Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 201203 CCA
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
403 AM AKDT WED MAY 20 2015

CORRECTION TO SOUTHCENTRAL FIRE WEATHER DISCUSSION

.ANALYSIS AND UPPER LEVELS...
THE OVERALL WEATHER PATTERN REMAINS VERY SIMILAR TO THAT OF THE
LAST FEW DAYS...WITH STRONG RIDGING STRETCHING INTO THE EASTERN
MAINLAND AND A BROAD LOW OVER THE BERING BRINGING ABUNDANT
MOISTURE TO THE WESTERN MAINLAND. THE BERING LOW IS CENTERED OVER
THE PRIBILOF ISLANDS AND IS BRINGING YET ANOTHER ROUND OF
RAINFALL THROUGHOUT THE SOUTHWEST MAINLAND WITH DIMINISHING
SOUTHEASTERLY WINDS. MOISTURE FROM THIS SYSTEM CAN BE SEEN
STRETCHING AS FAR SOUTH AS 35N...WITH PRECIPITABLE WATER VALUES
OVER 200% TO 45N. THE RIDGING THAT IS KEEPING THE WEATHER MOSTLY
CLEAR AND DRY EAST OF THE ALASKA RANGE NOW STRETCHES FROM THE
NORTHEAST PACIFIC INTO THE EASTERN MAINLAND AND THE PANHANDLE.
WELL OUTSIDE OF THE AOR BUT NOTABLE NONE THE LESS...TYPHOON
DOLPHIN CAN BE SEEN MOVING NORTHEASTWARD OFF THE COAST OF JAPAN.
THIS SYSTEM WILL CONTINUE TRACKING TOWARDS THE WESTERN ALEUTIANS
OVER THE COURSE OF THIS WEEK...AND IS EXPECTED TO BEGIN IMPACTING
THE WESTERN BERING SEA LATE THURSDAY.

&&

.MODEL DISCUSSION...
THE MODELS REMAIN IN VERY GOOD AGREEMENT WITH THE SYNOPTIC SCALE
FEATURES THROUGH THE END OF THE WEEK WHEN THEY CONTINUE TO HAVE
ISSUES AGREEING ON THE INTENSITY OF THE REMNANTS OF TYPHOON
DOLPHIN OVER THE WESTERN BERING. THE GOOD NEWS IS THAT THE MODELS
HAVE COME INTO MUCH BETTER AGREEMENT WITH THE SPEED OF THIS SYSTEM
WITH THE ADDITION OF THE 22/00Z EC...SO FORECAST CONFIDENCE IS
INCREASING IN THE TIMING OF THIS SYSTEM. THEY ALSO HAVE COME INTO
SLIGHTLY BETTER AGREEMENT WITH THE INTENSITY OF THE LOW...BUT THE
EC CONTINUES TO BE A CONSISTENT WEAK OUTLIER...WHILE THE NAM IS
THE SLIGHTLY DEEPER THAN THE GFS/GEM. THE GFS HAS BEEN THE MOST
CONSISTENT WITH THIS SYSTEM...SO IT WAS USED HEAVILY FOR THE
FORECAST PACKAGE TO FURTHER DEEPEN THE LOW. ONE INTERESTING NOTE
FROM THE GFS IS THAT THE GFS ENSEMBLE MEAN ACTUALLY DEEPER THAN
THE LAST TWO OPERATIONAL RUNS (AT TIMES AS MUCH AS 5 TO 6 MB).
WHILE THIS IS ALLOWING FOR HIGHER CONFIDENCE IN A DEEPER SYSTEM
THAN WAS PREVIOUSLY FORECAST...IT MAY NEED TO BE DEEPENED EVEN
FURTHER IF THIS TREND CONTINUES.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA...
HIGH PRESSURE CONTINUES TO DOMINATE THE SOUTHCENTRAL BUT THE
APPROACHING FRONT FROM THE SOUTHWEST IS BRINGING CLOUD COVER OVER
THE WESTERN PORTIONS OF THE SOUTHCENTRAL. HOWEVER...THE FRONT WILL
STALL OVER KODIAK ISLAND AND THE HIGH WILL REMAIN THE DOMINATE
FEATURE FOR THE NEXT COUPLE DAYS. THIS WILL KEEP DIURNAL TRENDS
GOING FOR WINDS WITH SEA BREEZES ALONG COASTAL AREAS. GAP FLOWS
WILL INCREASE THOUGH TODAY ACROSS SOUTHCENTRAL AS THE GULF RIDGE
BUILDS IN ADVANCE OF THE FRONTAL SYSTEM MOVING TOWARD KODIAK
ISLAND. STRONGEST FLOWS ARE EXPECTED ACROSS TURNAGAIN ARM (ESE
WIND)...ALONG THE COPPER RIVER(S WIND). GAP FLOWS SHOULD DIMINISH
TONIGHT AS GRADIENTS RELAX. TEMPERATURES WILL ALSO STAY
WARM...ESPECIALLY FOR PLACES IN THE COPPER RIVER BASIN.

&&

.FIRE WEATHER...
AREAS OF CONCERN ARE EXPANDING THROUGHOUT THE SOUTHCENTRAL AS
AFTERNOON AND EVENING WINDS INCREASE. THE TWO AREAS THAT WILL BE
THE CLOSEST TO CRITICAL LEVELS ARE THE COPPER RIVER BASIN AND TO A
LESSER EXTENT THE KNIK RIVER VALLEY. THE COPPER RIVER STILL
REMAINS THE PRIMARY AREA OF CONCERN THROUGH THU. RH VALUES ARE
EXPECTED TO DIP TO RED FLAG THRESHOLDS THIS AFTERNOON AND SOUTH
WINDS ARE ALSO EXPECTED TO GUST AT LEAST TO 25 MPH ALONG THE
COPPER RIVER. RH VALUES ARE EXPECTED TO RECOVER AND WINDS DIMINISH
BY LATE THIS EVENING. WARM AND DRY CONDITIONS WITH GENERALLY LIGHT
WINDS ARE EXPECTED IN THE COPPER RIVER BASIN THU. HOWEVER
CONDITIONS SHOULD BE SOMEWHAT DRIER AND ALLOW FOR RED FLAG RH
CONDITIONS TO REDEVELOP IN THE AFTERNOON AND EVENING THU. FOR THE
KNIK RIVER VALLEY RH VALUES WILL DROP TO AROUND 30 PERCENT DURING
THE AFTERNOON AND EVENING HOURS THROUGH THU. THE DIFFERENCE TODAY
WILL BE GUSTY SOUTHEAST WINDS AROUND 20 MPH.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE FRONTAL BOUNDARY WILL STALL OVER THE MAINLAND TODAY ALONG WITH
A DEEP STREAM OF MOISTURE ORIGINATING FROM THE SUBTROPICS. THESE
CONDITIONS WILL FACILITATE A CONTINUATION OF STEADY LIGHT RAIN
OVER MUCH OF THE AREA. STRONG AND DEEP LAYER CROSS BARRIER FLOW IS
TAKING SOME OF THE BITE OUT OF THE RAIN IN THE LEES OF THE
ALEUTIAN RANGE AND THE KILBUCKS BUT PLENTIFUL MOISTURE ALOFT IS
STILL MAKING IT TO THE SURFACE. THE FRONT WILL GRADUALLY WEAKEN
THROUGHOUT THE DAY DIMINISHING GUSTY SOUTHEASTERLY WINDS BY LATE
THIS EVENING. PRECIPITATION WILL ALSO STEADILY LIGHTEN UP DURING
THE OVERNIGHT HOURS INTO THURSDAY HOWEVER WEAK
STABILITY...LINGERING MOISTURE...AND A PERSISTENT JET ALOFT WILL
KEEP SOME AREAS OF LIGHT RAIN AROUND THROUGH THE DAY ON THURSDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE FRONTAL BOUNDARY HAS MAINLY CLEARED THE BERING SEA...LINGERING
TOWARD THE MAINLAND. CYCLONIC FLOW ALOFT WILL KEEP THE CHANCE FOR
SHOWERS FROM THE CENTRAL TO THE EASTERN BERING WITH PROBABILITIES
DECREASING TODAY AND TOMORROW. THIS EVENING INTO THURSDAY ALL EYES
TURN TO THE APPROACHING REMNANTS AND EXTRATROPICAL TRANSITION OF
TYPHOON DOLPHIN. A SURGE OF TROPICAL AIR WITH THE WARM FRONT AND
RAPIDLY DEEPENING SURFACE PRESSURES WILL BRING A STORM FORCE FRONT
INTO THE WESTERN AND CENTRAL BERING SEA. WIDESPREAD RAIN WILL
ACCOMPANY THE FRONT AS WELL AS SEAS QUICKLY BUILDING THURSDAY
MORNING UP TO TWENTY FEET.

&&

.LONG TERM FORECAST (FRIDAY THROUGH TUESDAY)...
BEGINNING THE EXTENDED FORECAST ON FRIDAY...THE STRONG NORTH EAST
PACIFIC RIDGE EXTENDING INTO NORTHERN ALASKA WILL REMAIN IN
PLACE...WITH THE STRONG REMNANTS OF FORMER TYPHOON DOLPHIN OVER
THE FAR WESTERN BERING. THIS WILL MEAN WARM AND DRY WEATHER ACROSS
SOUTHCENTRAL ALASKA...WITH A REMNANT WEAK FRONTAL ZONE OVER
SOUTHWEST AND THE EASTERN BERING KEEPING CLOUDS AND PRECIPITATION
OVER THAT REGION. EVENTUALLY...THE LARGE UPPER LOW OVER THE
WESTERN BERING WILL BEGIN TO MAKE EASTWARD PROGRESS AS NUMEROUS
LOBES OF ENERGY ROTATE AROUND THE LOW. THIS WILL SPREAD CLOUDS AND
PRECIPITATION INTO SOUTHCENTRAL ALASKA SATURDAY AND SUNDAY. BY
NEXT WEEK...THERE IS SOME DISCREPANCY WITH SMALLER SCALE
DETAILS...BUT THERE ARE SIGNS THAT THE STRONG NORTH EAST PACIFIC
RIDGE REBUILDS INTO ALASKA MONDAY AND TUESDAY...BRINGING MORE
WARMER AND DRIER WEATHER TO ALASKA...KEEPING THE STORM TRACK OVER
THE BERING SEA.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 177 178
GALE 175 176.
FIRE WEATHER...RED FLAG WARNING 141.

&&

$$

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


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