Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 271444
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
544 AM AKST TUE JAN 27 2015

.ANALYSIS AND UPPER LEVELS...
THE PATTERN ALOFT IS LOOKING LESS BLOCKY OUT WEST TODAY. FROM A
LONGWAVE PERSPECTIVE THE PATTERN IS LOOKING MORE AND MORE HIGH
AMPLITUDE AS A RIDGE BUILDS IN OVER KAMCHATKA AND THE WESTERN
BERING SEA. THE DISORGANIZED TROUGH STILL SPINS OVER THE BERING SEA
AND NORTHCENTRAL PACIFIC. ON THE EAST SIDE OF THE TROUGH THE FLOW
BEGINS TO GET A BIT MORE PROGRESSIVE WITH A FEW EMBEDDED WAVES THE
FIRST OF WHICH IS PUSHING OVER THE SOUTHWESTERN MAINLAND. THE
SECOND IS MUCH MORE ORGANIZED AND PRESENTING ITSELF AS A CLOSED
CIRCULATION ON THE WATER VAPOR. WEAK UPPER LEVEL RIDGING STRETCHES
FROM THE GULF TOWARD THE SEWARD PENINSULA. THE DEEP ARCTIC LOW
PRESSURE SLOWLY TRANSLATES EAST BUT STILL COVERS THE NORTHERN HALF
OF THE STATE.

SO WHAT DOES ALL THIS METEOROLOGICAL JARGON MEAN FROM A SENSIBLE
WEATHER PERSPECTIVE? AT THE SURFACE...BITTER ARCTIC AIR REMAINS
ENTRENCHED OVER THE INTERIOR AND NORTHERN PORTION OF THE STATE.
NOT SO BITTER BUT STILL BELOW NORMAL AIR RESIDES IN THE SOUTHWEST
AND SOUTHCENTRAL AS THE OUTFLOW PATTERN TRIES TO HOLD
STRONG...MEANWHILE WARMER SOUTHERLY FLOW ALOFT TRIES TO OVERRUN
IT...CREATING SNOW SHOWERS OVER THE SOUTHWEST MAINLAND AS WELL AS
SOME VERY LIGHT SNOW OVER THE SOUTHCENTRAL.

&&

.MODEL DISCUSSION...
SYNOPTICALLY MODELS SEEMINGLY HAVE A VERY GOOD HANDLE ON THE
EVOLUTION OF THE UPCOMING PATTERN...BOTH ALOFT AND AT THE SURFACE.
CONSENSUS HAS THE STRONG PACIFIC WAVE SOUTH OF THE ALASKA
PENINSULA ACTING TO PROPAGATE THE LONGWAVE EASTWARD AND BECOMING
THE NEW CENTER OF CIRCULATION IN THE PROCESS. BASED ON CURRENT
SATELLITE PRESENTATION THIS SEEMS LIKE A HIGH CONFIDENCE SCENARIO.
THAT FEATURE ALONG WITH THE BUILDING HIGH AMPLITUDE RIDGE OVER THE
BERING SEA WILL SHAPE THE PATTERN FOR THE NEXT FEW DAYS OR LONGER.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE FORECAST EARLY THIS MORNING CAN BE SUMMARIZED AS THE BATTLE
BETWEEN OUTFLOW AND OVERRUNNING. DRY NORTHERLY AIR AT THE SURFACE
REVERSES IN THE LOW TO MID LEVELS TO CREATE WEAK OVERRUNNING AND
SATURATION RESULTING IN VERY LIGHT SNOWFALL FOR THE SOUTHERN KENAI
AND ANCHORAGE AREA. THESE CONDITIONS SHOULD HOLD THROUGH THE
MORNING BEFORE THEY BECOME UNFAVORABLE. MIDDLE AND HIGH CLOUDS
WILL DISSIPATE OVERNIGHT WHILE NORTHERLY WINDS AND BELOW NORMAL
TEMPERATURES CONTINUE. ON WEDNESDAY A FRONT WILL MOVE TOWARD THE
NORTHERN GULF AND DISSIPATE BRINGING A ROUND OF SNOW SHOWERS LATE
WEDNESDAY NIGHT...MAINLY FOR THE NORTH GULF COAST.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (TODAY THROUGH THURSDAY
NIGHT)...

WARMER AIR HAS MOVED INTO THE SOUTHWEST MAINLAND OVERNIGHT...BRINGING
WIND CHILLS ACROSS THE KUSKOKWIM DELTA WARMER THAN 40 BELOW AND
WILL REMAIN THAT WAY...SO WE HAVE CANCELLED THE WIND CHILL
ADVISORY THERE. OVER THE WESTERN BRISTOL BAY AREA...WHILE THE
MAJORITY OF THE SNOW HAS FALLEN ON MONDAY AND MONDAY NIGHT...LIGHT
SNOW WILL CONTINUE FOR ANOTHER FEW HOURS. OVERALL...WINDS HAVE
DECREASED SOMEWHAT ACROSS THIS AREA AS WELL SO WIDESPREAD
VISIBILITIES BELOW ONE MILE ARE NOT EXPECTED BUT COULD HAPPEN AT
TIMES STILL THROUGH MID MORNING. WITH THAT IN MIND...WE WILL
CONTINUE THAT ADVISORY THROUGH 9AM. OTHERWISE...GENERALLY DRY
CONDITIONS ARE EXPECTED FOR THE NEXT COUPLE DAYS ACROSS THE
SOUTHWEST MAINLAND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (TODAY THROUGH THURSDAY
NIGHT)...

WITH THE LOW SOUTH OF THE ALEUTIAN CHAIN REMAINING IN THE SAME
GENERAL AREA FOR THE NEXT COUPLE DAYS...WINDS ACROSS MUCH OF THE
BERING SEA AND ALEUTIANS WILL REMAIN STRONG OUT OF THE NORTH AND
NORTHEAST. THIS WILL CONTINUE TO CAUSE BLOWING SNOW ACROSS THE
PRIBILOF ISLANDS AND WESTERN ALEUTIANS WHERE TEMPERATURES ARE COLD
ENOUGH AND THERE IS SNOW TO TRANSPORT. FOR THE PRIBILOFS...WE HAVE
CANCELLED THE SNOW ADVISORY FOR BLOWING SNOW AS VISIBILITIES ARE
EXPECTED TO REMAIN ABOVE ONE-HALF MILE. OTHERWISE...THIS REGION
CAN EXPECT CONTINUED STRONG AND GUSTY WINDS WITH RAIN AND SNOW
SHOWERS ALONG WITH COOLER TEMPERATURES COMING FOR THE MIDDLE OF
THE WEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
A WEAKENING FRONT/INVERTED TROUGH WILL BRING PRECIPITATION TO
KODIAK ISLAND...ALONG WITH AREAS ALONG THE ALASKA PENINSULA AND
NORTHERN GULF COAST TOWARDS THE END OF THE WEEK. OTHERWISE MUCH
OF THE SOUTHERN MAINLAND WILL REMAIN IN A DRY OFFSHORE FLOW
PATTERN THROUGH FRIDAY AS A STOUT UPPER RIDGE BUILDS OVER THE
WESTERN BERING AND TEMPERATURES SLOWLY MODERATE TO NEAR NORMAL
VALUES. A STRONGER NORTH PACIFIC LOW WILL SET UP JUST SOUTH OF THE
ALASKA PENINSULA (SIMILAR TO THE PREVIOUSLY MENTIONED SYSTEM)
OVER THE WEEKEND...AND BRING ANOTHER ROUND OF GUSTY WINDS AND
PRECIPITATION TO THE AREAS ALONG THE SOUTHERN GULF COAST AND
ALASKA PENINSULA.

FORECAST CONFIDENCE BEGINS TO DIMINISH EARLY NEXT WEEK AS THE
UPPER RIDGE MIGRATES EASTWARD AND EVOLVES INTO A CLOSED UPPER HIGH
OVER THE EASTERN BERING/WESTERN MAINLAND. WHERE THIS FEATURE
ULTIMATELY SETS UP WILL HAVE A LARGE IMPACT ON THE NORTHWARD
PROGRESSION OF A NORTH PACIFIC LOW MOVING TOWARDS THE SOUTHERN
GULF...AND THUS HAVE A LARGE IMPACT ON PRECIPITATION CHANCES OVER
THE MAINLAND. AT THIS POINT IT APPEARS THAT ANY PRECIP WILL REMAIN
FAR ENOUGH SOUTH TO MAINLY IMPACT AREAS FROM THE ALASKA PENINSULA
TO THE GULF COAST...WITH MUCH OF THE MAINLAND AND BERING SEA
REMAINING DRY AS PERSISTENT OFFSHORE FLOW KEEPS GUSTY WINDS ALONG
THE NORTH GULF COAST.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...SNOW/BLOWING SNOW ADVISORY 161.
MARINE...GALE WARNING 119 120 127 130 131 132 138 139 150 155 165
           170 172 173 174 175 176 177 178 179 185.
         HEAVY FRZ SPRAY 127 139 140 160 180 185.
FIRE WEATHER...NONE.

&&

$$

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


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