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000
FXAK68 PAFC 012331
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
331 PM AKDT SUN MAY 1 2016

.ANALYSIS AND UPPER LEVELS...
THE VERTICALLY STACKED LOW CENTERED OFF THE COAST OF KODIAK
ISLAND HAS BARELY MOVED SINCE YESTERDAY. IT CONTINUES TO ACT AS
THE STEERING SYSTEM FOR SEVERAL OTHER MUCH SMALLER FEATURES MOVING
ACROSS MAINLAND SOUTHERN ALASKA. MOISTURE FLOW UP THE EAST SIDE OF
THE ALASKA RANGE CONTINUES TO PRODUCE STEADY RAINFALL OVER THE
UPSLOPE AREAS OF THE WESTERN SUSITNA VALLEY AND WESTERN COOK
INLET. A MORE UNSTABLE AIR MASS MOVING INTO THE COAST CONTINUES TO
CAUSE SCATTERED SHOWERS ALONG THE NORTH GULF COAST AS THE CONSTANT
SOUTHEASTERLY FLOW OFF THE GULF MOVES A CONTINUOUS SUPPLY OF
MOISTURE ASHORE. THICKER CLOUD COVER OVER MUCH OF SOUTHCENTRAL HAS
HELPED TEMPER THE RISING TEMPERATURES A BIT...DESPITE THE DRY
CONDITIONS PREVAILING TO THE LEE OF THE CHUGACH AND KENAI
MOUNTAINS.

SOUTHWESTERN ALASKAS WEATHER ALSO IS BEING CONTROLLED BY THE LOW
OVER THE GULF...THOUGH LESS MOISTURE ALOFT HAS ONCE AGAIN ALLOWED
ABUNDANT MORNING SUNSHINE TO DESTABILIZE THE ATMOSPHERE TO THE
LEE OF THE ALASKA RANGE. THIS HAS RESULTED IN A BLOSSOMING CUMULUS
FIELD THIS AFTERNOON OVER THE AREA FROM NORTH OF PILOT POINT
THROUGH SPARREVOHN. THE WOOD RIVER MOUNTAINS ARE HELPING LIFT THE
AIR MASS ON THE WINDWARD SIDE OF THOSE MOUNTAINS...RESULTING IN
MORE NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS APPEARING ON KING
SALMON RADAR FROM DILLINGHAM NORTHWARD. A FEW LIGHTNING STRIKES
HAVE ALSO OCCURRED NEAR ANIAK. TOWARDS THE KUSKOKWIM DELTA NEARLY
FULL SUNSHINE CONTINUES FOR ALL AREAS AWAY FROM THE IMMEDIATE
COAST...WITH SOME CUMULUS STARTING TO DEVELOP EAST OF BETHEL.

FOR THE BERING SEA AND ALEUTIANS...UPPER LEVEL RIDGING PERSISTS
OVER THE CENTRAL AND EASTERN BERING AND ALEUTIANS THIS AFTERNOON.
LIGHT NORTHWESTERLY WINDS IN THE LOW LEVELS ARE DRAWING MOISTURE
FROM THE SEA SURFACE. THIS MOISTURE THEN IS HITTING THE WARM AIR
ABOVE IT...CAPPING ITS ASCENT. THE RESULT IS WIDESPREAD STRATUS
OVER NEARLY THE ENTIRE BERING...WITH THE EXCEPTION OF THE SOUTH
SIDE OF NUNIVAK ISLAND...AND SOUTHEAST OF THE PRIBILOFS...WHERE
THE STRATUS IS MORE BROKEN. THE NEXT VERTICALLY STACKED LOW IN THE
SERIES IS MOVING TOWARDS THE WESTERN ALEUTIANS...WITH THE
ASSOCIATED OCCLUDED FRONT HAVING MOVED THROUGH THE CHAIN EARLIER
TODAY. THIS LOW WILL BECOME THE DOMINANT WEATHER MAKER FOR MUCH OF
THE SOUTHERN BERING OVER THE COMING DAYS.

&&

.MODEL DISCUSSION...
WITH VERY FEW CHANGES IN THE WEATHER ANYWHERE IN SOUTHERN
ALASKA...THE MODELS REMAIN IN VERY GOOD AGREEMENT REGARDING THE
EVOLUTION OF THE BROAD WEATHER PATTERN IN THE SHORT-TERM. THE
HIGHER RESOLUTION MODELS WERE FAVORED FOR THEIR BETTER HANDLING OF
THE LOCAL WEATHER AND MESOSCALE FEATURES CRISS-CROSSING THE AREA.
MODEL DIFFERENCES EMERGE FOR THE MID AND LONG TERM FORECASTS WITH
THE GFS SHOWING THE LOW CURRENTLY MOVING TOWARDS THE WESTERN
ALEUTIANS RECURVING ALONG THE BRISTOL BAY COAST...WHILE THE NAM
KEEPS MOST OF THE ENERGY SOUTH AND INTO THE GULF. THE GFS WAS
PREFERRED FOR THIS SCENARIO...THOUGH WITH SOME FLIP-FLOPPING IN
THE MODELS HAVING OCCURRED THE PAST COUPLE DAYS...CONFIDENCE BY
THIS POINT WANES CONSIDERABLY. FOR THE SHORTER-TERM THE FORECAST
CONFIDENCE IS HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE MAIN CONCERN THROUGH MONDAY CONTINUES TO BE THE STRONGER GAP
AND CROSS BARRIER WIND ACROSS SOUTH CENTRAL ALASKA. AN OCCLUDED
FRONT IS PUSHING IN ALONG THE NORTH GULF COAST TODAY AND THAT WILL
BE FOLLOWED BY A RIDGE THAT IS BUILDING IN ALONG THE NORTH GULF
COAST. THE BUILDING RIDGE WILL SERVE TO ACCELERATE WINDS THROUGH
PORTAGE VALLEY AND ALONG TURNAGAIN ARM AS WELL AS ACROSS THE
ANCHORAGE HILLSIDE. RAIN ASSOCIATED WITH THE FRONT WILL MAINLY
STAY ON THE COASTAL SIDE OF THE MOUNTAINS AS THE DOWN SLOPE DRYING
ON THE LEE OF THE MOUNTAINS IS KEEPING ANY SIGNIFICANT RAIN FROM
FALLING. THE UPSLOPE FLOW INTO THE ALASKA RANGE SHOULD RESULT IN
INCREASED CHANCES FOR SHOWERS ALONG THE RANGE.

ANOTHER AREA OF CONCERN IS THE INCREASING POTENTIAL FOR
THUNDERSTORM ACTIVITY IN THE COPPER RIVER BASIN BY TOMORROW
AFTERNOON. THE VERTICAL TEMPERATURE SPREAD IS INCREASING ALONG
WITH THE MODELS INDICATING INCREASINGLY MORE UNSTABLE CONDITIONS
PARTICULARLY IN THE NORTHERN AND EASTERN COPPER RIVER BASIN. THERE
IS PLENTY OF MOISTURE TO ALLOW FOR THE DEVELOPMENT OF
THUNDERSTORMS AND WE WILL BE ADDING SOME ISOLATED INTO THE
FORECAST.

THE PATTERN WILL PERSIST THROUGH MONDAY WITH SHOWERS ACROSS THE
GULF AND INCREASING WINDS DEVELOPING AS ANOTHER TROUGH MOVES UP
FROM THE SOUTHERN GULF.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)...
WITH THE GRADUALLY WEAKENING VERTICALLY STACKED LOW IN THE
WESTERN GULF KEEPING SOUTHWEST ALASKA IN WEAK EASTERLY FLOW ALOFT
DIURNALLY ENHANCED INSTABILITY SHOWERS AND THE POTENTIAL FOR
ISOLATED THUNDERSTORMS WILL BE THE MAIN FORECAST CHALLENGE. THIS
AFTERNOON AND EVENING THE THERMAL TROUGH WILL EXTEND FROM INTERIOR
ALASKA ACROSS THE LOWER KUSKOKWIM VALLEY AND INTO THE NORTHERN
BRISTOL BAY AREA. THE FEATURE WILL BE FAIRLY DIFFUSE WITH MARGINAL
INSTABILITY SPREAD OVER MUCH OF SOUTHWEST ALASKA FROM AROUND
BETHEL WEST...BRINGING A SLIGHT CHANCE FOR A WEAK THUNDERSTORM OR
TWO THIS AFTERNOON OR EVENING.

ON MONDAY THE THERMAL TROUGH BECOMES BETTER DEFINED WITH STRONGER
INSTABILITY CONCENTRATED ALONG ITS AXIS. WHILE THIS WILL FOCUS THE
THUNDERSTORM THREAT OVER A SMALLER AREA GEOGRAPHICALLY (RUNNING
FROM THE LOWER YUKON RIVER VALLEY...ACROSS THE SOUTHERN HALF OF
THE KUSKOKWIM MOUNTAINS...THE HOLITNA RIVER VALLEY...THE EASTERN
KILBUCK AND AHKLUN MOUNTAINS...THE TAYLOR MOUNTAINS...THE NUSHAGAK
RIVER VALLEY AND THE WOOD RIVER LAKES AREA)...THE PROBABILITY OF
SEEING ISOLATED TO WIDELY SCATTERED THUNDERSTORMS IS HIGHER WITH A
BETTER CHANCE OF A GREATER NUMBER OF LIGHTNING STRIKES OUT OF
THEM.

ON TUESDAY THE THERMAL TROUGH RETREATS BACK NORTH WITH MORE
MINIMAL INSTABILITY LIMITING CONVECTION TO ISOLATED WITH A FEW
AREAS OF SCATTERED SHOWERS IN THE AFTERNOON AND EVENING. ON
WEDNESDAY A SURFACE LOW CROSSING BRISTOL BAY AND ASSOCIATED TROUGH
ROTATING ACROSS SOUTHWEST ALASKA WILL BRING MORE NUMEROUS AND
WIDESPREAD SHOWERS TO THE AREA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3)...
THE SURFACE LOW TO THE SOUTHWEST OF THE WESTERN ALEUTIANS WILL
TRACK EAST NORTHEAST TO INTERSECT THE ALEUTIAN CHAIN AROUND KISKA
MONDAY AFTERNOON WHILE THE ASSOCIATED SURFACE FRONT STRETCHES FROM
WEST TO EAST ACROSS THE BERING AROUND 56N. LOW WILL CONTINUE EAST
ALONG THE ALEUTIAN CHAIN MONDAY NIGHT AND TUESDAY THEN UP THE
ALASKA PENINSULA ALONG THE BERING SIDE TUESDAY NIGHT. THE ORIGINAL
SURFACE LOW WILL THEN CURL NORTH ACROSS BRISTOL BAY AND INTO
SOUTHWEST ALASKA WEDNESDAY WITH THE ASSOCIATED FRONT AND A
DEVELOPING TRIPLE POINT LOW SWINGING INTO THE SOUTHWESTERN GULF.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...WED THROUGH SUN)...
THE EXTENDED PORTION HAS HINGED THE PAST FEW DAYS ON HOW STRONG
THE RIDGING FROM THE NORTH PACIFIC WOULD HOLD AND HOW ENERGY
WOULD EVOLVE SURROUNDING THE UPPER LEVEL LOW NEAR THE ALASKA
PENINSULA WED-THU. MODELS DO SHOW SOME DISPARITY ON HANDLING WHAT
HAPPENS WITH THE REMNANTS OF THE UPPER LEVEL LOW OVER BRISTOL BAY.
THE GFS HOLDS IT TOGETHER BETTER THAN THE OTHER AND THIS SEEMS
QUITE PLAUSIBLE GIVEN THE PATTERN. THUS...WE KEPT POPS RATHER HIGH
THROUGH THE SOUTHWEST INTO THU. BEYOND THAT...FORECAST CONFIDENCE
CONTINUES TO INCREASE...ALBEIT SLOWLY...AS MODELS CONVERGE ON A
SOLUTION. THE RIDGE DOES BUILD RATHER QUICKLY ALONG THE ALCAN
BORDER WED-THU. THIS SETS THE STAGE FOR THE AKPEN UPPER LEVEL LOW
TO WORK IN TANDEM WITH SOME ENERGY FROM THE NORTH PACIFIC RIDING
UP THE WESTERN PERIPHERY OF THAT RIDGE. THIS WILL RESULT IN SOME
PHASING WITH A TRIPLE POINT LOW TAKING SHAPE OVER THE 45N 170W AND
WORKING ITS WAY TOWARD KODIAK BY EARLY FRI. BUT WHILE THE SYNOPTIC
PATTERN LOOKS SIMILAR FROM MODEL TO MODEL...THERE ARE STILL SOME
SIGNIFICANT DIFFERENCES. BY 06Z FRI...THE ECMWF MODEL HAS THE
SURFACE LOW JUST SOUTH OF KODIAK AT 995MB WHILE THE GFS PAINTS
IT AT 979MB. THE MODELS THEN AGREE THAT THE LOW WILL TRACK TOWARD
THE NE GULF THROUGH SAT. IT WILL HAVE AN HEALTHY AMOUNT OF
MOISTURE COMING WITH IT. THE QUESTION IS...EXACTLY WHERE DOES THE
LOW TRACK GO AND HOW MUCH CROSS BARRIER FLOW WILL BE PRESENT OVER
SOUTH CENTRAL AK. USING THE PAST FEW WEEKS AS A BASELINE...THE
INCLINATION IS TO THINK THE COAST WILL ONCE AGAIN RECEIVE A FEW
INCHES OF RAIN WHILE AREAS IN THE LEE OF THE MOUNTAINS MIGHT ONLY
SEE A FEW PASSING SHOWERS.

SUN INTO NEXT WEEK...WHILE THERE ARE STILL SOME SIGNS OF
RIDGING...FORECAST CONFIDENCE HAS NOT INCREASED. THE BIGGEST
CHANGE FROM YESTERDAY IS A FAIRLY DEEP LOW THAT QUICKLY MOVES INTO
PLACE OVER THE BERING SEA. IF THIS WERE TO VERIFY...AK COULD
EASILY RETURN TO THE SAME PATTERN WE HAVE BEEN IN THE PAST FEW
WEEKS.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...SA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...MO





000
FXAK68 PAFC 012331
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
331 PM AKDT SUN MAY 1 2016

.ANALYSIS AND UPPER LEVELS...
THE VERTICALLY STACKED LOW CENTERED OFF THE COAST OF KODIAK
ISLAND HAS BARELY MOVED SINCE YESTERDAY. IT CONTINUES TO ACT AS
THE STEERING SYSTEM FOR SEVERAL OTHER MUCH SMALLER FEATURES MOVING
ACROSS MAINLAND SOUTHERN ALASKA. MOISTURE FLOW UP THE EAST SIDE OF
THE ALASKA RANGE CONTINUES TO PRODUCE STEADY RAINFALL OVER THE
UPSLOPE AREAS OF THE WESTERN SUSITNA VALLEY AND WESTERN COOK
INLET. A MORE UNSTABLE AIR MASS MOVING INTO THE COAST CONTINUES TO
CAUSE SCATTERED SHOWERS ALONG THE NORTH GULF COAST AS THE CONSTANT
SOUTHEASTERLY FLOW OFF THE GULF MOVES A CONTINUOUS SUPPLY OF
MOISTURE ASHORE. THICKER CLOUD COVER OVER MUCH OF SOUTHCENTRAL HAS
HELPED TEMPER THE RISING TEMPERATURES A BIT...DESPITE THE DRY
CONDITIONS PREVAILING TO THE LEE OF THE CHUGACH AND KENAI
MOUNTAINS.

SOUTHWESTERN ALASKAS WEATHER ALSO IS BEING CONTROLLED BY THE LOW
OVER THE GULF...THOUGH LESS MOISTURE ALOFT HAS ONCE AGAIN ALLOWED
ABUNDANT MORNING SUNSHINE TO DESTABILIZE THE ATMOSPHERE TO THE
LEE OF THE ALASKA RANGE. THIS HAS RESULTED IN A BLOSSOMING CUMULUS
FIELD THIS AFTERNOON OVER THE AREA FROM NORTH OF PILOT POINT
THROUGH SPARREVOHN. THE WOOD RIVER MOUNTAINS ARE HELPING LIFT THE
AIR MASS ON THE WINDWARD SIDE OF THOSE MOUNTAINS...RESULTING IN
MORE NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS APPEARING ON KING
SALMON RADAR FROM DILLINGHAM NORTHWARD. A FEW LIGHTNING STRIKES
HAVE ALSO OCCURRED NEAR ANIAK. TOWARDS THE KUSKOKWIM DELTA NEARLY
FULL SUNSHINE CONTINUES FOR ALL AREAS AWAY FROM THE IMMEDIATE
COAST...WITH SOME CUMULUS STARTING TO DEVELOP EAST OF BETHEL.

FOR THE BERING SEA AND ALEUTIANS...UPPER LEVEL RIDGING PERSISTS
OVER THE CENTRAL AND EASTERN BERING AND ALEUTIANS THIS AFTERNOON.
LIGHT NORTHWESTERLY WINDS IN THE LOW LEVELS ARE DRAWING MOISTURE
FROM THE SEA SURFACE. THIS MOISTURE THEN IS HITTING THE WARM AIR
ABOVE IT...CAPPING ITS ASCENT. THE RESULT IS WIDESPREAD STRATUS
OVER NEARLY THE ENTIRE BERING...WITH THE EXCEPTION OF THE SOUTH
SIDE OF NUNIVAK ISLAND...AND SOUTHEAST OF THE PRIBILOFS...WHERE
THE STRATUS IS MORE BROKEN. THE NEXT VERTICALLY STACKED LOW IN THE
SERIES IS MOVING TOWARDS THE WESTERN ALEUTIANS...WITH THE
ASSOCIATED OCCLUDED FRONT HAVING MOVED THROUGH THE CHAIN EARLIER
TODAY. THIS LOW WILL BECOME THE DOMINANT WEATHER MAKER FOR MUCH OF
THE SOUTHERN BERING OVER THE COMING DAYS.

&&

.MODEL DISCUSSION...
WITH VERY FEW CHANGES IN THE WEATHER ANYWHERE IN SOUTHERN
ALASKA...THE MODELS REMAIN IN VERY GOOD AGREEMENT REGARDING THE
EVOLUTION OF THE BROAD WEATHER PATTERN IN THE SHORT-TERM. THE
HIGHER RESOLUTION MODELS WERE FAVORED FOR THEIR BETTER HANDLING OF
THE LOCAL WEATHER AND MESOSCALE FEATURES CRISS-CROSSING THE AREA.
MODEL DIFFERENCES EMERGE FOR THE MID AND LONG TERM FORECASTS WITH
THE GFS SHOWING THE LOW CURRENTLY MOVING TOWARDS THE WESTERN
ALEUTIANS RECURVING ALONG THE BRISTOL BAY COAST...WHILE THE NAM
KEEPS MOST OF THE ENERGY SOUTH AND INTO THE GULF. THE GFS WAS
PREFERRED FOR THIS SCENARIO...THOUGH WITH SOME FLIP-FLOPPING IN
THE MODELS HAVING OCCURRED THE PAST COUPLE DAYS...CONFIDENCE BY
THIS POINT WANES CONSIDERABLY. FOR THE SHORTER-TERM THE FORECAST
CONFIDENCE IS HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE MAIN CONCERN THROUGH MONDAY CONTINUES TO BE THE STRONGER GAP
AND CROSS BARRIER WIND ACROSS SOUTH CENTRAL ALASKA. AN OCCLUDED
FRONT IS PUSHING IN ALONG THE NORTH GULF COAST TODAY AND THAT WILL
BE FOLLOWED BY A RIDGE THAT IS BUILDING IN ALONG THE NORTH GULF
COAST. THE BUILDING RIDGE WILL SERVE TO ACCELERATE WINDS THROUGH
PORTAGE VALLEY AND ALONG TURNAGAIN ARM AS WELL AS ACROSS THE
ANCHORAGE HILLSIDE. RAIN ASSOCIATED WITH THE FRONT WILL MAINLY
STAY ON THE COASTAL SIDE OF THE MOUNTAINS AS THE DOWN SLOPE DRYING
ON THE LEE OF THE MOUNTAINS IS KEEPING ANY SIGNIFICANT RAIN FROM
FALLING. THE UPSLOPE FLOW INTO THE ALASKA RANGE SHOULD RESULT IN
INCREASED CHANCES FOR SHOWERS ALONG THE RANGE.

ANOTHER AREA OF CONCERN IS THE INCREASING POTENTIAL FOR
THUNDERSTORM ACTIVITY IN THE COPPER RIVER BASIN BY TOMORROW
AFTERNOON. THE VERTICAL TEMPERATURE SPREAD IS INCREASING ALONG
WITH THE MODELS INDICATING INCREASINGLY MORE UNSTABLE CONDITIONS
PARTICULARLY IN THE NORTHERN AND EASTERN COPPER RIVER BASIN. THERE
IS PLENTY OF MOISTURE TO ALLOW FOR THE DEVELOPMENT OF
THUNDERSTORMS AND WE WILL BE ADDING SOME ISOLATED INTO THE
FORECAST.

THE PATTERN WILL PERSIST THROUGH MONDAY WITH SHOWERS ACROSS THE
GULF AND INCREASING WINDS DEVELOPING AS ANOTHER TROUGH MOVES UP
FROM THE SOUTHERN GULF.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)...
WITH THE GRADUALLY WEAKENING VERTICALLY STACKED LOW IN THE
WESTERN GULF KEEPING SOUTHWEST ALASKA IN WEAK EASTERLY FLOW ALOFT
DIURNALLY ENHANCED INSTABILITY SHOWERS AND THE POTENTIAL FOR
ISOLATED THUNDERSTORMS WILL BE THE MAIN FORECAST CHALLENGE. THIS
AFTERNOON AND EVENING THE THERMAL TROUGH WILL EXTEND FROM INTERIOR
ALASKA ACROSS THE LOWER KUSKOKWIM VALLEY AND INTO THE NORTHERN
BRISTOL BAY AREA. THE FEATURE WILL BE FAIRLY DIFFUSE WITH MARGINAL
INSTABILITY SPREAD OVER MUCH OF SOUTHWEST ALASKA FROM AROUND
BETHEL WEST...BRINGING A SLIGHT CHANCE FOR A WEAK THUNDERSTORM OR
TWO THIS AFTERNOON OR EVENING.

ON MONDAY THE THERMAL TROUGH BECOMES BETTER DEFINED WITH STRONGER
INSTABILITY CONCENTRATED ALONG ITS AXIS. WHILE THIS WILL FOCUS THE
THUNDERSTORM THREAT OVER A SMALLER AREA GEOGRAPHICALLY (RUNNING
FROM THE LOWER YUKON RIVER VALLEY...ACROSS THE SOUTHERN HALF OF
THE KUSKOKWIM MOUNTAINS...THE HOLITNA RIVER VALLEY...THE EASTERN
KILBUCK AND AHKLUN MOUNTAINS...THE TAYLOR MOUNTAINS...THE NUSHAGAK
RIVER VALLEY AND THE WOOD RIVER LAKES AREA)...THE PROBABILITY OF
SEEING ISOLATED TO WIDELY SCATTERED THUNDERSTORMS IS HIGHER WITH A
BETTER CHANCE OF A GREATER NUMBER OF LIGHTNING STRIKES OUT OF
THEM.

ON TUESDAY THE THERMAL TROUGH RETREATS BACK NORTH WITH MORE
MINIMAL INSTABILITY LIMITING CONVECTION TO ISOLATED WITH A FEW
AREAS OF SCATTERED SHOWERS IN THE AFTERNOON AND EVENING. ON
WEDNESDAY A SURFACE LOW CROSSING BRISTOL BAY AND ASSOCIATED TROUGH
ROTATING ACROSS SOUTHWEST ALASKA WILL BRING MORE NUMEROUS AND
WIDESPREAD SHOWERS TO THE AREA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3)...
THE SURFACE LOW TO THE SOUTHWEST OF THE WESTERN ALEUTIANS WILL
TRACK EAST NORTHEAST TO INTERSECT THE ALEUTIAN CHAIN AROUND KISKA
MONDAY AFTERNOON WHILE THE ASSOCIATED SURFACE FRONT STRETCHES FROM
WEST TO EAST ACROSS THE BERING AROUND 56N. LOW WILL CONTINUE EAST
ALONG THE ALEUTIAN CHAIN MONDAY NIGHT AND TUESDAY THEN UP THE
ALASKA PENINSULA ALONG THE BERING SIDE TUESDAY NIGHT. THE ORIGINAL
SURFACE LOW WILL THEN CURL NORTH ACROSS BRISTOL BAY AND INTO
SOUTHWEST ALASKA WEDNESDAY WITH THE ASSOCIATED FRONT AND A
DEVELOPING TRIPLE POINT LOW SWINGING INTO THE SOUTHWESTERN GULF.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...WED THROUGH SUN)...
THE EXTENDED PORTION HAS HINGED THE PAST FEW DAYS ON HOW STRONG
THE RIDGING FROM THE NORTH PACIFIC WOULD HOLD AND HOW ENERGY
WOULD EVOLVE SURROUNDING THE UPPER LEVEL LOW NEAR THE ALASKA
PENINSULA WED-THU. MODELS DO SHOW SOME DISPARITY ON HANDLING WHAT
HAPPENS WITH THE REMNANTS OF THE UPPER LEVEL LOW OVER BRISTOL BAY.
THE GFS HOLDS IT TOGETHER BETTER THAN THE OTHER AND THIS SEEMS
QUITE PLAUSIBLE GIVEN THE PATTERN. THUS...WE KEPT POPS RATHER HIGH
THROUGH THE SOUTHWEST INTO THU. BEYOND THAT...FORECAST CONFIDENCE
CONTINUES TO INCREASE...ALBEIT SLOWLY...AS MODELS CONVERGE ON A
SOLUTION. THE RIDGE DOES BUILD RATHER QUICKLY ALONG THE ALCAN
BORDER WED-THU. THIS SETS THE STAGE FOR THE AKPEN UPPER LEVEL LOW
TO WORK IN TANDEM WITH SOME ENERGY FROM THE NORTH PACIFIC RIDING
UP THE WESTERN PERIPHERY OF THAT RIDGE. THIS WILL RESULT IN SOME
PHASING WITH A TRIPLE POINT LOW TAKING SHAPE OVER THE 45N 170W AND
WORKING ITS WAY TOWARD KODIAK BY EARLY FRI. BUT WHILE THE SYNOPTIC
PATTERN LOOKS SIMILAR FROM MODEL TO MODEL...THERE ARE STILL SOME
SIGNIFICANT DIFFERENCES. BY 06Z FRI...THE ECMWF MODEL HAS THE
SURFACE LOW JUST SOUTH OF KODIAK AT 995MB WHILE THE GFS PAINTS
IT AT 979MB. THE MODELS THEN AGREE THAT THE LOW WILL TRACK TOWARD
THE NE GULF THROUGH SAT. IT WILL HAVE AN HEALTHY AMOUNT OF
MOISTURE COMING WITH IT. THE QUESTION IS...EXACTLY WHERE DOES THE
LOW TRACK GO AND HOW MUCH CROSS BARRIER FLOW WILL BE PRESENT OVER
SOUTH CENTRAL AK. USING THE PAST FEW WEEKS AS A BASELINE...THE
INCLINATION IS TO THINK THE COAST WILL ONCE AGAIN RECEIVE A FEW
INCHES OF RAIN WHILE AREAS IN THE LEE OF THE MOUNTAINS MIGHT ONLY
SEE A FEW PASSING SHOWERS.

SUN INTO NEXT WEEK...WHILE THERE ARE STILL SOME SIGNS OF
RIDGING...FORECAST CONFIDENCE HAS NOT INCREASED. THE BIGGEST
CHANGE FROM YESTERDAY IS A FAIRLY DEEP LOW THAT QUICKLY MOVES INTO
PLACE OVER THE BERING SEA. IF THIS WERE TO VERIFY...AK COULD
EASILY RETURN TO THE SAME PATTERN WE HAVE BEEN IN THE PAST FEW
WEEKS.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...SA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...MO





000
FXAK68 PAFC 011258
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
458 AM AKDT SUN MAY 1 2016

.ANALYSIS AND UPPER LEVELS...
A LONGWAVE TROUGH REMAINS OVER MAINLAND ALASKA WITH AN AXIS ALONG
150W THIS MORNING WITH A HIGH AMPLITUDE RIDGE TO THE EAST OVER
THE WESTERN NORTH AMERICA COAST. TO THE WEST OF THE TROUGH...A
MUCH LOWER AMPLITUDE RIDGE ALONG 175W IS BEING ERODED BY A LARGE
UPPER LOW WITHIN A BROAD TROUGH NEAR THE KAMCHATKA PENINSULA THAT
IS PUSHING EASTWARD INTO THE SOUTHWEST BERING SEA. A CLOSED UPPER
LOW REMAINS EMBEDDED WITHIN THE MAIN LONGWAVE TROUGH AND IS MOVING
INTO SOUTHWEST ALASKA. THE POLAR JET REMAINS STOUT WITH A 155 KT
JET MAX IN THE POLEWARD LIMB ALONG THE EASTERN SIDE OF THE
LONGWAVE TROUGH AND A BROAD AREA OF 130+ KT WINDS SOUTH OF THE
KAMCHATKA LOW.

A 994 MB LOW NEAR KODIAK ISLAND IS THE DOMINATE SURFACE FEATURE
OVER ALASKA THIS MORNING WITH THE ASSOCIATED SURFACE FRONT PUSHING
ONSHORE OVER THE NORTH GULF COAST...PRODUCING WIDESPREAD SHOWERS
AND RAIN OVER THE COAST AND PORTIONS OF COOK INLET AND THE SUSITNA
VALLEY. ENERGY ROTATING AROUND THE LOW AND AHEAD OF THE FRONT IS
PRODUCING SHOWERS OVER MUCH OF SOUTHWEST ALASKA THIS MORNING. OVER
THE CENTRAL ALEUTIANS...A WEAKENING RIDGE IS MOVING EASTWARD
AHEAD OF A BROAD AND WEAKENING 986 MB LOW AND ITS ASSOCIATED FRONT
LOCATED NEAR KAMCHATKA.

&&

.MODEL DISCUSSION...
GLOBAL MODELS ALL INITIALIZED ACCEPTABLY FOR THE 00Z RUN WITH FEW
SIGNIFICANT DIFFERENCES. THROUGH 48 HOURS...MODELS ARE IN
REASONABLE AGREEMENT WITH THEIR HANDING OF FEATURES WITH ONLY
MINOR DIFFERENCES. FOR THIS PACKAGE...THE GFS WAS USED ON BOTH
EAST AND WEST FORECAST DOMAINS WITH THE NAM USED OVER LAND AREAS
IN SOUTHWEST ALASKA.

&&

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

THE MAIN CONCERN IN THE FORECAST THROUGH MONDAY SURROUNDS GUSTY
WINDS THAT DEVELOP IN RESPONSE TO A BUILDING RIDGE ALONG THE
NORTHEAST GULF COAST. SUNDAY MORNING STARTS OFF WITH LOW PRESSURE
SOUTH OF KODIAK ISLAND PUSHING A WEAK FRONT OVER THE NORTHERN GULF TO
THE SUSITNA AND COPPER RIVER VALLEYS. RAIN WILL LARGELY BE
CONFINED TO THE GULF AND COASTAL AREAS WITH SCATTERED SHOWERS
INLAND. THE DRIVING MECHANISM FOR THE BUILDING RIDGE TODAY IS FROM
THE AMPLIFICATION OF THE NORTH AMERICAN RIDGE TO THE COPPER
RIVER. A LOW LEVEL JET ACCELERATES TO 30 TO 45 MPH AS THE PRESSURE
GRADIENT TIGHTENS ALONG THE NORTHERN COAST THIS MORNING. WINDS MIX
DOWN TO THE SURFACE WITH DOWNWARD FORCING BEHIND THE FRONT. THERE
CONTINUES TO BE SOME UNCERTAINTY IN THE TIMING AND STRENGTH FOR
SURFACE WINDS AS MODELS STRUGGLE TO CAPTURE THE ORIENTATION OF THE
PRESSURE GRADIENT. FORECAST WINDS ACROSS EAST TO WEST GAPS AND
ALONG THE COPPER RIVER WERE INCREASED THIS AFTERNOON TO FOLLOW
TRENDS OF THE HIRES MODELS. A PERSISTENT PATTERN CONTINUES INTO
MONDAY WITH SHOWERS ACROSS THE GULF AND AFTERNOON GUSTS DEVELOPING
AS ANOTHER SHORTWAVE MOVES UP FROM THE SOUTHERN GULF.

&&

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

REMNANTS OF A TROUGH MOVING THROUGH THE BRISTOL BAY AREA IS
BRINGING SOME SHOWERS THIS MORNING. ELSEWHERE...A WEAK SURFACE LOW
WILL BE DEVELOPING LATER TODAY ACROSS THE WESTERN INTERIOR.
COMBINED WITH DAYTIME HEATING...SOME INSTABILITY IS EXPECTED TO
RETURN ALLOWING FOR DIURNAL SHOWERS AND THUNDERSTORMS. THIS LOW
WILL REMAIN IN PLACE FOR MONDAY AND EXPECT MUCH OF THE SAME WITH
DIURNAL SHOWERS AND THUNDERSTORMS.

&&

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

A SHORTWAVE RIDGE AXIS IS BUILDING INTO THE BERING SEA AHEAD OF A
ONCE STRONG LOW WHICH PEAKED IN STRENGTH SOUTH OF THE KAMCHATKA
PENINSULA. THE ASSOCIATED OCCLUDED FRONT WILL MAKE EASTWARD
PROGRESS AND REACH THE EASTERN ALEUTIANS BY TUESDAY. AS THE
REMNANTS OF THE CLOSED UPPER LOW MOVE EAST IN CONJUNCTION...SHOWERS
BEHIND THE FRONT WILL FILL IN ACROSS MOST OF THE BERING SEA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...TUE THROUGH SAT)...
THE LONG RANGE PATTERN WILL PRESENT SOME INTERESTING CHALLENGES
AND A POSSIBLE CHANGE IN THE LONGWAVE REGIME. THIS TIME FRAME
STARTS WITH ONE LOW FILLING AND MOVING INLAND OVER THE GULF OF AK.
MEANWHILE...OVER THE CENTRAL ALEUTIANS...THE NEXT UPPER LEVEL LOW
IS ALREADY TAKING A VERY FAMILIAR TRACK TOWARDS THE GULF. AS THE
FIRST LOW WEAKENS AND MOVES INLAND...THIS SHOULD ALLOW THE
GRADIENT TO RELAX. THIS WILL FINALLY BRING AN END TO THE GUSTY
SOUTHEAST WINDS THAT HAVE BEEN BLOWING THROUGH FAVORED
LOCATIONS SUCH AS THE TURNAGAIN ARM AND THE KNIK RIVER VALLEY.
RATHER MOIST ONSHORE FLOW WILL CONTINUE TO MAKE FOR SOME STEADY
RAIN FOR IMMEDIATE COASTAL AREAS. BUT PRECIPITATION INLAND SHOULD
BE LIMITED TO SHOWERS...MAINLY DRIVEN BY WEAK AFTERNOON
INSTABILITY WITH A COLD POCKET OF RELATIVELY COLD AIR AT 500MB.

BY LATE WED...THE LOW FROM THE CENTRAL ALEUTIANS WILL MAKE ITS WAY
TO THE ALASKA PENINSULA. IT WILL PUSH A WARM OCCLUSION IN FRONT OF
IT. THIS WILL BRING RAIN BACK INTO KODIAK WITH CLOUDS STARTING TO
OVERSPREAD SOUTH CENTRAL. BUT IT IS AT THIS POINT WHEN MODELS
DIVERGE DRAMATICALLY. THE BIGGEST QUESTION IS WHERE THE UPPER
LEVEL LOW SETS UP RESIDENCE. SOME OF THIS DEPENDS ON HOW EFFECTIVE
ENERGY TRACKING THROUGH THE GULF IS AT PUSHING THE NORTH AMERICAN
RIDGE OFF TO THE EAST. THE EC HOLDS THE LOW CENTER THE FURTHEST
NORTH AND WEST...WHILE THE GFS ALLOWS IT TO MIGRATE ALL THE WAY
INTO THE CENTRAL GULF. EARLIER RUNS WILL SHOWING SOME PHASING
OCCURRING WITH THIS LOW AND SOME ENERGY TRACKING ALONG THE JET IN
THE NORTH PACIFIC. THEY WERE SHOWING THE POTENTIAL FOR A TRIPLE-
POINT LOW TO FORM AND TRACK QUICKLY INTO SOUTH CENTRAL. SOLUTIONS
HAVE BACKED OFF THIS IDEA AND NOW MORE SETTLED ON JUST ANOTHER
UPPER LEVEL LOW SITTING OVER THE CENTRAL GULF BY NEXT SAT.

BY LATE NEXT WEEKEND INTO THE WEEK OF 9-13 MAY...THERE SEEMS TO BE
FAIR TO GOOD MODEL AGREEMENT IN SOME FORM OF RIDGE BUILDING OVER
THE EASTERN INTERIOR PORTION OF AK. MODELS HAVE VARIOUS SOLUTIONS
OF HOW THE RIDGE GETS THERE (SOME FROM THE NORTH PAC...SOME FROM
NW CONUS) BUT THEY ALL SHOW SIGNS OF IT. CLIMATOLOGICALLY THIS
MAKES SENSE AS WELL AS WE USUALLY SEE A WARMER STRETCH TOWARD THE
MIDDLE TO END OF MAY.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RLF
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA/LIW
LONG TERM...MO





000
FXAK68 PAFC 011258
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
458 AM AKDT SUN MAY 1 2016

.ANALYSIS AND UPPER LEVELS...
A LONGWAVE TROUGH REMAINS OVER MAINLAND ALASKA WITH AN AXIS ALONG
150W THIS MORNING WITH A HIGH AMPLITUDE RIDGE TO THE EAST OVER
THE WESTERN NORTH AMERICA COAST. TO THE WEST OF THE TROUGH...A
MUCH LOWER AMPLITUDE RIDGE ALONG 175W IS BEING ERODED BY A LARGE
UPPER LOW WITHIN A BROAD TROUGH NEAR THE KAMCHATKA PENINSULA THAT
IS PUSHING EASTWARD INTO THE SOUTHWEST BERING SEA. A CLOSED UPPER
LOW REMAINS EMBEDDED WITHIN THE MAIN LONGWAVE TROUGH AND IS MOVING
INTO SOUTHWEST ALASKA. THE POLAR JET REMAINS STOUT WITH A 155 KT
JET MAX IN THE POLEWARD LIMB ALONG THE EASTERN SIDE OF THE
LONGWAVE TROUGH AND A BROAD AREA OF 130+ KT WINDS SOUTH OF THE
KAMCHATKA LOW.

A 994 MB LOW NEAR KODIAK ISLAND IS THE DOMINATE SURFACE FEATURE
OVER ALASKA THIS MORNING WITH THE ASSOCIATED SURFACE FRONT PUSHING
ONSHORE OVER THE NORTH GULF COAST...PRODUCING WIDESPREAD SHOWERS
AND RAIN OVER THE COAST AND PORTIONS OF COOK INLET AND THE SUSITNA
VALLEY. ENERGY ROTATING AROUND THE LOW AND AHEAD OF THE FRONT IS
PRODUCING SHOWERS OVER MUCH OF SOUTHWEST ALASKA THIS MORNING. OVER
THE CENTRAL ALEUTIANS...A WEAKENING RIDGE IS MOVING EASTWARD
AHEAD OF A BROAD AND WEAKENING 986 MB LOW AND ITS ASSOCIATED FRONT
LOCATED NEAR KAMCHATKA.

&&

.MODEL DISCUSSION...
GLOBAL MODELS ALL INITIALIZED ACCEPTABLY FOR THE 00Z RUN WITH FEW
SIGNIFICANT DIFFERENCES. THROUGH 48 HOURS...MODELS ARE IN
REASONABLE AGREEMENT WITH THEIR HANDING OF FEATURES WITH ONLY
MINOR DIFFERENCES. FOR THIS PACKAGE...THE GFS WAS USED ON BOTH
EAST AND WEST FORECAST DOMAINS WITH THE NAM USED OVER LAND AREAS
IN SOUTHWEST ALASKA.

&&

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

THE MAIN CONCERN IN THE FORECAST THROUGH MONDAY SURROUNDS GUSTY
WINDS THAT DEVELOP IN RESPONSE TO A BUILDING RIDGE ALONG THE
NORTHEAST GULF COAST. SUNDAY MORNING STARTS OFF WITH LOW PRESSURE
SOUTH OF KODIAK ISLAND PUSHING A WEAK FRONT OVER THE NORTHERN GULF TO
THE SUSITNA AND COPPER RIVER VALLEYS. RAIN WILL LARGELY BE
CONFINED TO THE GULF AND COASTAL AREAS WITH SCATTERED SHOWERS
INLAND. THE DRIVING MECHANISM FOR THE BUILDING RIDGE TODAY IS FROM
THE AMPLIFICATION OF THE NORTH AMERICAN RIDGE TO THE COPPER
RIVER. A LOW LEVEL JET ACCELERATES TO 30 TO 45 MPH AS THE PRESSURE
GRADIENT TIGHTENS ALONG THE NORTHERN COAST THIS MORNING. WINDS MIX
DOWN TO THE SURFACE WITH DOWNWARD FORCING BEHIND THE FRONT. THERE
CONTINUES TO BE SOME UNCERTAINTY IN THE TIMING AND STRENGTH FOR
SURFACE WINDS AS MODELS STRUGGLE TO CAPTURE THE ORIENTATION OF THE
PRESSURE GRADIENT. FORECAST WINDS ACROSS EAST TO WEST GAPS AND
ALONG THE COPPER RIVER WERE INCREASED THIS AFTERNOON TO FOLLOW
TRENDS OF THE HIRES MODELS. A PERSISTENT PATTERN CONTINUES INTO
MONDAY WITH SHOWERS ACROSS THE GULF AND AFTERNOON GUSTS DEVELOPING
AS ANOTHER SHORTWAVE MOVES UP FROM THE SOUTHERN GULF.

&&

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

REMNANTS OF A TROUGH MOVING THROUGH THE BRISTOL BAY AREA IS
BRINGING SOME SHOWERS THIS MORNING. ELSEWHERE...A WEAK SURFACE LOW
WILL BE DEVELOPING LATER TODAY ACROSS THE WESTERN INTERIOR.
COMBINED WITH DAYTIME HEATING...SOME INSTABILITY IS EXPECTED TO
RETURN ALLOWING FOR DIURNAL SHOWERS AND THUNDERSTORMS. THIS LOW
WILL REMAIN IN PLACE FOR MONDAY AND EXPECT MUCH OF THE SAME WITH
DIURNAL SHOWERS AND THUNDERSTORMS.

&&

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

A SHORTWAVE RIDGE AXIS IS BUILDING INTO THE BERING SEA AHEAD OF A
ONCE STRONG LOW WHICH PEAKED IN STRENGTH SOUTH OF THE KAMCHATKA
PENINSULA. THE ASSOCIATED OCCLUDED FRONT WILL MAKE EASTWARD
PROGRESS AND REACH THE EASTERN ALEUTIANS BY TUESDAY. AS THE
REMNANTS OF THE CLOSED UPPER LOW MOVE EAST IN CONJUNCTION...SHOWERS
BEHIND THE FRONT WILL FILL IN ACROSS MOST OF THE BERING SEA.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...TUE THROUGH SAT)...
THE LONG RANGE PATTERN WILL PRESENT SOME INTERESTING CHALLENGES
AND A POSSIBLE CHANGE IN THE LONGWAVE REGIME. THIS TIME FRAME
STARTS WITH ONE LOW FILLING AND MOVING INLAND OVER THE GULF OF AK.
MEANWHILE...OVER THE CENTRAL ALEUTIANS...THE NEXT UPPER LEVEL LOW
IS ALREADY TAKING A VERY FAMILIAR TRACK TOWARDS THE GULF. AS THE
FIRST LOW WEAKENS AND MOVES INLAND...THIS SHOULD ALLOW THE
GRADIENT TO RELAX. THIS WILL FINALLY BRING AN END TO THE GUSTY
SOUTHEAST WINDS THAT HAVE BEEN BLOWING THROUGH FAVORED
LOCATIONS SUCH AS THE TURNAGAIN ARM AND THE KNIK RIVER VALLEY.
RATHER MOIST ONSHORE FLOW WILL CONTINUE TO MAKE FOR SOME STEADY
RAIN FOR IMMEDIATE COASTAL AREAS. BUT PRECIPITATION INLAND SHOULD
BE LIMITED TO SHOWERS...MAINLY DRIVEN BY WEAK AFTERNOON
INSTABILITY WITH A COLD POCKET OF RELATIVELY COLD AIR AT 500MB.

BY LATE WED...THE LOW FROM THE CENTRAL ALEUTIANS WILL MAKE ITS WAY
TO THE ALASKA PENINSULA. IT WILL PUSH A WARM OCCLUSION IN FRONT OF
IT. THIS WILL BRING RAIN BACK INTO KODIAK WITH CLOUDS STARTING TO
OVERSPREAD SOUTH CENTRAL. BUT IT IS AT THIS POINT WHEN MODELS
DIVERGE DRAMATICALLY. THE BIGGEST QUESTION IS WHERE THE UPPER
LEVEL LOW SETS UP RESIDENCE. SOME OF THIS DEPENDS ON HOW EFFECTIVE
ENERGY TRACKING THROUGH THE GULF IS AT PUSHING THE NORTH AMERICAN
RIDGE OFF TO THE EAST. THE EC HOLDS THE LOW CENTER THE FURTHEST
NORTH AND WEST...WHILE THE GFS ALLOWS IT TO MIGRATE ALL THE WAY
INTO THE CENTRAL GULF. EARLIER RUNS WILL SHOWING SOME PHASING
OCCURRING WITH THIS LOW AND SOME ENERGY TRACKING ALONG THE JET IN
THE NORTH PACIFIC. THEY WERE SHOWING THE POTENTIAL FOR A TRIPLE-
POINT LOW TO FORM AND TRACK QUICKLY INTO SOUTH CENTRAL. SOLUTIONS
HAVE BACKED OFF THIS IDEA AND NOW MORE SETTLED ON JUST ANOTHER
UPPER LEVEL LOW SITTING OVER THE CENTRAL GULF BY NEXT SAT.

BY LATE NEXT WEEKEND INTO THE WEEK OF 9-13 MAY...THERE SEEMS TO BE
FAIR TO GOOD MODEL AGREEMENT IN SOME FORM OF RIDGE BUILDING OVER
THE EASTERN INTERIOR PORTION OF AK. MODELS HAVE VARIOUS SOLUTIONS
OF HOW THE RIDGE GETS THERE (SOME FROM THE NORTH PAC...SOME FROM
NW CONUS) BUT THEY ALL SHOW SIGNS OF IT. CLIMATOLOGICALLY THIS
MAKES SENSE AS WELL AS WE USUALLY SEE A WARMER STRETCH TOWARD THE
MIDDLE TO END OF MAY.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RLF
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA/LIW
LONG TERM...MO





000
FXAK68 PAFC 302357
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
357 PM AKDT SAT APR 30 2016

.ANALYSIS AND UPPER LEVELS...
A VERTICALLY STACKED LOW SWIRLING ABOUT THE SOUTHWESTERN GULF OFF
OF KODIAK ISLAND REMAINS THE DOMINANT STEERING FEATURE FOR ALL OF
SOUTHERN ALASKA OUT TO THE EASTERN ALEUTIANS THIS AFTERNOON. NORTH
AND EAST OF THE LOW...BROAD SOUTH TO SOUTHEASTERLY FLOW IS PUMPING
MOISTURE AND CLOUDINESS INTO THE NORTHERN GULF COAST. AT WHICH
POINT THE MOISTURE IS VERY EFFECTIVELY WRUNG OUT BY THE CHUGACH
AND KENAI MOUNTAINS...LEAVING LITTLE MORE THAN BROAD CLOUDINESS
FOR INLAND LOCALES OF SOUTHCENTRAL. THE PRIMARY WEATHER STORIES
ALONG COOK INLET AND THE VALLEYS REMAIN THE PERIODIC GUSTY
WINDS...ABOVE AVERAGE TEMPERATURES...AND VERY DRY CONDITIONS. MORE
ON THE FORECAST IMPLICATIONS OF THESE WEATHER FACTORS BELOW. WITH
LITTLE OR NO PRECIPITATION EXPECTED FOR THE REST OF THE DAY IN
ANCHORAGE...THE PALTRY 0.02 INCHES OF PRECIPITATION FOR THE MONTH
WILL MAKE THIS THE 3RD DRIEST APRIL ON RECORD. MORE ON THE CLIMATE
STATS FOR ANCHORAGE TOMORROW.

OVER SOUTHWEST ALASKA...AN UNSTABLE ATMOSPHERE REMAINS THE
INGREDIENT MOST LIKELY TO RESULT IN NOTABLE WEATHER THIS EVENING.
THE MOST CLOUD COVER REMAINS NEAR THE ALASKA RANGE...THOUGH EVEN
THIS AREA IS SEEING BREAKS. OTHERWISE ITS A NICE SUNNY DAY OUT
TOWARDS THE COAST...A FACTOR THAT COULD HELP WITH THUNDERSTORM
DEVELOPMENT ONCE AGAIN TODAY. YESTERDAY...STORMS DEVELOPED ALONG A
SEA BREEZE FRONT ALONG THE KUSKOKWIM DELTA IN THE LATE AFTERNOON
AS THE FRONT HELPED PUSH AN AIR MASS THAT HAD SOME MOISTURE WITH
IT UPWARD...WHERE THE UNSTABLE ATMOSPHERE THAT REMAINS ON THIS
MORNINGS BETHEL SOUNDING TOOK OVER.

OVER THE BERING...UPPER LEVEL RIDGING BETWEEN THE UPPER LOW NEAR
KODIAK AND THE NEXT LOW PUSHING OFF THE EAST COAST OF ASIA IS IN
PLACE. THE UPPER LEVEL RIDGING IS INDICATIVE OF MUCH WARMER AIR
ALOFT. THIS CAN BE SEEN COMPARING THIS MORNINGS SHEMYA SOUNDING TO
BETHELS. THUS...IN THIS AREA...INSTABILITY IS ABSENT. A LACK OF
INSTABILITY MEANS A LACK OF VERTICAL MIXING. WITH ABUNDANT LOW
LEVEL MOISTURE FROM THE BERING ITSELF...THE WARM AIR ALOFT HAS
TRAPPED THAT MOISTURE BENEATH THE CAP OF WARM AIR...CAUSING
ABUNDANT LOW LEVEL STRATUS FROM NUNIVAK ISLAND ACROSS MOST OF THE
BERING AND ALEUTIANS.

&&

.MODEL DISCUSSION...
WITH SUCH A STAGNANT WEATHER PATTERN...THE MODELS ALL HAVE BEEN
IN EXCELLENT AGREEMENT TRACKING THE LARGER WEATHER FEATURES ACROSS
SOUTHERN ALASKA...AND SUCH REMAINS THE CASE THIS AFTERNOON.
THUS...THE MAIN FORECAST CHALLENGES REMAIN TRACKING THE SMALLER
SCALE FEATURES THAT HAVE A SIGNIFICANT IMPACT TO THE WEATHER.
THESE FEATURES INCLUDE FORECASTING WHERE ANY AFTERNOON
THUNDERSTORMS WILL DEVELOP AND MOVE...IF THE STRATUS PREVALENT
OVER THE BERING WILL DISSIPATE OR THICKEN AND LOWER INTO FOG...AND
TIMING ANY LOCAL WIND SHIFTS IN THE COOK INLET REGION CAUSED BY
DIFFERENTIAL HEATING OR THE PASSAGE OF MESOSCALE FRONTS. THE
HIGHER RESOLUTION MODELS SUCH AS THE ARW...NAM...AND GEM WERE USED
TO HELP WITH THESE FORECAST CHALLENGES. CONFIDENCE REMAINS VERY
HIGH ON THE BROADER SCALE WEATHER PATTERN...AND AVERAGE FOR THE
SMALLER FEATURES WE ARE TRACKING.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A STRONG LOW NOW IN THE GULF OF ALASKA HAS A FRONT EXTENDING ALONG
THE COAST FROM KODIAK ISLAND TO PRINCE WILLIAM SOUND SOUTHEAST.
THE MAIN CONCERN IS THE GUSTY POST FRONTAL WIND. AFTER THE FRONT
PUSHES INLAND AND WEAKENS TO A TROUGH A RIDGE FORMS IN BEHIND THIS
WHILE ANOTHER TROUGH THEN PUSHES TOWARD THE COAST LATE THIS
EVENING AND SUNDAY MORNING. WHILE WIND IS THE MAIN ISSUE...MODERATE
TO HEAVY RAINFALL IS OCCURRING ALONG THE COASTAL UP SLOPE SIDE OF
THE MOUNTAINS AS WELL AS INTO PORTAGE VALLEY. THE RAIN WILL
DIMINISH IN INTENSITY POST FRONTALLY THOUGH IT WILL CONTINUE
THROUGH SUNDAY IN THE PERSISTENT ONSHORE FLOW PATTERN.

INLAND THE TYPICAL CROSS BARRIER FLOW WILL RESULT IN THE RAIN
SHADOWING ON THE LEE OF THE MOUNTAINS. POST FRONTAL REDUCTION OF
WIND SHOULD ALLOW FOR INCREASED POTENTIAL FOR RAIN ON THE LEE SIDE
OF THE MOUNTAINS LATE THIS EVENING. THE INCREASE IN WIND AS THE
RIDGE BUILDS TONIGHT WILL INCREASE THE RAIN SHADOW AFFECT TONIGHT
INTO SUNDAY MORNING. INTO THE SUSITNA VALLEY AND NORTHERN COPPER
RIVER BASIN ALONG THE ALASKA RANGE EXPECT RAIN TO INCREASE
THROUGH THIS EVENING AND PERSIST THROUGH SUNDAY IN THE UP SLOPE
FLOW REGIME.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
MINIMAL CHANGE IS EXPECTED IN THE GENERAL PATTERN OVER SOUTHWEST
ALASKA FOR THE NEXT SEVERAL DAYS. A MODERATELY UNSTABLE AIR MASS
WILL CONTINUE TO SUPPORT ISOLATED TO SCATTERED DIURNAL SHOWERS
WITH PERIODIC SHORTWAVES ROTATING IN FROM THE EAST...ENHANCING AND
MAKING SHOWERS MORE NUMEROUS. ADDITIONALLY ISOLATED THUNDERSTORMS
WILL BE A POSSIBILITY AT TIMES. WITH THE THERMAL TROUGH STRETCHED
ACROSS THE KUSKOKWIM DELTA...STEERING FLOW FROM THE NORTHEAST AND
CLEARER SKIES OVER BOTH THE KUSKOKWIM DELTA AND TO THE NORTHEAST
BRINING GOOD SOLAR HEATING...CONDITIONS LOOK FAVORABLE FOR
ISOLATED THUNDERSTORMS IN THAT LOCATION THIS EVENING.

ON SUNDAY THE THERMAL TROUGH WILL BE FURTHER INLAND WITH THE
INSTABILITY SPREAD OVER LARGER AREA AND THE POTENTIAL FOR A FEW
ISOLATED THUNDERSTORMS OVER A BROADER PORTION OF INLAND SOUTHWEST
ALASKA. HOWEVER THE INSTABILITY SUNDAY DOES LOOKS MARGINAL ENOUGH
THAT A GOOD BIT OF SUNSHINE WILL BE A NECESSARY INGREDIENT TO
TRIGGER ANY THUNDERSTORMS AND CLOUD COVER LIMIT COULD WHERE THEY
DO FORM. ON MONDAY AFTERNOON/EVENING A MORE FOCUSED TROUGH WILL
BRING A STRONGER SWATH OF INSTABILITY TO THE KUSKOKWIM VALLEY AND
NORTHERN BRISTOL BAY AREA AND A BETTER CHANCE FOR ISOLATED OR
POSSIBLY WIDELY SCATTERED THUNDERSTORMS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE BROAD VERTICALLY STACKED LOW IN THE SOUTHWESTERN GULF WILL
GRADUALLY WEAKEN AS IT DRIFTS SLOWLY EAST NORTHEAST SUNDAY AND
MONDAY. THE NEXT INCOMING FRONTAL SYSTEM IS CURRENTLY PUSHING INTO
THE WESTERN ALEUTIANS WITH THE PARENT LOW SOUTH OF THE KAMCHATKA
PENINSULA. THE FRONT WILL CONTINUE NORTH AND EAST INTO THE
SOUTHERN BERING AND CENTRAL ALEUTIANS TONIGHT AND SUNDAY. THE LOW
WILL SKIRT JUST SOUTH OF THE WESTERN ALEUTIANS SUNDAY NIGHT THEN
CONTINUE EAST THROUGH THE CENTRAL ALEUTIANS MONDAY AND EASTERN
ALEUTIANS TUESDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...TUE THROUGH SAT)...
THE LONG RANGE PATTERN WILL PRESENT SOME INTERESTING CHALLENGES
AND A POSSIBLE CHANGE IN THE LONG-WAVE REGIME. THIS TIME FRAME
STARTS WITH ONE LOW FILLING AND MOVING INLAND OVER THE GULF OF AK.
MEANWHILE...OVER THE CENTRAL ALEUTIANS...THE NEXT UPPER LEVEL LOW
IS ALREADY TAKING A VERY FAMILIAR TRACK TOWARDS THE GULF. AS THE
FIRST LOW WEAKENS AND MOVES INLAND...THIS SHOULD ALLOW THE
GRADIENT TO RELAX. THIS WILL FINALLY BRING AN END TO THE GUSTY
SOUTHEAST WINDS THAT HAVE BEEN BLOWING THROUGH FAVORED LOCATIONS
SUCH AS THE TURNAGAIN ARM AND THE KNIK RIVER VALLEY. RATHER MOIST
ONSHORE FLOW WILL CONTINUE TO MAKE FOR SOME STEADY RAIN ALONG THE
IMMEDIATE COASTAL AREAS. BUT PRECIPITATION INLAND SHOULD BE
LIMITED TO SHOWERS...MAINLY DRIVEN BY WEAK AFTERNOON INSTABILITY
WITH A COLD POCKET OF RELATIVELY COLD AIR AT 500MB.

BY LATE WED...THE LOW FROM THE CENTRAL ALEUTIANS WILL MAKE ITS WAY
TO THE ALASKA PENINSULA. IT WILL PUSH A WARM OCCLUSION IN FRONT OF
IT. THIS WILL BRING RAIN BACK INTO KODIAK WITH CLOUDS STARTING TO
OVERSPREAD SOUTH CENTRAL. BUT IT IS AT THIS POINT WHEN MODELS
DIVERGE DRAMATICALLY. THE BIGGEST QUESTION IS WHERE THE UPPER
LEVEL LOW SETS UP RESIDENCE. SOME OF THIS DEPENDS ON HOW EFFECTIVE
ENERGY TRACKING THROUGH THE GULF IS AT PUSHING THE NORTH AMERICAN
RIDGE OFF TO THE EAST. THE EC HOLDS THE LOW CENTER THE FURTHEST
NORTH AND WEST...WHILE THE GFS ALLOWS IT TO MIGRATE ALL THE WAY
INTO THE CENTRAL GULF. EARLIER RUNS WERE SHOWING SOME PHASING
OCCURRING WITH THIS LOW AND SOME ENERGY TRACKING ALONG THE JET IN
THE NORTH PACIFIC. THEY WERE SHOWING THE POTENTIAL FOR A TRIPLE-
POINT LOW TO FORM AND TRACK QUICKLY INTO SOUTH CENTRAL. SOLUTIONS
HAVE BACKED OFF THIS IDEA AND NOW MORE SETTLED ON JUST ANOTHER
UPPER LEVEL LOW SITTING OVER THE CENTRAL GULF BY NEXT SAT.

BY LATE NEXT WEEKEND INTO THE WEEK OF 9-13 MAY...THERE SEEMS TO BE
FAIR TO GOOD MODEL AGREEMENT IN SOME FORM OF RIDGE BUILDING OVER
THE EASTERN INTERIOR PORTION OF AK. MODELS HAVE VARIOUS SOLUTIONS
OF HOW THE RIDGE GETS THERE (SOME FROM THE NORTH PAC...SOME FROM
NW CONUS) BUT THEY ALL SHOW SIGNS OF IT. CLIMATOLOGICALLY THIS
MAKES SENSE AS WELL AS WE USUALLY SEE A WARMER STRETCH TOWARD THE
MIDDLE TO END OF MAY.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 178.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...JW
SOUTHCENTRAL ALASKA...SA
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JR
LONG TERM...MO





000
FXAK68 PAFC 301259
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
459 AM AKDT SAT APR 30 2016

.ANALYSIS AND UPPER LEVELS...
THE NORTH PACIFIC AND ALASKA REMAIN UNDER THE INFLUENCE OF A BROAD
AND DEEPENING LONGWAVE TROUGH CENTERED ALONG 160W WITH SLIGHTLY
LOWER AMPLITUDE RIDGES ALONG THE NORTHEASTERN PACIFIC COAST AND
OVER THE NORTHWEST PACIFIC ALONG 175E. A CLOSED UPPER LOW REMAINS
EMBEDDED WITHIN THE LONGWAVE TROUGH CENTERED OVER THE ALASKA
PENINSULA. THE POLAR JET HAS BECOME SIGNIFICANTLY MORE MERIDIONAL
THAN THIS TIME YESTERDAY DUE TO THE AMPLIFICATION OF THE
TROUGH/RIDGE PATTERN...WITH A 130KT JET MAX ALONG THE EASTERN SIDE
OF THE TROUGH /ROUGHLY BETWEEN 40-50N AND ALONG 148W/ AND A
STRONGER 150KT MAX ON THE ON THE WESTERN SIDE OF THE RIDGE ALONG
165E.

AT THE SURFACE...WEATHER FOR MOST OF ALASKA IS DOMINATED BY A
983MB LOW LOCATED ABOUT 600 MILES SOUTH OF KODIAK ISLAND THIS
MORNING. THIS LOW HAS EXCELLENT SUPPORT FROM THE 130KT JET MAX
MENTIONED ABOVE. THE ASSOCIATED SURFACE FRONT IS MOVING NORTHWARD
THROUGH THE GULF OF ALASKA THIS MORNING...PRODUCING STORM FORCE
WINDS OVER THE NORTHERN GULF. THE AMPLITUDE OF THE TROUGH IS DEEP
ENOUGH THAT MOISTURE IS STREAMING NORTHWARD INTO THE SURFACE
SYSTEM FROM ABOUT 30N...ALTHOUGH MOST OF THIS MOISTURE IS BEING
SHUNTED TOWARDS SOUTHEASTERN ALASKA. OUT WEST...A LARGE 966 MB LOW
SOUTH OF THE KAMCHATKA PENINSULA IS PUSHING ITS ASSOCIATED FRONT
INTO THE WESTERN ALEUTIANS. FINALLY...A WEAK 1002 MB LOW OVER THE
KUSKOKWIM DELTA IS MOVING OFF SHORE AND DISSIPATING.

&&

.MODEL DISCUSSION...
MODEL GUIDANCE FROM THE MAJOR MODELS ALL INITIALIZED WITH FEW
ERRORS AND THE FORECAST GUIDANCE THROUGH 84 HOURS ARE ALL IN
REASONABLY GOOD AGREEMENT THROUGH THE DAY 3 PERIOD. IN THE SHORT
TERM...THE GFS IS KEEPING WINDS AT STORM FORCE WITH THE FRONT
PUSHING THROUGH THE NORTHERN GULF OF ALASKA THIS MORNING WHEREAS
THE OTHER MODELS ARE KEEPING WINDS IN THE GALE FORCE RANGE. FOR
THIS PACKAGE...THE GFS WAS GENERALLY USED FOR GUIDANCE THROUGH
DAY 3.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE MAIN FORECAST CHALLENGE THIS WEEKEND IS THE FRONT ALONG THE
GULF THAT WILL BRING INCREASED RAIN CHANCES AND GUSTY WINDS
THROUGH SUNDAY. THE FRONTAL BOUNDARY MOVES QUICKLY TO THE
NORTHERN COAST THIS MORNING BRINGING GUSTY WINDS AND A BAND OF
RAIN...FROM THE CENTRAL GULF AND ACROSS THE EASTERN KENAI...TO
THE COAST. GUSTY GALE TO STORM FORCE WINDS ACROSS THE GULF
CONTINUE THROUGH THE AFTERNOON EXCEPT FOR DIMINISHING CONDITIONS
ALONG THE SOUTHERN GULF DURING THE AFTERNOON. STRONG WINDS ACROSS
KODIAK ISLAND WILL END QUICKLY DURING THE AFTERNOON BEHIND THE
FRONT. THIS SYSTEM WEAKENS ALONG THE COAST THIS EVENING WITH
WINDS TAPERING DOWN THROUGH THE NIGHT.

WINDS BECOME GUSTY ON SUNDAY ACROSS GAP LOCATIONS...INCLUDING THE
COPPER RIVER VALLEY AS THE PRESSURE GRADIENT TIGHTENS BETWEEN THE
SURFACE LOW SOUTH OF KODIAK ISLAND AND A BUILDING RIDGE ALONG
THE NORTHEAST COAST. BY EARLY MONDAY MORNING...DRIER CONDITIONS
AND QUIETER WINDS SETTLE IN AS THE SURFACE LOW WEAKENS ALONG THE
WESTERN GULF.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...SAT AND SUN)...
A LOW MOVING INTO THE GULF TODAY WILL PROVIDE SHOWERS ACROSS
MAINLY THE ALASKA AND ALEUTIAN RANGES AS WELL AS THE BRISTOL BAY
AREA. FURTHER WEST...NORTHEASTERLY FLOW WILL KEEP MUCH OF THE
KUSKOKWIM VALLEY AND DELTA DRY ALTHOUGH DAYTIME HEATING MAY PROVIDE
ENOUGH INSTABILITY FOR A FEW SHOWERS TO DEVELOP AND DRIFT INTO THE
KUSKOKWIM DELTA THIS AFTERNOON. BY SUNDAY...THE NEXT LOW WILL BE
MOVING IN PROVIDING SHOWERS FOR INTERIOR LOCATIONS. THERE COULD
BE ENOUGH INSTABILITY FOR A FEW THUNDERSTORMS IN THE AFTERNOON AND
EVENING.

&&

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

A GALE FORCE LOW MOVING INTO THE GULF OF ALASKA WILL WEAKEN AND
MOVE NORTHEAST...WITH THE ASSOCIATED GALE FORCE FRONT OVER THE FAR
EASTERN ALEUTIANS MOVING INTO THE GULF...LEAVING BROAD NORTHERLY
FLOW IN ITS WAKE OVER THE REMAINDER OF THE BERING/ALEUTIANS. A
WEAKENING OCCLUDED FRONT WILL MOVE INTO THE WESTERN BERING TONIGHT
AND SUNDAY...THEN SLOWLY MOVE EASTWARD AS FAR AS THE CENTRAL
ALEUTIANS BY MONDAY...BRINGING A PERIOD OF RAIN AND SWITCHING
WINDS AROUND TO THE SOUTHEAST/SOUTHWEST. OTHERWISE....RATHER
QUIESCENT WEATHER WILL ABOUND.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...MON THROUGH FRI)...
NOT A LOT OF CHANGE EXPECTED IN THE LONG TERM. ONE UPPER-LEVEL
WILL SLOWLY FILL AND WEAKEN OVER THE GULF EARLY IN THE WEEK.
ANOTHER NEW LOW WILL DEVELOP OVER THE CENTRAL ALEUTIANS AND TRACK
SLOWLY EAST. THIS WILL ALLOW A RIDGE TO BUILD IN FRONT OF THE
SECOND LOW OVER SOUTHERN ALASKA ON TUE AND WED. THIS WILL BRING A
BRIEF BREAK TO THE CONTINUOUS SOUTHEAST FLOW AND ASSOCIATED
FRONTS IMPACTING THE GULF COAST. IT COULD ALSO BRING THE BEST
CHANCE FOR SOME WIDESPREAD SUNSHINE ACROSS MUCH OF THE SOUTHERN
MAINLAND. BY THE MIDDLE OF THE WEEK THOUGH...MODELS BEGIN TO
DIVERGE ON TWO SIGNIFICANT ISSUES. THE FIRST IS HOW MUCH ENERGY
PUSHES INTO THE RIDGE OVER SE ALASKA AND THE SECOND IS WHAT
STRUCTURE THE LOW APPROACHING FROM THE ALEUTIANS TAKES ON. IF
ENOUGH ENERGY PUSHES INTO THE RIDGE...IT WILL SIMPLY GIVE WAY AND
MOVE EAST. BUT IF SOME WARM AIR ADVECTED INTO IT CAUSING IT TO
BUILD...THE ENERGY MIGHT JUST RIDE UP ITS WESTERN FLANK STRAIGHT
INTO SOUTHERN AK. THE STRUCTURE OF THE LOW VARIES FROM THE GFS
DEPICTION OF A VERTICALLY STACKED LOW TRACKING SLOWLY EAST TO THE
EC SHOWING IT MORE PROGRESSIVE WITH A NEW TRIPLE-POINT LOW FORMING
OVER THE SOUTHERN GULF BY NEXT WEEKEND. THIS FORECAST PACKAGE
LEANED TOWARDS KEEPING THE HIGHEST POPS ALONG COASTAL LOCATIONS AT
THIS TIME. TEMPERATURES LOOK TO REMAINS NORMAL TO ABOVE NORMAL AS
WE START MAY. THIS COULD LEAD TO SOME WEAK INSTABILITY...SO WE
WILL BE WATCHING CHANCES FOR CONVECTION.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 119 120 130 131
         GALE 125 132 137 138 139 140 141 150 351 352

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RLF
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...LIW/JA
LONG TERM...MO





000
FXAK68 PAFC 301259
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
459 AM AKDT SAT APR 30 2016

.ANALYSIS AND UPPER LEVELS...
THE NORTH PACIFIC AND ALASKA REMAIN UNDER THE INFLUENCE OF A BROAD
AND DEEPENING LONGWAVE TROUGH CENTERED ALONG 160W WITH SLIGHTLY
LOWER AMPLITUDE RIDGES ALONG THE NORTHEASTERN PACIFIC COAST AND
OVER THE NORTHWEST PACIFIC ALONG 175E. A CLOSED UPPER LOW REMAINS
EMBEDDED WITHIN THE LONGWAVE TROUGH CENTERED OVER THE ALASKA
PENINSULA. THE POLAR JET HAS BECOME SIGNIFICANTLY MORE MERIDIONAL
THAN THIS TIME YESTERDAY DUE TO THE AMPLIFICATION OF THE
TROUGH/RIDGE PATTERN...WITH A 130KT JET MAX ALONG THE EASTERN SIDE
OF THE TROUGH /ROUGHLY BETWEEN 40-50N AND ALONG 148W/ AND A
STRONGER 150KT MAX ON THE ON THE WESTERN SIDE OF THE RIDGE ALONG
165E.

AT THE SURFACE...WEATHER FOR MOST OF ALASKA IS DOMINATED BY A
983MB LOW LOCATED ABOUT 600 MILES SOUTH OF KODIAK ISLAND THIS
MORNING. THIS LOW HAS EXCELLENT SUPPORT FROM THE 130KT JET MAX
MENTIONED ABOVE. THE ASSOCIATED SURFACE FRONT IS MOVING NORTHWARD
THROUGH THE GULF OF ALASKA THIS MORNING...PRODUCING STORM FORCE
WINDS OVER THE NORTHERN GULF. THE AMPLITUDE OF THE TROUGH IS DEEP
ENOUGH THAT MOISTURE IS STREAMING NORTHWARD INTO THE SURFACE
SYSTEM FROM ABOUT 30N...ALTHOUGH MOST OF THIS MOISTURE IS BEING
SHUNTED TOWARDS SOUTHEASTERN ALASKA. OUT WEST...A LARGE 966 MB LOW
SOUTH OF THE KAMCHATKA PENINSULA IS PUSHING ITS ASSOCIATED FRONT
INTO THE WESTERN ALEUTIANS. FINALLY...A WEAK 1002 MB LOW OVER THE
KUSKOKWIM DELTA IS MOVING OFF SHORE AND DISSIPATING.

&&

.MODEL DISCUSSION...
MODEL GUIDANCE FROM THE MAJOR MODELS ALL INITIALIZED WITH FEW
ERRORS AND THE FORECAST GUIDANCE THROUGH 84 HOURS ARE ALL IN
REASONABLY GOOD AGREEMENT THROUGH THE DAY 3 PERIOD. IN THE SHORT
TERM...THE GFS IS KEEPING WINDS AT STORM FORCE WITH THE FRONT
PUSHING THROUGH THE NORTHERN GULF OF ALASKA THIS MORNING WHEREAS
THE OTHER MODELS ARE KEEPING WINDS IN THE GALE FORCE RANGE. FOR
THIS PACKAGE...THE GFS WAS GENERALLY USED FOR GUIDANCE THROUGH
DAY 3.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE MAIN FORECAST CHALLENGE THIS WEEKEND IS THE FRONT ALONG THE
GULF THAT WILL BRING INCREASED RAIN CHANCES AND GUSTY WINDS
THROUGH SUNDAY. THE FRONTAL BOUNDARY MOVES QUICKLY TO THE
NORTHERN COAST THIS MORNING BRINGING GUSTY WINDS AND A BAND OF
RAIN...FROM THE CENTRAL GULF AND ACROSS THE EASTERN KENAI...TO
THE COAST. GUSTY GALE TO STORM FORCE WINDS ACROSS THE GULF
CONTINUE THROUGH THE AFTERNOON EXCEPT FOR DIMINISHING CONDITIONS
ALONG THE SOUTHERN GULF DURING THE AFTERNOON. STRONG WINDS ACROSS
KODIAK ISLAND WILL END QUICKLY DURING THE AFTERNOON BEHIND THE
FRONT. THIS SYSTEM WEAKENS ALONG THE COAST THIS EVENING WITH
WINDS TAPERING DOWN THROUGH THE NIGHT.

WINDS BECOME GUSTY ON SUNDAY ACROSS GAP LOCATIONS...INCLUDING THE
COPPER RIVER VALLEY AS THE PRESSURE GRADIENT TIGHTENS BETWEEN THE
SURFACE LOW SOUTH OF KODIAK ISLAND AND A BUILDING RIDGE ALONG
THE NORTHEAST COAST. BY EARLY MONDAY MORNING...DRIER CONDITIONS
AND QUIETER WINDS SETTLE IN AS THE SURFACE LOW WEAKENS ALONG THE
WESTERN GULF.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...SAT AND SUN)...
A LOW MOVING INTO THE GULF TODAY WILL PROVIDE SHOWERS ACROSS
MAINLY THE ALASKA AND ALEUTIAN RANGES AS WELL AS THE BRISTOL BAY
AREA. FURTHER WEST...NORTHEASTERLY FLOW WILL KEEP MUCH OF THE
KUSKOKWIM VALLEY AND DELTA DRY ALTHOUGH DAYTIME HEATING MAY PROVIDE
ENOUGH INSTABILITY FOR A FEW SHOWERS TO DEVELOP AND DRIFT INTO THE
KUSKOKWIM DELTA THIS AFTERNOON. BY SUNDAY...THE NEXT LOW WILL BE
MOVING IN PROVIDING SHOWERS FOR INTERIOR LOCATIONS. THERE COULD
BE ENOUGH INSTABILITY FOR A FEW THUNDERSTORMS IN THE AFTERNOON AND
EVENING.

&&

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

A GALE FORCE LOW MOVING INTO THE GULF OF ALASKA WILL WEAKEN AND
MOVE NORTHEAST...WITH THE ASSOCIATED GALE FORCE FRONT OVER THE FAR
EASTERN ALEUTIANS MOVING INTO THE GULF...LEAVING BROAD NORTHERLY
FLOW IN ITS WAKE OVER THE REMAINDER OF THE BERING/ALEUTIANS. A
WEAKENING OCCLUDED FRONT WILL MOVE INTO THE WESTERN BERING TONIGHT
AND SUNDAY...THEN SLOWLY MOVE EASTWARD AS FAR AS THE CENTRAL
ALEUTIANS BY MONDAY...BRINGING A PERIOD OF RAIN AND SWITCHING
WINDS AROUND TO THE SOUTHEAST/SOUTHWEST. OTHERWISE....RATHER
QUIESCENT WEATHER WILL ABOUND.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...MON THROUGH FRI)...
NOT A LOT OF CHANGE EXPECTED IN THE LONG TERM. ONE UPPER-LEVEL
WILL SLOWLY FILL AND WEAKEN OVER THE GULF EARLY IN THE WEEK.
ANOTHER NEW LOW WILL DEVELOP OVER THE CENTRAL ALEUTIANS AND TRACK
SLOWLY EAST. THIS WILL ALLOW A RIDGE TO BUILD IN FRONT OF THE
SECOND LOW OVER SOUTHERN ALASKA ON TUE AND WED. THIS WILL BRING A
BRIEF BREAK TO THE CONTINUOUS SOUTHEAST FLOW AND ASSOCIATED
FRONTS IMPACTING THE GULF COAST. IT COULD ALSO BRING THE BEST
CHANCE FOR SOME WIDESPREAD SUNSHINE ACROSS MUCH OF THE SOUTHERN
MAINLAND. BY THE MIDDLE OF THE WEEK THOUGH...MODELS BEGIN TO
DIVERGE ON TWO SIGNIFICANT ISSUES. THE FIRST IS HOW MUCH ENERGY
PUSHES INTO THE RIDGE OVER SE ALASKA AND THE SECOND IS WHAT
STRUCTURE THE LOW APPROACHING FROM THE ALEUTIANS TAKES ON. IF
ENOUGH ENERGY PUSHES INTO THE RIDGE...IT WILL SIMPLY GIVE WAY AND
MOVE EAST. BUT IF SOME WARM AIR ADVECTED INTO IT CAUSING IT TO
BUILD...THE ENERGY MIGHT JUST RIDE UP ITS WESTERN FLANK STRAIGHT
INTO SOUTHERN AK. THE STRUCTURE OF THE LOW VARIES FROM THE GFS
DEPICTION OF A VERTICALLY STACKED LOW TRACKING SLOWLY EAST TO THE
EC SHOWING IT MORE PROGRESSIVE WITH A NEW TRIPLE-POINT LOW FORMING
OVER THE SOUTHERN GULF BY NEXT WEEKEND. THIS FORECAST PACKAGE
LEANED TOWARDS KEEPING THE HIGHEST POPS ALONG COASTAL LOCATIONS AT
THIS TIME. TEMPERATURES LOOK TO REMAINS NORMAL TO ABOVE NORMAL AS
WE START MAY. THIS COULD LEAD TO SOME WEAK INSTABILITY...SO WE
WILL BE WATCHING CHANCES FOR CONVECTION.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 119 120 130 131
         GALE 125 132 137 138 139 140 141 150 351 352

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RLF
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...LIW/JA
LONG TERM...MO





000
FXAK68 PAFC 300011
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
411 PM AKDT FRI APR 29 2016

.ANALYSIS AND UPPER LEVELS...
WEATHER RADAR DEPICTS WIDESPREAD SCATTERED TO NUMEROUS SHOWER
COVERAGE ALONG COASTAL LOCATIONS...ESPECIALLY SOUTH AND EAST-
FACING SLOPES OF THE COASTAL MOUNTAIN RANGES. GUSTY SOUTHEAST
WINDS CONTINUE THROUGH THE SOUTHEAST GAPS OF THE MOUNTAIN
RANGES...IMPACTING AREAS SUCH AS ANCHORAGE PALMER GLENNALLEN AND
BRISTOL BAY. OTHERWISE...CONDITIONS ARE RELATIVELY BENIGN ACROSS
MUCH OF THE SOUTHCENTRAL AND SOUTHWEST PARTS OF THE STATE.

A PAIR OF MID-LEVEL LOWS...ONE A REMNANT UPPER LOW NEAR THE
SOUTHERN AKPEN AND THE OTHER A PART OF A FAIRLY STRONG NORTH
PACIFIC LOW CENTERED ABOUT 625 NM SOUTH-SOUTHWEST OF SITKINAK
ISLAND...ARE CURRENTLY BEGINNING THE PROCESS OF CONSOLIDATING OVER
THE NORTH PACIFIC SOUTH OF THE AKPEN. THE LARGE CIRCULATION
ENCOMPASSES MOST OF THE ANCHORAGE AREA OF RESPONSIBILITY...WITH
THE EXCEPTION OF A MID-LEVEL RIDGE CURRENTLY MOVING INTO THE FAR
SOUTHWEST BERING AND WESTERN ALEUTIANS.

THE SURFACE FEATURES OF NOTE ARE A FAIRLY ROBUST GALE-FORCE FRONT
WHICH EXTENDS WELL AHEAD OF THE SURFACE LOW AND IS HEADING TOWARD
ENTERING THE SOUTHERN GULF THIS EVENING.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT THROUGH SUNDAY AFTERNOON...RESULTING
IN A FAIRLY HIGH CONFIDENCE FORECAST FOR MOST LOCATIONS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A WARM FRONT CURRENTLY LOCATED OVER THE NORTH PACIFIC WILL
QUICKLY MOVE INTO THE GULF OF ALASKA TONIGHT AND MOVE TO THE
NORTHERN GULF COAST BY SATURDAY MORNING. THE FRONT WILL BE
FAVORABLY ORIENTED WITH THE COASTAL RANGE WHICH WILL ALLOW A STORM
FORCE BARRIER JET TO DEVELOP RIGHT ALONG THE GULF COAST. FOR THE
MOST PART...MOST COASTAL WATERS AND OFFSHORE ZONES WILL SEE GALE
FORCE WINDS ASSOCIATED WITH THIS QUICK MOVING FRONT BUT WILL BE
SHORT LIVED AS THE FRONT IS EXPECTED TO WEAKEN RAPIDLY BY THE TIME
IT MAKES IT TO THE GULF COAST. RAINFALL ASSOCIATED WITH THIS FRONT
COULD BE HEAVY AT TIMES ALONG THE IMMEDIATE GULF COAST AS RAIN
UPSLOPES ALONG THE COASTAL RANGE. A FEW SPRINKLES COULD MAKE IT
INLAND LATE SATURDAY AND SUNDAY BUT DOWNSLOPING WINDS SHOULD
MITIGATE THE AMOUNT OF RAINFALL THAT IS ABLE TO MAKE IT INLAND.

SPEAKING OF WINDS...THE COMBINATION OF A COASTAL RIDGE AND THE
APPROACHING FRONTAL BOUNDARY WILL CONTINUE A COMPACT GRADIENT
ORIENTED FROM EAST TO WEST. THIS WILL ALLOW THE GUSTY WINDS THAT
HAVE BEEN OBSERVED THROUGH THE PAST WEAK FROM EAST TO WEST
ORIENTED GAPS TO CONTINUE THROUGH THE WEEKEND. GUSTY WINDS IN THE
ANCHORAGE BOWL WILL COME TO AN END TONIGHT AS THE BOUNDARY LAYER
STABILIZES AFTER SUNSET.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE PATTERN WILL REMAIN MUCH THE SAME THROUGH THE WEEKEND. BROAD
CYCLONIC FLOW...CENTERED AROUND A LOW APPROACHING KODIAK...WILL
DOMINATE. THIS WILL KEEP MOIST AND MILD SOUTHEAST FLOW PUSHING
OVER THE ALASKA AND ALEUTIAN RANGES. THE NET EFFECT AT THE SURFACE
WILL BE CONTINUED WELL ABOVE NORMAL TEMPERATURES AND A CHANCE OF
RAIN THROUGHOUT THE AREA. BY SUNDAY...THERE SHOULD BE ENOUGH EARLY
SUN TO HELP TO BUILD SOME BETTER INSTABILITY ACROSS THE KUSKOKWIM
VALLEY. AS YET ANOTHER WEAK PIECE OF ENERGY ROTATES AROUND THE
LOW...THIS COULD BE JUST ENOUGH TO HELP TRIGGER A FEW
THUNDERSTORMS. SO WE HAVE INTRODUCED SOME ISOLATED THUNDERSTORMS
ACROSS THE NORTHERN HALF OF BRISTOL BAY AND MOST OF THE KUSKOKWIM
VALLEY. CONFIDENCE IS MARGINAL IN THIS EVENT...BUT A STRIKE OR TWO
IS NOT OUT OF THE QUESTION.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
AS THE PARENT NORTH PACIFIC LOW PULLS OFF TOWARDS KODIAK SAT...IT
WILL LEAVE WEAK NORTHERLY FLOW AND WIDESPREAD MARINE FOG/STRATUS
IN ITS WAKE. WHILE IT LOOKS LIKE MOST OF THIS WILL HOLD AS LOW
STRATUS...IT COULD DROP VISIBILITIES AT THE SURFACE FROM TIME TO
TIME. BY LATE SAT INTO SUN...A NEW WARM OCCLUSION WILL APPROACH
THE WESTERN ALEUTIANS. THIS WILL BRING MINIMUM GALE FORCE WINDS
TO THE EXTREME WESTERN MARINE AREAS WITH MORE RAIN SPREADING FROM
THE WESTERN TO THE CENTRAL ALEUTIANS ON SUN.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...MON THROUGH FRI)...
NOT A LOT OF CHANGE EXPECTED IN THE LONG TERM. ONE UPPER-LEVEL
WILL SLOWLY FILL AND WEAKEN OVER THE GULF EARLY IN THE WEEK.
ANOTHER NEW LOW WILL DEVELOP OVER THE CENTRAL ALEUTIANS AND TRACK
SLOWLY EAST. THIS WILL ALLOW A RIDGE TO BUILD IN FRONT OF THE
SECOND LOW OVER SOUTHERN ALASKA ON TUE AND WED. THIS WILL BRING A
BRIEF BREAK TO THE CONTINUOUS SOUTHEAST FLOW AND ASSOCIATED
FRONTS IMPACTING THE GULF COAST. IT COULD ALSO BRING THE BEST
CHANCE FOR SOME WIDESPREAD SUNSHINE ACROSS MUCH OF THE SOUTHERN
MAINLAND. BY THE MIDDLE OF THE WEEK THOUGH...MODELS BEGIN TO
DIVERGE ON TWO SIGNIFICANT ISSUES. THE FIRST IS HOW MUCH ENERGY
PUSHES INTO THE RIDGE OVER SE ALASKA AND THE SECOND IS WHAT
STRUCTURE THE LOW APPROACHING FROM THE ALEUTIANS TAKES ON. IF
ENOUGH ENERGY PUSHES INTO THE RIDGE...IT WILL SIMPLY GIVE WAY AND
MOVE EAST. BUT IF SOME WARM AIR ADVECTED INTO IT CAUSING IT TO
BUILD...THE ENERGY MIGHT JUST RIDE UP ITS WESTERN FLANK STRAIGHT
INTO SOUTHERN AK. THE STRUCTURE OF THE LOW VARIES FROM THE GFS
DEPICTION OF A VERTICALLY STACKED LOW TRACKING SLOWLY EAST TO THE
EC SHOWING IT MORE PROGRESSIVE WITH A NEW TRIPLE-POINT LOW FORMING
OVER THE SOUTHERN GULF BY NEXT WEEKEND. THIS FORECAST PACKAGE
LEANED TOWARDS KEEPING THE HIGHEST POPS ALONG COASTAL LOCATIONS AT
THIS TIME. TEMPERATURES LOOK TO REMAINS NORMAL TO ABOVE NORMAL AS
WE START MAY. THIS COULD LEAD TO SOME WEAK INSTABILITY...SO WE
WILL BE WATCHING CHANCES FOR CONVECTION.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING 119 120 130 131.
 GALE WARNING 125 132 136 137 138 139 150.

&&

$$

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





000
FXAK68 PAFC 300011
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
411 PM AKDT FRI APR 29 2016

.ANALYSIS AND UPPER LEVELS...
WEATHER RADAR DEPICTS WIDESPREAD SCATTERED TO NUMEROUS SHOWER
COVERAGE ALONG COASTAL LOCATIONS...ESPECIALLY SOUTH AND EAST-
FACING SLOPES OF THE COASTAL MOUNTAIN RANGES. GUSTY SOUTHEAST
WINDS CONTINUE THROUGH THE SOUTHEAST GAPS OF THE MOUNTAIN
RANGES...IMPACTING AREAS SUCH AS ANCHORAGE PALMER GLENNALLEN AND
BRISTOL BAY. OTHERWISE...CONDITIONS ARE RELATIVELY BENIGN ACROSS
MUCH OF THE SOUTHCENTRAL AND SOUTHWEST PARTS OF THE STATE.

A PAIR OF MID-LEVEL LOWS...ONE A REMNANT UPPER LOW NEAR THE
SOUTHERN AKPEN AND THE OTHER A PART OF A FAIRLY STRONG NORTH
PACIFIC LOW CENTERED ABOUT 625 NM SOUTH-SOUTHWEST OF SITKINAK
ISLAND...ARE CURRENTLY BEGINNING THE PROCESS OF CONSOLIDATING OVER
THE NORTH PACIFIC SOUTH OF THE AKPEN. THE LARGE CIRCULATION
ENCOMPASSES MOST OF THE ANCHORAGE AREA OF RESPONSIBILITY...WITH
THE EXCEPTION OF A MID-LEVEL RIDGE CURRENTLY MOVING INTO THE FAR
SOUTHWEST BERING AND WESTERN ALEUTIANS.

THE SURFACE FEATURES OF NOTE ARE A FAIRLY ROBUST GALE-FORCE FRONT
WHICH EXTENDS WELL AHEAD OF THE SURFACE LOW AND IS HEADING TOWARD
ENTERING THE SOUTHERN GULF THIS EVENING.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT THROUGH SUNDAY AFTERNOON...RESULTING
IN A FAIRLY HIGH CONFIDENCE FORECAST FOR MOST LOCATIONS.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A WARM FRONT CURRENTLY LOCATED OVER THE NORTH PACIFIC WILL
QUICKLY MOVE INTO THE GULF OF ALASKA TONIGHT AND MOVE TO THE
NORTHERN GULF COAST BY SATURDAY MORNING. THE FRONT WILL BE
FAVORABLY ORIENTED WITH THE COASTAL RANGE WHICH WILL ALLOW A STORM
FORCE BARRIER JET TO DEVELOP RIGHT ALONG THE GULF COAST. FOR THE
MOST PART...MOST COASTAL WATERS AND OFFSHORE ZONES WILL SEE GALE
FORCE WINDS ASSOCIATED WITH THIS QUICK MOVING FRONT BUT WILL BE
SHORT LIVED AS THE FRONT IS EXPECTED TO WEAKEN RAPIDLY BY THE TIME
IT MAKES IT TO THE GULF COAST. RAINFALL ASSOCIATED WITH THIS FRONT
COULD BE HEAVY AT TIMES ALONG THE IMMEDIATE GULF COAST AS RAIN
UPSLOPES ALONG THE COASTAL RANGE. A FEW SPRINKLES COULD MAKE IT
INLAND LATE SATURDAY AND SUNDAY BUT DOWNSLOPING WINDS SHOULD
MITIGATE THE AMOUNT OF RAINFALL THAT IS ABLE TO MAKE IT INLAND.

SPEAKING OF WINDS...THE COMBINATION OF A COASTAL RIDGE AND THE
APPROACHING FRONTAL BOUNDARY WILL CONTINUE A COMPACT GRADIENT
ORIENTED FROM EAST TO WEST. THIS WILL ALLOW THE GUSTY WINDS THAT
HAVE BEEN OBSERVED THROUGH THE PAST WEAK FROM EAST TO WEST
ORIENTED GAPS TO CONTINUE THROUGH THE WEEKEND. GUSTY WINDS IN THE
ANCHORAGE BOWL WILL COME TO AN END TONIGHT AS THE BOUNDARY LAYER
STABILIZES AFTER SUNSET.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE PATTERN WILL REMAIN MUCH THE SAME THROUGH THE WEEKEND. BROAD
CYCLONIC FLOW...CENTERED AROUND A LOW APPROACHING KODIAK...WILL
DOMINATE. THIS WILL KEEP MOIST AND MILD SOUTHEAST FLOW PUSHING
OVER THE ALASKA AND ALEUTIAN RANGES. THE NET EFFECT AT THE SURFACE
WILL BE CONTINUED WELL ABOVE NORMAL TEMPERATURES AND A CHANCE OF
RAIN THROUGHOUT THE AREA. BY SUNDAY...THERE SHOULD BE ENOUGH EARLY
SUN TO HELP TO BUILD SOME BETTER INSTABILITY ACROSS THE KUSKOKWIM
VALLEY. AS YET ANOTHER WEAK PIECE OF ENERGY ROTATES AROUND THE
LOW...THIS COULD BE JUST ENOUGH TO HELP TRIGGER A FEW
THUNDERSTORMS. SO WE HAVE INTRODUCED SOME ISOLATED THUNDERSTORMS
ACROSS THE NORTHERN HALF OF BRISTOL BAY AND MOST OF THE KUSKOKWIM
VALLEY. CONFIDENCE IS MARGINAL IN THIS EVENT...BUT A STRIKE OR TWO
IS NOT OUT OF THE QUESTION.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
AS THE PARENT NORTH PACIFIC LOW PULLS OFF TOWARDS KODIAK SAT...IT
WILL LEAVE WEAK NORTHERLY FLOW AND WIDESPREAD MARINE FOG/STRATUS
IN ITS WAKE. WHILE IT LOOKS LIKE MOST OF THIS WILL HOLD AS LOW
STRATUS...IT COULD DROP VISIBILITIES AT THE SURFACE FROM TIME TO
TIME. BY LATE SAT INTO SUN...A NEW WARM OCCLUSION WILL APPROACH
THE WESTERN ALEUTIANS. THIS WILL BRING MINIMUM GALE FORCE WINDS
TO THE EXTREME WESTERN MARINE AREAS WITH MORE RAIN SPREADING FROM
THE WESTERN TO THE CENTRAL ALEUTIANS ON SUN.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...MON THROUGH FRI)...
NOT A LOT OF CHANGE EXPECTED IN THE LONG TERM. ONE UPPER-LEVEL
WILL SLOWLY FILL AND WEAKEN OVER THE GULF EARLY IN THE WEEK.
ANOTHER NEW LOW WILL DEVELOP OVER THE CENTRAL ALEUTIANS AND TRACK
SLOWLY EAST. THIS WILL ALLOW A RIDGE TO BUILD IN FRONT OF THE
SECOND LOW OVER SOUTHERN ALASKA ON TUE AND WED. THIS WILL BRING A
BRIEF BREAK TO THE CONTINUOUS SOUTHEAST FLOW AND ASSOCIATED
FRONTS IMPACTING THE GULF COAST. IT COULD ALSO BRING THE BEST
CHANCE FOR SOME WIDESPREAD SUNSHINE ACROSS MUCH OF THE SOUTHERN
MAINLAND. BY THE MIDDLE OF THE WEEK THOUGH...MODELS BEGIN TO
DIVERGE ON TWO SIGNIFICANT ISSUES. THE FIRST IS HOW MUCH ENERGY
PUSHES INTO THE RIDGE OVER SE ALASKA AND THE SECOND IS WHAT
STRUCTURE THE LOW APPROACHING FROM THE ALEUTIANS TAKES ON. IF
ENOUGH ENERGY PUSHES INTO THE RIDGE...IT WILL SIMPLY GIVE WAY AND
MOVE EAST. BUT IF SOME WARM AIR ADVECTED INTO IT CAUSING IT TO
BUILD...THE ENERGY MIGHT JUST RIDE UP ITS WESTERN FLANK STRAIGHT
INTO SOUTHERN AK. THE STRUCTURE OF THE LOW VARIES FROM THE GFS
DEPICTION OF A VERTICALLY STACKED LOW TRACKING SLOWLY EAST TO THE
EC SHOWING IT MORE PROGRESSIVE WITH A NEW TRIPLE-POINT LOW FORMING
OVER THE SOUTHERN GULF BY NEXT WEEKEND. THIS FORECAST PACKAGE
LEANED TOWARDS KEEPING THE HIGHEST POPS ALONG COASTAL LOCATIONS AT
THIS TIME. TEMPERATURES LOOK TO REMAINS NORMAL TO ABOVE NORMAL AS
WE START MAY. THIS COULD LEAD TO SOME WEAK INSTABILITY...SO WE
WILL BE WATCHING CHANCES FOR CONVECTION.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING 119 120 130 131.
 GALE WARNING 125 132 136 137 138 139 150.

&&

$$

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





000
FXAK68 PAFC 291505 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
455 AM AKDT FRI APR 29 2016

.ANALYSIS AND UPPER LEVELS...
THE NORTHERN PACIFIC AND ALASKA REMAINS IN A BROAD LONGWAVE TROUGH
WITH A BROAD CLOSED UPPER LOW CENTERED OVER THE WESTERN ALASKA
PENINSULA WITH SHORTWAVE RIDGES OVER THE NORTHWESTERN PACIFIC TO
THE WEST AND OVER WESTERN CANADA TO THE EAST. MULTIPLE SHORTWAVES
CAN BE SEEN IN SATELLITE IMAGERY ROTATING THROUGH THE REGION
AROUND THE LOW. THE POLAR JET REMAINS SOUTH OF THE FORECAST AREA
BUT HAS BECOME MORE MERIDIONAL OVER THE LAST 24 HOURS AS A
SHORTWAVE /CURRENTLY AROUND 170W/ IN THE BROAD TROUGH DEEPENS AS
IT PROGRESSES EASTWARD. THE BRANCH OF THE POLAR JET JUST EAST OF
THIS SHORTWAVE HAS A MAXIMUM SPEED OF 130-140 KT...THUS PROVIDING
SOME SUPPORT TO THE CLOSED CYCLONE THAT IS DEVELOPING WITHIN THIS
SHORTWAVE.

AT THE SURFACE...A BROAD 995 MB LOW IS CENTERED UNDER THE CLOSED
LOW OVER THE WESTERN ALASKA PENINSULA AND IS SLOWLY DISSIPATING. A
980MB LOW IS RAPIDLY DEVELOPING AROUND 44N 167W UNDER THE
SHORTWAVE TROUGH MENTIONED ABOVE. THE REMNANTS OF THE OCCLUDED
FRONT THAT WAS ASSOCIATED WITH A WEAK LOW NEAR KODIAK ISLAND IS
MOVING ON SHORE THROUGH SOUTHERN ALASKA...PRODUCING SHOWERS ALONG
MOST OF THE GULF COAST WESTWARD INTO THE BRISTOL BAY REGION AND
THROUGH THE SOUTHERN SUSITNA VALLEY.

&&

.MODEL DISCUSSION...
THE QUARTET OF MODELS AT 00Z ALL INITIALIZED FAIRLY WELL WITH ONLY
MINOR ISSUES AROUND THE RAPIDLY DEVELOPING LOW NEAR 44N 167W AND THE
POTENTIAL ASSOCIATED DOWNSTREAM IMPACTS TOWARD SOUTHCENTRAL THIS
WEEKEND (MENTIONED IN THE SOUTHCENTRAL SHORT TERM FORECAST).
OTHERWISE...ALL MODELS THROUGH DAY 3 ARE IN REASONABLE AGREEMENT
WITH THE PLACEMENT AND MOVEMENT OF THE MAJOR FEATURES. THIS FORECAST
PACKAGE LEANS TOWARDS THE GFS FOR THE MAJOR SYNOPTIC FEATURES WITH
SOME USE OF THE NAM ON THE EASTERN DOMAIN FOR DETAIL.

&&

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

THE MAIN FOCUS IN THE SHORT TERM FORECAST THROUGH SATURDAY NIGHT
SURROUNDS THE STRONG FRONT MOVING UP FROM THE NORTH PACIFIC TOWARD
KODIAK ISLAND THIS EVENING. NEARLY STEADY CONDITIONS WILL OCCUR
TODAY AHEAD OF THIS SYSTEM WITH SHOWERS ALONG THE GULF AND DRY
INLAND. SOUTHEASTERLY FLOW WILL BE STRONGER T0DAY AS A RIDGE
BUILDS ACROSS SOUTHCENTRAL WHILE LOW PRESSURE MOVES CLOSER TO THE
SOUTHERN GULF. THE ANTICIPATED FRONT PUSHES INTO THE SOUTHERN
WATERS THIS EVENING WITH THE SURFACE LOW GAINING MOMENTUM
OVERNIGHT. WIDESPREAD GALE TO STORM STRENGTH WINDS INCREASE
QUICKLY SPREADING TO THE NORTHERN GULF BY EARLY SATURDAY MORNING.
THE KENAI PENINSULA WILL SEE CONDITIONS DIMINISH OVERNIGHT WITH
THE HEAVIEST RAIN ALONG THE EASTERN KENAI INITIALLY...THEN HEAVIER
AMOUNTS SPREADING INTO PRINCE WILLIAM SOUND AND THE NORTHEAST GULF
FOR SATURDAY. FORECAST WINDS AND PRECIPITATION SHOULD BE MONITORED
FOR UPDATES THROUGH THIS WEEKEND DUE TO UNCERTAINTY ON THE TRACK
OF THIS SYSTEM. THE MAIN CHALLENGES WITH A DIFFERENT TRACK COULD
BRING STRONGER WINDS THROUGH EAST TO WEST GAPS AND GREATER CHANCES
FOR PRECIPITATION FOR THE COPPER RIVER VALLEY ON SATURDAY.

&&

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

THE WEAK FRONTAL SYSTEM CURRENTLY STRETCHED ACROSS THE BRISTOL BAY
AREA WILL CONTINUE TO FALL APART WITH SHOWERS BECOMING MORE
SCATTERED IN COVERAGE OVERNIGHT. THE NEXT TROUGH WILL ROTATE
THROUGH ON FRIDAY BRINGING MORE NUMEROUS SHOWERS TO THE BRISTOL
BAY AREA IN THE MORNING AND THE KUSKOKWIM VALLEY AND DELTA IN THE
AFTERNOON. SHOWERS WILL TAPER BACK OFF FRIDAY NIGHT AND SATURDAY AS
A STRONGER FRONT MOVES INTO THE SOUTHWEST GULF AND INCREASES DRIER
NORTHEASTERLY FLOW OVER SOUTHWEST ALASKA.

&&

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

BROAD CYCLONIC FLOW OVER THE BERING WILL CONTINUE AS ANOTHER NORTH
PACIFIC LOW TRACKS TOWARD THE EASTERN ALEUTIANS LATE THIS AFTERNOON.
THE ASSOCIATED GALE FORCE FRONT WILL BRING STEADY RAIN TO THIS AREA
AND SHOWERS TO THE CENTRAL ALEUTIANS...WITH MUCH DRIER NORTHERLY
FLOW OVER THE REMAINDER OF THE BERING AND ALEUTIANS. HIGH PRESSURE
BUILDS OVER THE CENTRAL BERING SATURDAY WITH A WEAKENING FRONT
MOVING INTO THE WESTERN ALEUTIANS AND BERING SATURDAY NIGHT AND
SUNDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN UPPER LEVEL CLOSED LOW AT 500 MB WILL TRACK NEAR KODIAK BY
SATURDAY WITH AN ASSOCIATED SHORTWAVE DIGGING INTO THE BASE OF THE
LONGWAVE TROUGH. THIS FEATURE WILL RESULT IN THE STRONG SOUTHERLY
JET STREAM IN THE GULF BEFORE TRANSITIONING TO A MORE
SOUTHEASTERLY FLOW. THIS RESULTS IN AN NEGATIVELY TILTED AMPLIFIED
RIDGE OVER THE YUKON TERRITORY EXTENDING INTO THE ALASKA RANGE AND
CENTRAL INTERIOR. THEREFORE...SEVERAL SHORTWAVES WILL MOVE THROUGH
THE SOUTHCENTRAL AND THE GULF THROUGH TUESDAY. THIS SYNOPTIC
PATTERN WILL BRING PLENTY OF MOISTURE AND HEAVY RAIN AT TIMES TO
THE NORTHERN AND WESTERN COASTAL COMMUNITIES THROUGH THE WEDNESDAY.
WHILE THE BERING AND THE ALEUTIANS WILL START OUT WITH A SHOWERY
REGIME WITH NORTHERLY TO NORTHEASTERLY FLOW THIS WEEKEND. A GALE
FORCE LOW WILL DROP DOWN OFF THE KAMCHATKA PENINSULA BY SATURDAY
WITH AN ASSOCIATED WEATHER FRONT MOVING THROUGH THE WESTERN
ALEUTIANS BY SATURDAY EVENING. THIS LOW PRESSURE SYSTEM WILL THEN
TRACK ALONG THE CHAIN HEADING THROUGH THE MIDWEEK. THIS WILL BRING
A SWATH OF STRATUS WITH RAIN AND GUSTY SOUTHEASTERLY WINDS AS THE
FRONT MOVES THROUGH THE WESTERN ALEUTIANS THIS WEEKEND. AS THIS
SYSTEM MOVES ALONG THE CHAIN THIS WILL PRODUCE A SHOWERY WEATHER
REGIME ON THE BACKSIDE OF THE LOW PRESSURE. THE WESTERN BERING AND
THE ALEUTIANS WILL TRANSITION TO NORTHEASTERLY FLOW AS THE LOW
PRESSURE SYSTEM MOVES EAST HEADING INTO THE MIDWEEK TIME FRAME.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 119 131
         GALE 120 125 130 132 136 137 138 139 150 351 352

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RLF
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA/LIW
LONG TERM...PD





000
FXAK68 PAFC 291300 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
455 AM AKDT FRI APR 29 2016

.ANALYSIS AND UPPER LEVELS...
THE NORTHERN PACIFIC AND ALASKA REMAINS IN A BROAD LONGWAVE TROUGH
WITH A BROAD CLOSED UPPER LOW CENTERED OVER THE WESTERN ALASKA
PENINSULA WITH SHORTWAVE RIDGES OVER THE NORTHWESTERN PACIFIC TO
THE WEST AND OVER WESTERN CANADA TO THE EAST. MULTIPLE SHORTWAVES
CAN BE SEEN IN SATELLITE IMAGERY ROTATING THROUGH THE REGION
AROUND THE LOW. THE POLAR JET REMAINS SOUTH OF THE FORECAST AREA
BUT HAS BECOME MORE MERIDIONAL OVER THE LAST 24 HOURS AS A
SHORTWAVE /CURRENTLY AROUND 170W/ IN THE BROAD TROUGH DEEPENS AS
IT PROGRESSES EASTWARD. THE BRANCH OF THE POLAR JET JUST EAST OF
THIS SHORTWAVE HAS A MAXIMUM SPEED OF 130-140 KT...THUS PROVIDING
SOME SUPPORT TO THE CLOSED CYCLONE THAT IS DEVELOPING WITHIN THIS
SHORTWAVE.

AT THE SURFACE...A BROAD 995 MB LOW IS CENTERED UNDER THE CLOSED
LOW OVER THE WESTERN ALASKA PENINSULA AND IS SLOWLY DISSIPATING. A
980MB LOW IS RAPIDLY DEVELOPING AROUND 44N 167W UNDER THE
SHORTWAVE TROUGH MENTIONED ABOVE. THE REMNANTS OF THE OCCLUDED
FRONT THAT WAS ASSOCIATED WITH A WEAK LOW NEAR KODIAK ISLAND IS
MOVING ON SHORE THROUGH SOUTHERN ALASKA...PRODUCING SHOWERS ALONG
MOST OF THE GULF COAST WESTWARD INTO THE BRISTOL BAY REGION AND
THROUGH THE SOUTHERN SUSITNA VALLEY.

&&

.MODEL DISCUSSION...
THE QUARTET OF MODELS AT 00Z ALL INITIALIZED FAIRLY WELL WITH
ONLY MINOR ISSUES AROUND THE RAPIDLY DEVELOPING LOW NEAR 44N 167W.
NONE OF THESE DETAILS SIGNIFICANTLY IMPACT THE FORECAST...AND ALL
MODELS THROUGH DAY 3 ARE IN REASONABLE AGREEMENT WITH THE
PLACEMENT AND MOVEMENT THE MAJOR FEATURES. THIS FORECAST PACKAGE
LEANS TOWARDS THE GFS FOR THE MAJOR SYNOPTIC FEATURES WITH SOME
USE OF THE NAM ON THE EASTERN DOMAIN FOR DETAIL.

&&

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

THE MAIN FOCUS IN THE SHORT TERM FORECAST THROUGH SATURDAY NIGHT
SURROUNDS THE STRONG FRONT MOVING UP FROM THE NORTH PACIFIC TOWARD
KODIAK ISLAND THIS EVENING. NEARLY STEADY CONDITIONS WILL OCCUR
TODAY AHEAD OF THIS SYSTEM WITH SHOWERS ALONG THE GULF AND DRY
INLAND. SOUTHEASTERLY FLOW WILL BE STRONGER T0DAY AS A RIDGE
BUILDS ACROSS SOUTHCENTRAL WHILE LOW PRESSURE MOVES CLOSER TO THE
SOUTHERN GULF. THE ANTICIPATED FRONT PUSHES INTO THE SOUTHERN
WATERS THIS EVENING WITH THE SURFACE LOW GAINING MOMENTUM
OVERNIGHT. WIDESPREAD GALE TO STORM STRENGTH WINDS INCREASE
QUICKLY SPREADING TO THE NORTHERN GULF BY EARLY SATURDAY MORNING.
THE KENAI PENINSULA WILL SEE CONDITIONS DIMINISH OVERNIGHT WITH
THE HEAVIEST RAIN ALONG THE EASTERN KENAI INITIALLY...THEN HEAVIER
AMOUNTS SPREADING INTO PRINCE WILLIAM SOUND AND THE NORTHEAST GULF
FOR SATURDAY. FORECAST WINDS AND PRECIPITATION SHOULD BE MONITORED
FOR UPDATES THROUGH THIS WEEKEND DUE TO UNCERTAINTY ON THE TRACK
OF THIS SYSTEM. THE MAIN CHALLENGES WITH A DIFFERENT TRACK COULD
BRING STRONGER WINDS THROUGH EAST TO WEST GAPS AND GREATER CHANCES
FOR PRECIPITATION FOR THE COPPER RIVER VALLEY ON SATURDAY.

&&

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

THE WEAK FRONTAL SYSTEM CURRENTLY STRETCHED ACROSS THE BRISTOL BAY
AREA WILL CONTINUE TO FALL APART WITH SHOWERS BECOMING MORE
SCATTERED IN COVERAGE OVERNIGHT. THE NEXT TROUGH WILL ROTATE
THROUGH ON FRIDAY BRINGING MORE NUMEROUS SHOWERS TO THE BRISTOL
BAY AREA IN THE MORNING AND THE KUSKOKWIM VALLEY AND DELTA IN THE
AFTERNOON. SHOWERS WILL TAPER BACK OFF FRIDAY NIGHT AND SATURDAY AS
A STRONGER FRONT MOVES INTO THE SOUTHWEST GULF AND INCREASES DRIER
NORTHEASTERLY FLOW OVER SOUTHWEST ALASKA.

&&

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

BROAD CYCLONIC FLOW OVER THE BERING WILL CONTINUE AS ANOTHER NORTH
PACIFIC LOW TRACKS TOWARD THE EASTERN ALEUTIANS LATE THIS AFTERNOON.
THE ASSOCIATED GALE FORCE FRONT WILL BRING STEADY RAIN TO THIS AREA
AND SHOWERS TO THE CENTRAL ALEUTIANS...WITH MUCH DRIER NORTHERLY
FLOW OVER THE REMAINDER OF THE BERING AND ALEUTIANS. HIGH PRESSURE
BUILDS OVER THE CENTRAL BERING SATURDAY WITH A WEAKENING FRONT
MOVING INTO THE WESTERN ALEUTIANS AND BERING SATURDAY NIGHT AND
SUNDAY.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN UPPER LEVEL CLOSED LOW AT 500 MB WILL TRACK NEAR KODIAK BY
SATURDAY WITH AN ASSOCIATED SHORTWAVE DIGGING INTO THE BASE OF THE
LONGWAVE TROUGH. THIS FEATURE WILL RESULT IN THE STRONG SOUTHERLY
JET STREAM IN THE GULF BEFORE TRANSITIONING TO A MORE
SOUTHEASTERLY FLOW. THIS RESULTS IN AN NEGATIVELY TILTED AMPLIFIED
RIDGE OVER THE YUKON TERRITORY EXTENDING INTO THE ALASKA RANGE AND
CENTRAL INTERIOR. THEREFORE...SEVERAL SHORTWAVES WILL MOVE THROUGH
THE SOUTHCENTRAL AND THE GULF THROUGH TUESDAY. THIS SYNOPTIC
PATTERN WILL BRING PLENTY OF MOISTURE AND HEAVY RAIN AT TIMES TO
THE NORTHERN AND WESTERN COASTAL COMMUNITIES THROUGH THE WEDNESDAY.
WHILE THE BERING AND THE ALEUTIANS WILL START OUT WITH A SHOWERY
REGIME WITH NORTHERLY TO NORTHEASTERLY FLOW THIS WEEKEND. A GALE
FORCE LOW WILL DROP DOWN OFF THE KAMCHATKA PENINSULA BY SATURDAY
WITH AN ASSOCIATED WEATHER FRONT MOVING THROUGH THE WESTERN
ALEUTIANS BY SATURDAY EVENING. THIS LOW PRESSURE SYSTEM WILL THEN
TRACK ALONG THE CHAIN HEADING THROUGH THE MIDWEEK. THIS WILL BRING
A SWATH OF STRATUS WITH RAIN AND GUSTY SOUTHEASTERLY WINDS AS THE
FRONT MOVES THROUGH THE WESTERN ALEUTIANS THIS WEEKEND. AS THIS
SYSTEM MOVES ALONG THE CHAIN THIS WILL PRODUCE A SHOWERY WEATHER
REGIME ON THE BACKSIDE OF THE LOW PRESSURE. THE WESTERN BERING AND
THE ALEUTIANS WILL TRANSITION TO NORTHEASTERLY FLOW AS THE LOW
PRESSURE SYSTEM MOVES EAST HEADING INTO THE MIDWEEK TIME FRAME.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 119 131
         GALE 120 125 130 132 136 137 138 139 150 351 352

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RLF
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA/LIW
LONG TERM...PD





000
FXAK68 PAFC 291255
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
455 AM AKDT FRI APR 29 2016

.ANALYSIS AND UPPER LEVELS...
THE NORTHERN PACIFIC AND ALASKA REMAINS IN A BROAD LONGWAVE TROUGH
WITH A BROAD CLOSED UPPER LOW CENTERED OVER THE WESTERN ALASKA
PENINSULA WITH SHORTWAVE RIDGES OVER THE NORTHWESTERN PACIFIC TO
THE WEST AND OVER WESTERN CANADA TO THE EAST. MULTIPLE SHORTWAVES
CAN BE SEEN IN SATELLITE IMAGERY ROTATING THROUGH THE REGION
AROUND THE LOW. THE POLAR JET REMAINS SOUTH OF THE FORECAST AREA
BUT HAS BECOME MORE MERIDIONAL OVER THE LAST 24 HOURS AS A
SHORTWAVE /CURRENTLY AROUND 170W/ IN THE BROAD TROUGH DEEPENS AS
IT PROGRESSES EASTWARD. THE BRANCH OF THE POLAR JET JUST EAST OF
THIS SHORTWAVE HAS A MAXIMUM SPEED OF 130-140 KT...THUS PROVIDING
SOME SUPPORT TO THE CLOSED CYCLONE THAT IS DEVELOPING WITHIN THIS
SHORTWAVE.

AT THE SURFACE...A BROAD 995 MB LOW IS CENTERED UNDER THE CLOSED
LOW OVER THE WESTERN ALASKA PENINSULA AND IS SLOWLY DISSIPATING. A
980MB LOW IS RAPIDLY DEVELOPING AROUND 44N 167W UNDER THE
SHORTWAVE TROUGH MENTIONED ABOVE. THE REMNANTS OF THE OCCLUDED
FRONT THAT WAS ASSOCIATED WITH A WEAK LOW NEAR KODIAK ISLAND IS
MOVING ON SHORE THROUGH SOUTHERN ALASKA...PRODUCING SHOWERS ALONG
MOST OF THE GULF COAST WESTWARD INTO THE BRISTOL BAY REGION AND
THROUGH THE SOUTHERN SUSITNA VALLEY.

&&

.MODEL DISCUSSION...
THE QUARTET OF MODELS AT 00Z ALL INITIALIZED FAIRLY WELL WITH
ONLY MINOR ISSUES AROUND THE RAPIDLY DEVELOPING LOW NEAR 44N 167W.
NONE OF THESE DETAILS SIGNIFICANTLY IMPACT THE FORECAST...AND ALL
MODELS THROUGH DAY 3 ARE IN REASONABLE AGREEMENT WITH THE
PLACEMENT AND MOVEMENT THE MAJOR FEATURES. THIS FORECAST PACKAGE
LEANS TOWARDS THE GFS FOR THE MAJOR SYNOPTIC FEATURES WITH SOME
USE OF THE NAM ON THE EASTERN DOMAIN FOR DETAIL.

&&

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

THE MAIN FOCUS IN THE SHORT TERM FORECAST THROUGH SATURDAY NIGHT
SURROUNDS THE STRONG FRONT MOVING UP FROM THE NORTH PACIFIC TOWARD
KODIAK ISLAND THIS EVENING. NEARLY STEADY CONDITIONS WILL OCCUR
TODAY AHEAD OF THIS SYSTEM WITH SHOWERS ALONG THE GULF AND DRY
INLAND. SOUTHEASTERLY FLOW WILL BE STRONGER T0DAY AS A RIDGE
BUILDS ACROSS SOUTHCENTRAL WHILE LOW PRESSURE MOVES CLOSER TO THE
SOUTHERN GULF. THE ANTICIPATED FRONT PUSHES INTO THE SOUTHERN
WATERS THIS EVENING WITH THE SURFACE LOW GAINING MOMENTUM
OVERNIGHT. WIDESPREAD GALE TO STORM STRENGTH WINDS INCREASE
QUICKLY SPREADING TO THE NORTHERN GULF BY EARLY SATURDAY MORNING.
THE KENAI PENINSULA WILL SEE CONDITIONS DIMINISH OVERNIGHT WITH
THE HEAVIEST RAIN ALONG THE EASTERN KENAI INITIALLY...THEN HEAVIER
AMOUNTS SPREADING INTO PRINCE WILLIAM SOUND AND THE NORTHEAST GULF
FOR SATURDAY. FORECAST WINDS AND PRECIPITATION SHOULD BE MONITORED
FOR UPDATES THROUGH THIS WEEKEND DUE TO UNCERTAINTY ON THE TRACK
OF THIS SYSTEM. THE MAIN CHALLENGES WITH A DIFFERENT TRACK COULD
BRING STRONGER WINDS THROUGH EAST TO WEST GAPS AND GREATER CHANCES
FOR PRECIPITATION FOR THE COPPER RIVER VALLEY ON SATURDAY.

&&

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

THE WEAK FRONTAL SYSTEM CURRENTLY STRETCHED ACROSS THE BRISTOL BAY
AREA WILL CONTINUE TO FALL APART WITH SHOWERS BECOMING MORE
SCATTERED IN COVERAGE OVERNIGHT. THE NEXT TROUGH WILL ROTATE
THROUGH ON FRIDAY BRINGING MORE NUMEROUS SHOWERS TO THE BRISTOL
BAY AREA IN THE MORNING AND THE KUSKOKWIM VALLEY AND DELTA IN THE
AFTERNOON. SHOWERS WILL TAPER BACK OFF FRIDAY NIGHT AND SATURDAY AS
A STRONGER FRONT MOVES INTO THE SOUTHWEST GULF AND INCREASES DRIER
NORTHEASTERLY FLOW OVER SOUTHWEST ALASKA.

&&

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

THE LOW CENTERED JUST SOUTH OF THE THE EASTERN ALEUTIANS WILL
CONTINUE TO WEAKEN AS IT TRACKS SLOWLY EAST TONIGHT THEN
DISSIPATES SOUTH OF COLD BAY FRIDAY MORNING. THE MEAN LARGER SCALE
UPPER LEVEL LOW CENTER WILL REMAIN IN THIS GENERAL AREA AS A
DEVELOPING LOW FROM THE NORTH PACIFIC TRACKS INTO THE SOUTHWESTERN
GULF FRIDAY NIGHT AND SATURDAY. UPPER LEVEL RIDGING WILL BUILD
INTO THE WESTERN ALEUTIAN FRIDAY THEN SHIFT EAST OVER THE CENTRAL
ALEUTIANS AND BERING ON SATURDAY AS THE NEXT INCOMING FRONTAL
SYSTEM APPROACHES THE WESTERN ALEUTIANS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
AN UPPER LEVEL CLOSED LOW AT 500 MB WILL TRACK NEAR KODIAK BY
SATURDAY WITH AN ASSOCIATED SHORTWAVE DIGGING INTO THE BASE OF THE
LONGWAVE TROUGH. THIS FEATURE WILL RESULT IN THE STRONG SOUTHERLY
JET STREAM IN THE GULF BEFORE TRANSITIONING TO A MORE
SOUTHEASTERLY FLOW. THIS RESULTS IN AN NEGATIVELY TILTED AMPLIFIED
RIDGE OVER THE YUKON TERRITORY EXTENDING INTO THE ALASKA RANGE AND
CENTRAL INTERIOR. THEREFORE...SEVERAL SHORTWAVES WILL MOVE THROUGH
THE SOUTHCENTRAL AND THE GULF THROUGH TUESDAY. THIS SYNOPTIC
PATTERN WILL BRING PLENTY OF MOISTURE AND HEAVY RAIN AT TIMES TO
THE NORTHERN AND WESTERN COASTAL COMMUNITIES THROUGH THE WEDNESDAY.
WHILE THE BERING AND THE ALEUTIANS WILL START OUT WITH A SHOWERY
REGIME WITH NORTHERLY TO NORTHEASTERLY FLOW THIS WEEKEND. A GALE
FORCE LOW WILL DROP DOWN OFF THE KAMCHATKA PENINSULA BY SATURDAY
WITH AN ASSOCIATED WEATHER FRONT MOVING THROUGH THE WESTERN
ALEUTIANS BY SATURDAY EVENING. THIS LOW PRESSURE SYSTEM WILL THEN
TRACK ALONG THE CHAIN HEADING THROUGH THE MIDWEEK. THIS WILL BRING
A SWATH OF STRATUS WITH RAIN AND GUSTY SOUTHEASTERLY WINDS AS THE
FRONT MOVES THROUGH THE WESTERN ALEUTIANS THIS WEEKEND. AS THIS
SYSTEM MOVES ALONG THE CHAIN THIS WILL PRODUCE A SHOWERY WEATHER
REGIME ON THE BACKSIDE OF THE LOW PRESSURE. THE WESTERN BERING AND
THE ALEUTIANS WILL TRANSITION TO NORTHEASTERLY FLOW AS THE LOW
PRESSURE SYSTEM MOVES EAST HEADING INTO THE MIDWEEK TIMEFRAME.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 119 131
         GALE 120 125 130 132 136 137 138 139 150 351 352

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RLF
SOUTHCENTRAL ALASKA...KH
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...JA/LIW
LONG TERM...PD





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