMING OF THESE SHOWERS AND THUNDERSTORMS OVER MOST OF
SOUTHERN ALASKA.

THE MODELS CONTINUE TO AGREE THAT THE TROUGH WILL GRADUALLY BREAK
DOWN OVER MAINLAND ALASKA...LEAVING A CUTOFF LOW OVER THE GULF AND
THE WESTERN BERING RIDGE SPREADING EASTWARD TO REPLACE THE
TROUGH. INITIALLY THE HEIGHT RISES WILL BE DUE TO SUBSIDENCE AND
THE UPPER LOW OVER THE SOUTHWESTERN GULF CUTTING OFF FROM THE COLD
POOL OF AIR ALONG THE ARCTIC COAST...AND NOT SIGNIFICANT WARMING
OF THE UPPER LEVELS UNTIL THE WEEKEND. THIS PATTERN WILL HELP
PROLONG THE INSTABILITY NEEDED FOR THUNDERSTORM DEVELOPMENT NEAR
THE MOUNTAINS AND LOCAL CONVERGENCE ZONES FOR THE REMAINDER OF THE
WORKWEEK.

&&

.FIRE WEATHER...

THE DEEP...MOIST...NEARLY STAGNANT AIR MASS IN PLACE CONTINUES TO
KEEP FIRE WEATHER CONCERNS MINIMAL FOR MOST OF SOUTHERN ALASKA
WITH CONTINUED HIGH RELATIVE HUMIDITY...LIGHT WINDS...AND
EXTENSIVE CLOUD COVER. WET THUNDERSTORMS REMAIN A POSSIBILITY
NEAR THE MOUNTAINS AS THE ATMOSPHERE REMAINS MOIST AND UNSTABLE. A
WARMING AND DRYING TREND REMAINS IN THE FORECAST OVER THE COMING
DAYS WITH THE BUILDING UPPER LEVEL RIDGE INTO SOUTHERN ALASKA.
RELATIVE HUMIDITIES THOUGH SHOULD REMAIN ALMOST ENTIRELY ABOVE 30
PERCENT EVEN WITH OFFSHORE FLOW. WARMING IN THE UPPER LEVELS BY
THE WEEKEND WILL INCREASE STABILITY AND HELP CAP POTENTIAL
CONVECTION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH OF SOUTHCENTRAL WILL HAVE PERSISTENT CLOUDY AND SHOWERY
WEATHER TODAY AS WEAK SYNOPTIC FORCING WILL PREVENT ANY
SIGNIFICANT CHANGE IN THE WEATHER. THE ATMOSPHERE REMAINS VERY
MOIST HOWEVER...SO ANY SHOWERS THAT DO FORM HAVE THE POTENTIAL TO
PRODUCE BRIEF PERIODS OF MODERATE TO HEAVY RAIN. AFTERNOON/EVENING
THUNDERSTORMS WILL OCCUR ONCE AGAIN MAINLY OVER THE TALKEETNA
MOUNTAINS...ALASKA RANGE AND THE WESTERN KENAI PENINSULA TODAY...HOWEVER
WITH WEAK WINDS ALOFT THERE SHOULD BE LITTLE IF ANY MOVEMENT OF THESE
SHOWERS. WINDS WILL REMAIN LIGHT IN MOST AREAS.

BY FRIDAY...RIDGING ALOFT BUILDING IN FROM THE WEST WILL BEGIN TO
STRENGTHEN AND BRING WARMER AND DRIER CONDITIONS TO MOST AREAS.
THUNDERSTORM ACTIVITY SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
CLOSER TO THE GULF COAST WHERE THE BEST COMBINATION OF LOW-LEVEL
MOISTURE...MID-LEVEL DRYING...AND A MID-LEVEL DISTURBANCE WILL BE
LOCATED. INCREASING OFFSHORE FLOW IN THE LOWER LEVELS WILL LIKELY
MEAN NORTH GULF COAST LOCATIONS SUCH AS SEWARD COULD SEE
TEMPERATURES CLIMB INTO THE 70S FOR HIGHS.

CONVECTION SHOULD BE GREATLY LIMITED FOR SATURDAY TO LOCATIONS
TOWARD THE FAR SOUTHEASTERN COPPER RIVER BASIN AND THE FAR EASTERN
CHUGACH RANGE.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK THERMAL TROUGH ACROSS THE INTERIOR WITH AN AXIS EXTENDING
INTO THE SOUTHWEST...WILL REMAIN A FOCUS FOR AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS TO DEVELOP THROUGH THIS EVENING. CONDITIONS
WILL BECOME MORE STABLE FROM NORTH TO SOUTH FRIDAY...WITH GREATEST
INSTABILITY AND POTENTIAL FOR SHOWERS AND STORMS TO BE LOCATED
TOWARD THE BRISTOL BAY COAST AND NORTHERN ALASKA PENINSULA...FIRST
IN THE AFTERNOON WITH INTERACTION OF LOCALIZED CONVERGENCE
BOUNDARIES (SEA-BREEZE)...AND LATER WELL INTO THE OVERNIGHT WITH
A MID-LEVEL DISTURBANCE APPROACHING FROM THE NORTH.

 &&

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

RIDGING BUILDS INTO THE CENTRAL BERING THROUGH FRIDAY NIGHT WITH
A WEAKENING UPPER LOW ALONG THE WESTERN AND CENTRAL ALEUTIANS.
THIS IS A RELATIVELY BENIGN SURFACE PATTERN WITH SMALL CRAFT WINDS
CONFINED TO THE WESTERN HALF OF THE ALEUTIANS. CLOUDY CONDITIONS
WILL ENCOMPASS THE BERING WITH WEAK EMBEDDED SHORTWAVES PRODUCING
OCCASIONAL SHOWERS. AREAS OF DENSE FOG IS EXPECTED TO FORM TODAY
INTO FRIDAY AS STABLE CONDITIONS SETTLE ACROSS THE CENTRAL
BERING.


&&

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

AN UPPER LEVEL RIDGE WILL OVERSPREAD THE MAJORITY OF THE STATE
THROUGH THE WEEKEND. WHILE THIS RIDGE BUILDS ACROSS THE STATE...A
PORTION OF THE LONGWAVE TROUGH THAT HAS BEEN CREATING THE SHOWERY
WEATHER ACROSS THE STATE WILL GET CUT OFF AS RIDGING BUILDS ACROSS
THE NORTH PACIFIC. THIS WILL CREATE A CUT OFF LOW SOUTH OF THE
EASTERN ALEUTIANS THAT IS EXPECTED TO DEVELOP ON SATURDAY AS A
SHORTWAVE INTERACTS WITH MULTIPLE FRAGMENTS OF ENERGY ASSOCIATED
WITH THE UPPER LEVEL TROUGH THAT IS GETTING CUT OFF. THE
DETERMINISTIC AND ENSEMBLE MEMBERS HAVE THE DEVELOPMENT OF THIS
LOW PROGGED FAIRLY WELL AS IT DEVELOPS SOUTH OF THE EASTERN
ALEUTIANS SATURDAY. MODELS THEN BEGIN TO STRUGGLE WITH THE
PLACEMENT OF THIS UPPER LEVEL FEATURE AND AN ASSOCIATED SURFACE
LOW THAT DEVELOPS IN RESPONSE TO MID AND UPPER LEVEL CYCLOGENESIS.
THE REASON FOR THE DIFFICULTY IN TIMING AND PLACEMENT IS BECAUSE
STEERING CURRENTS CAN BE QUITE DIFFICULT TO DETERMINE WHEN A LOW
IS NO LONGER LOCATED IN A TROUGH BUT RATHER STUCK BETWEEN TWO
UPPER LEVEL RIDGES. IN SHORT...DEPENDING ON HOW THE LONGWAVE
TROUGH (ROSSBY WAVE) OVER RUSSIA DEVELOPS IN RESPONSE TO A
DEEPENING AREA OF LOW PRESSURE WILL INFLUENCE THE WESTERN RIDGE
OVER THE BERING SEA AND HOW IT WILL FORCE THE AREA OF LOW PRESSURE
IN THE NORTH PACIFIC EAST INTO THE GULF OF ALASKA OR POSSIBLY EVEN
INTO THE ALASKA MAINLAND. WHAT THIS MEANS FOR ALASKA IS THAT A
PERIOD OF WARMER TEMPERATURES...DRIER CONDITIONS AND LESS CLOUDY
SKIES WILL LIKELY BE OBSERVED THROUGH THE WEEKEND AND INTO THE
BEGINNING OF NEXT WEEK. DEPENDING ON THE TRACK OF THE UPPER LEVEL
AND SURFACE LOWS...RAIN CHANCES MAY SNEAK BACK IN TOWARD THE
MIDDLE OF NEXT WEEK BUT CONFIDENCE IS NOT HIGH WITH MORE THAN
SCATTERED SHOWERS AT THIS TIME.

&&




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

&&

$$

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





000
FXAK68 PAFC 301253
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
453 AM AKDT THU JUL 30 2015

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL TROUGH AXIS RESIDES FROM THE NORTHWEST TERRITORIES
THROUGH THE YUKON THROUGH THE SOUTHERN GULF TO THE SOUTHEASTERN
BERING. ANOTHER STACKED LOW RESIDES ABOUT 250 MILES SOUTHEAST OF
SHEMYA. AN UPPER LEVEL HIGH RESIDES OVER THE FAR WESTERN
BERING...WITH SUBTLE RIDGING FROM NEAR THE BERING STRAIT EXTENDING
SOUTH AND EAST AND NOSING INTO THE UPPER COOK INLET REGION.

THERE IS VERY LITTLE CHANGE IN THE GEOPOTENTIAL HEIGHT FIELD BETWEEN
THE UPPER LEVEL TROUGH AND EMBEDDED LOWS AND THE UPPER LEVEL
RIDGING...AN INDICATION THAT VERY WEAK FLOW EXISTS ACROSS THE
REGION. THE SURFACE PATTERN IS NOT MUCH DIFFERENT...WITH A WEAK
THERMAL TROUGH OVER THE SOUTHERN INTERIOR OF ALASKA WITH A WEAK
SURFACE RIDGE OVER THE NORTH GULF COAST.

&&

.MODEL DISCUSSION...

OVER THE NEXT DAY OR TWO THE STAGNANT SLOW-CHANGING WEATHER
PATTERN CONTINUES TO AID THE MODELS` EXCELLENT AGREEMENT IN
SHOWING A LACK OF ANY STRONG FEATURES. THEREFORE ONCE AGAIN THE
PRIMARY DRIVERS OF THE WEATHER ARE MUCH SMALLER TRANSIENT FEATURES
THAT ARE GENERALLY NOT WELL RESOLVED BY THE MODELS. BECAUSE OF
THEIR BETTER RESOLUTION AND LESS SMOOTHING...THE LOCAL MODELS WERE
PREFERRED FOR THIS FORECAST PACKAGE. LOCAL CONVERGENCE ZONES IN
OTHERWISE VERY SLOW MOVING FLOW WILL CONTINUE TO PRODUCE SHOWER
ACTIVITY...WITH A FEW THUNDERSTORMS ALONG THE MOUNTAINS IN THE
MOIST ENVIRONMENT. CONFIDENCE REMAINS LOWER THAN NORMAL CONCERNING
THE TIMING OF THESE SHOWERS AND THUNDERSTORMS OVER MOST OF
SOUTHERN ALASKA.

THE MODELS CONTINUE TO AGREE THAT THE TROUGH WILL GRADUALLY BREAK
DOWN OVER MAINLAND ALASKA...LEAVING A CUTOFF LOW OVER THE GULF AND
THE WESTERN BERING RIDGE SPREADING EASTWARD TO REPLACE THE
TROUGH. INITIALLY THE HEIGHT RISES WILL BE DUE TO SUBSIDENCE AND
THE UPPER LOW OVER THE SOUTHWESTERN GULF CUTTING OFF FROM THE COLD
POOL OF AIR ALONG THE ARCTIC COAST...AND NOT SIGNIFICANT WARMING
OF THE UPPER LEVELS UNTIL THE WEEKEND. THIS PATTERN WILL HELP
PROLONG THE INSTABILITY NEEDED FOR THUNDERSTORM DEVELOPMENT NEAR
THE MOUNTAINS AND LOCAL CONVERGENCE ZONES FOR THE REMAINDER OF THE
WORKWEEK.

&&

.FIRE WEATHER...

THE DEEP...MOIST...NEARLY STAGNANT AIR MASS IN PLACE CONTINUES TO
KEEP FIRE WEATHER CONCERNS MINIMAL FOR MOST OF SOUTHERN ALASKA
WITH CONTINUED HIGH RELATIVE HUMIDITY...LIGHT WINDS...AND
EXTENSIVE CLOUD COVER. WET THUNDERSTORMS REMAIN A POSSIBILITY
NEAR THE MOUNTAINS AS THE ATMOSPHERE REMAINS MOIST AND UNSTABLE. A
WARMING AND DRYING TREND REMAINS IN THE FORECAST OVER THE COMING
DAYS WITH THE BUILDING UPPER LEVEL RIDGE INTO SOUTHERN ALASKA.
RELATIVE HUMIDITIES THOUGH SHOULD REMAIN ALMOST ENTIRELY ABOVE 30
PERCENT EVEN WITH OFFSHORE FLOW. WARMING IN THE UPPER LEVELS BY
THE WEEKEND WILL INCREASE STABILITY AND HELP CAP POTENTIAL
CONVECTION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH OF SOUTHCENTRAL WILL HAVE PERSISTENT CLOUDY AND SHOWERY
WEATHER TODAY AS WEAK SYNOPTIC FORCING WILL PREVENT ANY
SIGNIFICANT CHANGE IN THE WEATHER. THE ATMOSPHERE REMAINS VERY
MOIST HOWEVER...SO ANY SHOWERS THAT DO FORM HAVE THE POTENTIAL TO
PRODUCE BRIEF PERIODS OF MODERATE TO HEAVY RAIN. AFTERNOON/EVENING
THUNDERSTORMS WILL OCCUR ONCE AGAIN MAINLY OVER THE TALKEETNA
MOUNTAINS...ALASKA RANGE AND THE WESTERN KENAI PENINSULA TODAY...HOWEVER
WITH WEAK WINDS ALOFT THERE SHOULD BE LITTLE IF ANY MOVEMENT OF THESE
SHOWERS. WINDS WILL REMAIN LIGHT IN MOST AREAS.

BY FRIDAY...RIDGING ALOFT BUILDING IN FROM THE WEST WILL BEGIN TO
STRENGTHEN AND BRING WARMER AND DRIER CONDITIONS TO MOST AREAS.
THUNDERSTORM ACTIVITY SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
CLOSER TO THE GULF COAST WHERE THE BEST COMBINATION OF LOW-LEVEL
MOISTURE...MID-LEVEL DRYING...AND A MID-LEVEL DISTURBANCE WILL BE
LOCATED. INCREASING OFFSHORE FLOW IN THE LOWER LEVELS WILL LIKELY
MEAN NORTH GULF COAST LOCATIONS SUCH AS SEWARD COULD SEE
TEMPERATURES CLIMB INTO THE 70S FOR HIGHS.

CONVECTION SHOULD BE GREATLY LIMITED FOR SATURDAY TO LOCATIONS
TOWARD THE FAR SOUTHEASTERN COPPER RIVER BASIN AND THE FAR EASTERN
CHUGACH RANGE.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK THERMAL TROUGH ACROSS THE INTERIOR WITH AN AXIS EXTENDING
INTO THE SOUTHWEST...WILL REMAIN A FOCUS FOR AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS TO DEVELOP THROUGH THIS EVENING. CONDITIONS
WILL BECOME MORE STABLE FROM NORTH TO SOUTH FRIDAY...WITH GREATEST
INSTABILITY AND POTENTIAL FOR SHOWERS AND STORMS TO BE LOCATED
TOWARD THE BRISTOL BAY COAST AND NORTHERN ALASKA PENINSULA...FIRST
IN THE AFTERNOON WITH INTERACTION OF LOCALIZED CONVERGENCE
BOUNDARIES (SEA-BREEZE)...AND LATER WELL INTO THE OVERNIGHT WITH
A MID-LEVEL DISTURBANCE APPROACHING FROM THE NORTH.

 &&

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

RIDGING BUILDS INTO THE CENTRAL BERING THROUGH FRIDAY NIGHT WITH
A WEAKENING UPPER LOW ALONG THE WESTERN AND CENTRAL ALEUTIANS.
THIS IS A RELATIVELY BENIGN SURFACE PATTERN WITH SMALL CRAFT WINDS
CONFINED TO THE WESTERN HALF OF THE ALEUTIANS. CLOUDY CONDITIONS
WILL ENCOMPASS THE BERING WITH WEAK EMBEDDED SHORTWAVES PRODUCING
OCCASIONAL SHOWERS. AREAS OF DENSE FOG IS EXPECTED TO FORM TODAY
INTO FRIDAY AS STABLE CONDITIONS SETTLE ACROSS THE CENTRAL
BERING.


&&

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

AN UPPER LEVEL RIDGE WILL OVERSPREAD THE MAJORITY OF THE STATE
THROUGH THE WEEKEND. WHILE THIS RIDGE BUILDS ACROSS THE STATE...A
PORTION OF THE LONGWAVE TROUGH THAT HAS BEEN CREATING THE SHOWERY
WEATHER ACROSS THE STATE WILL GET CUT OFF AS RIDGING BUILDS ACROSS
THE NORTH PACIFIC. THIS WILL CREATE A CUT OFF LOW SOUTH OF THE
EASTERN ALEUTIANS THAT IS EXPECTED TO DEVELOP ON SATURDAY AS A
SHORTWAVE INTERACTS WITH MULTIPLE FRAGMENTS OF ENERGY ASSOCIATED
WITH THE UPPER LEVEL TROUGH THAT IS GETTING CUT OFF. THE
DETERMINISTIC AND ENSEMBLE MEMBERS HAVE THE DEVELOPMENT OF THIS
LOW PROGGED FAIRLY WELL AS IT DEVELOPS SOUTH OF THE EASTERN
ALEUTIANS SATURDAY. MODELS THEN BEGIN TO STRUGGLE WITH THE
PLACEMENT OF THIS UPPER LEVEL FEATURE AND AN ASSOCIATED SURFACE
LOW THAT DEVELOPS IN RESPONSE TO MID AND UPPER LEVEL CYCLOGENESIS.
THE REASON FOR THE DIFFICULTY IN TIMING AND PLACEMENT IS BECAUSE
STEERING CURRENTS CAN BE QUITE DIFFICULT TO DETERMINE WHEN A LOW
IS NO LONGER LOCATED IN A TROUGH BUT RATHER STUCK BETWEEN TWO
UPPER LEVEL RIDGES. IN SHORT...DEPENDING ON HOW THE LONGWAVE
TROUGH (ROSSBY WAVE) OVER RUSSIA DEVELOPS IN RESPONSE TO A
DEEPENING AREA OF LOW PRESSURE WILL INFLUENCE THE WESTERN RIDGE
OVER THE BERING SEA AND HOW IT WILL FORCE THE AREA OF LOW PRESSURE
IN THE NORTH PACIFIC EAST INTO THE GULF OF ALASKA OR POSSIBLY EVEN
INTO THE ALASKA MAINLAND. WHAT THIS MEANS FOR ALASKA IS THAT A
PERIOD OF WARMER TEMPERATURES...DRIER CONDITIONS AND LESS CLOUDY
SKIES WILL LIKELY BE OBSERVED THROUGH THE WEEKEND AND INTO THE
BEGINNING OF NEXT WEEK. DEPENDING ON THE TRACK OF THE UPPER LEVEL
AND SURFACE LOWS...RAIN CHANCES MAY SNEAK BACK IN TOWARD THE
MIDDLE OF NEXT WEEK BUT CONFIDENCE IS NOT HIGH WITH MORE THAN
SCATTERED SHOWERS AT THIS TIME.

&&




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

&&

$$

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




000
FXAK68 PAFC 301253
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
453 AM AKDT THU JUL 30 2015

.ANALYSIS AND UPPER LEVELS...

UPPER LEVEL TROUGH AXIS RESIDES FROM THE NORTHWEST TERRITORIES
THROUGH THE YUKON THROUGH THE SOUTHERN GULF TO THE SOUTHEASTERN
BERING. ANOTHER STACKED LOW RESIDES ABOUT 250 MILES SOUTHEAST OF
SHEMYA. AN UPPER LEVEL HIGH RESIDES OVER THE FAR WESTERN
BERING...WITH SUBTLE RIDGING FROM NEAR THE BERING STRAIT EXTENDING
SOUTH AND EAST AND NOSING INTO THE UPPER COOK INLET REGION.

THERE IS VERY LITTLE CHANGE IN THE GEOPOTENTIAL HEIGHT FIELD BETWEEN
THE UPPER LEVEL TROUGH AND EMBEDDED LOWS AND THE UPPER LEVEL
RIDGING...AN INDICATION THAT VERY WEAK FLOW EXISTS ACROSS THE
REGION. THE SURFACE PATTERN IS NOT MUCH DIFFERENT...WITH A WEAK
THERMAL TROUGH OVER THE SOUTHERN INTERIOR OF ALASKA WITH A WEAK
SURFACE RIDGE OVER THE NORTH GULF COAST.

&&

.MODEL DISCUSSION...

OVER THE NEXT DAY OR TWO THE STAGNANT SLOW-CHANGING WEATHER
PATTERN CONTINUES TO AID THE MODELS` EXCELLENT AGREEMENT IN
SHOWING A LACK OF ANY STRONG FEATURES. THEREFORE ONCE AGAIN THE
PRIMARY DRIVERS OF THE WEATHER ARE MUCH SMALLER TRANSIENT FEATURES
THAT ARE GENERALLY NOT WELL RESOLVED BY THE MODELS. BECAUSE OF
THEIR BETTER RESOLUTION AND LESS SMOOTHING...THE LOCAL MODELS WERE
PREFERRED FOR THIS FORECAST PACKAGE. LOCAL CONVERGENCE ZONES IN
OTHERWISE VERY SLOW MOVING FLOW WILL CONTINUE TO PRODUCE SHOWER
ACTIVITY...WITH A FEW THUNDERSTORMS ALONG THE MOUNTAINS IN THE
MOIST ENVIRONMENT. CONFIDENCE REMAINS LOWER THAN NORMAL CONCERNING
THE TIMING OF THESE SHOWERS AND THUNDERSTORMS OVER MOST OF
SOUTHERN ALASKA.

THE MODELS CONTINUE TO AGREE THAT THE TROUGH WILL GRADUALLY BREAK
DOWN OVER MAINLAND ALASKA...LEAVING A CUTOFF LOW OVER THE GULF AND
THE WESTERN BERING RIDGE SPREADING EASTWARD TO REPLACE THE
TROUGH. INITIALLY THE HEIGHT RISES WILL BE DUE TO SUBSIDENCE AND
THE UPPER LOW OVER THE SOUTHWESTERN GULF CUTTING OFF FROM THE COLD
POOL OF AIR ALONG THE ARCTIC COAST...AND NOT SIGNIFICANT WARMING
OF THE UPPER LEVELS UNTIL THE WEEKEND. THIS PATTERN WILL HELP
PROLONG THE INSTABILITY NEEDED FOR THUNDERSTORM DEVELOPMENT NEAR
THE MOUNTAINS AND LOCAL CONVERGENCE ZONES FOR THE REMAINDER OF THE
WORKWEEK.

&&

.FIRE WEATHER...

THE DEEP...MOIST...NEARLY STAGNANT AIR MASS IN PLACE CONTINUES TO
KEEP FIRE WEATHER CONCERNS MINIMAL FOR MOST OF SOUTHERN ALASKA
WITH CONTINUED HIGH RELATIVE HUMIDITY...LIGHT WINDS...AND
EXTENSIVE CLOUD COVER. WET THUNDERSTORMS REMAIN A POSSIBILITY
NEAR THE MOUNTAINS AS THE ATMOSPHERE REMAINS MOIST AND UNSTABLE. A
WARMING AND DRYING TREND REMAINS IN THE FORECAST OVER THE COMING
DAYS WITH THE BUILDING UPPER LEVEL RIDGE INTO SOUTHERN ALASKA.
RELATIVE HUMIDITIES THOUGH SHOULD REMAIN ALMOST ENTIRELY ABOVE 30
PERCENT EVEN WITH OFFSHORE FLOW. WARMING IN THE UPPER LEVELS BY
THE WEEKEND WILL INCREASE STABILITY AND HELP CAP POTENTIAL
CONVECTION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH OF SOUTHCENTRAL WILL HAVE PERSISTENT CLOUDY AND SHOWERY
WEATHER TODAY AS WEAK SYNOPTIC FORCING WILL PREVENT ANY
SIGNIFICANT CHANGE IN THE WEATHER. THE ATMOSPHERE REMAINS VERY
MOIST HOWEVER...SO ANY SHOWERS THAT DO FORM HAVE THE POTENTIAL TO
PRODUCE BRIEF PERIODS OF MODERATE TO HEAVY RAIN. AFTERNOON/EVENING
THUNDERSTORMS WILL OCCUR ONCE AGAIN MAINLY OVER THE TALKEETNA
MOUNTAINS...ALASKA RANGE AND THE WESTERN KENAI PENINSULA TODAY...HOWEVER
WITH WEAK WINDS ALOFT THERE SHOULD BE LITTLE IF ANY MOVEMENT OF THESE
SHOWERS. WINDS WILL REMAIN LIGHT IN MOST AREAS.

BY FRIDAY...RIDGING ALOFT BUILDING IN FROM THE WEST WILL BEGIN TO
STRENGTHEN AND BRING WARMER AND DRIER CONDITIONS TO MOST AREAS.
THUNDERSTORM ACTIVITY SHOULD BE CONFINED TO THE HIGHER ELEVATIONS
CLOSER TO THE GULF COAST WHERE THE BEST COMBINATION OF LOW-LEVEL
MOISTURE...MID-LEVEL DRYING...AND A MID-LEVEL DISTURBANCE WILL BE
LOCATED. INCREASING OFFSHORE FLOW IN THE LOWER LEVELS WILL LIKELY
MEAN NORTH GULF COAST LOCATIONS SUCH AS SEWARD COULD SEE
TEMPERATURES CLIMB INTO THE 70S FOR HIGHS.

CONVECTION SHOULD BE GREATLY LIMITED FOR SATURDAY TO LOCATIONS
TOWARD THE FAR SOUTHEASTERN COPPER RIVER BASIN AND THE FAR EASTERN
CHUGACH RANGE.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK THERMAL TROUGH ACROSS THE INTERIOR WITH AN AXIS EXTENDING
INTO THE SOUTHWEST...WILL REMAIN A FOCUS FOR AFTERNOON AND
EVENING SHOWERS AND THUNDERSTORMS TO DEVELOP THROUGH THIS EVENING. CONDITIONS
WILL BECOME MORE STABLE FROM NORTH TO SOUTH FRIDAY...WITH GREATEST
INSTABILITY AND POTENTIAL FOR SHOWERS AND STORMS TO BE LOCATED
TOWARD THE BRISTOL BAY COAST AND NORTHERN ALASKA PENINSULA...FIRST
IN THE AFTERNOON WITH INTERACTION OF LOCALIZED CONVERGENCE
BOUNDARIES (SEA-BREEZE)...AND LATER WELL INTO THE OVERNIGHT WITH
A MID-LEVEL DISTURBANCE APPROACHING FROM THE NORTH.

 &&

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

RIDGING BUILDS INTO THE CENTRAL BERING THROUGH FRIDAY NIGHT WITH
A WEAKENING UPPER LOW ALONG THE WESTERN AND CENTRAL ALEUTIANS.
THIS IS A RELATIVELY BENIGN SURFACE PATTERN WITH SMALL CRAFT WINDS
CONFINED TO THE WESTERN HALF OF THE ALEUTIANS. CLOUDY CONDITIONS
WILL ENCOMPASS THE BERING WITH WEAK EMBEDDED SHORTWAVES PRODUCING
OCCASIONAL SHOWERS. AREAS OF DENSE FOG IS EXPECTED TO FORM TODAY
INTO FRIDAY AS STABLE CONDITIONS SETTLE ACROSS THE CENTRAL
BERING.


&&

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

AN UPPER LEVEL RIDGE WILL OVERSPREAD THE MAJORITY OF THE STATE
THROUGH THE WEEKEND. WHILE THIS RIDGE BUILDS ACROSS THE STATE...A
PORTION OF THE LONGWAVE TROUGH THAT HAS BEEN CREATING THE SHOWERY
WEATHER ACROSS THE STATE WILL GET CUT OFF AS RIDGING BUILDS ACROSS
THE NORTH PACIFIC. THIS WILL CREATE A CUT OFF LOW SOUTH OF THE
EASTERN ALEUTIANS THAT IS EXPECTED TO DEVELOP ON SATURDAY AS A
SHORTWAVE INTERACTS WITH MULTIPLE FRAGMENTS OF ENERGY ASSOCIATED
WITH THE UPPER LEVEL TROUGH THAT IS GETTING CUT OFF. THE
DETERMINISTIC AND ENSEMBLE MEMBERS HAVE THE DEVELOPMENT OF THIS
LOW PROGGED FAIRLY WELL AS IT DEVELOPS SOUTH OF THE EASTERN
ALEUTIANS SATURDAY. MODELS THEN BEGIN TO STRUGGLE WITH THE
PLACEMENT OF THIS UPPER LEVEL FEATURE AND AN ASSOCIATED SURFACE
LOW THAT DEVELOPS IN RESPONSE TO MID AND UPPER LEVEL CYCLOGENESIS.
THE REASON FOR THE DIFFICULTY IN TIMING AND PLACEMENT IS BECAUSE
STEERING CURRENTS CAN BE QUITE DIFFICULT TO DETERMINE WHEN A LOW
IS NO LONGER LOCATED IN A TROUGH BUT RATHER STUCK BETWEEN TWO
UPPER LEVEL RIDGES. IN SHORT...DEPENDING ON HOW THE LONGWAVE
TROUGH (ROSSBY WAVE) OVER RUSSIA DEVELOPS IN RESPONSE TO A
DEEPENING AREA OF LOW PRESSURE WILL INFLUENCE THE WESTERN RIDGE
OVER THE BERING SEA AND HOW IT WILL FORCE THE AREA OF LOW PRESSURE
IN THE NORTH PACIFIC EAST INTO THE GULF OF ALASKA OR POSSIBLY EVEN
INTO THE ALASKA MAINLAND. WHAT THIS MEANS FOR ALASKA IS THAT A
PERIOD OF WARMER TEMPERATURES...DRIER CONDITIONS AND LESS CLOUDY
SKIES WILL LIKELY BE OBSERVED THROUGH THE WEEKEND AND INTO THE
BEGINNING OF NEXT WEEK. DEPENDING ON THE TRACK OF THE UPPER LEVEL
AND SURFACE LOWS...RAIN CHANCES MAY SNEAK BACK IN TOWARD THE
MIDDLE OF NEXT WEEK BUT CONFIDENCE IS NOT HIGH WITH MORE THAN
SCATTERED SHOWERS AT THIS TIME.

&&




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

&&

$$

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




000
FXAK68 PAFC 300032
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
432 PM AKDT WED JUL 29 2015

.ANALYSIS AND UPPER LEVELS...

THE UPPER LEVEL PATTERN OVER SOUTHERN ALASKA REMAINS IN A STAGNANT
STATE. A TROUGH WITH TWO UPPER LEVEL LOWS IS CENTERED OVER
SOUTHERN ALASKA. ONE OF THE LOWS IS CENTERED OVER THE KUSKOKWIM
DELTA...AND THE OTHER IS OVER YAKUTAT. SMALLER EMBEDDED
DISTURBANCES ARE ROTATING AROUND THE LOWS PRODUCING LOCALIZED
ENHANCED LIFT. THE 00Z SOUNDINGS FROM AROUND SOUTHERN ALASKA
CONTINUE TO SHOW A DEEP MOISTURE-RICH AIR MASS IN PLACE. THUS THE
ENHANCED LIFT CAUSED BY THE SMALL DISTURBANCES IS TAPPING THE
ABUNDANT MOISTURE TO PRODUCE SHOWER ACTIVITY. TERRAIN ADDING TO
THAT LIFT IS CAUSING SOME THUNDERSTORM DEVELOPMENT AGAIN TODAY
ACROSS THE ALASKA RANGE...TALKEETNAS...AND THE KENAI MOUNTAINS.

OVER THE WESTERN BERING...A RIDGE IS IN PLACE WITH A VERTICALLY
STACKED LOW CUT OFF SOUTH OF ATTU ISLAND...KEEPING THE WEATHER
UNSETTLED ALONG THE WESTERN ALEUTIANS. THE JET STREAM IS FLOWING
ACROSS THE CENTRAL AND EASTERN BERING...BETWEEN THE WESTERN RIDGE
AND THE UPPER TROUGH.

&&

.MODEL DISCUSSION...

OVER THE NEXT DAY OR TWO THE MODELS REMAIN IN EXCELLENT AGREEMENT
IN SHOWING A LACK OF ANY STRONG FEATURES. ONCE AGAIN THE PRIMARY
DRIVERS OF THE WEATHER ARE MUCH SMALLER TRANSIENT FEATURES THAT
ARE GENERALLY NOT WELL RESOLVED BY THE MODELS. BECAUSE OF THEIR
BETTER RESOLUTION AND LESS SMOOTHING...THE LOCAL MODELS WERE
PREFERRED FOR THIS FORECAST PACKAGE. LOCAL CONVERGENCE ZONES IN
OTHERWISE VERY SLOW MOVING FLOW WILL CONTINUE TO PRODUCE SHOWER
ACTIVITY...WITH A FEW THUNDERSTORMS ALONG THE MOUNTAINS IN THE
MOIST ENVIRONMENT. CONFIDENCE REMAINS LOWER THAN NORMAL CONCERNING
THE TIMING OF THESE SHOWERS AND THUNDERSTORMS OVER MOST OF
SOUTHERN ALASKA.

THE MODELS CONTINUE TO AGREE THAT THE TROUGH WILL GRADUALLY BREAK
DOWN OVER MAINLAND ALASKA. AS THE UPPER LOW OVER THE SOUTHWESTERN
GULF CUTS OFF FROM THE COLD POOL OF AIR ALONG THE ARCTIC
COAST...IT WILL ALLOW THE WESTERN BERING RIDGE TO SPREAD EASTWARD.
INITIALLY THE HEIGHT RISES WILL BE DUE TO SUBSIDENCE. SIGNIFICANT
WARMING OF THE UPPER LEVELS WILL NOT BEGIN UNTIL THE WEEKEND.
THIS PATTERN WILL HELP PROLONG THE INSTABILITY NEEDED FOR
THUNDERSTORM DEVELOPMENT NEAR THE MOUNTAINS AND LOCAL CONVERGENCE
ZONES FOR THE REMAINDER OF THE WORKWEEK.

&&

.FIRE WEATHER...

THE STAGNANT AIR MASS IN PLACE CONTINUES TO KEEP FIRE WEATHER
CONCERNS MINIMAL FOR MOST OF SOUTHERN ALASKA...WITH CONTINUED
HIGH RELATIVE HUMIDITY...LIGHT WINDS...AND EXTENSIVE CLOUD COVER.
WET THUNDERSTORMS REMAIN A POSSIBILITY NEAR THE MOUNTAINS AS THE
ATMOSPHERE REMAINS MOIST AND UNSTABLE. A WARMING AND DRYING TREND
REMAINS IN THE FORECAST OVER THE COMING DAYS WITH THE BUILDING
UPPER LEVEL RIDGE INTO SOUTHERN ALASKA...THOUGH RELATIVE
HUMIDITIES SHOULD REMAIN ABOVE CRITICAL LEVELS. WARMING
TEMPERATURES IN THE UPPER LEVELS BY THE WEEKEND WILL INCREASE
STABILITY AND HELP CAP POTENTIAL CONVECTION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH OF SOUTHCENTRAL WILL HAVE PERSISTENT CLOUDY AND SHOWERY
WEATHER THROUGH THURSDAY AS WEAK SYNOPTIC FORCING WILL PREVENT ANY
SIGNIFICANT CHANGE IN THE WEATHER. THE ATMOSPHERE REMAINS VERY
MOIST HOWEVER...SO ANY SHOWERS THAT DO FORM HAVE THE POTENTIAL TO
PRODUCE BRIEF PERIODS OF MODERATE TO HEAVY RAIN...ESPECIALLY OVER
THE WESTERN KENAI PENINSULA THIS EVENING WHERE A WEAK SHORTWAVE
IS MOVING OVERHEAD. AFTERNOON/EVENING THUNDERSTORMS WILL OCCUR
ONCE AGAIN MAINLY OVER THE TALKEETNA MOUNTAINS...ALASKA RANGE AND THE
WESTERN KENAI PENINSULA THROUGH THURSDAY...HOWEVER WITH WEAK
WINDS ALOFT THERE SHOULD BE LITTLE IF ANY MOVEMENT...AND THESE
SHOWERS WILL REMAIN CONFINED TO THE HIGHER ELEVATIONS. ONE
EXCEPTION TO THIS WILL BE OVER THE WESTERN KENAI PENINSULA...WHERE
EASTERLY FLOW WILL ALLOW THUNDERSTORMS FORMING OVER THE CHUGACH
MOUNTAINS TO DRIFT OVER THE LOWER ELEVATIONS THROUGH THURSDAY.
WINDS WILL REMAIN LIGHT IN MOST AREAS...WITH THE EXCEPTION OF GAP
WIND PRONE AREAS SUCH AS TURNAGAIN ARM...WHICH WILL SEE CONTINUED
SOUTHEASTERLY WINDS THROUGH THIS EVENING. BY FRIDAY...RIDGING
ALOFT BUILDING IN FROM THE WEST WILL BEGIN TO STRENGTHEN AND BRING
WARMER AND DRIER CONDITIONS TO MOST AREAS. THUNDERSTORM ACTIVITY
SHOULD BE CONFINED TO THE HIGHER ELEVATIONS OF THE NORTHERN
SUSITNA VALLEY AND COPPER RIVER BASIN ON FRIDAY...AND SHOULD BE
LESS WIDESPREAD THAN THE NEXT TWO DAYS AS INSTABILITY WEAKENS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK THERMAL TROUGH ACROSS THE INTERIOR...WITH AN AXIS
EXTENDING INTO THE SOUTHWEST...WILL REMAIN A FOCUS FOR AFTERNOON
AND EVENING SHOWER AND THUNDERSTORM DEVELOPMENT THROUGH THE END
OF THE WEEK. CONDITIONS WILL BE SLIGHTLY MORE STABLE ACROSS THE
KUSKOKWIM DELTA AS IT COMES UNDER THE INFLUENCE OF A COOLER
MARITIME ENVIRONMENT. PATCHY FOG WILL MAINLY AFFECT THE COASTAL
AREAS OF THE KUSKOKWIM...HOWEVER AREAS INLAND MAY EXPERIENCE BRIEF
PERIODS AS TEMPERATURES COOL TO NEAR THE DEW POINT DURING THE
LATE NIGHT HOURS.


&&

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

RIDGING BUILDS INTO THE CENTRAL BERING THROUGH FRIDAY NIGHT WITH
A WEAKENING UPPER LOW ALONG THE WESTERN AND CENTRAL ALEUTIANS.
THIS IS A RELATIVELY BENIGN SURFACE PATTERN WITH SMALL CRAFT WINDS
CONFINED TO THE WESTERN HALF OF THE ALEUTIANS. CLOUDY CONDITIONS
WILL ENCOMPASS THE BERING WITH WEAK EMBEDDED SHORTWAVES PRODUCING
OCCASIONAL SHOWERS. AREAS OF DENSE FOG IS EXPECTED TO FORM ON THURSDAY
AS STABLE CONDITIONS SETTLE ACROSS THE CENTRAL BERING.

&&

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

AN UPPER LEVEL RIDGE WILL BEGIN TO BUILD ACROSS THE INTERIOR OF
ALASKA FROM THE BERING SEA FRIDAY AFTERNOON AND OVERSPREAD THE
MAJORITY OF THE STATE THROUGH THE WEEKEND. WHILE THIS RIDGE BUILDS
ACROSS THE STATE...A PORTION OF THE LONGWAVE TROUGH THAT HAS BEEN
CREATING THE SHOWERY WEATHER ACROSS THE STATE WILL GET CUT OFF AS
RIDGING BUILDS ACROSS THE NORTH PACIFIC. THIS WILL CREATE A CUT
OFF LOW THAT IS EXPECTED TO DEVELOP ON SATURDAY AS A SHORTWAVE
INTERACTS WITH MULTIPLE FRAGMENTS OF ENERGY ASSOCIATED WITH THE
UPPER LEVEL TROUGH THAT IS GETTING CUT OFF. THE DETERMINISTIC AND
ENSEMBLE MEMBERS HAVE THE DEVELOPMENT OF THIS LOW PROGGED FAIRLY
WELL AS IT DEVELOPS SOUTH OF THE EASTERN ALEUTIANS SATURDAY.
MODELS THEN BEGIN TO STRUGGLE WITH THE PLACEMENT OF THIS UPPER
LEVEL FEATURE AND AN ASSOCIATED SURFACE LOW THAT DEVELOPS IN
RESPONSE TO MID AND UPPER LEVEL CYCLOGENESIS. THE REASON FOR THE
DIFFICULTY IN TIMING AND PLACEMENT IS BECAUSE STEERING CURRENTS
CAN BE QUITE DIFFICULT TO DETERMINE WHEN A LOW IS NO LONGER
LOCATED IN A TROUGH BUT RATHER STUCK BETWEEN TWO UPPER LEVEL
RIDGES.

IN SHORT...HOW THE LONGWAVE TROUGH (ROSBY WAVE) OVER RUSSIA
DEVELOPS IN RESPONSE TO A DEEPENING AREA OF LOW PRESSURE WILL
INFLUENCE THE WESTERN RIDGE OVER THE BERING SEA...AND HOW IT WILL
FORCE THE AREA OF LOW PRESSURE IN THE NORTH PACIFIC EAST INTO THE
GULF OF ALASKA OR POSSIBLY EVEN INTO THE ALASKA MAINLAND. WHAT
THIS MEANS FOR ALASKA IS THAT A PERIOD OF WARMER TEMPERATURES...DRIER
CONDITIONS AND LESS CLOUDY SKIES WILL LIKELY BE OBSERVED THROUGH
THE WEEKEND AND INTO THE BEGINNING OF NEXT WEEK. DEPENDING ON THE
TRACK OF THE UPPER LEVEL AND SURFACE LOWS...RAIN CHANCES MAY SNEAK
BACK IN TOWARD THE MIDDLE OF NEXT WEEK BUT CONFIDENCE IS NOT HIGH
WITH MORE THAN SCATTERED SHOWERS AT THIS TIME.

&&


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

&&

$$

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




000
FXAK68 PAFC 300032
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
432 PM AKDT WED JUL 29 2015

.ANALYSIS AND UPPER LEVELS...

THE UPPER LEVEL PATTERN OVER SOUTHERN ALASKA REMAINS IN A STAGNANT
STATE. A TROUGH WITH TWO UPPER LEVEL LOWS IS CENTERED OVER
SOUTHERN ALASKA. ONE OF THE LOWS IS CENTERED OVER THE KUSKOKWIM
DELTA...AND THE OTHER IS OVER YAKUTAT. SMALLER EMBEDDED
DISTURBANCES ARE ROTATING AROUND THE LOWS PRODUCING LOCALIZED
ENHANCED LIFT. THE 00Z SOUNDINGS FROM AROUND SOUTHERN ALASKA
CONTINUE TO SHOW A DEEP MOISTURE-RICH AIR MASS IN PLACE. THUS THE
ENHANCED LIFT CAUSED BY THE SMALL DISTURBANCES IS TAPPING THE
ABUNDANT MOISTURE TO PRODUCE SHOWER ACTIVITY. TERRAIN ADDING TO
THAT LIFT IS CAUSING SOME THUNDERSTORM DEVELOPMENT AGAIN TODAY
ACROSS THE ALASKA RANGE...TALKEETNAS...AND THE KENAI MOUNTAINS.

OVER THE WESTERN BERING...A RIDGE IS IN PLACE WITH A VERTICALLY
STACKED LOW CUT OFF SOUTH OF ATTU ISLAND...KEEPING THE WEATHER
UNSETTLED ALONG THE WESTERN ALEUTIANS. THE JET STREAM IS FLOWING
ACROSS THE CENTRAL AND EASTERN BERING...BETWEEN THE WESTERN RIDGE
AND THE UPPER TROUGH.

&&

.MODEL DISCUSSION...

OVER THE NEXT DAY OR TWO THE MODELS REMAIN IN EXCELLENT AGREEMENT
IN SHOWING A LACK OF ANY STRONG FEATURES. ONCE AGAIN THE PRIMARY
DRIVERS OF THE WEATHER ARE MUCH SMALLER TRANSIENT FEATURES THAT
ARE GENERALLY NOT WELL RESOLVED BY THE MODELS. BECAUSE OF THEIR
BETTER RESOLUTION AND LESS SMOOTHING...THE LOCAL MODELS WERE
PREFERRED FOR THIS FORECAST PACKAGE. LOCAL CONVERGENCE ZONES IN
OTHERWISE VERY SLOW MOVING FLOW WILL CONTINUE TO PRODUCE SHOWER
ACTIVITY...WITH A FEW THUNDERSTORMS ALONG THE MOUNTAINS IN THE
MOIST ENVIRONMENT. CONFIDENCE REMAINS LOWER THAN NORMAL CONCERNING
THE TIMING OF THESE SHOWERS AND THUNDERSTORMS OVER MOST OF
SOUTHERN ALASKA.

THE MODELS CONTINUE TO AGREE THAT THE TROUGH WILL GRADUALLY BREAK
DOWN OVER MAINLAND ALASKA. AS THE UPPER LOW OVER THE SOUTHWESTERN
GULF CUTS OFF FROM THE COLD POOL OF AIR ALONG THE ARCTIC
COAST...IT WILL ALLOW THE WESTERN BERING RIDGE TO SPREAD EASTWARD.
INITIALLY THE HEIGHT RISES WILL BE DUE TO SUBSIDENCE. SIGNIFICANT
WARMING OF THE UPPER LEVELS WILL NOT BEGIN UNTIL THE WEEKEND.
THIS PATTERN WILL HELP PROLONG THE INSTABILITY NEEDED FOR
THUNDERSTORM DEVELOPMENT NEAR THE MOUNTAINS AND LOCAL CONVERGENCE
ZONES FOR THE REMAINDER OF THE WORKWEEK.

&&

.FIRE WEATHER...

THE STAGNANT AIR MASS IN PLACE CONTINUES TO KEEP FIRE WEATHER
CONCERNS MINIMAL FOR MOST OF SOUTHERN ALASKA...WITH CONTINUED
HIGH RELATIVE HUMIDITY...LIGHT WINDS...AND EXTENSIVE CLOUD COVER.
WET THUNDERSTORMS REMAIN A POSSIBILITY NEAR THE MOUNTAINS AS THE
ATMOSPHERE REMAINS MOIST AND UNSTABLE. A WARMING AND DRYING TREND
REMAINS IN THE FORECAST OVER THE COMING DAYS WITH THE BUILDING
UPPER LEVEL RIDGE INTO SOUTHERN ALASKA...THOUGH RELATIVE
HUMIDITIES SHOULD REMAIN ABOVE CRITICAL LEVELS. WARMING
TEMPERATURES IN THE UPPER LEVELS BY THE WEEKEND WILL INCREASE
STABILITY AND HELP CAP POTENTIAL CONVECTION.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MUCH OF SOUTHCENTRAL WILL HAVE PERSISTENT CLOUDY AND SHOWERY
WEATHER THROUGH THURSDAY AS WEAK SYNOPTIC FORCING WILL PREVENT ANY
SIGNIFICANT CHANGE IN THE WEATHER. THE ATMOSPHERE REMAINS VERY
MOIST HOWEVER...SO ANY SHOWERS THAT DO FORM HAVE THE POTENTIAL TO
PRODUCE BRIEF PERIODS OF MODERATE TO HEAVY RAIN...ESPECIALLY OVER
THE WESTERN KENAI PENINSULA THIS EVENING WHERE A WEAK SHORTWAVE
IS MOVING OVERHEAD. AFTERNOON/EVENING THUNDERSTORMS WILL OCCUR
ONCE AGAIN MAINLY OVER THE TALKEETNA MOUNTAINS...ALASKA RANGE AND THE
WESTERN KENAI PENINSULA THROUGH THURSDAY...HOWEVER WITH WEAK
WINDS ALOFT THERE SHOULD BE LITTLE IF ANY MOVEMENT...AND THESE
SHOWERS WILL REMAIN CONFINED TO THE HIGHER ELEVATIONS. ONE
EXCEPTION TO THIS WILL BE OVER THE WESTERN KENAI PENINSULA...WHERE
EASTERLY FLOW WILL ALLOW THUNDERSTORMS FORMING OVER THE CHUGACH
MOUNTAINS TO DRIFT OVER THE LOWER ELEVATIONS THROUGH THURSDAY.
WINDS WILL REMAIN LIGHT IN MOST AREAS...WITH THE EXCEPTION OF GAP
WIND PRONE AREAS SUCH AS TURNAGAIN ARM...WHICH WILL SEE CONTINUED
SOUTHEASTERLY WINDS THROUGH THIS EVENING. BY FRIDAY...RIDGING
ALOFT BUILDING IN FROM THE WEST WILL BEGIN TO STRENGTHEN AND BRING
WARMER AND DRIER CONDITIONS TO MOST AREAS. THUNDERSTORM ACTIVITY
SHOULD BE CONFINED TO THE HIGHER ELEVATIONS OF THE NORTHERN
SUSITNA VALLEY AND COPPER RIVER BASIN ON FRIDAY...AND SHOULD BE
LESS WIDESPREAD THAN THE NEXT TWO DAYS AS INSTABILITY WEAKENS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
A WEAK THERMAL TROUGH ACROSS THE INTERIOR...WITH AN AXIS
EXTENDING INTO THE SOUTHWEST...WILL REMAIN A FOCUS FOR AFTERNOON
AND EVENING SHOWER AND THUNDERSTORM DEVELOPMENT THROUGH THE END
OF THE WEEK. CONDITIONS WILL BE SLIGHTLY MORE STABLE ACROSS THE
KUSKOKWIM DELTA AS IT COMES UNDER THE INFLUENCE OF A COOLER
MARITIME ENVIRONMENT. PATCHY FOG WILL MAINLY AFFECT THE COASTAL
AREAS OF THE KUSKOKWIM...HOWEVER AREAS INLAND MAY EXPERIENCE BRIEF
PERIODS AS TEMPERATURES COOL TO NEAR THE DEW POINT DURING THE
LATE NIGHT HOURS.


&&

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

RIDGING BUILDS INTO THE CENTRAL BERING THROUGH FRIDAY NIGHT WITH
A WEAKENING UPPER LOW ALONG THE WESTERN AND CENTRAL ALEUTIANS.
THIS IS A RELATIVELY BENIGN SURFACE PATTERN WITH SMALL CRAFT WINDS
CONFINED TO THE WESTERN HALF OF THE ALEUTIANS. CLOUDY CONDITIONS
WILL ENCOMPASS THE BERING WITH WEAK EMBEDDED SHORTWAVES PRODUCING
OCCASIONAL SHOWERS. AREAS OF DENSE FOG IS EXPECTED TO FORM ON THURSDAY
AS STABLE CONDITIONS SETTLE ACROSS THE CENTRAL BERING.

&&

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

AN UPPER LEVEL RIDGE WILL BEGIN TO BUILD ACROSS THE INTERIOR OF
ALASKA FROM THE BERING SEA FRIDAY AFTERNOON AND OVERSPREAD THE
MAJORITY OF THE STATE THROUGH THE WEEKEND. WHILE THIS RIDGE BUILDS
ACROSS THE STATE...A PORTION OF THE LONGWAVE TROUGH THAT HAS BEEN
CREATING THE SHOWERY WEATHER ACROSS THE STATE WILL GET CUT OFF AS
RIDGING BUILDS ACROSS THE NORTH PACIFIC. THIS WILL CREATE A CUT
OFF LOW THAT IS EXPECTED TO DEVELOP ON SATURDAY AS A SHORTWAVE
INTERACTS WITH MULTIPLE FRAGMENTS OF ENERGY ASSOCIATED WITH THE
UPPER LEVEL TROUGH THAT IS GETTING CUT OFF. THE DETERMINISTIC AND
ENSEMBLE MEMBERS HAVE THE DEVELOPMENT OF THIS LOW PROGGED FAIRLY
WELL AS IT DEVELOPS SOUTH OF THE EASTERN ALEUTIANS SATURDAY.
MODELS THEN BEGIN TO STRUGGLE WITH THE PLACEMENT OF THIS UPPER
LEVEL FEATURE AND AN ASSOCIATED SURFACE LOW THAT DEVELOPS IN
RESPONSE TO MID AND UPPER LEVEL CYCLOGENESIS. THE REASON FOR THE
DIFFICULTY IN TIMING AND PLACEMENT IS BECAUSE STEERING CURRENTS
CAN BE QUITE DIFFICULT TO DETERMINE WHEN A LOW IS NO LONGER
LOCATED IN A TROUGH BUT RATHER STUCK BETWEEN TWO UPPER LEVEL
RIDGES.

IN SHORT...HOW THE LONGWAVE TROUGH (ROSBY WAVE) OVER RUSSIA
DEVELOPS IN RESPONSE TO A DEEPENING AREA OF LOW PRESSURE WILL
INFLUENCE THE WESTERN RIDGE OVER THE BERING SEA...AND HOW IT WILL
FORCE THE AREA OF LOW PRESSURE IN THE NORTH PACIFIC EAST INTO THE
GULF OF ALASKA OR POSSIBLY EVEN INTO THE ALASKA MAINLAND. WHAT
THIS MEANS FOR ALASKA IS THAT A PERIOD OF WARMER TEMPERATURES...DRIER
CONDITIONS AND LESS CLOUDY SKIES WILL LIKELY BE OBSERVED THROUGH
THE WEEKEND AND INTO THE BEGINNING OF NEXT WEEK. DEPENDING ON THE
TRACK OF THE UPPER LEVEL AND SURFACE LOWS...RAIN CHANCES MAY SNEAK
BACK IN TOWARD THE MIDDLE OF NEXT WEEK BUT CONFIDENCE IS NOT HIGH
WITH MORE THAN SCATTERED SHOWERS AT THIS TIME.

&&


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

&&

$$

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





    US Dept of Commerce
    National Oceanic and Atmospheric Administration
    National Weather Service
    1325 East West Highway
    Silver Spring, MD 20910
    Page Author: NWS Internet Services Team
Disclaimer
Information Quality
Credits
Glossary
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities