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000
FXAK68 PAFC 302132
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
132 PM AKDT WED JUL 30 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS A STABLE "OMEGA BLOCK" OVER THE AREA WITH THE UPPER LEVEL
RIDGE OVER THE CENTRAL/EASTERN BERING SEA AND AN UPPER LOW OVER
THE GULF OF ALASKA AND ANOTHER LOW TO THE SOUTHWEST OF THE WESTERN
ALEUTIANS.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT TODAY. THIS IS NOT A
SURPRISE...CONSIDERING THE STABLE BLOCKING PATTERN OVER THE AREA.
FORECAST CONFIDENCE IS HIGHER THAN NORMAL FOR THE AFTERNOON
PACKAGE.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...MAINLY DRY CONDITIONS ARE EXPECTED
INTO FRIDAY WITH THE BLOCKING HIGH KEEPING ANY ORGANIZED WEATHER
SYSTEMS AWAY FROM THE AREA. THE EXCEPTION IS SOME DIURNAL MOUNTAIN
CONVECTION. THIS CONVECTION WILL BE VERY LIMITED THIS
EVENING...THEN INCREASES SLIGHTLY FOR THURSDAY AND FRIDAY. LATE
FRIDAY INTO SATURDAY A SYSTEM WILL SLIDE AROUND THE TOP OF THE
RIDGE AND PUSH INTO SOUTH CENTRAL ALASKA FROM THE NORTHWEST.
PRECIPITATION FROM THIS SYSTEM WILL LIKELY PUSH INTO THE SUSITNA
VALLEY ON SATURDAY...BUT NOT MUCH FURTHER SOUTH AS IT STALLS AND
WEAKENS.

FOR SOUTHWEST ALASKA...SOME MOISTURE WILL SNEAK AROUND THE TOP OF
THE RIDGE LATE TONIGHT AND VERY SLOWLY PUSH ACROSS THE AREA INTO
SATURDAY. THIS PUSH CHANCES OF RAIN/SHOWERS SLOWLY TOWARDS THE
SOUTHEAST...ALTHOUGH SLOWING ALMOST TO A STOP ON SATURDAY.

FOR THE BERING SEA/ALEUTIANS...THE PATTERN WILL CHANGE VERY LITTLE
OVER THE NEXT FEW DAYS. THE BLOCKING RIDGE WILL SLOWLY DRIFT
NORTHWEST...WITH THE CENTER OF THE HIGH MOVING FROM THE CENTRAL
BERING SEA TONIGHT TO THE NORTHWEST COAST OF THE BERING ON
SATURDAY AFTERNOON.

&&

.LONG TERM FORECAST...
THE OMEGA BLOCKING OVER THE BERING SEA WILL CONTINUE WITH STRATUS
AND FOG WITH LIGHT WINDS THROUGH SUNDAY. BY MONDAY AN UPPER LEVEL
WEAK SHORTWAVE TROUGH WILL DROP DOWN FROM THE UPPER KUSKOKWIM
VALLEY INTO THE SOUTHWEST ALASKA REGION. THIS WILL BRING INCREASED
CLOUDS AND SHOWERS THROUGHOUT THE AREA. BY SUNDAY THE THE WEAK
UPPER LEVEL RIDGE IN SOUTHCENTRAL ALASKA WILL BE EXITING THE
REGION...FOLLOWED BY AN UPPER LEVEL TROUGH PUSHING INTO THE GULF
OF ALASKA BRINGING NORTHEASTERLY WINDS AND INCREASED CLOUD COVER
WITH RAIN ALONG THE COASTLINE BEFORE SPREADING INLAND.

&&

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

$$

LUDWIG/PD JUL 14




000
FXAK68 PAFC 302132
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
132 PM AKDT WED JUL 30 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS A STABLE "OMEGA BLOCK" OVER THE AREA WITH THE UPPER LEVEL
RIDGE OVER THE CENTRAL/EASTERN BERING SEA AND AN UPPER LOW OVER
THE GULF OF ALASKA AND ANOTHER LOW TO THE SOUTHWEST OF THE WESTERN
ALEUTIANS.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT TODAY. THIS IS NOT A
SURPRISE...CONSIDERING THE STABLE BLOCKING PATTERN OVER THE AREA.
FORECAST CONFIDENCE IS HIGHER THAN NORMAL FOR THE AFTERNOON
PACKAGE.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...MAINLY DRY CONDITIONS ARE EXPECTED
INTO FRIDAY WITH THE BLOCKING HIGH KEEPING ANY ORGANIZED WEATHER
SYSTEMS AWAY FROM THE AREA. THE EXCEPTION IS SOME DIURNAL MOUNTAIN
CONVECTION. THIS CONVECTION WILL BE VERY LIMITED THIS
EVENING...THEN INCREASES SLIGHTLY FOR THURSDAY AND FRIDAY. LATE
FRIDAY INTO SATURDAY A SYSTEM WILL SLIDE AROUND THE TOP OF THE
RIDGE AND PUSH INTO SOUTH CENTRAL ALASKA FROM THE NORTHWEST.
PRECIPITATION FROM THIS SYSTEM WILL LIKELY PUSH INTO THE SUSITNA
VALLEY ON SATURDAY...BUT NOT MUCH FURTHER SOUTH AS IT STALLS AND
WEAKENS.

FOR SOUTHWEST ALASKA...SOME MOISTURE WILL SNEAK AROUND THE TOP OF
THE RIDGE LATE TONIGHT AND VERY SLOWLY PUSH ACROSS THE AREA INTO
SATURDAY. THIS PUSH CHANCES OF RAIN/SHOWERS SLOWLY TOWARDS THE
SOUTHEAST...ALTHOUGH SLOWING ALMOST TO A STOP ON SATURDAY.

FOR THE BERING SEA/ALEUTIANS...THE PATTERN WILL CHANGE VERY LITTLE
OVER THE NEXT FEW DAYS. THE BLOCKING RIDGE WILL SLOWLY DRIFT
NORTHWEST...WITH THE CENTER OF THE HIGH MOVING FROM THE CENTRAL
BERING SEA TONIGHT TO THE NORTHWEST COAST OF THE BERING ON
SATURDAY AFTERNOON.

&&

.LONG TERM FORECAST...
THE OMEGA BLOCKING OVER THE BERING SEA WILL CONTINUE WITH STRATUS
AND FOG WITH LIGHT WINDS THROUGH SUNDAY. BY MONDAY AN UPPER LEVEL
WEAK SHORTWAVE TROUGH WILL DROP DOWN FROM THE UPPER KUSKOKWIM
VALLEY INTO THE SOUTHWEST ALASKA REGION. THIS WILL BRING INCREASED
CLOUDS AND SHOWERS THROUGHOUT THE AREA. BY SUNDAY THE THE WEAK
UPPER LEVEL RIDGE IN SOUTHCENTRAL ALASKA WILL BE EXITING THE
REGION...FOLLOWED BY AN UPPER LEVEL TROUGH PUSHING INTO THE GULF
OF ALASKA BRINGING NORTHEASTERLY WINDS AND INCREASED CLOUD COVER
WITH RAIN ALONG THE COASTLINE BEFORE SPREADING INLAND.

&&

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

$$

LUDWIG/PD JUL 14





000
FXAK68 PAFC 301218
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
418 AM AKDT WED JUL 30 2014

.ANALYSIS AND UPPER LEVELS...

THE OMEGA BLOCKING PATTERN CENTERED OVER THE CENTRAL BERING SEA
CONTINUES TO BE THE DOMINANT FACTOR OVER SOUTHERN ALASKA AND THE
BERING SEA. AN UPPER LEVEL LOW LOCATED BETWEEN THE KAMCHATKA
PENINSULA AND THE WESTERN ALEUTIANS (THE WESTERN ANCHOR OF THE
OMEGA BLOCK) CONTINUES TO EJECT WEAK SHORTWAVES ACROSS THE WESTERN
ALEUTIANS. THIS HAS CONTINUED THE RAINY PERIOD ACROSS MUCH OF THE
WESTERN ALEUTIANS AS WEAK FRONTAL BOUNDARIES ASSOCIATED WITH A
SURFACE REFLECTION OF THE UPPER LOW PUSH THROUGH THE AREA TOWARD
THE CENTRAL BERING SEA. ANOTHER...AND MORE COMPLEX...UPPER LEVEL
LOW IS LOCATED ACROSS THE SOUTHERN GULF OF ALASKA/NORTHERN PACIFIC
(THE EASTERN ANCHOR OF THE OMEGA BLOCK). THIS UPPER LEVEL LOW HAS
BEGUN TO SLOWLY DRIFT SOUTHWARD AND AMPLIFY THE LONGWAVE TROUGHING
ON THE EASTERN PERIPHERY OF AN ANOMALOUSLY STRONG RIDGE OF HIGH
PRESSURE CENTERED OVER THE BERING SEA. A WEAKENING EASTERLY WAVE
WILL CONTINUE TO ROTATE ALONG THE PERIPHERY OF THE UPPER LEVEL
LOW AND CONTINUE TO BRING RAIN TO THE NORTHERN GULF COAST AND
SOUTHERN PORTIONS OF THE COPPER RIVER BASIN. THE AFOREMENTIONED
RIDGE OVER THE BERING SEA (THE FINAL COMPONENT OF THE OMEGA BLOCK)
HAS BEGUN TO BUILD EASTWARD OVER SOUTHWEST ALASKA AND PARTS OF
SOUTHCENTRAL ALASKA. UNTIL A STRONG UPPER LEVEL SYSTEM PUSHES
THROUGH THE BERING SEA OR NORTH PACIFIC...THIS BLOCKING PATTERN
SHOULD REMAIN FIRMLY ENTRENCHED.

&&

.MODEL DISCUSSION...

NUMERICAL GUIDANCE IS IN EXCELLENT SYNOPTIC AGREEMENT THROUGH THE
SHORT-TERM. A FEW DISCREPANCIES ARE OBSERVED WITH THE TIMING/STRENGTH
OF A WEAK WAVE DROPPING SOUTH ALONG THE EASTERN PERIPHERY OF THE
BERING SEA RIDGE LATE THIS WEEK. REGARDLESS...PRECIPITATION WILL
RETURN TO PARTS OF SOUTHWEST ALASKA LATE THIS WEEK AND PARTS OF
SOUTH CENTRAL ALASKA THIS WEEKEND. ANOTHER MINOR DISCREPANCY IS
NOTED WITH THE UPPER LEVEL LOW OVER THE SOUTHERN GULF/NORTH PACIFIC
HEADING TOWARD THE WEEKEND. THE GFS IS TRYING TO KEEP THIS UPPER
LOW MUCH FURTHER NORTH THAN ALL OTHER GUIDANCE AND SEEMS TO GO
AGAINST WHAT ONE WOULD GENERALLY THINK IN THIS TYPE OF PATTERN.
OVERALL...WENT WITH AN ECMWF/NAM BLEND FOR FORECAST UPDATES THIS
MORNING.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...AN EASTERLY WAVE ROTATING AROUND AN UPPER
LOW IN THE SOUTHERN GULF OF ALASKA WILL CONTINUE TO BRING
PRECIPITATION TO PARTS OF THE NORTHERN GULF COAST AND SOUTHERN
PORTIONS OF THE COPPER RIVER BASIN THROUGH LATE THIS MORNING.
PRECIPITATION WILL BEGIN TO TAPER OFF LATE THIS MORNING AS THE
UPPER LOW SLOWLY DRIFTS INTO THE NORTH PACIFIC AND THE EASTERLY
WAVE MOVES OFFSHORE. THE RIDGE OF HIGH PRESSURE LOCATED OVER THE
BERING SEA AND SOUTHWEST ALASKA WILL BUILD ACROSS SOUTHCENTRAL
ALASKA DURING THE DAY TODAY AND PERSIST THROUGH THE REMAINDER OF
THE WEEK. THIS SHOULD BRING MOSTLY CLEAR SKIES TO THE REGION...WITH
HIGH TEMPERATURES 5 TO 10 DEGREES ABOVE NORMAL FOR MOST LOCATIONS.
THERE WILL ONLY BE A SLIGHT CHANCE FOR CONVECTIVE SHOWERS NEAR THE
MOUNTAINS IN THE AFTERNOONS DUE IN LARGE PART TO STRONG SUBSIDENCE
ASSOCIATED WITH THE STRENGTHENING RIDGE.

SOUTHWEST ALASKA...HIGH PRESSURE WILL DOMINATE THE OVERALL WEATHER
PATTERN THROUGH MOST OF THURSDAY. MOSTLY CLEAR SKIES WITH A FEW
CUMULUS CLOUDS DEVELOPING NEAR THE MOUNTAINOUS REGIONS WILL BE THE
NORM FOR TODAY AND THURSDAY. TEMPERATURES ACROSS THE REGION WILL
BE 5 TO 10 DEGREES ABOVE NORMAL TODAY AND AGAIN ON THURSDAY. BY
THURSDAY EVENING/EARLY FRIDAY MORNING...A SHORT WAVE WILL DROP OUT
OF THE ARCTIC AND BRING RAIN CHANCES BACK TO THE KUSKOKWIM DELTA
AND LOWER KUSKOKWIM VALLEY...AND LINGER THROUGH AT LEAST THE FIRST
HALF OF THE WEEKEND.

BERING SEA/ALEUTIANS...HIGH PRESSURE WILL CONTINUE TO DOMINATE THE
EASTERN TWO-THIRDS OF THE BERING SEA THROUGH THE SHORT-TERM. LOW
STRATUS AND PATCHY FOG/AREAS OF FOG WILL CONTINUE TO BE SEEN
ACROSS THE BERING SEA AND ALEUTIAN CHAIN. SOME COLLISION
COALESCENCE SHOULD TAKE PLACE WITH THE ESTABLISHED STRATUS
DECK...LEADING TO AREAS OF LIGHT DRIZZLE ALONG THE ALEUTIAN CHAIN
AND OVER THE BERING SEA. AN UPPER LEVEL LOW AND ITS SURFACE
REFLECTION WILL CONTINUE TO PUSH UPPER LEVEL SHORT WAVES AND
FRONTAL BOUNDARIES ACROSS THE WESTERN ALEUTIANS AND WESTERN BERING
SEA...LEADING TO YET ANOTHER WET PERIOD FOR THE WESTERN BERING SEA.

&&

.LONG TERM FORECAST...

THE OMEGA BLOCKING OVER THE CENTRAL TO NORTHERN BERING SEA WILL
CONTINUE THROUGH THIS UPCOMING WEEKEND. THE PREDOMINATE FEATURE
WILL BE STRATUS AND FOG WITH LIGHT WINDS FOR THE BERING SEA. THE
SOUTHCENTRAL ALASKA WILL BE UNDER THE INFLUENCE OF WEAK SHORTWAVE
RIDGING KEEPING MOST OF THE REGION SLIGHTLY WARMER THAN AVERAGE
WITH SHOWERS ALONG THE MOUNTAINS THROUGH THE WEEKEND.

&&

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

$$

MCLAY JUL 14




000
FXAK68 PAFC 301218
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
418 AM AKDT WED JUL 30 2014

.ANALYSIS AND UPPER LEVELS...

THE OMEGA BLOCKING PATTERN CENTERED OVER THE CENTRAL BERING SEA
CONTINUES TO BE THE DOMINANT FACTOR OVER SOUTHERN ALASKA AND THE
BERING SEA. AN UPPER LEVEL LOW LOCATED BETWEEN THE KAMCHATKA
PENINSULA AND THE WESTERN ALEUTIANS (THE WESTERN ANCHOR OF THE
OMEGA BLOCK) CONTINUES TO EJECT WEAK SHORTWAVES ACROSS THE WESTERN
ALEUTIANS. THIS HAS CONTINUED THE RAINY PERIOD ACROSS MUCH OF THE
WESTERN ALEUTIANS AS WEAK FRONTAL BOUNDARIES ASSOCIATED WITH A
SURFACE REFLECTION OF THE UPPER LOW PUSH THROUGH THE AREA TOWARD
THE CENTRAL BERING SEA. ANOTHER...AND MORE COMPLEX...UPPER LEVEL
LOW IS LOCATED ACROSS THE SOUTHERN GULF OF ALASKA/NORTHERN PACIFIC
(THE EASTERN ANCHOR OF THE OMEGA BLOCK). THIS UPPER LEVEL LOW HAS
BEGUN TO SLOWLY DRIFT SOUTHWARD AND AMPLIFY THE LONGWAVE TROUGHING
ON THE EASTERN PERIPHERY OF AN ANOMALOUSLY STRONG RIDGE OF HIGH
PRESSURE CENTERED OVER THE BERING SEA. A WEAKENING EASTERLY WAVE
WILL CONTINUE TO ROTATE ALONG THE PERIPHERY OF THE UPPER LEVEL
LOW AND CONTINUE TO BRING RAIN TO THE NORTHERN GULF COAST AND
SOUTHERN PORTIONS OF THE COPPER RIVER BASIN. THE AFOREMENTIONED
RIDGE OVER THE BERING SEA (THE FINAL COMPONENT OF THE OMEGA BLOCK)
HAS BEGUN TO BUILD EASTWARD OVER SOUTHWEST ALASKA AND PARTS OF
SOUTHCENTRAL ALASKA. UNTIL A STRONG UPPER LEVEL SYSTEM PUSHES
THROUGH THE BERING SEA OR NORTH PACIFIC...THIS BLOCKING PATTERN
SHOULD REMAIN FIRMLY ENTRENCHED.

&&

.MODEL DISCUSSION...

NUMERICAL GUIDANCE IS IN EXCELLENT SYNOPTIC AGREEMENT THROUGH THE
SHORT-TERM. A FEW DISCREPANCIES ARE OBSERVED WITH THE TIMING/STRENGTH
OF A WEAK WAVE DROPPING SOUTH ALONG THE EASTERN PERIPHERY OF THE
BERING SEA RIDGE LATE THIS WEEK. REGARDLESS...PRECIPITATION WILL
RETURN TO PARTS OF SOUTHWEST ALASKA LATE THIS WEEK AND PARTS OF
SOUTH CENTRAL ALASKA THIS WEEKEND. ANOTHER MINOR DISCREPANCY IS
NOTED WITH THE UPPER LEVEL LOW OVER THE SOUTHERN GULF/NORTH PACIFIC
HEADING TOWARD THE WEEKEND. THE GFS IS TRYING TO KEEP THIS UPPER
LOW MUCH FURTHER NORTH THAN ALL OTHER GUIDANCE AND SEEMS TO GO
AGAINST WHAT ONE WOULD GENERALLY THINK IN THIS TYPE OF PATTERN.
OVERALL...WENT WITH AN ECMWF/NAM BLEND FOR FORECAST UPDATES THIS
MORNING.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...AN EASTERLY WAVE ROTATING AROUND AN UPPER
LOW IN THE SOUTHERN GULF OF ALASKA WILL CONTINUE TO BRING
PRECIPITATION TO PARTS OF THE NORTHERN GULF COAST AND SOUTHERN
PORTIONS OF THE COPPER RIVER BASIN THROUGH LATE THIS MORNING.
PRECIPITATION WILL BEGIN TO TAPER OFF LATE THIS MORNING AS THE
UPPER LOW SLOWLY DRIFTS INTO THE NORTH PACIFIC AND THE EASTERLY
WAVE MOVES OFFSHORE. THE RIDGE OF HIGH PRESSURE LOCATED OVER THE
BERING SEA AND SOUTHWEST ALASKA WILL BUILD ACROSS SOUTHCENTRAL
ALASKA DURING THE DAY TODAY AND PERSIST THROUGH THE REMAINDER OF
THE WEEK. THIS SHOULD BRING MOSTLY CLEAR SKIES TO THE REGION...WITH
HIGH TEMPERATURES 5 TO 10 DEGREES ABOVE NORMAL FOR MOST LOCATIONS.
THERE WILL ONLY BE A SLIGHT CHANCE FOR CONVECTIVE SHOWERS NEAR THE
MOUNTAINS IN THE AFTERNOONS DUE IN LARGE PART TO STRONG SUBSIDENCE
ASSOCIATED WITH THE STRENGTHENING RIDGE.

SOUTHWEST ALASKA...HIGH PRESSURE WILL DOMINATE THE OVERALL WEATHER
PATTERN THROUGH MOST OF THURSDAY. MOSTLY CLEAR SKIES WITH A FEW
CUMULUS CLOUDS DEVELOPING NEAR THE MOUNTAINOUS REGIONS WILL BE THE
NORM FOR TODAY AND THURSDAY. TEMPERATURES ACROSS THE REGION WILL
BE 5 TO 10 DEGREES ABOVE NORMAL TODAY AND AGAIN ON THURSDAY. BY
THURSDAY EVENING/EARLY FRIDAY MORNING...A SHORT WAVE WILL DROP OUT
OF THE ARCTIC AND BRING RAIN CHANCES BACK TO THE KUSKOKWIM DELTA
AND LOWER KUSKOKWIM VALLEY...AND LINGER THROUGH AT LEAST THE FIRST
HALF OF THE WEEKEND.

BERING SEA/ALEUTIANS...HIGH PRESSURE WILL CONTINUE TO DOMINATE THE
EASTERN TWO-THIRDS OF THE BERING SEA THROUGH THE SHORT-TERM. LOW
STRATUS AND PATCHY FOG/AREAS OF FOG WILL CONTINUE TO BE SEEN
ACROSS THE BERING SEA AND ALEUTIAN CHAIN. SOME COLLISION
COALESCENCE SHOULD TAKE PLACE WITH THE ESTABLISHED STRATUS
DECK...LEADING TO AREAS OF LIGHT DRIZZLE ALONG THE ALEUTIAN CHAIN
AND OVER THE BERING SEA. AN UPPER LEVEL LOW AND ITS SURFACE
REFLECTION WILL CONTINUE TO PUSH UPPER LEVEL SHORT WAVES AND
FRONTAL BOUNDARIES ACROSS THE WESTERN ALEUTIANS AND WESTERN BERING
SEA...LEADING TO YET ANOTHER WET PERIOD FOR THE WESTERN BERING SEA.

&&

.LONG TERM FORECAST...

THE OMEGA BLOCKING OVER THE CENTRAL TO NORTHERN BERING SEA WILL
CONTINUE THROUGH THIS UPCOMING WEEKEND. THE PREDOMINATE FEATURE
WILL BE STRATUS AND FOG WITH LIGHT WINDS FOR THE BERING SEA. THE
SOUTHCENTRAL ALASKA WILL BE UNDER THE INFLUENCE OF WEAK SHORTWAVE
RIDGING KEEPING MOST OF THE REGION SLIGHTLY WARMER THAN AVERAGE
WITH SHOWERS ALONG THE MOUNTAINS THROUGH THE WEEKEND.

&&

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

$$

MCLAY JUL 14





000
FXAK68 PAFC 292136
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
136 PM AKDT TUE JUL 29 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER THE GULF OF ALASKA. A STRONG
BLOCKING RIDGE IS OVER THE CENTRAL/EASTERN BERING SEA. AN UPPER
LOW IS LURKING OFF TO THE SOUTHWEST OF THE WESTERN ALEUTIANS. THIS
IS AN "OMEGA BLOCK" AND IS A STABLE PATTERN.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT. CONSIDERING
THIS...AND THE STABILITY OF THE PATTERN...FORECAST CONFIDENCE
TODAY IS HIGH.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...SOME (MAINLY MOUNTAIN) SHOWERS ARE
POSSIBLE THIS EVENING WITH SOME RESIDUAL MOISTURE AND THE FLOW
ALOFT STILL A LITTLE CYCLONIC. SOME "WRAP AROUND" MOISTURE FROM
THE GULF LOW IS PUSHING INTO SOUTHERN ALASKA FROM THE EAST WILL
PROVIDE SOME RAIN/SHOWERS TO THE EASTERN COPPER RIVER BASIN AND
THE EASTERN GULF COAST/EASTERN PRINCE WILLIAM SOUND. THIS WILL
TAPER OFF ON WEDNESDAY AND COME TO AND END WEDNESDAY NIGHT.
OTHERWISE MAINLY DRY CONDITIONS (SOME DIURNAL MOUNTAIN SHOWERS ARE
POSSIBLE) ARE EXPECTED ACROSS THE AREA INTO FRIDAY AFTERNOON AS
THE BERING RIDGE BUILDS EASTWARD ACROSS SOUTHERN ALASKA.

FOR SOUTHWEST ALASKA...DRY CONDITIONS ARE EXPECTED THROUGH
THURSDAY NIGHT AS THE RIDGE DOMINATES THE WEATHER PICTURE. SOME
MOISTURE MAY SLIDE AROUND THE RIDGE AND ENTER SOUTHWEST ALASKA
FROM THE NORTHWEST ON FRIDAY FOR A CHANCE OF SHOWERS.

FOR THE BERING SEA/ALEUTIANS...THE PATTERN CHANGES VERY LITTLE
DURING THE WEEK. THE BERING RIDGE WILL KEEP PRECIPITATION AND
SOUTHEASTERLY WINDS ASSOCIATED WITH THE LOW SOUTHWEST OF THE
WESTERN ALEUTIANS CONFINED TO AREAS GENERALLY FROM ATKA WEST.

&&

.LONG TERM FORECAST...
THE OMEGA BLOCKING OVER THE CENTRAL TO NORTHERN BERING SEA WILL
CONTINUE THROUGH THIS UPCOMING WEEKEND. THE PREDOMINATE FEATURE
WILL BE STRATUS AND FOG WITH LIGHT WINDS FOR THE BERING SEA. THE
SOUTHCENTRAL ALASKA WILL BE UNDER THE INFLUENCE OF WEAK SHORTWAVE
RIDGING KEEPING MOST OF THE REGION SLIGHTLY WARMER THAN AVERAGE
WITH SHOWERS ALONG THE MOUNTAINS THROUGH THE WEEKEND.

&&

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

$$

LUDWIG/PD JUL 14




000
FXAK68 PAFC 292136
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
136 PM AKDT TUE JUL 29 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER THE GULF OF ALASKA. A STRONG
BLOCKING RIDGE IS OVER THE CENTRAL/EASTERN BERING SEA. AN UPPER
LOW IS LURKING OFF TO THE SOUTHWEST OF THE WESTERN ALEUTIANS. THIS
IS AN "OMEGA BLOCK" AND IS A STABLE PATTERN.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN VERY GOOD AGREEMENT. CONSIDERING
THIS...AND THE STABILITY OF THE PATTERN...FORECAST CONFIDENCE
TODAY IS HIGH.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...SOME (MAINLY MOUNTAIN) SHOWERS ARE
POSSIBLE THIS EVENING WITH SOME RESIDUAL MOISTURE AND THE FLOW
ALOFT STILL A LITTLE CYCLONIC. SOME "WRAP AROUND" MOISTURE FROM
THE GULF LOW IS PUSHING INTO SOUTHERN ALASKA FROM THE EAST WILL
PROVIDE SOME RAIN/SHOWERS TO THE EASTERN COPPER RIVER BASIN AND
THE EASTERN GULF COAST/EASTERN PRINCE WILLIAM SOUND. THIS WILL
TAPER OFF ON WEDNESDAY AND COME TO AND END WEDNESDAY NIGHT.
OTHERWISE MAINLY DRY CONDITIONS (SOME DIURNAL MOUNTAIN SHOWERS ARE
POSSIBLE) ARE EXPECTED ACROSS THE AREA INTO FRIDAY AFTERNOON AS
THE BERING RIDGE BUILDS EASTWARD ACROSS SOUTHERN ALASKA.

FOR SOUTHWEST ALASKA...DRY CONDITIONS ARE EXPECTED THROUGH
THURSDAY NIGHT AS THE RIDGE DOMINATES THE WEATHER PICTURE. SOME
MOISTURE MAY SLIDE AROUND THE RIDGE AND ENTER SOUTHWEST ALASKA
FROM THE NORTHWEST ON FRIDAY FOR A CHANCE OF SHOWERS.

FOR THE BERING SEA/ALEUTIANS...THE PATTERN CHANGES VERY LITTLE
DURING THE WEEK. THE BERING RIDGE WILL KEEP PRECIPITATION AND
SOUTHEASTERLY WINDS ASSOCIATED WITH THE LOW SOUTHWEST OF THE
WESTERN ALEUTIANS CONFINED TO AREAS GENERALLY FROM ATKA WEST.

&&

.LONG TERM FORECAST...
THE OMEGA BLOCKING OVER THE CENTRAL TO NORTHERN BERING SEA WILL
CONTINUE THROUGH THIS UPCOMING WEEKEND. THE PREDOMINATE FEATURE
WILL BE STRATUS AND FOG WITH LIGHT WINDS FOR THE BERING SEA. THE
SOUTHCENTRAL ALASKA WILL BE UNDER THE INFLUENCE OF WEAK SHORTWAVE
RIDGING KEEPING MOST OF THE REGION SLIGHTLY WARMER THAN AVERAGE
WITH SHOWERS ALONG THE MOUNTAINS THROUGH THE WEEKEND.

&&

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

$$

LUDWIG/PD JUL 14





000
FXAK68 PAFC 291253
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
453 AM AKDT TUE JUL 29 2014

.ANALYSIS AND UPPER LEVELS...

WATER VAPOR IMAGERY THIS MORNING DEPICTS A SHORTWAVE ENHANCED
UPPER LOW OVER THE LOWER KUSKOKWIM VALLEY AND BRISTOL BAY AREA.
THIS UPPER LOW HAS BEGUN TO PHASE WITH ANOTHER UPPER LOW LOCATED
IN THE GULF OF ALASKA. THIS ULTIMATELY CREATED A DEFORMATION BAND
OVER THE COOK INLET AREA OVERNIGHT AND EARLY THIS MORNING...WHICH
HAS ALLOWED PRECIPITATION TO LINGER A TAD LONGER THAN ORIGINALLY
EXPECTED. THE PHASING OF THESE TWO LOWS WILL HAVE A LASTING IMPACT
ON THE LONGWAVE PATTERN AS TROUGHING ALONG THE EASTERN PERIPHERY
OF AN OMEGA BLOCK OVER THE BERING SEA BECOMES MORE AMPLIFIED.
ANOTHER UPPER LOW LOCATED BETWEEN THE KAMCHATKA PENINSULA AND THE
WESTERN ALEUTIANS CONTINUES TO SLOWLY PUSH EASTWARD AS IT EJECTS
MULTIPLE SHORTWAVES OVER THE WESTERN ALEUTIANS. AN UNUSUALLY
STRONG RIDGE RESIDES ACROSS THE CENTRAL AND EASTERN BERING
SEA...WITH THE 00Z AND 12Z RAOBS AT ST PAUL ISLAND REPORTING 500
MB HEIGHTS BETWEEN 583 AND 584 DECAMETERS. THE COMBINATION OF THE
LOW WEST OF THE ALEUTIANS ISLANDS...THE LOW IN THE GULF OF ALASKA
AND THE STRONG RIDGE OVER THE BERING SEA ARE IN TEXTBOOK OMEGA
BLOCK CONFIGURATION. WATER VAPOR IMAGERY IS ALSO DEPICTING AN
EASTERLY WAVE PRESENTLY LOCATED ALONG THE ALCAN BORDER ROTATING
AROUND THE AFOREMENTIONED LOW IN THE GULF OF ALASKA.

&&

.MODEL DISCUSSION...

MODELS ARE VERY GOOD SYNOPTIC AGREEMENT THIS MORNING. THE 00Z NAM
WAS A DISTINCT OUTLIER WITH THE UPPER LOW OVER SOUTHWEST ALASKA...AS
IT TRIED TO PLACE THIS FEATURE FURTHER EAST INTO THE SUSITNA VALLEY.
THE 06Z RUN OF THE NAM CORRECTED THIS INITIALIZATION DEFECT AND
PLACED THE UPPER LOW IN IN THE CORRECT LOCATION COMPARED TO
CURRENT SATELLITE OBSERVATIONS. NUMERICAL GUIDANCE HAS COME INTO
BETTER AGREEMENT WITH AN EASTERLY WAVE CURRENTLY LOCATED ALONG THE
ALCAN BORDER. THERE ARE STILL SMALL DIFFERENCES AMONGST THE
GUIDANCE...BUT SHOULD HAVE VERY MINOR IMPACTS ON THE EVOLUTION OF
PRECIPITATION TODAY AS THE WAVES PUSHES INTO THE COPPER RIVER
BASIN. THE ECMWF WAS PREFERRED THIS MORNING FOR FORECAST UPDATES
GIVEN THE BEST RUN-TO-RUN CONSISTENCY AND BEST INITIALIZATION.
ALL NUMERICAL GUIDANCE SUGGESTS THAT THE OMEGA BLOCK OVER THE
BERING SEA AND SOUTHWEST ALASKA IS HERE TO STAY THROUGH AT LEAST
THE END OF THE WORK WEEK.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...PRECIPITATION WILL CONTINUE TO TAPER OFF
FROM NORTHEAST TO SOUTHWEST THIS MORNING AS AN UPPER LEVEL LOW
OVER SOUTHWEST ALASKA PUSHES SOUTH TOWARD KODIAK ISLAND AND
EVENTUALLY INTO THE NORTH PACIFIC. SOME BREAKS IN THE CLOUDS WILL
BE OBSERVED OVER THE WESTERN COPPER RIVER BASIN AND INTO THE MAT-
SU VALLEY AND ANCHORAGE BOWL THIS MORNING THROUGH THIS AFTERNOON.
PATCHY FOG WILL BE AN ISSUE ACROSS THE MAT-SU VALLEY AND ANCHORAGE
AREA EARLY THIS MORNING AS RESIDUAL MOISTURE FROM OVERNIGHT
RAINFALL BECOMES TRAPPED NEAR THE SURFACE. THE PATCHY FOG SHOULD
BE QUICK TO BURN OFF SHORTLY AFTER SUNRISE. AN EASTERLY WAVE
PRESENTLY LOCATED OVER THE ALCAN BORDER WILL PUSH WESTWARD INTO
THE COPPER RIVER BASIN DURING THE DAY TODAY. THIS WILL BRING
LIGHT TO MODERATE RAINFALL TO THE EASTERN HALF OF THE COPPER RIVER
BASIN...AND SCATTERED SHOWERS AND THE POTENTIAL FOR AN ISOLATED
THUNDERSTORM OR TWO FOR THE REMAINDER OF THE BASIN. MODELS ARE
HINTING AT A DECENT CHANCE FOR CONVECTIVE SHOWERS AND A FEW
THUNDERSTORMS ALONG THE TALKEETNA MOUNTAINS IN THE MAT-SU VALLEY
AS ENERGY ASSOCIATED WITH THE EASTERLY WAVE PIVOTS THROUGH THE
AREA LATE THIS AFTERNOON AND EVENING. THERE WILL ALSO BE A SLIGHT
CHANCE FOR CONVECTIVE SHOWERS AND THUNDERSTORMS IN THE ANCHORAGE
AREA THIS EVENING...BUT CONFIDENCE WITH THIS IS LOW AND OPTED TO
NEGLECT IT FROM THE FORECAST FOR THE TIME BEING. HIGH PRESSURE
WILL BEGIN TO BUILD ACROSS THE AREA ON WEDNESDAY...WHICH WILL
ALLOW FOR SKIES TO CLEAR ACROSS MUCH OF SOUTHCENTRAL ALASKA
THROUGH THE END OF THE WEEK WITH NEAR NORMAL TO ABOVE NORMAL
TEMPERATURES OBSERVED.

SOUTHWEST ALASKA...SCATTERED SHOWERS WILL CONTINUE ALONG THE
ALEUTIAN RANGE AND THE ALASKA PENINSULA THROUGH THIS MORNING WITH
AN UPPER LEVEL LOW PUSHING OUT OF SOUTHWEST ALASKA AND INTO THE
GULF OF ALASKA. A RIDGE OF HIGH PRESSURE OVER THE BERING SEA WILL
BUILD EASTWARD OVER SOUTHWEST ALASKA DURING THE DAY TODAY. THIS
WILL ALLOW FOR SKIES TO CONTINUE TO CLEAR IN THE WAKE OF THE UPPER
LEVEL LOW THAT PUSHED THROUGH THE AREA ON MONDAY. ABOVE NORMAL
TEMPERATURES WILL BE OBSERVED THROUGH THE END OF THE WEEK ACROSS
MUCH OF SOUTHWEST ALASKA.

BERING SEA/ALEUTIANS...THE EASTERN HALF OF THE BERING SEA WILL
REMAIN DRY WITH A POTENT LONGWAVE RIDGE THOROUGHLY ENTRENCHED
ACROSS THE AREA. LOW STRATUS AND PATCHY/AREAS OF FOG ARE LIKELY TO
PERSIST THROUGH THE END OF THE WEEK. AN UPPER LEVEL LOW WEST OF
THE ALEUTIAN CHAIN WILL SLOWLY DRIFT EASTWARD AND EJECT A SERIES
OF SHORTWAVES ACROSS THE WESTERN BERING SEA. PERIODS OF RAIN CAN
BE EXPECTED FOR THE WESTERN BERING SEA...WITH NO APPRECIABLE CHANGE
IN THE WEATHER PATTERN EXPECTED THROUGH THE END OF THE WEEK.

&&

.LONG TERM FORECAST...

OMEGA BLOCKING CENTERED OVER THE NORTHERN BERING SEA WILL
CONTINUE TO DRIVE THE SENSIBLE WEATHER ACROSS MOST OF ALASKA
REGION ON FRIDAY. MUCH OF SOUTHERN ALASKA WILL REMAIN UNDER THE
INFLUENCE OF WEAK SHORTWAVE RIDGING...WHICH WILL KEEP MOST OF THE
AREA SLIGHTLY WARMER THAN AVERAGE...WITH SHOWERS RELEGATED TO THE
MOUNTAINS. SOUTHWEST ALASKA WILL REMAIN ALONG THE PERIPHERY OF THE
BLOCKING HIGH OVER THE BERING AND TROUGHING ACROSS THE NORTH
SLOPE...WITH RAIN AND SHOWER THREATS ALONG THE QUASI-STATIONARY
FRONT. RIDGING WILL REMAIN PERSISTENT ACROSS THE BERING THROUGH
THE WEEKEND...BUT UNCERTAINTY ARISES ACROSS SOUTHERN ALASKA BY
SUNDAY. THE ECMWF CONTINUES TO HINT AT NORTHERN STREAM ENERGY
DIVING INTO THE GULF AND INTERACTING WITH THE CURRENT CLOSED
LOW...WHILE THE CANADIAN GDPS AND GFS BUILD THE BERING RIDGE INTO
SOUTHERN ALASKA. THE CURRENT FORECAST WILL TAKE A MIDDLE GROUND
APPROACH...HIGHLIGHTING THE POTENTIAL FOR INCREASING PRECIPITATION
CHANCES BY SUNDAY AND MONDAY...AND NEAR CLIMATOLOGICAL TEMPERATURES.

&&

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

$$

MCLAY/JA JUL 14





000
FXAK68 PAFC 282141
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
141 PM AKDT MON JUL 28 2014

.ANALYSIS AND UPPER LEVELS...
THE MAIN PATTERN CONSISTS OF AN UPPER LEVEL RIDGE OVER THE
CENTRAL/EASTERN BERING SEA AND A TROUGH OVER MAINLAND ALASKA AND
THE GULF. THERE IS ANOTHER TROUGH WEST OF OF THE RIDGE OVER THE
WESTERN BERING AND KAMCHATKA PENINSULA. WITHIN THE MAINLAND TROUGH
THERE IS AN UPPER LEVEL LOW OVER SOUTHERN ALASKA RAPIDLY MOVING
SOUTH.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH 84 HOURS WITH
JUST A FEW DIFFERENCES IN MINOR DETAILS. AS A RESULT OF THIS...THE
FORECAST CONFIDENCE IS ABOVE NORMAL FOR THE AFTERNOON PACKAGE.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...THE UPPER LOW OVER THE AREA WILL
RAPIDLY PUSH INTO THE GULF OF ALASKA THROUGH TUESDAY MORNING.
DECENT RATES OF PRECIPITATION ARE EXPECTED FROM THE
MATANUSKA/SUSITNA VALLEYS THROUGH THE COOK INLET AREA TONIGHT.
TOTAL RAINFALL AMOUNTS WILL BE LIMITED DUE TO THE FAST MOVEMENT
OF THE LOW. ON TUESDAY THE BERING RIDGE WILL ASSERT ITSELF INTO
THE AREA AND DRY CONDITIONS AREA EXPECTED THROUGH THURSDAY. SOME
"WRAP AROUND" MOISTURE FROM THE GULF LOW WILL PUSH INTO THE COPPER
RIVER BASIN AND EASTERN PRINCE WILLIAM SOUND AREA TUESDAY AND
TUESDAY NIGHT FOR SOME SHOWERS/RAIN...THEN ON WEDNESDAY THE RIDGE
WILL PUSH EAST INTO THOSE AREAS AS WELL.

FOR SOUTHWEST ALASKA...SHOWERS WILL CONTINUE TONIGHT THEN TAPER
OFF ON TUESDAY AS THE UPPER LOW OVER THE AREA PUSHES TO THE
SOUTH...ENDING BY TUESDAY EVENING. THEN THE EASTERN BERING RIDGE
WILL BUILD STRONGLY OVER THE AREA THROUGH THURSDAY...KEEPING
CONDITIONS DRY.

FOR THE BERING SEA/ALEUTIANS...THE UPPER LEVEL RIDGE WILL HOLD
OVER THE CENTRAL/EASTERN BERING/ALEUTIANS THROUGH THURSDAY. A
SERIES OF FRONTS ASSOCIATED WITH THE KAMCHATKA/WESTERN BERING LOW
WILL PUSH UP THE WEST SIDE OF THE RIDGE THROUGH THURSDAY...WITH
PRECIPITATION AND SOUTHEASTERLY WINDS POSSIBLY PUSHING AS FAR EAST
AS ATKA.

&&

.LONG TERM FORECAST...
OMEGA BLOCKING CENTERED OVER THE NORTHERN BERING SEA WILL
CONTINUE TO DRIVE THE SENSIBLE WEATHER ACROSS MOST OF ALASKA
REGION ON FRIDAY. MUCH OF SOUTHERN ALASKA WILL REMAIN UNDER THE
INFLUENCE OF WEAK SHORTWAVE RIDGING...WHICH WILL KEEP MOST OF THE
AREA SLIGHTLY WARMER THAN AVERAGE...WITH SHOWERS RELEGATED TO THE
MOUNTAINS. SOUTHWEST ALASKA WILL REMAIN ALONG THE PERIPHERY OF THE
BLOCKING HIGH OVER THE BERING AND TROUGHING ACROSS THE NORTH
SLOPE...WITH RAIN AND SHOWER THREATS ALONG THE QUASISTATIONARY
FRONT. RIDGING WILL REMAIN PERSISTENT ACROSS THE BERING THROUGH
THE WEEKEND...BUT UNCERTAINTY ARISES ACROSS SOUTHERN ALASKA BY
SUNDAY. THE ECMWF CONTINUES TO HINT AT NORTHERN STREAM ENERGY
DIVING INTO THE GULF AND INTERACTING WITH THE CURRENT CLOSED
LOW...WHILE THE CANADIAN GDPS AND GFS BUILD THE BERING RIDGE INTO
SOUTHERN ALASKA. THE CURRENT FORECAST WILL TAKE A MIDDLE GROUND
APPROACH...HIGHLIGHTING THE POTENTIAL FOR INCREASING PRECIPITATION
CHANCES BY SUNDAY AND MONDAY...AND NEAR CLIMATOLOGICAL
TEMPERATURES.

&&

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

$$

LUDWIG/JA JUL 14





000
FXAK68 PAFC 282141
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
141 PM AKDT MON JUL 28 2014

.ANALYSIS AND UPPER LEVELS...
THE MAIN PATTERN CONSISTS OF AN UPPER LEVEL RIDGE OVER THE
CENTRAL/EASTERN BERING SEA AND A TROUGH OVER MAINLAND ALASKA AND
THE GULF. THERE IS ANOTHER TROUGH WEST OF OF THE RIDGE OVER THE
WESTERN BERING AND KAMCHATKA PENINSULA. WITHIN THE MAINLAND TROUGH
THERE IS AN UPPER LEVEL LOW OVER SOUTHERN ALASKA RAPIDLY MOVING
SOUTH.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH 84 HOURS WITH
JUST A FEW DIFFERENCES IN MINOR DETAILS. AS A RESULT OF THIS...THE
FORECAST CONFIDENCE IS ABOVE NORMAL FOR THE AFTERNOON PACKAGE.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...THE UPPER LOW OVER THE AREA WILL
RAPIDLY PUSH INTO THE GULF OF ALASKA THROUGH TUESDAY MORNING.
DECENT RATES OF PRECIPITATION ARE EXPECTED FROM THE
MATANUSKA/SUSITNA VALLEYS THROUGH THE COOK INLET AREA TONIGHT.
TOTAL RAINFALL AMOUNTS WILL BE LIMITED DUE TO THE FAST MOVEMENT
OF THE LOW. ON TUESDAY THE BERING RIDGE WILL ASSERT ITSELF INTO
THE AREA AND DRY CONDITIONS AREA EXPECTED THROUGH THURSDAY. SOME
"WRAP AROUND" MOISTURE FROM THE GULF LOW WILL PUSH INTO THE COPPER
RIVER BASIN AND EASTERN PRINCE WILLIAM SOUND AREA TUESDAY AND
TUESDAY NIGHT FOR SOME SHOWERS/RAIN...THEN ON WEDNESDAY THE RIDGE
WILL PUSH EAST INTO THOSE AREAS AS WELL.

FOR SOUTHWEST ALASKA...SHOWERS WILL CONTINUE TONIGHT THEN TAPER
OFF ON TUESDAY AS THE UPPER LOW OVER THE AREA PUSHES TO THE
SOUTH...ENDING BY TUESDAY EVENING. THEN THE EASTERN BERING RIDGE
WILL BUILD STRONGLY OVER THE AREA THROUGH THURSDAY...KEEPING
CONDITIONS DRY.

FOR THE BERING SEA/ALEUTIANS...THE UPPER LEVEL RIDGE WILL HOLD
OVER THE CENTRAL/EASTERN BERING/ALEUTIANS THROUGH THURSDAY. A
SERIES OF FRONTS ASSOCIATED WITH THE KAMCHATKA/WESTERN BERING LOW
WILL PUSH UP THE WEST SIDE OF THE RIDGE THROUGH THURSDAY...WITH
PRECIPITATION AND SOUTHEASTERLY WINDS POSSIBLY PUSHING AS FAR EAST
AS ATKA.

&&

.LONG TERM FORECAST...
OMEGA BLOCKING CENTERED OVER THE NORTHERN BERING SEA WILL
CONTINUE TO DRIVE THE SENSIBLE WEATHER ACROSS MOST OF ALASKA
REGION ON FRIDAY. MUCH OF SOUTHERN ALASKA WILL REMAIN UNDER THE
INFLUENCE OF WEAK SHORTWAVE RIDGING...WHICH WILL KEEP MOST OF THE
AREA SLIGHTLY WARMER THAN AVERAGE...WITH SHOWERS RELEGATED TO THE
MOUNTAINS. SOUTHWEST ALASKA WILL REMAIN ALONG THE PERIPHERY OF THE
BLOCKING HIGH OVER THE BERING AND TROUGHING ACROSS THE NORTH
SLOPE...WITH RAIN AND SHOWER THREATS ALONG THE QUASISTATIONARY
FRONT. RIDGING WILL REMAIN PERSISTENT ACROSS THE BERING THROUGH
THE WEEKEND...BUT UNCERTAINTY ARISES ACROSS SOUTHERN ALASKA BY
SUNDAY. THE ECMWF CONTINUES TO HINT AT NORTHERN STREAM ENERGY
DIVING INTO THE GULF AND INTERACTING WITH THE CURRENT CLOSED
LOW...WHILE THE CANADIAN GDPS AND GFS BUILD THE BERING RIDGE INTO
SOUTHERN ALASKA. THE CURRENT FORECAST WILL TAKE A MIDDLE GROUND
APPROACH...HIGHLIGHTING THE POTENTIAL FOR INCREASING PRECIPITATION
CHANCES BY SUNDAY AND MONDAY...AND NEAR CLIMATOLOGICAL
TEMPERATURES.

&&

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

$$

LUDWIG/JA JUL 14




000
FXAK68 PAFC 281232
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
432 AM AKDT MON JUL 28 2014

.ANALYSIS AND UPPER LEVELS...

AN OMEGA BLOCK PATTERN CONTINUES TO DEVELOP ACROSS THE BERING SEA
AND THE FAR WEST COAST OF ALASKA THIS MORNING. AN UPPER LEVEL LOW
(THE FIRST ANCHOR POINT OF THE OMEGA BLOCK) LOCATED BETWEEN THE
KAMCHATKA PENINSULA AND THE WESTERN ALEUTIANS HAS BEGUN TO PHASE
WITH A POTENT SHORTWAVE DROPPING SOUTH OUT OF RUSSIA. THIS PHASING
HAS ALREADY BEGUN TO SHOW SIGNS OF AMPLIFYING THE LONGWAVE TROUGH
ALONG THE WESTERN PERIPHERY OF THE OMEGA BLOCK. ANOTHER UPPER
LEVEL LOW (THE SECOND ANCHOR POINT OF THE OMEGA BLOCK) IS CURRENTLY
LOCATED IN THE GULF OF ALASKA. SCATTERED RAIN SHOWERS HAVE CONTINUED
ALONG THE NORTHERN GULF COAST WITH A WEAK EASTERLY WAVE ROTATING
AROUND THE AFOREMENTIONED LOW. A POTENT SHORTWAVE DROPPING OUT OF
THE ARCTIC HAS ALREADY MOVED INLAND OVER NORTHWESTERN ALASKA WHICH
IS DEPICTED WELL BY BOTH INFRARED AND WATER VAPOR SATELLITE
IMAGES. RAINFALL AND INCREASED CLOUDINESS WILL BE OBSERVED ACROSS
THE MAJORITY OF THE WESTERN HALF OF THE STATE AS THE WAVE CONTINUES
TO PUSH SOUTH DURING THE MORNING HOURS. THIS WAVE HAS BEGUN TO
INTERACT WITH THE LOW IN THE NORTHERN GULF AND SHOULD PHASE WITH
THE UPPER LOW LATE THIS AFTERNOON AND INTO THIS EVENING.

AN ANOMALOUSLY STRONG RIDGE (THE FINAL COMPONENT OF THE OMEGA
BLOCK) IS CENTERED ACROSS THE CENTRAL BERING SEA THIS MORNING.
THE 12Z RAOB FROM PASN (SAINT PAUL) SHOWS THE 500 MB HEIGHTS AT
584 DECAMETERS...WITH EVEN HIGHER HEIGHTS EXPECTED FURTHER SOUTH
NEAR THE CENTRAL ALEUTIANS. THE RIDGE OF HIGH PRESSURE HAS
CONTINUED THE PERIOD OF LOW STRATUS AND FOG ACROSS THE MAJORITY OF
THE BERING SEA AND ALEUTIAN ISLANDS BECAUSE OF THE STABLE AIR MASS
IN PLACE. EVEN WITH THE ABUNDANT CLOUD COVER...TEMPERATURES HAVE
STILL MANAGED TO CLIMB INTO THE UPPER 50S TO LOWER 60S...WHICH IS
SLIGHTLY UNCOMMON WITH A STRATUS DECK THAT IS THOROUGHLY ENTRENCHED.

&&

.MODEL DISCUSSION...

MODELS APPEAR TO BE ON THE SLOW SIDE WITH THE UPPER LEVEL SHORTWAVE
DROPPING SOUTH FROM THE ARCTIC OVER THE WESTERN HALF OF THE
ALASKA MAINLAND. WHEN COMPARING THE 400 MB RELATIVE HUMIDITY
FIELDS TO THE WATER VAPOR IMAGES AT BOTH 00Z AND 06Z...A DISCREPANCY
OF 3 TO 6 HOURS WAS OBSERVED. SURFACE OBSERVATIONS ALONG THE
NORTHWESTERN COAST HAVE PROVIDED GROUND TRUTH THAT HELPED VERIFY
THAT THE MODELS ARE INDEED ON THE SLOW SIDE. THE 06Z RUNS HAVE
STARTED TO CATCH ONTO THIS TREND BUT ARE STILL NOT QUITE CAUGHT UP
AT THIS TIME. DUE TO THIS NEW DATA...THE DECISION WAS MADE TO
SPEED UP THE PRECIPITATION MOVING ACROSS THE WESTERN HALF OF
ALASKA DURING THE DAY TODAY BY 3 TO 6 HOURS.

WITH THE UPPER LEVEL LOW SPINNING IN THE GULF...MULTIPLE WEAK
EASTERLY WAVES ARE LIKELY TO TRAVERSE THE NORTHERN GULF COAST.
HOWEVER...MODEL CONFIDENCE GENERALLY TENDS TO LACK WITH THE TIMING
OF EACH WAVE AS THE POSITION OF THE LOW AND THE HEIGHT FALLS/POTENTIAL
VORTICITY ANOMALIES ASSOCIATED WITH THE SHORTWAVES BEING EJECTED
ARE NOT RESOLVED WELL BY MODELS GENERALLY PAST 24 TO 36 HOURS.

OVERALL THOUGH...THE MODELS ARE IN PRETTY GOOD SYNOPTIC AGREEMENT.
THERE ARE OF COURSE THE TYPICAL TIMING ISSUES WITH WAVES (AS
MENTIONED ABOVE) AND THE EXACT POSITIONS OF THE UPPER LOWS.
HOWEVER...THE OMEGA BLOCK PATTERN SEEMS TO BE LOCKED IN THROUGH
THE SHORT-TERM AND INTO THE LONG-TERM PENDING SOME DRASTIC SHIFT
IN THE LONGWAVE PATTERN...WHICH DOES NOT SEEM REALISTIC AT THIS
TIME. ENDED UP UTILIZING THE ECMWF FOR FORECAST UPDATES THIS
MORNING...DUE IN LARGE PART TO THE INITIALIZATION OF THE SHORTWAVE
THAT WILL PUSH ACROSS SOUTHWEST AND SOUTHCENTRAL ALASKA THIS
AFTERNOON AND EVENING.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...A POTENT SHORTWAVE WILL PUSH THROUGH THE
SUSITNA VALLEY THIS AFTERNOON AND THEN PUSH SOUTH TOWARD KODIAK
ISLAND OVERNIGHT TONIGHT. THIS WILL ALLOW STEADY RAINFALL TO
DEVELOP IN THE SUSITNA VALLEY BY THIS AFTERNOON AND SPREAD ACROSS
THE MATANUSKA VALLEY...THE ANCHORAGE BOWL AND KENAI PENINSULA
MID TO LATE AFTERNOON. THIS WAVE WILL BE FAST MOVING AND MOST
PLACES WILL SEE PRECIPITATION TAPER OFF OVERNIGHT TONIGHT...WITH
THE EXCEPTION OF KODIAK AND THE SOUTHERN KENAI PENINSULA WHERE
PRECIPITATION WILL LIKELY LINGER THROUGH TUESDAY MORNING. AN
EASTERLY WAVE WILL PUSH INTO THE COPPER RIVER BASIN ON TUESDAY AND
BRING ANOTHER ROUND OF RAINFALL TO THE BASIN. DUE TO INCREASED
CLOUD COVER FROM THE SHORTWAVE PUSHING THROUGH THE REGION
TODAY...THE ATMOSPHERE SHOULD HAVE LITTLE TO NO TIME TO
DESTABILIZE PRIOR TO THE ONSET OF PRECIPITATION ON TUESDAY.
HOWEVER...MODELS ARE STARTING TO HINT AT THE POTENTIAL FOR AN
ISOLATED THUNDERSTORM OR TWO TUESDAY EVENING ACROSS THE MATANUSKA
VALLEY...ANCHORAGE BOWL AND NORTHERN PORTIONS OF THE KENAI
PENINSULA AS A PORTION OF ENERGY ASSOCIATED WITH THE EASTERLY WAVE
PIVOTS ACROSS THE AREA.

SOUTHWEST ALASKA...AREAS OF FOG WILL BE SEEN ALONG THE SOUTHWEST
COAST OF ALASKA THIS MORNING AS THE RIDGE OVER THE BERING SEA
BEGINS TO SLOWLY SLIDE EASTWARD. THIS WILL ALLOW WEAK ONSHORE FLOW
TO PERSIST OVER THE REGION OVER THE NEXT DAY OR TWO...BRINGING
PERIODS OF FOG TO MAINLY THE COASTAL AREAS OF SOUTHWEST ALASKA
DURING THE OVERNIGHT AND THE EARLY MORNING HOURS. A SHORTWAVE
DROPPING SOUTH FROM NORTHWESTERN ALASKA WILL BRING RAIN TO THE
LOWER KUSKOKWIM VALLEY AND EASTERN SECTIONS OF THE BRISTOL BAY
AREA DURING THE DAY TODAY. PRECIPITATION WILL BECOME MORE SHOWERY
LATE THIS EVENING BEFORE ULTIMATELY TAPERING OFF TUESDAY AFTERNOON.

BERING SEA/ALEUTIANS...AN UPPER LEVEL LOW WILL EJECT A SERIES OF
WAVES ACROSS THE WESTERN ALEUTIANS THROUGH THE SHORT-TERM AND
BRING SMALL CRAFT WINDS AND SEAS. PERIODS OF LIGHT TO MODERATE
RAINFALL WILL ALSO BE SEEN AS THESE UPPER LEVEL WAVES PROPAGATE
THROUGH THE AREA. ELSEWHERE...AN ANOMALOUSLY STRONG RIDGE WILL
ALLOW PATCHY/AREAS OF FOG AS WELL AS A LOW STRATUS DECK TO PERSIST
THROUGH THE SHORT-TERM. WITH THE LOW STRATUS DECK WELL ESTABLISHED...
WOULD NOT BE SHOCKED TO SEE SOME COLLISION COALESCENCE TAKE PLACE
AND ALLOW A FEW AREAS TO SEE SOME LIGHT DRIZZLE/SPRINKLES.

&&

.LONG TERM FORECAST...
AN OMEGA BLOCK SETTING UP SHOP OVER THE BERING SEA AND MAINLAND
WILL DOMINATE THE PATTERN...AT LEAST FOR THE BEGINNING OF THE
EXTENDED FORECAST. THE SAME HIGH AMPLITUDE RIDGE CURRENTLY OVER
THE BERING WILL CLOSE OFF AT THE UPPER LEVELS...BOOKENDED BY TWO
UPPER LOW PRESSURE CENTERS...ONE OVER THE GULF OF ALASKA AND THE
OTHER SOUTHWEST OF THE WESTERN ALEUTIANS. THE GULF SYSTEM WILL
CONTROL SENSIBLE WEATHER ACROSS THE SOUTHCENTRAL WITH THE MAIN
FEATURE BEING AN EASTERLY WAVE TOWARD THE BEGINNING OF THE
FORECAST. GUIDANCE HAS COME INTO BETTER AGREEMENT WITH PLACEMENT
AND TIMING OF THE FEATURE BUT THESE DISTURBANCES GENERALLY GIVE
GUIDANCE FITS WITH BOTH TIMING AND INTENSITY. THAT SHORTWAVE WILL
AFFECT THE SOUTHCENTRAL MAINLAND MID TO LATE WEEK. BEYOND THAT
TIME FRAME PRECIPITATION CHANCES REVOLVE AROUND DIURNAL CONVECTION
OVER THE MOUNTAINS...MOSTLY DRY AT THE LOWEST ELEVATIONS BUT CHANCES
FOR SHOWERS ALONG HIGHER TERRAIN. THE UPCOMING PATTERN LOOKS TO BE
VERY CLIMATOLOGICAL AS FAR AS TEMPERATURES AND PRECIPITATION GO.

&&

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

$$

MCLAY JUL 14





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