Small Craft Advisory 100, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
450 PM AKDT MON SEP 17 2012

.DISCUSSION...
A SERIES OF ACTIVE LOW PRESSURE SYSTEMS MOVING NORTHWARD FROM THE
CENTRAL PACIFIC UP TO THE BERING SEA COAST OF THE ALASKA MAINLAND
WILL CONTINUE TO BRING ACTIVE WEATHER TO MUCH OF THE
REALM...MAINLY THE ALASKA RANGE AND IN THE WEST.

THE FIRST IN THE SERIES IS A WEAKENING LOW ABOUT 100 MILES NORTH
OF BARROW. THIS SYSTEM BROUGHT STRONG WINDS TO THE ARCTIC AND
NORTHWEST COASTAL WATERS...THE ARCTIC OFFSHORE WATERS...AND A GOOD
PORTION OF THE INTERIOR.

THE FAIRBANKS WEATHER RADAR HAS BEEN OBSERVING WELL DEFINED
PLUMES OF BLOWING SNOW OFF THE ALASKA RANGE MOUNTAINS...FROM MOUNT
MCKINLEY SINCE 7 PM SATURDAY...AND FROM MOUNT HAYES SINCE 1 PM
THIS AFTERNOON. SUCH FEATURES ARE RARELY SEEN ON THIS RADAR...AND
THEY REFLECT STRONG WINDS ACROSS THE MOUNTAINS. THESE PLUMES ARE
NOT DISCERNIBLE ON INFRARED SATELLITE IMAGERY...BUT ARE EASILY
SEEN ON VISIBLE IMAGERY.

THE SECOND LOW IN THE SERIES IS MOVING THROUGH THE EASTERN
ALEUTIANS NOW AND WILL REACH NUNIVAK ISLAND TUESDAY AFTERNOON.
THIS SYSTEM WILL BE RELATIVELY WEAK COMPARED TO ITS PREDECESSOR.

THE THIRD LOW IN THE SERIES IS NOT YET FIRMLY IN HAND...BUT THE
GFS COMPUTER WEATHER FORECAST MODEL PROJECTS IT TO MOVE AT A HIGH
SPEED...ABOUT 70 / SEVENTY / MPH...NORTHWARD OUT OF THE PACIFIC TO
REACH THE ALASKA PENINSULA TUESDAY EVENING. AGAIN...SATELLITE
IMAGERY HAS NOT YET DEFINED A CLEAR PATTERN THAT SUCH A LOW
PRESSURE SYSTEM MUST HAVE TO BE CREDIBLE. HENCE...THE CONFIDENCE
FACTOR IS NOT HIGH YET. IT IS CLEAR THAT THIS SYSTEM COULD BE THE
ONE MOST CRITICAL TO NORTHERN ALASKA WEATHER FOR THE REST OF THIS
WEEK.

THE COMMONLY USED TERM APPLIED TO OUR THIRD LOW IS... A PINEAPPLE
EXPRESS... MEANING THAT ITS PATTERN INCLUDES STRONG FLOW ALOFT
FROM THE PACIFIC NEAR HAWAII STRAIGHT NORTH TO THE ALASKA
MAINLAND. THE GFS COMPUTER WEATHER FORECAST MODEL FORECASTS THE
SURFACE LOW TO STRENGTHEN...BUT NOT TO A GREAT EXTENT. SINCE THE
LOW IS FORECAST TO MOVE OVER LAND ONCE IT REACHES ALASKA...IT WILL
NOT HAVE THE FLUX OF ENERGY FROM THE OCEAN TO FUEL ITS POWER.

THE IMPORTANT PART OF THE PATTERN IS THE COMPRESSION OF FLOW OVER
THE ALASKA RANGE STARTING TUESDAY NIGHT AND CONTINUING INTO
WEDNESDAY. THIS IS THE BASIS OF THE HIGH WIND WATCH FOR ZONES
223...225...226 FOR ALL DAY WEDNESDAY.

THE STRONG INFLUX OF MOISTURE FROM THE SOUTH BROUGHT SIGNIFICANT
SNOWFALL TO THE BROOKS RANGE HIGHLANDS. SIX INCHES OF NEW SNOW WAS
REPORTED IN ATIGUN PASS THIS AFTERNOON. INDEED...THIS AFTERNOONS
POLAR ORBITING SATELLITE IMAGERY SHOWS A LOW PRESSURE CIRCULATION
AREA ALOFT OVER THE CENTRAL BROOKS RANGE. SUCH MEDIUM SIZED
WEATHER FEATURES SUCH AS THIS ONE CAN BRING SIGNIFICANT
PRECIPITATION...EITHER RAIN OR SNOW. THIS ONE HAS DONE SO. THIS
AFTERNOONS VISIBLE SATELLITE IMAGERY ALSO SHOWS EXTENSIVE AREAS IN
THE BROOKS RANGE COVERED BY SNOW.

ANOTHER SIGNIFICANT FEATURE OF THE WEATHER THAT THE THE THIRD LOW
IS EXPECTED TO BRING TO THE INTERIOR IS WARM TEMPERATURES...INTO
THE 60S LATER THIS WEEK. THE MEDIUM RANGE FORECAST MODELS PREDICT
ONGOING MILD WEATHER THROUGHOUT THE REALM FOR THE NEXT 10 DAYS OR
SO. THE SNOW COVER IN THE BROOKS RANGE NOTHWITHSTANDING...REAL
WINTER IS...FOR NOW...FAR AWAY FROM NORTHERN ALASKA.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE. WINDS OVER THE
BERING AND CHUKCHI SEA COAST WILL MOSTLY BE FROM THE NORTH...A
DIRECTION OF WIND THAT DISFAVORS HIGH TIDES AND SURF...EXCEPT FOR
THE NORTH SHORE OF SAINT LAWRENCE ISLAND.

&&

.HYDROLOGY...
HEAVY RAIN THAT FELL IN THE ALASKA RANGE ON SATURDAY THROUGH
SUNDAY WAS INTERCEPTED MAINLY ON THE SOUTH SIDE OF THE MOUNTAINS.
ONLY A SMALL CREST -- LESS THAN ONE FOOT -- WAS OBSERVED ON
PHELAN CREEK NEAR PAXON.

.FIRE WEATHER...
ON SUNDAY...THE GREY HAZE BETWEEN FAIRBANKS AND THE ALASKA RANGE
WAS BLOWING DUST OFF THE MOUNTAINS AND THEIR NORTHERN FOOTHILLS.
THE WIND QUICKLY FANNED THE DRY CREEK FIRE INTO RENEWED RAPID
GROWTH...THIS AFTER WEEKS OF GENTLE SMOLDERING. SMOKE WAS RAPIDLY
BLOWN NORTHWARD INTO FAIRBANKS SUNDAY EVENING. THEN...LATE SUNDAY
NIGHT AND BEFORE SUNRISE THIS MORNING...THERE WAS A LARGE DARK RED
DOME OVER THE THE FIRE. SUCH A WILDFIRE EVENT IS VERY RARE IN
ALASKA.

THE RESUMPTION OF HIGH WINDS THROUGH THE ALASKA RANGE ON WEDNESDAY
COULD BRING A RESUMPTION TO THE DRY CREEK FIRE.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR PKZ200-PKZ215-PKZ220-PKZ240-PKZ245.

WIND ADVISORY FOR AKZ223-AKZ225-AKZ226.

HIGH WIND WATCH FOR AKZ223-AKZ225-AKZ226.

&&

TF SEP 12