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000
FXAK68 PAFC 021239
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
439 AM AKDT MON MAY 2 2016

.ANALYSIS AND UPPER LEVELS...
THE SYNOPTIC PATTERN OVER THE NORTHERN PACIFIC AND ALASKA HAS
BECOME SLIGHTLY MORE ZONAL THAN THIS TIME YESTERDAY WITH THE
MERIDIONAL LONGWAVE TROUGH PREVIOUSLY ALONG 150W STARTING TO
BECOME MORE NEGATIVELY TILTED AND NOW ROUGHLY CENTERED ALONG 140W.
THE HIGH AMPLITUDE RIDGE REMAINS IN PLACE OVER THE WEST NORTH
AMERICAN COAST. FURTHER WEST...THE RIDGE HAS FLATTED OUT SOMEWHAT
AS IT PROGRESSES WEST WITH A RIDGE AXIS ROUGHLY ALONG 170W. OVER
THE WESTERN PACIFIC...A DEEP POSITIVELY TILTED TROUGH IS STARING
TO PROGRESS EASTWARD WITH A CLOSED LOW MOVING INTO THE SOUTHWEST
BERING THIS MORNING. THE POLEWARD LIMB OF THE POLAR JET IS PEAKING
AT ABOUT 100KT THIS MORNING AS IT MOVES INTO SOUTHEASTERN ALASKA.
THE MAIN BRANCH OF THE POLAR JET IS CENTERED SOUTH OF THE ALEUTIAN
CHAIN WITH A 140KT JET STARTING TO ROUND THE TOP OF THE RIDGE
AXIS.

FOR MAINLAND ALASKA...THE DOMINATE WEATHER FEATURE AT THE SURFACE
IS THE STILL WEAKENING 1000 MB LOW NEAR KODIAK ISLAND WITH THE
REMAINS OF THE ASSOCIATED SURFACE FRONT SLOWLY DISSIPATING OVER
SOUTHERN ALASKA THIS MORNING. MULTIPLE WEAK MESO-LOWS CAN BE
IDENTIFIED IN SURFACE OBSERVATIONS OVER SOUTHWEST ALASKA...MAINLY
OVER THE KUSKOKWIM DELTA AND NEAR THE KING SALMON AREA. THE WEAK
SURFACE RIDGE ALONG 165W IS BEING SHUNTED SOUTHEASTWARD OUT OF THE
AREA AS THE FRONT ASSOCIATED WITH THE 994 MB LOW NEAR SHEMYA MOVES
THROUGH THE CENTRAL ALEUTIANS AND INTO THE BERING SEA.

&&

.MODEL DISCUSSION...
THE 00Z RUNS OF THE MAIN GLOBAL MODELS INITIALIZED REASONABLY WELL
WITH FEW SIGNIFICANT ISSUES. MODELS ARE IN GOOD GENERAL AGREEMENT
THROUGH THE SHORT-TERM WITH MOST OF THE SYNOPTIC FEATURES ALOFT.
STARTING TUESDAY MORNING THEY BEGIN TO DEVIATE SOME FROM EACH
OTHER WITH THE PLACEMENT AND STRENGTH OF THE DECAYING LOW NEAR
THE ALASKA PENINSULA AS WELL AS THE DEVELOPMENT OF A NEW LOW
AROUND 43N 173W. THE GFS WAS SELECTED AS THE PRIMARY GUIDANCE FOR
THE WESTERN FORECAST DOMAIN THROUGH THE SHORT TERM WITH THE NAM
BEING USED FOR THE HIGHER RESOLUTION OVER THE EASTERN DOMAIN.

&&

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

A MODERATE-STRENGTH UPPER LEVEL DISTURBANCE OVER THE NORTHERN GULF
WILL MOVE INLAND OVER THE COPPER RIVER BASIN TODAY. DESPITE THE
FACT THAT TEMPERATURES ACROSS THE BASIN DROPPED TO NEAR OR BELOW
FREEZING OVERNIGHT BEFORE CLOUDS INCREASED...ENOUGH WARMING SHOULD
TAKE PLACE TO RESULT IN MAINLY LIGHT RAIN...THOUGH SOME LIGHT SNOW
CAN NOT BE RULED OUT ACROSS PARTS OF THE BASIN TODAY OR
TONIGHT...ESPECIALLY TO THE SOUTH TOWARD THOMPSON PASS.
THUNDERSTORMS ARE NO LONGER EXPECTED IN THE EASTERN BASIN AS
MODELS HAVE DEPICTED A MORE STABLE REGIME TODAY.

THE OTHER AREA OF CONCERN TODAY IS THE RAPIDLY BUILDING RIDGING
EXPECTED ALONG THE NORTH GULF COAST FROM EAST TO WEST THIS
AFTERNOON AND EVENING. THIS WILL ALLOW FOR EAST TO SOUTHEAST GAP
WINDS THROUGH PORTAGE VALLEY AND TURNAGAIN ARM TO INCREASE THIS
AFTERNOON AND PERSIST WELL INTO THE OVERNIGHT TONIGHT.

RAINFALL OVER THE NEXT COUPLE OF DAYS WILL BE HEAVIEST OVER THE
WESTERN PRINCE WILLIAM SOUND REGION WITH PERSISTENT SOUTHEASTERLY
FLOW...AS HAS BEEN THE CASE FOR THE LAST SEVERAL MONTHS. ISOLATED
TO SCATTERED LIGHT RAIN SHOWERS OR SPRINKLES WILL OCCASIONALLY
MAKE IT ACROSS THE CHUGACH RANGE THE NEXT FEW DAYS IN AN
OTHERWISE UNUSUALLY CLOUDY SPRING WEATHER PATTERN...BUT THESE
CLOUDS WILL NOT BRING THE WETTING RAINS WE NEED TO NEGATE THE
INCREASING WILDFIRE RISK.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)...
THE DIURNAL INSTABILITY SHOWERS COMBINED WITH THE THERMAL TROUGH
WILL ENHANCE THE CHANCES FOR ISOLATED THUNDERSTORMS FOR THE
SOUTHWEST REGION THE NEXT SEVERAL AFTERNOON AND EVENINGS. THIS
WILL INCLUDE THE BRISTOL BAY EXTENDING NORTHWARD INTO THE LOWER
KUSKOKWIM VALLEY THROUGH MONDAY BEFORE SPREADING INTO THE
KUSKOKWIM DELTA BY TUESDAY HEADING INTO WEDNESDAY. THIS MOVEMENT
WILL COINCIDE WITH THE THERMAL TROUGH GRADUALLY SHIFTING WESTWARD
INTO THE KUSKOKWIM DELTA BY TUESDAY. BY WEDNESDAY MORNING AN UPPER
LEVEL SHORTWAVE WILL ROTATE THROUGH THE BRISTOL BAY REGION. THIS
WILL RESULT IN INCREASED MOISTURE WITH WIDESPREAD SHOWERS THROUGH
THE REGION. THE OTHER ISSUE WILL BE THE SWATH OF STRATUS AND AREAS
OF FOG ALONG THE SOUTHWEST COASTLINE WITH SOME LOCALIZED AREAS OF
DENSE FOG THIS MORNING BEFORE DISSIPATING BY THE LATE MORNING
HOURS. THIS SAME FOG PATTERN WILL REFORM BY LATE TUESDAY EVENING
THROUGH THE EARLY WEDNESDAY MORNING HOURS.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3)...
THE WESTERN ALEUTIANS WILL CONTINUE TO HAVE A WEAK LOW PRESSURE
SYSTEM THIS MORNING THAT WILL TRACK EASTWARD NEAR ADAK BY TUESDAY
AFTERNOON. THIS SYSTEM WILL BECOME ENLONGATED BEFORE PHASING IN
WITH A GALE FORCE NORTH PACIFIC LOW LOCATED FARTHER SOUTH IN THE
NORTH PACIFIC BY WEDNESDAY MORNING. THIS WILL RESULT IN A
NORTHERLY FLOW THROUGH THE BERING/ALEUTIAN CHAIN WITH A SHOWERY
WEATHER REGIME HEADING INTO THE MIDWEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...WED THROUGH SUN)...
THE EXTENDED PORTION HAS HINGED THE PAST FEW DAYS ON HOW STRONG
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. THAT 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 MORNING...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...RLF
SOUTHCENTRAL ALASKA...CC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...PD
LONG TERM...MO



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000
FXAK69 PAFG 021021
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
221 AM AKDT MON MAY 2 2016

.DISCUSSION...
MODELS IN DECENT AGREEMENT THROUGH 48 HOURS WITH UPPER LEVEL
FEATURES. LONG WAVE TROUGH OVER ALASKA WILL PERSIST THROUGH
AROUND THE MIDDLE PORTION OF THE WEEK AT LEAST. THE RIDGE OVER THE
WESTERN UNITED STATES WILL BEGIN TO PUSH WESTWARD FROM CANADA BY
LATE WED OR THU BUT APPEARS TO GET BEAT BACK AGAIN BY THE TROUGH
TOWARDS THE END OF THE WEEK.

SEVERAL SHORT WAVES WILL MOVE NORTHWARD FROM THE GULF OF ALASKA
THROUGH THE WEEK WHICH WILL ALSO UNDERCUT THE RIDGE OVER WESTERN
CANADA. STRONG VERTICALLY STACKED LOW IN THE WESTERN ALEUTIANS
WILL MOVE EASTWARD TOWARDS THE CENTRAL ALEUTIANS BY TUE
AFTERNOON. AFTER TUE THE MODELS DO NOT RESOLVE THE MOVEMENT TOO
WELL. THE NAM CONTINUES TO CARRY THE LOW EASTWARD TO ABOUT COLD
BAY LATE TUE NIGHT AND THEN WEAKENS IT. MEANWHILE THE GFS AND THE
ECMWF HANG THE LOW BACK AND ALSO CONTINUE TO WEAKEN IT.

COLDER TEMPERATURES WILL CONTINUE TO PERSIST ALONG THE ARCTIC
COAST AS THE LOWER LEVEL COLD AIR REMAINS STUCK THERE WITHOUT ANY
MECHANISM TO FORCE IT OUT.

THE NAM IS COMPLETELY DIFFERENT THAN THE OTHER MODELS IN TERMS OF
SURFACE REFLECTION. THE NEW MODEL RUN AT 06Z INDICATES WITH THE
NEW VERTICALLY STACKED UPPER AND SURFACE LOW MOVING NORTH NEAR THE
ALCAN BORDER THROUGH MON AFTERNOON...THAT THE PRECIP BAND WILL
STAY SOUTH OF THE MIDDLE TANANA VALLEY. WHEREAS THE OTHER MODELS
PAINT THE HIGHEST PRECIP OVER THE MIDDLE TANANA VALLEY. AT THIS
POINT WE ARE WEIGHTING OUR FORECAST MORE IN LINE WITH THE GFS AND
THE ECMWF. THE SHORTWAVE TROUGH WILL INTERACT WITH THE SURFACE
THERMAL TROUGH AND PRODUCE MODERATE RAINFALL OVER A PORTION OF
THE CENTRAL INTERIOR THROUGH TUE.

CONVECTIVE INDICES ARE THE BEST OVER THE WESTERN INTERIOR AND
NEAR THE WEST COAST TO EXTEND DOWN INTO THE Y-K DELTA. THIS WILL
LIKELY PERSIST THROUGH AT LEAST THE MIDDLE PORTION OF THE WEEK.
ALTHOUGH THUNDERSTORMS WILL BE OVER A WIDE AREA BUT LIKELY TO BE
SPARSELY POPULATED IN TERMS ANY LARGE CONCENTRATION.

&&

.FIRE WEATHER...
FOR THE NEXT COUPLE OF DAYS MOISTURE WILL MOVE INTO THE CENTRAL
INTERIOR AND KEEP RH VALUES HIGHER THAN ON PREVIOUS DAYS. THIS
ALONG WITH WEAKER SURFACE WINDS WILL KEEP THE POSSIBILITY OF ANY
RED FLAG CONDITIONS TO A MINIMUM AND ARE NOT LIKELY THROUGH AT
LEAST THE MIDDLE PART OF THE WEEK.

&&

.HYDROLOGY...
ALTHOUGH THE GFS MODEL IS INDICATING RAINFALL IN EXCESS OF 1 INCH
IN SEVERAL AREAS IN THE INTERIOR...THIS REMAINS TO BE SEEN IF IN
FACT THIS IS REALITY. WE ARE NOT BUYING INTO THAT AMOUNT OF
RAINFALL QUITE YET. THE POSSIBILITY FOR HEAVY DOWNPOURS IN
THUNDERSTORMS WILL EXIST THOUGH BUT THERE IS UPPER LEVEL WINDS
SUFFICIENT ENOUGH TO NOT ALLOW ANY CELLS TO REMAIN OVER ANY ONE
AREA TOO LONG.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

CF MAY 16



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000
FXAK67 PAJK 020030
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
430 PM AKDT SUN MAY 1 2016

.SHORT TERM...A FRONT ACROSS THE CENTRAL PANHANDLE SSW INTO THE SE
GULF WILL MOVE NWWD AND BACK INTO THE ERN GULF AS A SLOWLY
DEEPENING LOW PRESSURE WAVE MOVES N THRU THE ERN GULF TONIGHT. THE
FRONT WILL THEN PUSH BACK ONSHORE MON MORNING BUT STALL AGAIN OVER
THE FAR ERN INNER CHANNELS BY LATE AFTERNOON. USED BLEND OF THE
12Z GEM AND GFS THROUGH MON...MAINLY FOR WAY THEY HANDLED THE LOW
PRESSURE WAVE. ECMWF WAS ALSO USABLE. NAM APPEARED TOO FAST WITH
THE WAVE.

MAIN FORECAST CONCERNS WILL BE PRECIP POTENTIAL/AMOUNTS AND WINDS.
STEADIER RAIN IS CURRENTLY SPREADING INTO THE NRN AREA LATE THIS
AFTERNOON. RAIN WILL INCREASE IN INTENSITY THIS EVENING AS STRONG
LIFT ASSOCIATED WITH THE LOW PRESSURE WAVE OVERSPREADS THE AREA.
HOWEVER...THE FAR SERN AREA WILL LIKELY SEE THE PRECIP LIFT N OF
THEM BY LATE EVENING AS DRIER MID-LEVEL AIR WITH THE WARM SECTOR
MOVES IN. THE PAYA AREA SHOULD SEE THEIR SHOWERS BECOME A STEADIER
RAIN DURING THIS EVENING. AFTER THE FRONT PUSHED BACK
ONSHORE...PRECIP WILL TRANSITION TO SHOWERS WITH MAINLY SCATTERED
COVERAGE EXPECTED BEHIND THE FRONT. THE FAR ERN INNER CHANNELS
WILL STAY IN THE STEADIER RAIN ESPECIALLY ACROSS THE CENTRAL AREA
AS FRONT HANGS UP THERE AGAIN. THE RAINFALL INTENSITY SHOULD
DECREASE MON THOUGH AS STRONGER LIFT WITH THE LOW PRESSURE WAVE
WILL MOVE NE OF THE AREA BY LATE MORNING.

RAINFALL WILL BE LOCALLY HEAVY ESPECIALLY ACROSS THE CENTRAL AND
NRN AREAS TONIGHT. UP TO 2.5 INCHES OF RAIN IS POSSIBLE WITH
LOCALLY HIGHER AMOUNTS IN THE MTNS THROUGH 15Z MON. THERE MAY BE
AN ADDITIONAL 0.5 TO 1.5 INCHES MON WITH HIGHEST AMOUNTS OVER THE
ERN AREAS. SEE HYDROLOGY SECTION FOR IMPACTS ON AREA RIVERS.

STRONGEST WINDS WILL BE ON E SIDE OF THE LOW PRESSURE WAVE. GALE
FORCE S-SE WINDS WILL OCCUR OVER THE FAR ERN GULF TONIGHT WITH SCA
TO GALE FORCE WINDS OVER THE CENTRAL AND SRN INNER CHANNELS. WILL
ALSO HAVE STRONG WIND HEADLINE FOR THE EVENING HOURS IN PUBLIC
ZONE 27. ZONES 23 AND 28 COULD BE A CLOSE CALL AS WELL. THESE
WINDS WILL DECREASE AS LOW PRESSURE WAVE MOVES ONSHORE MON MORNING
AND FRONT MOVES INLAND. BY MON AFTERNOON...STRONGEST WINDS ARE
EXPECTED OVER NRN LYNN CANAL WHERE SCA LEVEL S WINDS WILL DEVELOP.
WHILE WINDS OVER THE GULF WILL DROP BELOW SCA MON...SEAS WILL
REMAIN RATHER HIGH SO SCA FOR SEAS WILL CONTINUE AFTER WINDS DROP
OFF. SOME OF THESE HIGHER SEAS WILL REACH OCEAN ENTRANCES OF THE
INNER CHANNELS AND MOST OF YAKUTAT BAY.

.LONG TERM...RAIN WILL LINGER OVER THE EASTERN HALF OF THE
PANHANDLE MONDAY NIGHT...NAMELY EAST OF CHATHAM STRAIT THEN
DIMINISH TO SCATTERED SHOWERS ALONG THE COASTAL MOUNTAINS TUESDAY.
WEST OF CHATHAM STRAIT/ADMIRALTY ISOLATED TUESDAY LOOKS TO BE THE
DRIEST DAY OF THE WEEK DUE TO A BROAD RIDGE OF HIGH PRESSURE OVER
THE EASTERN GULF. THIS WILL RESULT IN LIGHT WESTERLY WINDS OVER
THE AREA ANS SOME SUNNY BREAKS OVER THE NORTHERN INNER CHANNELS.
WEDNESDAY THERE MAY BE ISOLATED SHOWERS AROUND STILL BUT THESE
WILL DIMINISH OVERNIGHT AS ENERGY IS PULLED INTO THE NEXT SYSTEM
MOVING INTO THE GULF. THE RIDGE WILL SHIFT EAST OVER THE PANHANDLE
AND WINDS WILL TURN BACK TO A MORE SE DIRECTION BY THURS MORNING.

EXPECT RAIN ASSOC WITH THE NEXT SYSTEM TO ARRIVE THURS NIGHT
(EARLIER FOR YAKUTAT) AND MAKE FOR A WET DAY FRIDAY. MODELS DIFFER
SOME ON HOW THIS SYSTEM AND THE NEXT FOR SATURDAY MOVE THROUGH...BUT
THEY AGREE THAT IT WILL BE WET. THESE TWO SYSTEMS WILL LIKELY HAVE
SOME HEAVY RAIN AND WIND TO GALE FORCE OVER THE OUTSIDE WATERS AS
WELL.

USED AN ENSEMBLE APPROACH FOR FORECAST UPDATES TODAY WITH AN
EMPHASIS ON THE GFS22. FORECAST CONFIDENCE IS AVERAGE.

&&

.HYDROLOGY...THE LARGEST RISES ON RIVERS WILL LIKELY BE AROUND THE
JUNEAU AREA. LATEST FORECAST HAS BOTH JORDAN CREEK AND MONTANA
CREEKS RISING SIGNIFICANTLY BUT STAYING BELOW BANKFULL LEVELS.
THE TAKU RIVER SHOULD ALSO RISE QUITE A BIT...6 TO 7 FEET...BY
TUE MORNING...BUT IT SHOULD REMAIN WELL BELOW BANKFULL AS WELL.
STILL...PEOPLE SHOULD BE AWARE OF THE RISING WATERS AROUND THE
JUNEAU AREA TONIGHT AND MON. REST OF THE AREA WILL SEE LESSER
RISES...OR EVEN FALL SOME TONIGHT AND MON OVER THE S DUE TO PRECIP
DIMINISHING.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 10 PM AKDT THIS EVENING FOR AKZ027.
MARINE...GALE WARNING FOR PKZ036-041>043.
     SMALL CRAFT ADVISORY FOR PKZ012-021-022-031>035-052.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ051-053.
&&

$$

RWT/FERRIN

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU




000
FXAK69 PAFG 012342 CCA
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE FAIRBANKS AK
342 PM AKDT SUN MAY 1 2016

CORRECTED TYPO IN SURFACE PARAGRAPH

.DISCUSSION...

UPPER AIR...
A BROAD UPPER LEVEL TROUGH WITH A WEAK WIND FLOW PATTERN WILL
PERSIST OVER NORTHERN ALASKA THROUGH MONDAY NIGHT. WEAK RIDGING
WILL BEGIN TO BUILD OVER THE SOUTHERN INTERIOR TUESDAY...THEN
MOVE SLOWLY NORTHEASTWARD TO EXTEND ALONG THE BROOKS RANGE THEN
SOUTHEASTWARD INTO CANADA BY THURSDAY AFTERNOON. A VERY WEAK SHORT
WAVE TROUGH WILL MOVE NORTHWARD ACROSS THE EASTERN INTERIOR MONDAY
THROUGH MONDAY NIGHT AND EXIT NORTHEASTWARD OUT OF NORTHERN ALASKA
TUESDAY AFTERNOON.

SURFACE...
A THERMAL TROUGH EXTENDING ON A LINE 50 MILES EAST OF
ANIAK-50 MILES NORTH OF FAIRBANKS-50 MILES NORTH OF NORTHWAY
WILL REMAIN NEARLY STATIONARY THROUGH MONDAY...THEN MOVE
NORTHWARD TO A LINE 50 MILES NORTH OF GALENA-FORT YUKON AND
EASTWARD BY TUESDAY AFTERNOON. A 1000 MB LOW WILL DEVELOP 50
MILES EAST OF NORTHWAY MONDAY MORNING...THEN WEAKEN TO A 1003 MB
LOW NEAR INUVIK BY TUESDAY MORNING. A RIDGE ALONG THE EASTERN
NORTH GULF COAST WILL BECOME A BROAD BUT WEAK 1007 MB HIGH
CENTERED NEAR ANCHORAGE LATE TONIGHT WHICH WILL BREAK DOWN TUESDAY
MORNING WITH THE RIDGE BECOMING RE- ESTABLISHED ALONG THE NORTH
GULF COAST BY MONDAY AFTERNOON. THIS RIDGE WILL PERSIST THROUGH
WEDNESDAY WITH LITTLE MOVEMENT EXPECTED. THIS RIDGING SOUTH OF THE
ALASKA RANGE COMBINED WITH THE THERMAL TROUGH NORTH OF THE ALASKA
WILL MAINTAIN SOUTHERLY WINDS THROUGH THE PASSES IN DENALI AND THE
EASTERN ALASKA RANGE.

ALONG THE ARCTIC COAST...LIGHT MAINLY EAST TO NORTHEAST WINDS WILL
PERSIST THROUGH WEDNESDAY ALONG WITH LOW STRATUS AND AREAS OF
FLURRIES AND FOG.

ISOLATED AFTERNOON AND EARLY EVENING THUNDERSTORMS ARE EXPECTED
OVER THE NORTHERN AND WESTERN INTERIOR TODAY THROUGH WEDNESDAY...
GFS INDICATING SURFACE CAPES 100 TO 400+ J/KG AND SURFACE-500 MB
LIFTED INDEXES TO AROUND -2 IN THE PERSISTENT BAND OF INSTABILITY.
MORE WIDESPREAD STRATIFORM PRECIPITATION IS EXPECTED TO DEVELOP
OVER THE ALASKA RANGE AND MUCH OF THE EASTERN INTERIOR MONDAY
AFTERNOON AS A WEAK SHORT WAVE TROUGH MOVES NORTHWARD ACROSS THE
EASTERN INTERIOR. MAINLY STRATIFORM PRECIPITATION IS EXPECTED TO
PERSIST OVER MUCH OF THE INTERIOR TONIGHT THROUGH TUESDAY NIGHT.

&&

.FIRE WEATHER...
MIN RH VALUES MONDAY AND TUESDAY MAINLY 25-45 PERCENT
IN THE CENTRAL AND EASTERN INTERIOR...28-43 PERCENT IN THE
WESTERN INTERIOR AND ABOVE 40 PERCENT ON THE WEST COAST.
GUSTY SOUTH WINDS CONTINUING THROUGH ALASKA RANGE PASSES
MOST OF THE TIME THROUGH TUESDAY. ISOLATED AFTERNOON/EARLY
EVENING THUNDERSTORMS OVER MOST AREAS OF THE NORTHERN AND WESTERN
INTERIOR THROUGH WEDNESDAY.

&&

.HYDROLOGY...
NONE.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

RF MAY 16




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
FXAK69 PAFG 012323
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
323 PM AKDT SUN MAY 1 2016

.DISCUSSION...

UPPER AIR...
A BROAD UPPER LEVEL TROUGH WITH A WEAK WIND FLOW PATTERN WILL
PERSIST OVER NORTHERN ALASKA THROUGH MONDAY NIGHT. WEAK RIDGING
WILL BEGIN TO BUILD OVER THE SOUTHERN INTERIOR TUESDAY...THEN
MOVE SLOWLY NORTHEASTWARD TO EXTEND ALONG THE BROOKS RANGE THEN
SOUTHEASTWARD INTO CANADA BY THURSDAY AFTERNOON. A VERY WEAK SHORT
WAVE TROUGH WILL MOVE NORTHWARD ACROSS THE EASTERN INTERIOR MONDAY
THROUGH MONDAY NIGHT AND EXIT NORTHEASTWARD OUT OF NORTHERN ALASKA
TUESDAY AFTERNOON.

SURFACE...
A THERMAL TROUGH EXTENDING ON A LINE 50 MILES EAST OF
ANIAK-50 MILES NORTH OF FAIRBANKS-50 MILES NORTH OF NORTHWAY
WILL REMAIN NEARLY STATIONARY THROUGH MONDAY...THEN MOVE
NORTHWARD TO A LINE 50 MILES NORTH OF GALENA-FORT YUKON AND
EASTWARD BY TUESDAY AFTERNOON. A 1000 MB LOW WILL DEVELOP 50
MILES EAST OF NORTHWAY MONDAY MORNING...THEN WEAKEN TO A 1003 MB
LOW NEAR INUVIK BY TUESDAY MORNING. A RIDGE ALONG THE EASTERN
NORTH GULF COAST WILL BECOME A BROAD BUT WEAK 1007 MB HIGH
CENTERED NEAR ANCHORAGE LATE TONIGHT WHICH WILL BREAK DOWN TUESDAY
MORNING WITH THE RIDGE BECOMING RE- ESTABLISHED ALONG THE NORTH
GULF COAST BY MONDAY AFTERNOON. THIS RIDGE WILL PERSIST THROUGH
WEDNESDAY WITH LITTLE MOVEMENT EXPECTED. THIS RIDGING SOUTH OF THE
ALASKA RANGE COMBINED WITH THE THERMAL TROUGH NORTH OF THE ALASKA
WILL MAINTAIN SOUTHERLY WINDS THROUGH THE PASSES IN DENALI AND THE
EASTERN ALASKA RANGE.RANGE.

ALONG THE ARCTIC COAST...LIGHT MAINLY EAST TO NORTHEAST WINDS WILL
PERSIST THROUGH WEDNESDAY ALONG WITH LOW STRATUS AND AREAS OF
FLURRIES AND FOG.

ISOLATED AFTERNOON AND EARLY EVENING THUNDERSTORMS ARE EXPECTED
OVER THE NORTHERN AND WESTERN INTERIOR TODAY THROUGH WEDNESDAY...
GFS INDICATING SURFACE CAPES 100 TO 400+ J/KG AND SURFACE-500 MB
LIFTED INDEXES TO AROUND -2 IN THE PERSISTENT BAND OF INSTABILITY.
MORE WIDESPREAD STRATIFORM PRECIPITATION IS EXPECTED TO DEVELOP
OVER THE ALASKA RANGE AND MUCH OF THE EASTERN INTERIOR MONDAY
AFTERNOON AS A WEAK SHORT WAVE TROUGH MOVES NORTHWARD ACROSS THE
EASTERN INTERIOR. MAINLY STRATIFORM PRECIPITATION IS EXPECTED TO
PERSIST OVER MUCH OF THE INTERIOR TONIGHT THROUGH TUESDAY NIGHT.

&&

.FIRE WEATHER...
MIN RH VALUES MONDAY AND TUESDAY MAINLY 25-45 PERCENT
IN THE CENTRAL AND EASTERN INTERIOR...28-43 PERCENT IN THE
WESTERN INTERIOR AND ABOVE 40 PERCENT ON THE WEST COAST.
GUSTY SOUTH WINDS CONTINUING THROUGH ALASKA RANGE PASSES
MOST OF THE TIME THROUGH TUESDAY. ISOLATED AFTERNOON/EARLY
EVENING THUNDERSTORMS OVER MOST AREAS OF THE NORTHERN AND WESTERN
INTERIOR THROUGH WEDNESDAY.

&&

.HYDROLOGY...
NONE.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$

RF MAY 16




000
FXAK67 PAJK 011344
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
544 AM AKDT SUN MAY 1 2016

.SHORT TERM...MORE RAIN TO AFFLICT THE PANHANDLE THROUGH THE NEXT
30 HOURS. BREEZY CONDITIONS TO CONTINUE AS WELL.

AN IMPRESSIVE JET AT 300 MB APPROACHING 150 KT CONTINUES TO AIM AN
ATMOSPHERIC RIVER INTO SOUTHEAST ALASKA. NAEFS MEAN PRECIPITABLE
WATER PREDICTIONS OF AROUND 1 INCH FALLS AROUND 4 STANDARD
DEVIATIONS ABOVE NORMAL FOR EARLY MAY. THE ANNETTE ISLAND 12Z
SOUNDING`S MEASUREMENT OF 1.02 INCHES CONFIRMS THESE VALUES AND
PLACES OUR ATMOSPHERE ABOVE THE 99TH PERCENTILE AGAINST
CLIMATOLOGY. WHAT HAS THIS MEANT AND WHAT DOES THIS PORTEND? LOTS
OF RAIN. 24 HOUR TOTALS HAVE RANGED BETWEEN 1 AND 3 INCHES FOR THE
SOUTHERN PANHANDLE. AMOUNTS FOR THE NORTHERN PANHANDLE MEASURED
FAR LESS AT LESS THAN AN INCH, OWING TO THE SPEED OF THE FRONT`S
PROGRESS. BUT FOR THE NORTH, THE RAIN WILL BE MOVING BACK IN, THIS
TIME MUCH HEAVIER. A WAVE FORMING IN THE 45 N 145 W VICINITY WILL
HELP STEER THIS RIVER NORTHWESTWARD OVER THE NEXT 24 HOURS. THUS
READERS OF THE FORECAST WILL FIND THE WORDS...RAIN HEAVY AT
TIMES...MIGRATING NORTHWARD INTO TONIGHT. THE SOUTHERLY DIRECTION
OF THE LOW-LEVEL JET SHOULD EVEN HELP THE RAINFALL THREAD THE
NEEDLE OF LYNN CANAL BETWEEN THE COAST MOUNTAINS AND THE CHILKAT
RANGE. THUS, TYPICALLY DRIER HAINES AND SKAGWAY SHOULD SEE MUCH
HIGHER RAIN RATES THAN IS CUSTOMARY. RAIN WILL ONLY INCREASE INTO
TONIGHT FOR MUCH OF THE NORTH, WHILE THE SOUTHERN PANHANDLE BEGINS
TO RELENT A LITTLE AS THE JET ENERGY MIGRATES NORTHWESTWARD.

RIVER RISES HAVE BEEN RECORDED OVER THE SOUTHERN PANHANDLE IN
PARTICULAR. AS THE WAVE APPROACHES FROM THE SOUTH, SOME OF THESE
RIVERS WILL SEE MORE RISES TODAY INTO THE EVENING BEFORE BEGINNING
TO FALL AS RATES RELAX. LOW WATER LEVELS OVER THE NORTH WILL BEGIN
TO RISE LATE TONIGHT AS RAINS INCREASE OVERNIGHT. NO FLOODING IS
EXPECTED THOUGH.

OVERALL THE WIND FORECAST WORKED WELL YESTERDAY. MORE EXPOSED
AREAS SUCH AS HYDABURG AND SITKA GUSTED BETWEEN 45 AND 55 MPH. AND
YAKUTAT, WHERE THE FRONT WAS STRONGEST, GUSTED TO 48 MPH YESTERDAY
AFTERNOON. INLAND IT WAS WINDY WITH SEVERAL PEAK GUSTS AROUND 40
MPH. THE WIND FORECAST TODAY IS MORE OF A CHALLENGE. THE FRONT
STILL LIES DRAPED ACROSS THE CENTRAL PANHANDLE WITH BREEZY
SOUTHERLIES EAST OF THE FRONT AND LIGHTER SOUTHERLIES TO THE WEST.
AS A SURFACE LOW DEVELOPS UNDERNEATH THE WAVE WELL TO THE SOUTH,
THERE WILL BE A TENDENCY FOR SOME WINDS ACROSS THE NORTH TO WANT
TO BACK NORTHERLY. BUT AN EXPANDING LOW LEVEL 925 MB JET WILL
OPPOSE THIS ALOFT, AT FIRST FROM THE SOUTH AND THEN EXTENDING
NORTH THROUGH TONIGHT. WITH GENERALLY STABLE CONDITIONS ACROSS
SOUTHEAST, WE THINK THIS MOMENTUM TRANSFER WILL TAKE SOME TIME,
BUT TONIGHT, THESE SOUTHERLIES WILL SPREAD THROUGH MUCH OF THE
NORTHERN PANHANDLE. IN FACT, THE LOW-LEVEL JET WAS SO STRONG OVER
THE SOUTH, THAT WE RAISED WINDS OVER WESTERN PRINCE OF WALES THIS
AFTERNOON AND OVER CHANNELS SUCH AS SUMNER AND FREDERICK TONIGHT.
CONFIDENCE IS SUSPECT OVER TIMING OF THE DIRECTIONAL SWITCH AS
WELL AS ANY ACCELERATION TONIGHT OVER THE FAR NORTH. THIS WILL
ALL DEPEND ON HOW QUICKLY THE LOW MOVES ASHORE NEAR CAPE
FAIRWEATHER OR CAPE SPENCER. READ THE FORECAST FOR SOME STARK
TRANSITIONS BETWEEN TONIGHT AND MONDAY WHEN THE RIDGE BEGINS TO
BUILD BEHIND THE LOW AND UNDERSTAND THEY COULD HAPPEN EARLIER THAN
INDICATED. THE NEXT SHIFT WILL STUDY THE TRANSITION AS WELL.

USED A GFS22/NAM12 BLEND FOR WINDS WITH GUIDANCE FROM 925 MB
MODELED JETS. CONFIDENCE IS THROUGH THE ROOF ON RAIN. CONFIDENCE
IS CLOSER TO AVERAGE ON THE DIFFICULT WIND PATTERN.

.LONG TERM...GENERAL THINKING FOR THE LONG RANGE REMAINS ON TRACK
FROM THE PAST FEW DAYS. THE WEAK WAVE OF LOW PRESSURE MENTIONED
ABOVE WILL QUICKLY BE MOVING INLAND INTO THE YUKON ON MONDAY
MORNING. A RIDGE OF HIGH PRESSURE WILL BUILD IN BEHIND THE
DEPARTING WAVE WHICH WILL RESULT IN INCREASED SOUTHERLY WINDS.
EXPECT A PERIOD OF SMALL CRAFT WINDS IN THE NORTHERN INNER CHANNELS
MONDAY MORNING AND GUSTS OF 30 TO 35 MPH OVER THE CENTRAL AND
NORTHERN AREAS. AS THE RIDGE CONTINUES TO BUILD OVER THE PANHANDLE
LATER MONDAY INTO TUESDAY EXPECT DECREASING WINDS AS THE PRESSURE
GRADIENT RELAXES. ALONG WITH THE WEAKENING WINDS, PRECIPITATION
CHANCES WILL BE ON THE DECREASE AS WELL ON TUESDAY AND WEDNESDAY.
HOWEVER THIS DRIER PERIOD OF WEATHER WILL BE SHORTLIVED AS ANOTHER
POTENT UPPER LOW MOVES INTO THE CENTRAL GULF BY THE THURSDAY-FRIDAY
TIMEFRAME. IT WILL BE ACCOMPANIED BY A 120-130 KT SOUTHWESTERLY
UPPER JET AIMED RIGHT AT THE PANHANDLE MEANING A RETURN TO WET AND
POTENTIALLY WINDY WEATHER IS LIKELY IN STORE FOR THE LATTER HALF OF
THE WEEK AND INTO THE WEEKEND.

USED THE 06Z NAM/00Z GFS FOR MINOR UPDATES TO THE INHERITED
FORECAST.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 1 PM AKDT THIS AFTERNOON THROUGH THIS EVENING
     FOR AKZ027.
MARINE...GALE WARNING FOR PKZ036-041.
     SMALL CRAFT ADVISORY FOR PKZ012-031>035-042-043-051-052.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ022-053.
&&

$$

JWA/TPS

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU




000
FXAK67 PAJK 011344
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
544 AM AKDT SUN MAY 1 2016

.SHORT TERM...MORE RAIN TO AFFLICT THE PANHANDLE THROUGH THE NEXT
30 HOURS. BREEZY CONDITIONS TO CONTINUE AS WELL.

AN IMPRESSIVE JET AT 300 MB APPROACHING 150 KT CONTINUES TO AIM AN
ATMOSPHERIC RIVER INTO SOUTHEAST ALASKA. NAEFS MEAN PRECIPITABLE
WATER PREDICTIONS OF AROUND 1 INCH FALLS AROUND 4 STANDARD
DEVIATIONS ABOVE NORMAL FOR EARLY MAY. THE ANNETTE ISLAND 12Z
SOUNDING`S MEASUREMENT OF 1.02 INCHES CONFIRMS THESE VALUES AND
PLACES OUR ATMOSPHERE ABOVE THE 99TH PERCENTILE AGAINST
CLIMATOLOGY. WHAT HAS THIS MEANT AND WHAT DOES THIS PORTEND? LOTS
OF RAIN. 24 HOUR TOTALS HAVE RANGED BETWEEN 1 AND 3 INCHES FOR THE
SOUTHERN PANHANDLE. AMOUNTS FOR THE NORTHERN PANHANDLE MEASURED
FAR LESS AT LESS THAN AN INCH, OWING TO THE SPEED OF THE FRONT`S
PROGRESS. BUT FOR THE NORTH, THE RAIN WILL BE MOVING BACK IN, THIS
TIME MUCH HEAVIER. A WAVE FORMING IN THE 45 N 145 W VICINITY WILL
HELP STEER THIS RIVER NORTHWESTWARD OVER THE NEXT 24 HOURS. THUS
READERS OF THE FORECAST WILL FIND THE WORDS...RAIN HEAVY AT
TIMES...MIGRATING NORTHWARD INTO TONIGHT. THE SOUTHERLY DIRECTION
OF THE LOW-LEVEL JET SHOULD EVEN HELP THE RAINFALL THREAD THE
NEEDLE OF LYNN CANAL BETWEEN THE COAST MOUNTAINS AND THE CHILKAT
RANGE. THUS, TYPICALLY DRIER HAINES AND SKAGWAY SHOULD SEE MUCH
HIGHER RAIN RATES THAN IS CUSTOMARY. RAIN WILL ONLY INCREASE INTO
TONIGHT FOR MUCH OF THE NORTH, WHILE THE SOUTHERN PANHANDLE BEGINS
TO RELENT A LITTLE AS THE JET ENERGY MIGRATES NORTHWESTWARD.

RIVER RISES HAVE BEEN RECORDED OVER THE SOUTHERN PANHANDLE IN
PARTICULAR. AS THE WAVE APPROACHES FROM THE SOUTH, SOME OF THESE
RIVERS WILL SEE MORE RISES TODAY INTO THE EVENING BEFORE BEGINNING
TO FALL AS RATES RELAX. LOW WATER LEVELS OVER THE NORTH WILL BEGIN
TO RISE LATE TONIGHT AS RAINS INCREASE OVERNIGHT. NO FLOODING IS
EXPECTED THOUGH.

OVERALL THE WIND FORECAST WORKED WELL YESTERDAY. MORE EXPOSED
AREAS SUCH AS HYDABURG AND SITKA GUSTED BETWEEN 45 AND 55 MPH. AND
YAKUTAT, WHERE THE FRONT WAS STRONGEST, GUSTED TO 48 MPH YESTERDAY
AFTERNOON. INLAND IT WAS WINDY WITH SEVERAL PEAK GUSTS AROUND 40
MPH. THE WIND FORECAST TODAY IS MORE OF A CHALLENGE. THE FRONT
STILL LIES DRAPED ACROSS THE CENTRAL PANHANDLE WITH BREEZY
SOUTHERLIES EAST OF THE FRONT AND LIGHTER SOUTHERLIES TO THE WEST.
AS A SURFACE LOW DEVELOPS UNDERNEATH THE WAVE WELL TO THE SOUTH,
THERE WILL BE A TENDENCY FOR SOME WINDS ACROSS THE NORTH TO WANT
TO BACK NORTHERLY. BUT AN EXPANDING LOW LEVEL 925 MB JET WILL
OPPOSE THIS ALOFT, AT FIRST FROM THE SOUTH AND THEN EXTENDING
NORTH THROUGH TONIGHT. WITH GENERALLY STABLE CONDITIONS ACROSS
SOUTHEAST, WE THINK THIS MOMENTUM TRANSFER WILL TAKE SOME TIME,
BUT TONIGHT, THESE SOUTHERLIES WILL SPREAD THROUGH MUCH OF THE
NORTHERN PANHANDLE. IN FACT, THE LOW-LEVEL JET WAS SO STRONG OVER
THE SOUTH, THAT WE RAISED WINDS OVER WESTERN PRINCE OF WALES THIS
AFTERNOON AND OVER CHANNELS SUCH AS SUMNER AND FREDERICK TONIGHT.
CONFIDENCE IS SUSPECT OVER TIMING OF THE DIRECTIONAL SWITCH AS
WELL AS ANY ACCELERATION TONIGHT OVER THE FAR NORTH. THIS WILL
ALL DEPEND ON HOW QUICKLY THE LOW MOVES ASHORE NEAR CAPE
FAIRWEATHER OR CAPE SPENCER. READ THE FORECAST FOR SOME STARK
TRANSITIONS BETWEEN TONIGHT AND MONDAY WHEN THE RIDGE BEGINS TO
BUILD BEHIND THE LOW AND UNDERSTAND THEY COULD HAPPEN EARLIER THAN
INDICATED. THE NEXT SHIFT WILL STUDY THE TRANSITION AS WELL.

USED A GFS22/NAM12 BLEND FOR WINDS WITH GUIDANCE FROM 925 MB
MODELED JETS. CONFIDENCE IS THROUGH THE ROOF ON RAIN. CONFIDENCE
IS CLOSER TO AVERAGE ON THE DIFFICULT WIND PATTERN.

.LONG TERM...GENERAL THINKING FOR THE LONG RANGE REMAINS ON TRACK
FROM THE PAST FEW DAYS. THE WEAK WAVE OF LOW PRESSURE MENTIONED
ABOVE WILL QUICKLY BE MOVING INLAND INTO THE YUKON ON MONDAY
MORNING. A RIDGE OF HIGH PRESSURE WILL BUILD IN BEHIND THE
DEPARTING WAVE WHICH WILL RESULT IN INCREASED SOUTHERLY WINDS.
EXPECT A PERIOD OF SMALL CRAFT WINDS IN THE NORTHERN INNER CHANNELS
MONDAY MORNING AND GUSTS OF 30 TO 35 MPH OVER THE CENTRAL AND
NORTHERN AREAS. AS THE RIDGE CONTINUES TO BUILD OVER THE PANHANDLE
LATER MONDAY INTO TUESDAY EXPECT DECREASING WINDS AS THE PRESSURE
GRADIENT RELAXES. ALONG WITH THE WEAKENING WINDS, PRECIPITATION
CHANCES WILL BE ON THE DECREASE AS WELL ON TUESDAY AND WEDNESDAY.
HOWEVER THIS DRIER PERIOD OF WEATHER WILL BE SHORTLIVED AS ANOTHER
POTENT UPPER LOW MOVES INTO THE CENTRAL GULF BY THE THURSDAY-FRIDAY
TIMEFRAME. IT WILL BE ACCOMPANIED BY A 120-130 KT SOUTHWESTERLY
UPPER JET AIMED RIGHT AT THE PANHANDLE MEANING A RETURN TO WET AND
POTENTIALLY WINDY WEATHER IS LIKELY IN STORE FOR THE LATTER HALF OF
THE WEEK AND INTO THE WEEKEND.

USED THE 06Z NAM/00Z GFS FOR MINOR UPDATES TO THE INHERITED
FORECAST.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND FROM 1 PM AKDT THIS AFTERNOON THROUGH THIS EVENING
     FOR AKZ027.
MARINE...GALE WARNING FOR PKZ036-041.
     SMALL CRAFT ADVISORY FOR PKZ012-031>035-042-043-051-052.
     SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ022-053.
&&

$$

JWA/TPS

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU




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
FXAK69 PAFG 011047
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
247 AM AKDT SUN MAY 1 2016

.DISCUSSION...
MODELS IN DECENT AGREEMENT THROUGH ABOUT 60 HOURS BEFORE BEGINNING
TO DIVERGE. LONG WAVE TROUGH PATTERN OVER NORTHERN ALASKA. VERY
STRONG UPPER LEVEL RIDGE OVER NORTHWESTERN UNITED STATES NUDGING
NORTHWARD AND WILL POSITION ITSELF TO A MORE SOUTH TO NORTH
ORIENTATION BY MON AFTERNOON. THIS WILL ATTEMPT TO PUSH THE RIDGE
INTO EASTERN ALASKA BUT IT WILL GET BEAT BACK BY THE UPPER LEVEL
TROUGH THAT IS STUBBORN TO MOVE OUT OF NORTHERN ALASKA.

THE ARCTIC COAST WILL FAIL TO REALIZE SPRING AS SUCCESSIVE PUSHES
OF COLD AIR FROM THE NORTH CONTINUE TO INVADE THE ARCTIC COAST
THROUGH THE WEEK. THIS WILL AMOUNT TO CONTINUES FOG AND FLURRIES.

THE INTERIOR WILL CONTINUE TO HARBOR THE THERMAL TROUGH AS IT
REMAINS FAIRLY CONSTANT OVER THE CENTRAL INTERIOR. REPETITIVE
SHORT WAVES WILL CONTINUE TO MOVE NORTH FROM THE GULF OF ALASKA
OVER THE NEXT WEEK. THIS WILL BE THE MAIN IMPETUS FOR SHOWERS AND
CONVECTIVE DEVELOPMENT OVER CENTRAL ALASKA. MOST OF THE CONVECTION
WILL BE LOCATED TO THE WEST OF TANANA SUCH AS THE Y-K
DELTA...NULATO HILLS AND THE MIDDLE YUKON VALLEY AS WELL AS THE
LOWER KOYUKUK VALLEY FOR MONDAY AND THEN SLIDING A BIT NORTH OF
TUE AND EXTENDING FURTHER EAST TO ENCOMPASS TANANA.

A VERY SHORT LIVED CHINOOK IS OCCURRING OVER THE EASTERN ALASKA
RANGE AREA PASSES THROUGH LATE MORNING OR EARLY AFTERNOON AS UPPER
LEVEL GRADIENT WEAKENS SLIGHTLY.

&&

.FIRE WEATHER...
LOW RH VALUES OCCURRED OVER THE CENTRAL INTERIOR ON SAT AND MORE
LOOKS TO BE IN STORE TODAY. SLIGHTLY HIGHER RH VALUES MAY RETURN
ON MON AS THE NEXT TROUGH MOVES NORTH FROM THE GULF OF ALASKA WITH
GULF MOISTURE.

&&

.HYDROLOGY...
NONE AT THIS TIME.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR AKZ226.
&&

$$

CF MAY 16




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
FXAK67 PAJK 302304
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
304 PM AKDT SAT APR 30 2016

.SHORT TERM...A STRONG OCCLUDED FRONT ALONG THE CENTRAL OUTER
COAST WILL MOVE INLAND AND STALL ACROSS THE S-CENTRAL PANHANDLE
SSW INTO THE SE GULF BY LATE EVENING. A LOW PRESSURE WAVE WILL
DEVELOP ALONG THE FRONT AND MOVE N TO JUST W OF HAIDA GWAII BY
LATE SUN AFTERNOON. USED BLEND OF THE 12Z GFS AND NAM TO HANDLE
THE FORECAST THROUGH SUN.

MAIN FORECAST CONCERNS ARE PRECIP POTENTIAL/AMOUNTS AND WINDS.
RIGHT NOW...RAIN IS FALLING OVER NEARLY THE ENTIRE PANHANDLE WITH
FRONT ALONG THE COAST. AS FRONT MOVES INLAND THIS EVENING...THE
STEADIER RAIN WILL TRANSITION TO SHOWERS OVER THE NW HALF OF THE
AREA AFTER FROPA. THE SERN HALF OF THE AREA WILL STAY ON THE E
SIDE OF THE FRONT AND REMAIN IN STEADIER PRECIP TONIGHT. AS THE
LOW PRESSURE WAVE MOVES N THOUGH...THE FRONT WILL SHIFT N AND
PRECIP WILL TRANSITION BACK TO STEADIER RAIN OVER MUCH OF THE N
THROUGH THE DAY.

THE RAIN MAY BE HEAVY AT TIMES ESPECIALLY OVER THE S. RAINFALL OF
1 TO 2.5 INCHES IS EXPECTED OVER THE S...AND MAY EXCEED 3 INCHES
IN SOME AREAS THROUGH SUN AFTERNOON. THE N WILL LIKELY GET UP TO 1
INCH OF ADDITIONAL RAIN WITH HIGHER AMOUNTS IN THE MTNS THROUGH
SUN AFTERNOON. THE IMPACTS OF THIS WILL BE DISCUSSED IN THE
HYDROLOGY SECTION.

RIGHT NOW...WINDS AHEAD OF THE FRONT ARE MOSTLY GALE FORCE OVER
THE FAR ERN GULF. THESE WINDS WILL DROP TO SCA LEVELS OR LESS THIS
EVENING AFTER FROPA. INNER CHANNELS WILL SEE WINDS UP TO GALE
FORCE DIMINISH TO SCA LEVELS OR LESS OVER THE AREA BY LATE EVENING
...EVEN AHEAD OF THE FRONT...AS IT WILL WEAKEN SOME. KEEPING IN
SOME STRONG WIND HEADLINES THRU EARLY THIS EVENING MAINLY OVER
THE ERN INNER CHANNELS AND SRN COAST. WINDS WILL INCREASE OVER THE
FAR SRN AREA SUN AS LOW PRESSURE WAVE MOVES CLOSER TO THE AREA
WHILE THE NRN AREA WINDS DECREASE FURTHER WITH WEAKENING PRESSURE
GRADIENT DURING THE DAY.

.LONG TERM...PARENT LOW ON THE WESTERN GULF WILL CONTINUE TO
WEAKEN SUNDAY EVENING. A LOW PRESSURE WAVE WILL DEVELOP IN THE E
PACIFIC THE TRACK N ALONG THE STALLED FRONT EXTENDING FROM THE
WESTERN GULF PARENT LOW. THE WAVE WILL MOVE INTO THE SE GULF
SUNDAY EVENING BECOMING AN OPEN WAVE TROUGH AS IT MOVES NORTH OVER
THE PANHANDLE THROUGH MONDAY. A HIGH PRESSURE RIDGE WILL BEGIN TO
BUILD BEHIND THE LOW PRESSURE WAVE THROUGH WEDNESDAY. MEANWHILE
THE NEXT MAJOR LOW PRESSURE SYSTEM MOVES OVER THE ALEUTIANS AND
THEN JUST SOUTH OF THE AK PENINSULA WEDNESDAY NIGHT INTO THURSDAY.
AS OF NOW EXPECT THE FRONTAL BOUNDARY ASSOCIATED WITH THIS LOW TO
CROSS INTO THE EASTERN GULF THURSDAY THEN OVER THE PANHANDLE
FRIDAY. HOWEVER STILL SOME MODEL SPREAD REGARDING THIS FEATURE AS
MODELS HAVING DIFFICULTY WITH SPRING PATTERN TRANSITION.

THE SUNDAY NIGHT WAVE WILL BRING ANOTHER ROUND OF HEAVY RAINFALL
AND BREEZY CONDITIONS, BUT NOT AS STRONG AS THE SYSTEM CURRENTLY
MOVING OVER THE AREA. VARIABLE WIND DIRECTIONS WITH THE PASSING
LOW THEN TRANSITIONS TO MOVE SOUTHERLY FLOW AS THE RIDGE BUILDS
IN. RAIN WILL DIMINISH OVER MOST OF THE PANHANDLE UNDER THE
BUILDING RIDGE. STILL SOME VORT MAX ON LEE SIDE OF RIDGE KEEPING
PRECIP ALONG THE COAST MOUNTAINS. EVEN WITH THE MODEL DIFFERENCES
HAVE BIT MORE CONFIDENCE ON THE NEXT FRONT REACHING THE E GULF
FRIDAY BRINGING MORE RAIN AND STRONGER WINDS. IN THE EXTENDED
RANGE GFS/GEM HAVE BEEN CONSISTENT RUN TO RUN AND WITH EACH OTHER
AND ECMWF AS AN OUTLIER HAS BEEN SHOWING MORE RUN TO RUN
VARIATION.

USED 12Z GFS/NAM WITH ONLY MINOR TIMING CHANGES ON WIND DIRECTION
COMPARED TO INHERITED FORECAST TO DAY 4. NEW WPC GUIDANCE STILL
IN LINE WITH PREVIOUS FORECAST TO DAY 8 SO FEW CHANGES MADE THERE.
FORECAST CONFIDENCE IS AVERAGE.


&&

.HYDROLOGY...SO FAR UP TO 1 INCH OF RAIN HAS FALLEN ACROSS THE
AREA THROUGH LATE THIS AFTERNOON AND MANY SMALLER STREAMS HAVE
BEGUN TO RISE. WITH THE ADDITIONAL RAINFALL AMOUNTS EXPECTED...AREA
RIVERS AND STREAMS WILL RISE FURTHER WITH THE BIGGEST RISES
EXPECTED OVER THE SRN PANHANDLE. NOT EXPECTING ANY FLOODING AT
THIS TIME HOWEVER AS WATER LEVELS WERE FAIRLY LOW TO START.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND UNTIL 7 PM AKDT THIS EVENING FOR AKZ025>028.
     STRONG WIND UNTIL 4 PM AKDT THIS AFTERNOON FOR AKZ017-021>024.
MARINE...STORM WARNING FOR PKZ052.
     GALE WARNING FOR PKZ022-033>036-041>043-051-053.
     SMALL CRAFT ADVISORY FOR PKZ011>013-021-031-032.
&&

$$

RWT/PRB

VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU




000
FXAK69 PAFG 302039
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
1239 PM AKDT SAT APR 30 2016

.DISCUSSION...

UPPER AIR...
UPPER LEVEL RIDGE OVER NORTHWEST CANADA WILL GRADUALLY BUILD
THROUGH MONDAY...THEN SHIFT EASTWARD THROUGH WEDNESDAY. UPPER
LOW CENTER JUST SOUTHEAST OF KODIAK ISLAND WILL REMAIN NEARLY
STATIONARY WHILE WEAKENING THROUGH MONDAY AND DISSIPATING MONDAY
NIGHT. A WEAK UPPER LOW CENTER NEAR BARROW WILL DRIFT SLOWLY
WESTWARD TO 200 MILES NORTHWEST OF BARROW BY MONDAY EVENING. A
WEAK FLOW PATTERN WILL PERSIST OVER THE NORTHERN ALASKA
MAINLAND...WITH MAINLY SOUTHERLY WIND FLOW CONTINUING OVER THE
EASTERN THIRD. A VERY WEAK SHORT WAVE TROUGH WILL MOVE NORTHWARD
ACROSS THE EASTERN THIRD OF NORTHERN ALASKA MONDAY AND MONDAY
NIGHT.

SURFACE...
A WEAK THERMAL TROUGH WILL DEVELOP ALONG A LINE DELTA JUNCTION-50
MILES EAST OF NORTHWAY THIS EVENING...THEN STRENGTHEN THROUGH
SUNDAY EVENING AS IT MOVES NORTHWARD AND EXPANDS WESTWARD.
TROUGH AXIS SUNDAY EVENING WILL LINE ALONG A LINE 50 MILES
EAST OF ANIAK-TANANA-60 MILES NORTH OF FAIRBANKS-40 MILES SOUTH
OF EAGLE. THE THE EASTERN PART OF THE TROUGH WILL DRIFT FARTHER
NORTHWARD THROUGH MONDAY EVENING. TROUGH AXIS MONDAY EVENING WILL
LINE ON A LINE 50 MILES EAST OF ANIAK-100 MILES NORTH OF
FAIRBANKS-120 MILES NORTH OF EAGLE. A 1032 MB HIGH CENTERED NEAR
80N 120W WILL MOVE TO NEAR 80N 135W BY MONDAY AFTERNOON.

LIGHT EAST TO NORTHEAST WINDS WILL CONTINUE ALONG THE
ARCTIC COAST...LOW STRATUS WILL BE ACCOMPANIED BY
AREAS OF FLURRIES AND FOG.

CONVECTIVE ACTIVITY THIS AFTERNOON AND EVENING... ISOLATED TO
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS EXPECTED THIS
AFTERNOON AND EVENING OVER MUCH OF THE NORTHERN AND WESTERN
INTERIOR AND INLAND AREAS OF ZONES 212 AND 214.

CONVECTIVE OUTLOOK FOR SUNDAY...ISOLATED TO SCATTERED
AFTERNOON/EVENING SHOWERS EXPECTED OVER MOST AREAS OF THE INTERIOR
AND INLAND WEST COAST AREAS SOUTH AND EAST OF NORTON SOUND. THE
BEST POTENTIAL FOR ISOLATED THUNDERSTORMS WILL BE OVER THE
NORTHEAST INTERIOR WITH SURFACE-500 MB LIFTED INDEXES AS LOW AS
-3 AND SURFACE CAPES 100 TO 200+ J/KG.J/KG.

CONVECTIVE OUTLOOK FOR MONDAY...ISOLATED TO SCATTERED
AFTERNOON/EVENING SHOWERS EXPECTED AGAIN OVER MOST AREAS OF THE
INTERIOR AND INLAND WEST COAST AREAS SOUTH AND EAST OF NORTON
SOUND. ISOLATED AFTERNOON/EVENING THUNDERSTORMS EXPECTED OVER
THE NORTHERN AND WESTERN INTERIOR WITH CAPES 100-300+J/KG AND
SURFACE-500 MB LIFTED INDEXES AS LOW AS -3.

CONVECTIVE OUTLOOK FOR TUESDAY...ISOLATED TO SCATTERED
AFTERNOON/EVENING SHOWERS EXPECTED OVER MOST INTERIOR AREAS.
ISOLATED THUNDERSTORMS EXPECTED OVER THE NORTHERN AND WESTERN
INTERIOR WITH SURFACE-500 MB LIFTED INDEXES AS LOW AS -4 AND CAPES
100=400+ J/KG.

MEDIUM RANGE OUTLOOK...A WEAK FLOW PATTERN ALOFT WITH ABOVE NORMAL
SURFACE TEMPERATURES IS EXPECTED TO CONTINUE OVER NORTHERN ALASKA
THROUGH FRIDAY. BEYOND FRIDAY...FORECAST CONFIDENCE DECREASES AS
CURRENT GFS/ECMWF SOLUTIONS BECOME INCREASINGLY DIVERGENT. THE GFS
AND ITS ENSEMBLE MEAN MAINTAIN A SLIGHTLY WARMISH WEAK FLOW
PATTERN ALOFT OVER THE NORTHERN ALASKA WITH A STRONG RIDGE OVER
NORTHWEST CANADA WHILE THE ECMWF AND ITS ENSEMBLE MEAN TRENDS TO A
WESTERLY PROGRESSIVE FLOW PATTERN WHICH WOULD BRING IN MORE CLOUD
COVER...COOLER TEMPERATURES...AND A CHANCE OF RAIN AT TIMES.

&&

.FIRE WEATHER...
WARM AND DRY CONDITIONS IN THE SOUTHERN ZONES CONTINUING THROUGH
MONDAY...WITH MINIMUM RH MAINLY 22-37 PERCENT IN MOST AREAS.
GUSTY SOUTH WINDS ARE EXPECTED TO DEVELOP IN ALASKA RANGE PASSES
AFTER MIDNIGHT TONIGHT AND CONTINUE THROUGH SUNDAY NIGHT. WINDS
ARE EXPECTED TO BECOME LIGHT/VARIABLE MONDAY...GUSTY SOUTH WINDS
REDEVELOPING MONDAY NIGHT. THE STRONGEST WINDS ARE EXPECTED IN THE
EASTERN ALASKA RANGE LATER TONIGHT THROUGH AROUND NOON SUNDAY...AND
AGAIN MONDAY NIGHT...SOUTH WINDS 20-35 MPH WITH GUSTS TO 50 MPH.
SINCE THE STRONGEST WINDS ARE EXPECTED TO OCCUR DURING THE NIGHT
AND MORNING HOURS...HUMIDITIES ARE EXPECTED TO BE ABOVE 25 PERCENT
AND RED FLAG CONDITIONS ARE NOT ANTICIPATED. SEE MAIN DISCUSSION
FOR THUNDERSTORMS.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR AKZ226.

&&

$$

RF APR 16




000
FXAK69 PAFG 302031
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
1231 PM AKDT SAT APR 30 2016

.DISCUSSION...

UPPER AIR...
UPPER LEVEL RIDGE OVER NORTHWEST CANADA WILL GRADUALLY BUILD
THROUGH MONDAY...THEN SHIFT EASTWARD THROUGH WEDNESDAY. UPPER
LOW CENTER JUST SOUTHEAST OF KODIAK ISLAND WILL REMAIN NEARLY
STATIONARY WHILE WEAKENING THROUGH MONDAY AND DISSIPATING MONDAY
NIGHT. A WEAK UPPER LOW CENTER NEAR BARROW WILL DRIFT SLOWLY
WESTWARD TO 200 MILES NORTHWEST OF BARROW BY MONDAY EVENING. A
WEAK FLOW PATTER WILL PERSIST OVER THE NORTHERN ALASKA
MAINLAND...WITH MAINLY SOUTHERLY WIND FLOW CONTINUING OVER THE
EASTERN THIRD. A VERY WEAK SHORT WAVE TROUGH WILL MOVE NORTHWARD
ACROSS THE EASTERN THIRD OF NORTHERN ALASKA MONDAY AND MONDAY
NIGHT.

SURFACE...
A WEAK THERMAL TROUGH WILL DEVELOP ALONG A LINE DELTA JUNCTION-50
MILES EAST OF NORTHWAY THIS EVENING...THEN STRENGTHEN THROUGH
SUNDAY EVENING AS IT MOVES NORTHWARD AND EXPANDS WESTWARD.
TROUGH AXIS SUNDAY EVENING WILL LINE ALONG A LINE 50 MILES
EAST OF ANIAK-TANANA-60 MILES NORTH OF FAIRBANKS-40 MILES SOUTH
OF EAGLE. THE THE EASTERN PART OF THE TROUGH WILL DRIFT FARTHER
NORTHWARD THROUGH MONDAY EVENING. TROUGH AXIS MONDAY EVENING WILL
LINE ON A LINE 50 MILES EAST OF ANIAK-100 MILES NORTH OF
FAIRBANKS-120 MILES NORTH OF EAGLE. A 1032 MB HIGH CENTERED NEAR
80N 120W WILL MOVE TO NEAR 80N 135W BY MONDAY AFTERNOON.

LIGHT EAST TO NORTHEAST WINDS WILL CONTINUE ALONG THE
ARCTIC COAST...LOW STRATUS WILL BE ACCOMPANIED BY
AREAS OF FLURRIES AND FOG.

CONVECTIVE ACTIVITY THIS AFTERNOON AND EVENING... ISOLATED TO
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS EXPECTED THIS
AFTERNOON AND EVENING OVER MUCH OF THE NORTHERN AND WESTERN
INTERIOR AND INLAND AREAS OF ZONES 212 AND 214.

CONVECTIVE OUTLOOK FOR SUNDAY...ISOLATED TO SCATTERED
AFTERNOON/EVENING SHOWERS EXPECTED OVER MOST AREAS OF THE INTERIOR
AND INLAND WEST COAST AREAS SOUTH AND EAST OF NORTON SOUND. THE
BEST POTENTIAL FOR ISOLATED THUNDERSTORMS WILL BE OVER THE
NORTHEAST INTERIOR WITH SURFACE-500 MB LIFTED INDEXES AS LOW AS
-3 AND SURFACE CAPES 100 TO 200+ J/KG.J/KG.

CONVECTIVE OUTLOOK FOR MONDAY...ISOLATED TO SCATTERED
AFTERNOON/EVENING SHOWERS EXPECTED AGAIN OVER MOST AREAS OF THE
INTERIOR AND INLAND WEST COAST AREAS SOUTH AND EAST OF NORTON
SOUND. ISOLATED AFTERNOON/EVENING THUNDERSTORMS EXPECTED OVER
THE NORTHERN AND WESTERN INTERIOR WITH CAPES 100-300+J/KG AND
SURFACE-500 MB LIFTED INDEXES AS LOW AS -3.

CONVECTIVE OUTLOOK FOR TUESDAY...ISOLATED TO SCATTERED
AFTERNOON/EVENING SHOWERS EXPECTED OVER MOST INTERIOR AREAS.
ISOLATED THUNDERSTORMS EXPECTED OVER THE NORTHERN AND WESTERN
INTERIOR WITH SURFACE-500 MB LIFTED INDEXES AS LOW AS -4 AND CAPES
100=400+ J/KG.

MEDIUM RANGE OUTLOOK...A WEAK FLOW PATTERN ALOFT WITH ABOVE NORMAL
SURFACE TEMPERATURES IS EXPECTED TO CONTINUE OVER NORTHERN ALASKA
THROUGH FRIDAY. BEYOND FRIDAY...FORECAST CONFIDENCE DECREASES AS
CURRENT GFS/ECMWF SOLUTIONS BECOME INCREASINGLY DIVERGENT. THE GFS
AND ITS ENSEMBLE MEAN MAINTAIN A SLIGHTLY WARMISH WEAK FLOW
PATTERN ALOFT OVER THE NORTHERN ALASKA WITH A STRONG RIDGE OVER
NORTHWEST CANADA WHILE THE ECMWF AND ITS ENSEMBLE MEAN TRENDS TO A
WESTERLY PROGRESSIVE FLOW PATTERN WHICH WOULD BRING IN MORE CLOUD
COVER...COOLER TEMPERATURES...AND A CHANCE OF RAIN AT TIMES.

&&

.FIRE WEATHER...
WARM AND DRY CONDITIONS IN THE SOUTHERN ZONES CONTINUING THROUGH
MONDAY...WITH MINIMUM RH MAINLY 22-37 PERCENT IN MOST AREAS.
GUSTY SOUTH WINDS ARE EXPECTED TO DEVELOP IN ALASKA RANGE PASSES
AFTER MIDNIGHT TONIGHT AND CONTINUE THROUGH SUNDAY NIGHT. WINDS
ARE EXPECTED TO BECOME LIGHT/VARIABLE MONDAY...GUSTY SOUTH WINDS
REDEVELOPING MONDAY NIGHT. THE STRONGEST WINDS ARE EXPECTED IN THE
EASTERN ALASKA RANGE LATER TONIGHT THROUGH AROUND NOON SUNDAY...AND
AGAIN MONDAY NIGHT...SOUTH WINDS 20-35 MPH WITH GUSTS TO 50 MPH.
SINCE THE STRONGEST WINDS ARE EXPECTED TO OCCUR DURING THE NIGHT
AND MORNING HOURS...HUMIDITIES ARE EXPECTED TO BE ABOVE 25 PERCENT
AND RED FLAG CONDITIONS ARE NOT ANTICIPATED.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR AKZ226.

&&

$$

RF APR 16




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




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