Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 221319
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
419 AM AKST SAT NOV 22 2014

.ANALYSIS AND UPPER LEVELS...
A BROAD LOW IS CENTERED OVER THE ALASKA PENINSULA EARLY THIS
MORNING AND IS THE MAIN INFLUENCE ACROSS THE SOUTHERN MAINLAND
AND SURROUNDING WATERS. A SHORTWAVE MOVING AHEAD OF THE MAIN LOW
CENTER CAN BE SEEN ON WV/IR SATELLITE IMAGERY MOVING NORTH INTO
THE CENTRAL GULF OF ALASKA. RAIN IS DEVELOPING ALONG THIS WAVE
WITH SCATTERED SHOWERS CONTINUING ALONG THE NORTHERN GULF ALONG A
DIMINISHING BOUNDARY. A FEW SHOWERS ARE MAKING IT INLAND ALONG THE
GULF COAST AND ACROSS THE KENAI...OTHERWISE DRY CONDITIONS
CONTINUE ACROSS THE SOUTHERN MAINLAND. A COLDER AIR MASS FILTERED
IN FROM THE YUKON AND HAS SETTLED ACROSS THE CENTRAL INTERIOR AND
INTO THE COPPER RIVER BASIN. TO THE WEST ACROSS THE BERING AND
ALEUTIANS...NORTHERLY FLOW HAS SET UP ON THE BACKSIDE OF THE LOW
WITH SHOWERY CONDITIONS CONTINUING ALONG WEAKER SHORTWAVES BEHIND
THE LOW PRESSURE SYSTEM.

&&

.MODEL DISCUSSION(SHORT TERM)...
MODELS CONTINUE TO BE IN GOOD AGREEMENT WITH THE SYNOPTIC PATTERN
THROUGH THE WEEKEND WITH ONLY MINOR CHANGES NEEDED FOR THE CURRENT
FORECAST PACKAGE. THE UPPER LOW CENTERED OVER THE ALASKA
PENINSULA REMAINS NEARLY STATIONARY UNTIL SUNDAY AFTERNOON AND
THEN BEGINS TO SHIFT EAST. THE HIGHER RESOLUTION MODELS OF THE NAM
AND CANADIAN REGIONAL WERE USED FOR HANDLING THE SHORTWAVES MOVING
AROUND THE LOW CENTER. THE MAIN FOCUS FOR PRECIPITATION OVER THE
WEEKEND IS ALONG SEVERAL SHORTWAVES MOVING NORTH THROUGH THE GULF
OF ALASKA AND THE NEXT FRONT APPROACHING THE WESTERN ALEUTIANS
ON SUNDAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE FORECAST CHALLENGE THROUGH THE END OF THE WEEKEND WILL BE TIMING
AND PLACEMENT OF UPPER LEVEL DISTURBANCES AS THEY MAKE THE JOURNEY
AROUND THE PERIPHERY OF A NEARLY STATIONARY LOW ALONG THE ALASKA
PENINSULA. ASIDE FROM ONE STRONGER AND WELL-DEFINED DISTURBANCE
OVER THE GULF THIS MORNING...MODELS INDICATE A PLETHORA OF WEAK
WAVES EMBEDDED IN THE FLOW. BECAUSE OF THE DIFFICULTY IN TRYING
TO TIME THESE MORE THAN 6 HOURS OUT...FORECAST CONFIDENCE IS LOW
IN THE DETAILS OF WHEN AND WHERE PRECIP WILL FALL.

GENERALLY SPEAKING THE BULK OF PRECIP WITH THESE DISTURBANCES WILL
FALL ALONG THE GULF COAST/KODIAK ISLAND. HOWEVER...WEAK FLOW ACROSS
THE COASTAL MOUNTAINS COMBINED WITH WIDESPREAD MID LEVEL INSTABILITY
WILL ALLOW SOME SHOWERS TO MOVE INLAND DIRECTLY OUT AHEAD OF EACH
DISTURBANCE. PERSISTENT OFFSHORE FLOW AT THE SURFACE IS MAINTAINING
DRY AIR IN THE COOK INLET TO SUSITNA VALLEY CORRIDOR...SO ONLY THE
HEAVIER SHOWERS WILL REACH THE GROUND.

&&

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

AN AREA OF LOW PRESSURE CENTERED BETWEEN COLD BAY AND SAND POINT
CONTINUES TO REMAIN QUASISTATIONARY...WITH VERY LITTLE EASTWARD
PROPAGATION OBSERVED OVER THE PAST 12 TO 24 HOURS. WITH THE LOW
NOT EXPECTED TO MOVE MUCH OVER THE NEXT 36 TO 48 HOURS...RAIN WILL
CONTINUE ACROSS THE ALASKA PENINSULA AND UPSLOPE LOCATIONS ALONG
THE ALASKA RANGE. RAIN WILL BEGIN TO TAPER OFF TO SHOWERS BY
SUNDAY AFTERNOON AS THE LOW BEGINS TO PUSH TOWARD THE GULF OF
ALASKA. FOR THE KUSKOKWIM DELTA AND LOWER KUSKOKWIM VALLEY...TEMPERATURES
WILL DROP CLOSER TO NORMAL VALUES OVERNIGHT TONIGHT AND AGAIN ON
SUNDAY NIGHT. TEMPERATURES WILL ONCE AGAIN BE ON A WARMING TREND
BY THE BEGINNING OF NEXT WEEK AS WINDS SHIFT BACK TOWARD THE SOUTH
AND CLOUD COVER INCREASES OVER THE REGION.

&&

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

THE LOW OVER THE ALASKA PENINSULA WILL ALLOW RAIN TO PERSIST ACROSS
THE EASTERN ALEUTIANS DURING THE DAY TODAY BEFORE TAPERING OFF TO
SHOWERS BY EARLY SUNDAY. MUCH OF THE BERING SEA AND ALEUTIANS WILL
CONTINUE TO SEE SCATTERED RAIN (MIXED WITH SNOW FOR THE WESTERN
HALF OF THE BERING SEA) THROUGH MUCH OF THE FORECAST WITH BROAD
CYCLONIC FLOW ASSOCIATED WITH THE LOW OVER THE ALASKA PENINSULA
COUPLED WITH COLDER AIR FILTERING OUT OF RUSSIA. THIS SETS UP A
FAVORABLE ENVIRONMENT FOR COLD AIR ADVECTION SHOWERS WITH TEMPERATURES
ALOFT COOLER THAN THE PRESENT SEA SURFACE TEMPERATURES.

AN AREA OF LOW PRESSURE PUSHING OFF OF KAMCHATKA WILL DRIVE A
FRONT ACROSS THE WESTERN BERING SEA ON SUNDAY. A SECOND AREA OF
LOW PRESSURE FROM THE NORTH PACIFIC IS EXPECTED TO DEVELOP ALONG
THE FRONT AND PUSH NORTHWARD TOWARD THE ALEUTIAN ISLANDS BY LATE
MONDAY OR EARLY TUESDAY. THIS WILL BRING YET ANOTHER ROUND OF RAIN
TO THE BERING SEA AND ALEUTIAN ISLANDS WITH THE WESTERN HALF OF
THE BERING SEA EXPERIENCING GALE FORCE WINDS EARLY NEXT WEEK.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
SYNOPTICALLY SPEAKING THE PATTERN LOOKS GENERALLY THE SAME FOR THE
INTO NEXT WEEK BUT SOME SMALLER SCALE DIFFERENCE HAVE ARISEN. THE
CURRENT LOW NEAR THE ALASKA PENINSULA/WESTERN GULF WILL CONTINUE
TO WEAKEN AS IT DRIFTS EASTWARD KEEPING MOST OF THE SHOWER
ACTIVITY CONFINED TO THE NORTH GULF COAST AND KODIAK ISLAND BEFORE
DISSIPATING ON TUESDAY. INLAND...THE CHANCE FOR SHOWERS IS
GREATLY REDUCED...EXPECT MOSTLY CLOUDY CONDITIONS WITH LIGHT NORTH
WINDS FOR MOST AREAS. A ROUND OF CLEAR CONDITIONS WILL SET UP MID-
WEEK BEFORE HIGHER CLOUDS BEGIN TO STREAM IN FROM THE WEST LATE
WEEK. FURTHER OUT WEST...THE FORECAST WILL CONTINUE TO BE
DOMINATED BY A DEVELOPING KAMCHATKA LOW PRESSURE AND ATTENDANT
FRONT SWINGING ACROSS THE ALEUTIANS FROM WEST TO EAST. THE BIGGEST
DIFFERENCE TODAY IS SLOWER PROGRESSION OF THE FRONT AND
DEVELOPMENT OF A NEW COMPACT SYSTEM ALONG THE FRONT ON
TUESDAY...WHICH WILL BRING A STRONG SYSTEM INTO THE CENTRAL BERING
SEA. A COMPLEX LOW PATTERN WILL SET UP THROUGH THE WEEK WITH
DETAILS STILL UNRESOLVED. THE SOUTHWESTERN MAINLAND COULD SEE
SOME PRECIPITATION WITH THE FRONT BY WEDNESDAY. COLD ARCTIC AIR
REMAINS NOWHERE OVER ALASKA AT THIS TIME WITH NO MAJOR SYSTEMS ON
THE HORIZON.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY 181.
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...KH
SOUTHCENTRAL ALASKA...SEB
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CLAY
LONG TERM...MTL



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