Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 280206
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
606 PM AKDT SAT JUN 27 2015

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LOW OVER THE NORTHWEST GULF OF ALASKA CENTERED
JUST SOUTHEAST OF KODIAK ISLAND. THERE IS A LOW OVER THE EASTERN
BERING SEA THAT IS MOVING TO THE SOUTH. THIS BERING LOW IS MOVING
TOWARD THE GULF AND IS CAUSING THE KODIAK LOW TO BEGIN LIFTING
NORTHWESTWARD. SEVERAL BANDS OF MOISTURE ARE ASSOCIATED WITH
THESE LOWS. ONE OF THEM IS A DEFORMATION ZONE OVER SOUTHWEST
ALASKA THAT IS WEAKENING. ANOTHER IS A FRONT OVER THE NORTHERN
GULF...AND THERE IS ALSO A BAND OF MOISTURE ALONG THE GULF COAST.

THERE IS A SHARP RIDGE OVER THE CENTRAL BERING AND CENTRAL
ALEUTIANS THAT IS SLIGHTLY NEGATIVELY TILTED AND IS SHOWING LITTLE
OR NO SIGNS OF MOVEMENT. AN UPPER LOW WEST OF THE WESTERN
ALEUTIANS IS ALSO HOLDING IN PLACE.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT THROUGH 48 HOURS (EARLY
MONDAY MORNING). AFTER THIS THE NAM BEGINS TO DIVERGE FROM THE
OTHER MODELS BY TAKING THE LOW IN THE WESTERN GULF WESTWARD
TOWARDS THE ALASKA PENINSULA...WHILE THE OTHER MODELS KEEP IT IN
PLACE TO THE SOUTH OF KODIAK ISLAND. FORECAST CONFIDENCE IS NEAR
TO SLIGHTLY BELOW NORMAL.

&&

.FIRE WEATHER...

THE GULF COAST AND KENAI PENINSULA WILL GENERALLY REMAIN ON THE
COOL AND WET SIDE THROUGH EARLY NEXT WEEK. THE WESTERN KENAI WILL
REMAIN DRIER...BUT ANY SHOWERS THAT DO SURVIVE THE TRIP ACROSS THE
KENAI MOUNTAINS COULD PRODUCE ISOLATED AREAS OF MODERATE RAIN OVER
THE NEXT COUPLE DAYS. THE BULK OF DIURNAL CONVECTION AND THE
DEVELOPMENT OF AFTERNOON/EVENING ISOLATED THUNDERSTORM WILL REMAIN
CONFINED TO THE TALKEETNA RANGE AND NORTHERN ALASKA RANGE THROUGH
MONDAY. MARGINALLY DRIER AND WARMER CONDITIONS ARE EXPECTED OVER
THE INTERIOR PORTIONS OF SOUTHCENTRAL...WITH SOME SUNSHINE PEAKING
THROUGH OVER THE WESTERN KENAI AND COPPER RIVER BASIN THROUGH
MONDAY. WITH GUSTY WINDS BUILDING OVER THE COPPER RIVER BASIN
SUNDAY AND MONDAY...AND RELATIVE HUMIDITY VALUES NEARING 30
PERCENT...THERE REMAINS THE POTENTIAL OF APPROACHING RED FLAG
CRITERIA. HOWEVER...AT THIS TIME VALUES REMAIN ABOVE CRITICAL
THRESHOLDS.

THE SOUTHWEST MAINLAND WILL SEE A DRYING TREND OVER THE NEXT FEW
DAYS AS THE TWO LOWS CONSOLIDATE IN THE FAR SOUTHWEST GULF. THIS
WILL SET THE AREA UP IN NORTHEAST TO SOUTHWEST FLOW. AS
INSTABILITY BEGINS TO INCREASE AS THE THERMAL TROUGH TRIES TO
DEVELOP THERE IS A GOOD CHANCE OF THUNDERSTORMS EACH OF THE NEXT
FEW DAYS...MAINLY OVER HIGHER TERRAIN. THE MOST NOTABLE EXCEPTION
WILL BE DURING THE DAY TOMORROW AS A STRONG VORT MAX MOVES THROUGH
THE AREA AND MAY HELP THUNDERSTORMS BECOME MORE WIDESPREAD FROM
THE KUSKOKWIM VALLEY THROUGH THE WESTERN BRISTOL BAY ZONE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
AN UPPER LEVEL LOW OVER THE WESTERN GULF WILL TRACK NORTHWARD
THROUGH THE KENAI PENINSULA BY TOMORROW MORNING...WHILE SLOWLY
PHASING WITH ANOTHER LOW TRACKING SOUTHWARD THROUGH THE AKPEN
OVERNIGHT TONIGHT. COOL AND WET CONDITIONS ARE EXPECTED TO
PERSIST THROUGH THE WEEKEND FROM KODIAK ISLAND UP TO WESTERN
PRINCE WILLIAM SOUND/EASTERN KENAI PENINSULA. EASTERLY FLOW ACROSS
THE KENAI MOUNTAINS WILL KEEP THE WESTERN KENAI DRIER...THOUGH
SHOWERS WILL PERIODICALLY MAKE IT OVER THE MOUNTAINS AS EACH UPPER
DISTURBANCE MOVES THROUGH. THE POTENTIAL FOR DIURNAL CONVECTION
AND THUNDERSTORM DEVELOPMENT REMAINS CONFINED TO THE NORTHERN
ALASKA RANGE AND TALKEETNA MOUNTAINS THROUGH THE BEGINNING OF NEXT
WEEK....AS INSTABILITY OVER THE AREA REMAINS MARGINAL.

SURFACE RIDGING OVER THE NORTHERN GULF COAST ALONG WITH THE
THERMAL TROUGH OVER INTERIOR ALASKA WILL ACT TO TIGHTEN THE
GRADIENT OVER PARTS OF SOUTHCENTRAL. THIS WILL BE THE DRIVER FOR
AFTERNOON AND EVENING GAP WINDS DEVELOPING THROUGH THE COASTAL
RANGE AND TURNAGAIN ARM THROUGH EARLY NEXT WEEK...WITH THE MOST
WIDESPREAD WINDS THROUGH THE HEART OF THE COPPER BASIN. THESE WINDS
WILL PROVIDE A BIT OF DOWNSLOPING ALONG THE CHUGACH WHICH WILL
ALLOW SOME SUN TO PEAK THROUGH EACH AFTERNOON AND EVENING.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE MAINLAND WILL REMAIN UNDER THE INFLUENCE OF AN UPPER LEVEL LOW
THROUGH MID-WEEK. MOST OF THE SHOWERS AND THUNDERSTORMS WILL BE
DIURNALLY DRIVEN WITH ACTIVITY INCREASING DURING THE AFTERNOON AND
EVENING HOURS. THE BEST CHANCES FOR THUNDERSTORMS COMES SUNDAY
AFTERNOON AS A DISTURBANCE FROM THE GULF MOVES WESTWARD OVER THE
KUSKOKWIM MOUNTAINS NEAR PEAK HEATING WHICH SHOULD FACILITATE SOME
LIGHTNING STRIKES.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
HIGH PRESSURE EXISTS BOTH ALOFT AND AT THE SURFACE OVER THE BERING
MAKING FOR WIDESPREAD STRATUS. THE EASTERN ALEUTIANS AND ALASKA
PENINSULA WILL HAVE THE CHANCE FOR SHOWERS AS THE MAINLAND UPPER
LEVEL LOW KEEPS THEM IN HIGHER MOISTURE AND CYCLONIC FLOW. A
STATIONARY FRONT SITS NEAR THE WESTERN ALEUTIANS KEEPING A CHANCE
OF RAIN FOR THE NEXT FEW DAYS...OTHERWISE QUIET OVER THE BERING.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

BEGINNING THE EXTENDED FORECAST MONDAY EVENING...THE SPRAWLING
KODIAK CLOSED LOW CENTER WILL REMAIN THE MAIN WEATHER FEATURE OF
INTEREST WITH RIDGING OVER THE BERING SEA. THE LOW WILL EVENTUALLY
BEGIN TO LIFT NORTHWARD TUESDAY...WITH CONTINUED INLAND SHOWERS
AND INTERMITTENT RAIN ALONG THE COAST. LATE WEDNESDAY INTO EARLY
THURSDAY...A CENTRAL PACIFIC LOW WILL MERGE WITH THE
AFOREMENTIONED KODIAK LOW...BRINGING A WARM FRONT TO THE GULF OF
ALASKA. THERE IS MUCH UNCERTAINTY WITH THE TRACK OF THE LOW AND
ASSOCIATED FRONT...AS WELL AS THE POSITION OF THE UPPER LOW. THIS
RESULTS IN RATHER LARGE UNCERTAINTY WITH RESPECT TO PRECIPITATION
ACROSS SOUTHERN ALASKA...AND THE POTENTIAL FOR GALE FORCE WINDS
ALONG THE GULF COAST. THE ONE TREND AMONG ALL THE GLOBAL GUIDANCE
HAS BEEN TO SLIGHTLY SHIFT THE POSITION OF THE UPPER LOW
EASTWARD...RESULTING IN THE ASSOCIATED MOISTURE STREAM LIKELY
STAYING MAINLY OVER THE GULF COAST INTO SOUTHCENTRAL
ALASKA...KEEPING MORE DRY WEATHER OVER SOUTHWEST. HOWEVER...GIVEN
THE LARGE UNCERTAINTY WITH THIS SYSTEM...A MODERATED AND BLENDED
WPC APPROACH WAS UTILIZED...WHICH HIGHLIGHTS RAIN CHANCES OVER
INLAND SOUTHCENTRAL...AND MORE LIKELY RAIN ALONG THE GULF COAST LATE
WEDNESDAY THROUGH THURSDAY. THEREAFTER...THE UPPER LEVEL WAVE
PATTERN BECOMES A LITTLE MORE MUDDY...BUT IN GENERAL...WITH THE
GULF LOW WEAKENING AND MOVING EAST...THIS SHOULD ALLOW FOR A
GRADUAL WARMUP AND DIMINISHING CHANCES FOR PRECIP HEADING INTO
FRIDAY AND SATURDAY. THERE ARE HINTS IN BOTH THE ECMWF AND GFS
ENSEMBLE SYSTEMS...AS WELL AS THE DETERMINISTIC MODELS...THAT
POTENTIAL RIDGING BUILDS OVER SOUTHERN ALASKA AS EARLY AS THIS
WEEKEND...AND POSSIBLY INTO THE NEXT WEEK. SHOULD THIS OCCUR THE
POTENTIAL EXISTS FOR MORE HOT AND DRY CONDITIONS OVER PORTIONS OF
ALASKA...BUT RIGHT NOW THAT IS TOO FAR OUT IN TIME TO GET CAUGHT
UP IN THE DETAILS. STAY TUNED.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...TP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MTL
LONG TERM...JA



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