Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 191406
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
506 AM AKST WED NOV 19 2014

.ANALYSIS AND UPPER LEVELS...
THE AMPLIFIED UPPER LEVEL REMAINS OVER THE PACIFIC NORTHWEST
COASTLINE EXTENDING NORTHWEST INTO THE YUKON TERRITORY THROUGH
BARROW. THE WATER VAPOR IMAGERY IS SHOWING A SWATH OF DRY AIR
OVER THE EASTERN GULF NORTHWARD INTO THE COPPER RIVER BASIN.
WHILE THE SOUTHWEST ALASKA HAS AN UPPER LEVEL CLOSED LOW JUST
NORTH OF ATKA. AN INVERTED TROUGH ASSOCIATED WITH THIS LOW EXTENDS
THROUGH THE KUSKOKWIM DELTA REGION NORTHWARD INTO THE BROOKS
RANGE. THE RADAR IS SHOWING THE PRECIPITATION TAPERING OFF FROM
ANIAK WESTWARD INTO BETHEL THIS MORNING WITH THE TROUGH PASSAGE.
THE SOUTHWEST ALASKA AREA HAS ONSHORE FLOW WITH WARM AIR ADVECTION
RESULTING IN THE TEMPERATURES GRADUALLY RISING ABOVE FREEZING.
THE PRECIPITATION HAS CHANGED FROM FREEZING RAIN TO ALL RAIN
THROUGHOUT KUSKOKWIM DELTA REGION...EXCEPT NORTH OF BETHEL WITH
SOME COLD AIR REMAINING IN LOWER LYING AREAS. IN THE LOWER
CENTRAL BERING SEA...AT THE SURFACE THERE IS A GALE FORCE LOW
POSITIONED JUST NORTHEAST OF ATKA THIS MORNING BEFORE WEAKENING AS
THIS LOW BECOMES NEARLY STATIONARY. THE SURFACE OBSERVATIONS ALONG
THE CENTRAL ALEUTIANS ARE REPORTING SMALL CRAFT WINDS WITH THIS
LOW.

&&

.MODEL DISCUSSION...
THE MODELS ARE IN GOOD AGREEMENT WITH THE LOW OVER THE LOWER
CENTRAL BERING SEA. THIS LOW WILL BECOME ALMOST STATIONARY BEFORE
DISSIPATING BY THURSDAY. THE NAM/GFS WERE THE PREFERRED MODELS
WITH THE NEXT NORTH PACIFIC LOW TRACKING JUST SOUTH OF SAND POINT
BY THURSDAY MORNING. THE EC SEEMS TO BE THE OUTLIER WITH THIS
SYSTEM AS IT TRACKS THE LOW FARTHER EAST. BY THURSDAY EVENING THE
MODELS TRACK THE LOW JUST EAST OF THE SHUMAGIN ISLANDS. THIS LOW
WILL BECOME NEAR STATIONARY HEADING INTO THIS WEEKEND. THIS WILL
BRING GALE/STORM FORCE WINDS ALONG THE EASTERN ALEUTIAN CHAIN. THE
EASTERN BERING SEA THROUGH THE BRISTOL BAY INTERIOR WILL HAVE
EASTERLY GALE FORCE WINDS THROUGH FRIDAY. THE GULF WILL CONTINUE
WITH SOUTH TO SOUTHEASTERLY FLOW WITH A FRONTAL BOUNDARY ENTERING
THE SOUTHWESTERN GULF BY THURSDAY BEFORE TRACKING TO THE NORTHERN
GULF BY LATE THURSDAY NIGHT. THIS WILL BRING GALE FORCE WINDS WITH
A BARRIER JET FORMING IN THE NORTHERN GULF. THE FORECAST CONFIDENCE
REMAINS ABOVE AVERAGE FOR THE REMAINDER OF THE WEEK.


&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
SOUTHERLY FLOW ALOFT WILL CONTINUE THROUGH THURSDAY MORNING AND
THIS WILL CONTINUE THE TREND OF WARM WEATHER. THERE ARE A COUPLE
OF WEAK DISTURBANCES IN THE FLOW. THE FIRST ONE WILL CROSS SOUTH
CENTRAL ALASKA TODAY. THE ATMOSPHERE IS FAIRLY UNSTABLE (STEEP
LAPSE RATES) WITH THIS SYSTEM...SO ISOLATED TO SCATTERED SHOWERS
ARE EXPECTED. THE NEXT DISTURBANCE WILL PUSH INTO THE AREA THURSDAY
MORNING. THIS SYSTEM IS A LITTLE MORE COHESIVE...BUT THE MOISTURE
WILL BE CONFINED MAINLY TO COASTAL AREAS. THIS IS DUE TO A RIDGE
BUILDING AHEAD OF A STRONG LOW THAT WILL PUSH INTO THE PANHANDLE
LATE THURSDAY AND THURSDAY NIGHT. A FRONTAL SYSTEM ASSOCIATED WITH
THIS LOW WILL PUSH ACROSS THE GULF FROM SOUTHWEST TO NORTHEAST
THURSDAY AND THURSDAY NIGHT...REACHING THE COAST LATE THURSDAY
NIGHT.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 THROUGH 3)...

A MIX OF RAIN AND ISOLATED POCKETS OF FREEZING RAIN CONTINUES TO
FALL ACROSS THE EASTERN HALF OF THE KUSKOKWIM DELTA THIS
MORNING...WITH A MIX OF RAIN AND SNOW ALONG THE COAST. WINDS HAVE
ALREADY BEGUN TO SHIFT TO THE SOUTHEAST...WHICH SHOULD ALLOW
WARMER AIR TO BE ADVECTED NORTHWARD AND RAISE SURFACE TEMPERATURES
ABOVE FREEZING EARLY THIS MORNING. THIS WILL BRING AN END TO THE
FREEZING RAIN POTENTIAL...BUT RAIN AND SNOW WILL REMAIN LIKELY
THROUGH THIS MORNING UNTIL THE UPPER LEVEL TROUGH PUSHES THROUGH
THE AREA. OVER THE LOWER KUSKOKWIM VALLEY...TEMPERATURES HAVE
STEADILY ROSE OVERNIGHT WITH MOST OF THE LOW LYING LOCATIONS
CURRENTLY ABOVE FREEZING. A MIX OF RAIN AND SNOW SHOWERS WILL BE
SEEN DURING THE DAY TODAY AND BEGIN TO TAPER OFF THIS EVENING.
OVER THE BRISTOL BAY AREA...NUMEROUS RAIN SHOWERS ARE EXPECTED TO
CONTINUE ACROSS THE AREA...ESPECIALLY ALONG THE ALEUTIAN RANGE AND
THE AHKLUN MOUNTAINS. PRECIPITATION WILL ONCE AGAIN CONTINUE
THROUGH THE DAY AND TAPER OFF THIS EVENING.

ATTENTION THEN TURNS TO A RAPIDLY DEVELOPING NORTH PACIFIC LOW
THAT IS FORECASTED TO PUSH TOWARD THE ALASKA PENINSULA THURSDAY
AFTERNOON. DUE TO THE RAPID INTENSIFICATION EXPECTED OVER THE
NORTH PACIFIC...A SWATH OF HIGH-END GALE FORCE WINDS IS EXPECTED
FROM THE EASTERN ALEUTIANS EASTWARD TOWARD THE GULF OF ALASKA.
THIS LOW WILL REMAIN NEARLY STATIONARY OVER THE ALASKA PENINSULA
THROUGH SATURDAY WITH WEAK UPPER LEVEL FLOW WITH THE JET STREAM
FURTHER SOUTH IN THE NORTH PACIFIC. EXPECT PERIODS OF RAIN
(POTENTIALLY HEAVY AT TIMES) ALONG THE ALASKA PENINSULA... WITH
DOWNSLOPING REMOVING THE MAJORITY OF RAIN CHANCES ACROSS THE
BRISTOL BAY AREA.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 THROUGH 3)...

A WEAKENING AREA OF LOW PRESSURE WILL CONTINUE TO RESIDE OVER THE
CENTRAL ALEUTIANS AND CENTRAL BERING SEA THROUGH THURSDAY MORNING.
AT THIS POINT...THE LOW BEGINS PHASING WITH THE RAPIDLY DEVELOPING
LOW IN THE NORTH PACIFIC AS IT PUSHES TOWARD THE ALASKA PENINSULA.
THIS WILL CREATE A BROAD AREA OF CYCLONIC FLOW ACROSS THE BERING
SEA AND ALEUTIAN ISLANDS. SCATTERED RAIN SHOWERS (POTENTIALLY
MIXED WITH SNOW OVER THE WESTERN BERING SEA/WESTERN ALEUTIANS)
WILL BE COMMON THROUGH THE UPCOMING WEEKEND...WITH GREATEST
CHANCES OF RAINFALL OVER THE EASTERN ALEUTIANS DUE TO THE
PROXIMITY OF THE LOW PRESSURE SYSTEM OVER THE ALASKA PENINSULA.

&&

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

THE ALEUTIAN LOW POSITION WILL SHIFT EAST TOWARD THE ALASKA
PENINSULA BY THE BEGINNING OF THE EXTENDED PERIOD FRIDAY...WITH
BROAD CYCLONIC SURFACE PRESSURE ACROSS THE ENTIRE REGION. THIS
MEANS A GENERAL OFFSHORE FLOW PATTERN ACROSS SOUTHWEST...AND
SOUTHEAST ONSHORE FLOW AND CLOUDINESS ACROSS SOUTHCENTRAL.
PRECIPITATION WILL MAINLY IMPACT COASTAL LOCATIONS AS THE
ASSOCIATED FRONTAL ZONE WEAKENS ALONG THE NORTH GULF COAST THROUGH
THE WEEKEND. TEMPERATURES WILL REMAIN ABOVE AVERAGE THROUGH THE
WEEKEND...BUT THEY WILL GRADUALLY COOL CLOSER TO CLIMATOLOGY. THE
GENERAL PATTERN WILL CHANGE EARLY NEXT WEEK..BECOMING MORE
PROGRESSIVE AS THE WESTERN NORTH AMERICAN BLOCKING RIDGE WEAKENS.
CURRENTLY...HOWEVER...THERE IS MUCH UNCERTAINTY BY MIDWEEK WITH
THE TIMING OF INDIVIDUAL SYSTEMS...AND JUST HOW MUCH COLD AIR
FILTERS IN FROM THE ARCTIC REGIONS. THE ECMWF AND GFS DEPICT THIS
PATTERN CHANGE...BUT DIFFER WILDLY WITH THE OVERALL UPPER WAVE
PATTERN. IT DOES...HOWEVER...SEEM THAT THE PERSISTENT BLOCKING
PATTERN WHICH LED THE CURRENT PROLONGED WARM PATTERN FOR ALASKA
WILL FINALLY COME TO AN END.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 120 130 131 132 136 137 138 139 150 155 160 165 180
              185.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...LUDWIG
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CLAY
LONG TERM...AHSENMACHER


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