Small Craft Advisory 109, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
206 AM AKDT SAT SEP 22 2012

.DISCUSSION...
UPPER AIR...
AN ACTIVE AND PROGRESSIVE UPPER FLOW PATTERN WILL CONTINUE
OVER THE FORECAST AREA. THE FORECAST PERIOD BEGINS WITH
A HIGH AMPLITUDE RIDGE OVER NW CANADA AND A TROUGH EXTENDING
FROM EASTERN SIBERIA SEWD INTO THE GULF OF ALASKA. THE TROUGH
WILL SWEEP NORTHWARD ACROSS THE FORECAST AREA SUNDAY INTO MONDAY.
AN UPPER LOW CENTER OVER THE GULF OF ANADYR WILL MOVE TO THE
NORTHWEST ALASKA COAST BY MONDAY AFTERNOON. FAST SOUTHERLY FLOW
ALOFT WILL CONTINUE OVER THE EASTERN INTERIOR AND ACROSS THE
ALASKA RANGE THROUGH SUNDAY...BECOMING SOUTHWESTERLY AND
DIMINISHING SOME SUNDAY NIGHT AS THE SHORT WAVE TROUGH MOVES NWD.
A SHORT WAVE RIDGE ALOFT WILL FOLLOW THE EXITING TROUGH.

SURFACE...
A BROAD AREA OF 990 MB LOW PRESSURE WILL DEVELOP OVER
NORTHWEST ALASKA SATURDAY NIGHT...SPLITTING INTO 990 MB
LOW CENTERS NEAR CAPE LISBURNE AND ABOUT 200 MILES NNE OF
BARROW BY SUN AFTERNOON. THE WESTERN LOW WILL DEEPEN TO 985-990 MB
150-200 MILES NW OF ICY CAPE BY LATE SUN NIGHT...THIS IS A
COMPROMISE SOLUTION BETWEEN THE NAM AND GFS WHICH DIFFER ON THE
CENTRAL PRESSURE AND POSITION. WIDESPREAD RAIN IS EXPECTED OVER
MUCH OF THE WEST COAST AND WESTERN INTERIOR TODAY THROUGH
SUNDAY. EXPECTED RAINFALL AMOUNTS WILL BE 0.5 TO 1 INCH WITH
LOCAL AREAS OVER 1 INCH. ANOTHER DOSE OF HEAVY RAIN IS LIKELY OVER
THE SOUTH FACING SLOPES OF THE ALASKA RANGE. AMOUNTS OF 2 INCHES
OR MORE CAN BE EXPECTED THROUGH SUNDAY NIGHT...NAM MODEL
INDICATES TOTAL RAINFALL UP TO 6 INCHES ALONG THE SOUTH FACING
SLOPES OF THE ALASKA RANGE IN AKZ225...AND UP TO 2-2.5 INCHES
ALONG THE SOUTH FACING SLOPES OF THE ALASKA RANGE IN AKZ226.

COASTAL HAZARD POTENTIAL...HIGH SURF POSSIBLE IN AKZ207 SUN
AFTERNOON THROUGH MON AND IN AKZ209 SUN NIGHT INTO MONDAY WITH A
PERIOD OF BRISK W TO NW WINDS. NAM AND GFS SOLUTIONS DIFFER SO
THIS WILL NEED TO BE WATCHED ON SUBSEQUENT MODEL RUNS.

&&

.HYDROLOGY...
A FLOOD WARNING REMAINS IN EFFECT THROUGH 1215 PM AKDT SATURDAY
FOR THE NENANA RIVER FROM CARLO CREEK TO THE CONFLUENCE WITH THE
TANANA RIVER. WATER LEVELS AT THIS TIME ARE STILL HIGH BUT SHOULD
BE STARTING TO FALL BY MORNING. THE NENANA RIVER AT HEALY IS STILL
NEAR ITS CREST OF 14.7 FEET...BUT IS EXPECTED TO BEGIN FALLING
TOWARDS MORNING AND CONTINUE TO FALL DURING THE DAY SATURDAY. THE
RIVER FLOW IS VERY FAST WITH A LARGE AMOUNTS OF DEBRIS AND BANK
EROSION. MINOR FLOODING WAS REPORTED AT HEALY. MINOR FLOODING CAN
BE EXPECTED DOWNSTREAM FROM HEALY TO THE CONFLUENCE WITH THE
TANANA RIVER THROUGH NOON SATURDAY AS THE HIGH WATER MOVES
DOWNSTREAM. THIS COULD IMPACT HUNTERS IN THE AREA BY FLOODING
VEHICLES LEFT NEAR THE RIVER OR MAKING RIVER TRAVEL IMPOSSIBLE DUE
TO LARGE AMOUNTS OF DEBRIS. MORE RAIN IS EXPECTED ALONG THE SOUTH
SIDE OF THE ALASKA RANGE DURING THE NEXT 48 HOURS...WITH ADDITIONAL
AMOUNTS OF 2 INCHES OR MORE LIKELY. THIS COULD BRING THE NENANA
RIVER BACK UP TO HIGH LEVELS.

.FIRE WEATHER...UNSEASONABLY WARM AND DRY CONDITIONS EXPECTED
SOUTHEASTERN INTERIOR TODAY THROUGH SUNDAY...ALONG WITH STRONG
CHINOOK WINDS NEAR THE ALASKA RANGE IN ZONES 223-225-226.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
FLOOD WARNING FOR AKZ221-AKZ225...NENANA RIVER FROM CARLO
CREEK TO THE CONFLUENCE WITH THE TANANA RIVER.

WIND ADVISORY FOR AKZ223-AKZ225-AKZ226-AKZ227.

SMALL CRAFT ADVISORY FOR PKZ210-PKZ220-PKZ225-PKZ230-PKZ235-PKZ240.

GALE WARNING FOR PKZ245-PKZ510.
&&

RF SEP 12