Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 221340 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
540 AM AKDT WED APR 22 2015

CORRECTED MARINE WARNING

.ANALYSIS AND UPPER LEVELS...
BROAD CYCLONIC FLOW RESIDES OVER THE GREAT LAND THIS MORNING AS
THE UPPER LEVEL JET RESIDES WELL SOUTH IN THE GULF...WITH AN
EXTENSION OF THE EAST ASIA JET POKING INTO THE NORTH PACIFIC.
THERE ARE TWO DISTINCT CENTERS WITHIN THE BROAD FLOW...ONE NORTH
OF SAINT MATTHEW ISLAND WHICH IS THE REMNANT OF THE PAST WEEK`S
ACTIVE WEATHER PATTERN...AND ANOTHER SOUTH OF KODIAK ISLAND WHICH
IS MORE OF A STRONG SHORTWAVE TROUGH (BECOMING AN UPPER LOW
CENTER) AND A BEAUTY OF A MATURE CYCLONE ON VISIBLE SATELLITE
IMAGERY. THIS SYSTEM IS THE MAIN FEATURE ON THE WEATHER MAP THIS
MORNING WITH A GALE FORCE FRONT STRETCHING FROM KODIAK ISLAND
SOUTH AND EASTWARD. SHOWER ACTIVITY ACROSS THE MAINLAND DRIVEN BY
AN IMPRESSIVE COLD POOL ALOFT IS ON THE DECLINE AS THE COLDEST AIR
ALOFT PUSHES NORTHWARD INTO THE INTERIOR. THE OTHER MAJOR FEATURE
ON THE MAP IS A WARM/OCCLUDED FRONT PUSHING ACROSS THE CENTRAL
BERING SEA...ASSOCIATED WITH A DECAYING KAMCHATKA LOW PRESSURE
SYSTEM.

&&

.MODEL DISCUSSION...
FROM A BROAD SYNOPTIC PERSPECTIVE...GUIDANCE IS IN GREAT AGREEMENT
WITH BOTH THE EXITING OF THE GULF SYSTEM TO THE EAST AS WELL AS
THE INCOMING FRONT/TROUGH TO THE WEST. CONFIDENCE IS HIGH FOR THIS
FORECAST PACKAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A STRONG LOW ENTERING THE SOUTHWEST GULF IS BRINGING STRONG WINDS
AND RAINFALL TO KODIAK ISLAND THIS MORNING. CONDITIONS WILL
IMPROVE THIS AFTERNOON AS THE LOW CONTINUES TO MOVE TO THE EAST.
THIS LOW IS REMAINING FAR ENOUGH SOUTH IN THE GULF THAT THE IMPACT
ON THE REST OF SOUTHCENTRAL ALASKA WILL BE MINIMAL FOR A STRONG
LOW. AS THIS LOW MOVES EASTWARD THE UPPER LEVEL FLOW WILL BECOME
MORE NORTHEASTERLY AND BRING IN A CLEARING TREND THE NEXT FEW
DAYS.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...WED AND
THU)...GOING TO BE A RELATIVELY INTERESTING WEATHER DAY ACROSS
THE AREA. CONDITIONS WILL START OFF RELATIVELY QUIETLY. THE FORMER
COLD UPPER LEVEL LOW THAT WAS NEAR NUNIVAK THE PAST COUPLE OF DAYS
WILL SWING ONE LAST PIECE OF ENERGY IN FROM THE WEST. THIS WILL
COLLIDE WITH THE WARM AND MOIST EAST TO SOUTHEAST FLOW WRAPPING
AROUND THE LOW IN THE GULF OF AK. THESE TWO FEATURES WORK IN
TANDEM TO CREATE SOME BANDS OF PRECIPITATION ACROSS NORTHERN
BRISTOL BAY AND THE WESTERN LOWER KUSKOKWIM VALLEY. PRECIPITATION
COULD BE HEAVY AT TIMES AS SOME SHOWERS ARE LIKELY TO DEVELOP
ALONG THIS BOUNDARY WITH SOME AFTERNOON INSTABILITY AND A 35-40
MPH LOW-LEVEL JET. MODELS ARE SHOWING THAT THE BAND WILL WEAKEN
SOME THROUGH THE EVENING HOURS AND LIKELY LOOSE ITS CONVECTIVE
COMPONENT. BUT THEN THE FRONT FROM THE WEST STARTS TO ARRIVE AND
REINFORCES THE LOW LEVEL CONVERGENCE. THIS SHOULD BRING YET
ANOTHER ROUND OF STEADY PRECIPITATION TO MUCH OF THE SAME AREA.
THE ONE SAVING GRACE WITH ALL OF THIS IS THAT IT LOOKS LIKE MOST
OF THE COLD AIR WILL BE TO THE WEST OF THE HEAVIEST PRECIPITATION.
SO WHILE THERE MAY BE A COUPLE INCHES OF WET SNOW
ACCUMULATION...ESPECIALLY OVER HIGHER TERRAIN...IT SHOULD MOSTLY
FALL AS RAIN.

MEANWHILE...THE SAME FRONT MENTIONED ABOVE WILL PUSH INTO THE
DELTA COAST LATE TONIGHT. IT WILL BRING MODERATE SOUTHERLY WINDS
AND SOME DECENT SNOWFALL TO THE AREA. A WINTER WEATHER ADVISORY
FOR BLOWING SNOW HAS BEEN ISSUED TO ADDRESS THE LOWER
VISIBILITIES THAT WILL RESULT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2...WED AND
THU)...A 970 MB LOW OUT OVER THE WESTERN BERING IS SLINGING A
BROAD WARM OCCLUDED FRONT ACROSS THE ENTIRE REGION. ALONG THE
FRONT IS A FAIRLY WIDE SWATH OF GALE FORCE WINDS THAT WILL
CONTINUE TO WORK FROM THE CENTRAL ALEUTIANS TO THE EASTERN
ALEUTIANS THROUGH THE DAY. THIS FRONT IS ALSO BRINGING UP SOME
WARMER AIR WITH THOSE SOUTH WINDS HELPING TO TURN PRECIPITATION
OVER TO MOSTLY RAIN. THE FRONT WILL RIDE THE JET QUICKLY EAST BUT
THE LOW WILL BECOME VERTICALLY STACKED AND JUST DRIFT SLOWLY TO
THE SOUTHEAST. THIS WILL KEEP A FAIRLY LARGE AREA OF GALE-FORCE
WINDS OVER THE WESTERN ALEUTIANS THROUGH LATE THURSDAY BEFORE THE
WINDS TURN NORTHWESTERLY.

&&

.LONG TERM FORECAST (DAYS 3-7)...
THE EASTERN BERING SEA WILL HAVE A GALE FORCE LOW JUST NORTH OF
DUTCH HARBOR ON FRIDAY BEFORE CROSSING THE EASTERN ALEUTIANS INTO
THE NORTH PACIFIC. BY SUNDAY THE LOW WILL BE LOCATED IN THE LOWER
SOUTHWESTERN GULF BEFORE GRADUALLY TRACKING TO THE LOWER EASTERN
GULF BY TUESDAY. THIS SYSTEM WILL BRING RAIN/SNOW TO THE EASTERN
BERING/ALEUTIANS AND SNOW SHOWERS TO THE PRIBILOF ISLAND HEADING
INTO THE WEEKEND. BY SATURDAY THE BERING SEA WILL HAVE SHOWERY
PRECIPITATION IN THE FORM OF SNOW WITH THE COLDER TEMPERATURES
ACCOMPANIED BY NORTHERLY WINDS. BY SUNDAY THE BERING SEA WILL HAVE
A RIDGE OF HIGH PRESSURE BUILDING INTO THE CENTRAL BERING EXCEPT
FOR A KAMCHATKA LOW TRACKING INTO THE WESTERN ALEUTIANS. THIS WILL
BRING WARMER TEMPERATURES WITH A WARM FRONT MOVING THROUGH THE
WESTERN ALEUTIANS. THIS SYSTEM WILL TRACK EASTWARD THROUGH TUESDAY
BEFORE BEING LOCATED IN THE CENTRAL ALEUTIANS. THE MODELS ARE IN
GOOD AGREEMENT WITH THE BERING LOW AS IT MOVES INTO THE GULF OVER
THE WEEKEND. THE NAM/GFS MODELS WERE IN GOOD AGREEMENT WITH THIS
LOW EXCEPT FOR THE ECMWF BEING FASTER WITH THIS SYSTEM. THE
FORECAST CONFIDENCE REMAINS ABOVE AVERAGE.

THE SOUTHCENTRAL REGION WILL HAVE AN UPPER LEVEL RIDGE WHICH WILL
KEEP THE WEATHER SYSTEMS TRACKING ALONG IN THE SOUTHERN GULF REGION
THROUGH TUESDAY. THE PRECIPITATION WILL SLIGHTLY EFFECT THE NORTHERN
COASTLINES. TEMPERATURES WILL CONTINUE TO BE ABOVE NORMAL GOING
INTO THE EARLY PART OF NEXT WEEK.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...WINTER WEATHER ADVISORY FOR BLOWING SNOW...155.
MARINE...STORM WARNING...132.
         GALE WARNING...120 130 131 136 137 138 150 170 172
                        173 174 175 176 177 178.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...MTL
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MO
LONG TERM...PLD


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