Small Craft Advisory 108, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
422 AM AKDT TUE SEP 13 2011

.DISCUSSION...
THERE IS AN UPPER LOW IN THE NW BERING SEA EARLY THIS MORNING WITH
A TROUGH EXTENDING FROM THE LOW CENTER TO SOUTHEAST TO NIKOLSKI.
SHORTWAVE ENERGY ROTATING AROUND THE MAIN LOW CENTER WILL CAUSE
THE LOW TO RE-ORGANIZE FURTHER EAST NEAR THE PRIBILOF'S TONIGHT.
THE LOW IS EXPECTED TO MOVE INTO BRISTOL BAY BY 00Z FRI. A STRONG
RIDGE EXTENDS FROM THE NORTHEAST PAC AND THROUGH BC AND INTO
NORTHERN AK THIS MORNING. THE RIDGE WILL GRADUALLY GET NUDGED EAST
THE NEXT COUPLE OF DAYS BY THE ENERGY IN THE BERING SEA. A PIECE
OF THE RIDGE IS EXPECTED TO SPLIT OFF ACROSS THE SOUTHERN CHUKCHI
SEA WEDNESDAY.

SURFACE...A 990 MB LOW ASSOCIATED WITH THE LOW ALOFT IN THE NW
BERING SEA MOVES IN STEP WITH THE UPPER LOW...ENDING UP IN
BRISTOL BAY BY 00Z FRI. LITTLE CHANGE IN THE DEPTH OF THE LOW IS
EXPECTED AS IT MOVES EAST. ANOTHER LOW IN THE SOUTHEAST BERING SEA
THIS MORNING ROTATES OUT TO THE NORTHWEST AND PASSES SOUTH OF ST
LAWRENCE ISLAND TONIGHT AND CONTINUE WEST INTO THE WESTERN BERING
SEA AND WEAKENS THURSDAY. A RIDGE OF HIGH PRESSURE ACROSS CENTRAL
RUSSIA WILL EXPAND TO THE EAST ACROSS THE CHUKCHI AND BEAUFORT
SEAS THROUGH THU.

INTERIOR...A WARM AIRMASS FOR MID-SEPTEMBER WILL REMAIN ACROSS THE
INTERIOR THROUGH MID WEEK. THE 850 MB TEMP ON THE 00Z SOUNDING WAS
+8C...AND HAS CONTINUED TO WARM TO +12C AT 12Z THIS MORNING.
HIGHS YESTERDAY WERE IN THE 60S...AND TODAY SHOULD BE JUST AS
WARM...AND IN MOST AREAS A LITTLE WARMER. CERTAINLY IN LOW
ELEVATION AREAS WHERE THERE IS ENOUGH SUN TEMPS WILL HIT 70
DEGREES (IN ALL LIKELIHOOD FOR THE LAST TIME THIS YEAR). THERE ARE
MORE SCRAPS OF HIGH AND MID LEVEL CLOUDS EVIDENT ON SAT PICTS
MOVING NORTH FROM A WEAK LOW IN THE GULF WHICH IF THERE WAS ENOUGH
CLOUD COVER IT COULD CUT DOWN A BIT ON THE HEATING. CHINOOK FLOW
MAYBE ENOUGH THOU TO COUNTERACT SOME INCREASE IN THE CLOUD COVER
TODAY. AS THE RIDGE AXIS ALOFT MOVES EAST AND A WEAK SURFACE RIDGE
DEVELOPS SOUTH OF THE ALASKA RANGE THERE WILL BE SUPPORT BOTH
SURFACE AND ALOFT FOR STRONGER WIND IN THE AK RANGE PASSES. WIND
GUSTS TO AROUND 50 MPH ARE LIKELY THIS AFTERNOON AND TONIGHT AT
WINDY PASS WITH GUSTS TO 40 MPH IN THE NORMAL WINDY SPOTS IN/NEAR
THE EASTERN AK RANGE BY LATE THIS AFTERNOON. MAINLY DRY THE NEXT
COUPLE OF DAYS WITH ISOLATED SHOWERS POSSIBLE THIS MORNING ALONG
THE SOUTH SLOPES OF THE AK RANGE. A SHORTWAVE MOVES NORTH ACROSS
THE INTERIOR WEDNESDAY NIGHT INTO THURSDAY WITH A FEW SHOWERS.

NORTH SLOPE...AS THE LOW LEVEL FLOW HAS BECOME WEAKLY ONSHORE THERE
ARE PATCHES OF STATUS AND FOG ALONG THE BEAUFORT SEA COAST. THE
VISIBILITY AT DEADHORSE IS 1/4 MILE OR LESS EARLY THIS MORNING AND
WILL ADD A DENSE FOG HEADLINE FOR ZONE 203 THIS MORNING. THE
VISIBILITY AT OTHER SITES ALONG THE BEAUFORT SEA COAST HAS BEEN
ONE MILE OR LESS AT TIMES. MUCH OF THE FOG WILL LIKELY BE DIURNAL
AND WILL LIFT BY LATE THIS MORNING. OTHERWISE THERE ARE ONLY A FEW
SCRAPS OF HIGH/MID LEVEL CLOUDS EVIDENT ON SAT PICTS EARLY THIS
MORNING. AS THE HIGH BEGINS TO BUILD OFFSHORE THE ELY FLOW WILL
INCREASE...AND AREAS OF STATUS AND FOG SHOULD BECOME MORE EXTENSIVE
BY MID WEEK. TEMPERATURES WHICH HAVE BEEN WELL ABOVE NORMAL WILL
TREND TOWARD MORE SEASONABLE LEVELS AS THE ELY FLOW STRENGTHS THE
NEXT COUPLE OF DAYS.

WEST COAST...SHORTWAVES ROTATING AROUND THE LOW IN THE BERING SEA
WILL PRODUCE SOME SHOWERS/AREAS OF RAIN ALONG PARTS OF THE WEST
COAST TODAY AND TONIGHT FROM THE SEWARD PENINSULA SOUTH. THE BEST
CHANCE OF RAIN WILL BE FROM NOME WEST TO SAINT LAWRENCE ISLAND
TONIGHT AS A SHORTWAVE MOVES THROUGH.

MID-RANGE GUIDANCE IN BROAD AGREEMENT EARLY IN THE MID-RANGE...WITH
LOW ALOFT OVR BRISTOL BAY DECAYING INTO A WEAK FLOW REGIME OVER
NORTHERN ALASKA BY LATE FRI. THEREAFTER MODELS DIVERGE ON HANDLING
DEVELOPING LOWS OVER THE CENTRAL ALEUTIANS...SIBERIA AND NRN
GREENLAND. MUCH OF THIS UNCERTAINTY IS PERIPHERAL TO NORTHERN ALASKA
BUT ULTIMATELY WILL IMPACT TEMPS AND PRECIP CHANGES. 00Z MON RMOPS
FROM THE GFS SHOW FAIRLY LOW PREDICTABILITY OVR MOST OF THE CWA. AT
THIS POINT WE HAVE OPTED TO LEAN TOWARD HPC GUIDANCE THOUGH
CONFIDENCE BEYOND DAY FIVE LOWER THAN USUAL.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE.

&&

.FIRE WEATHER...MIN RH'S WILL DROP TO 30 TO 35 PCT IN MUCH OF THE
CENTRAL AND EASTERN INTERIOR THIS AFTERNOON. CHINOOK FLOW
INCREASES TODAY WITH WIND GUSTS TO 50 MPH POSSIBLE BY THIS
AFTERNOON AT WINDY PASS...AND TO 40 MPH IN PASSES WEST OF THE TOK
CUTOFF. CONDITIONS WILL LIKELY BE CLOSE TO RED FLAG CRITERIA AT
DELTA JUNCTION FROM 2-7 PM TODAY.

&&

.HYDROLOGY...NONE.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR PKZ225-PKZ230.

SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FOR PKZ210.
&&

CB/RT SEP 11