FXAK69 PAFG 091212
AFDAFG
NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
412 AM AKDT SAT MAY 9 2009
.DISCUSSION...
BUILDING RIDGE...SFC AND ALOFT..OVER SERN BERING SEA WILL BE THE
DOMINATE SYNOPTIC SCALE FEATURE FOR MOST OF NORTHERN ALASKA FOR
THE NEXT 5-7 DAYS. UNLIKE THE RIDGE 10 DAYS AGO THAT WAS ABOUT AS
STRONG BUT CENTERED 700 MILES FARTHER EAST...TEMPS ALOFT WITH THIS
FEATURE WILL NOT BE UNUSUALLY MILD EXCEPT RIGHT NEAR THE
HIGH...AND EAST OF 150W TREND BY EARLY NEXT WEEK SEEMS TO BE FOR
COOLER AIR TO FILTER S FROM WESTERN CANADIAN ARCTIC.
WHILE MODELS IN AGREEMENT ON THE BASIC PATTERN...SGFNT DIFFS IN
QPF S OF THE BROOKS RANGE RIGHT FROM THE START. ECMWF AND GFS LOOK
MUCH OVERDONE WITH LARGE AREA OF VERY LIGHT PREICP AND SREF POPS
MUCH TOO HIGH. WITH COOLING AT LOW LEVELS NEXT 36 HOURS IN MOST
AREAS OF THE INTERIOR ATMOSPHERE WILL BE TOO STABLE FOR CONVECTIVE
PRECIP...SO ON THE WHOLE WE FAVOR THE NAM QPF...WHICH IS MUCH THE
LOWEST OF ANY OF THE AVAILABLE GUIDANCE.
IN THE MID RANGE... THERE CONTINUES TO BE ABOVE AVERAGE AGREEMENT
AMONGST THE OPERATIONAL MODELS AND ENSEMBLES THAT A STRONG RIDGE
ACROSS THE EASTERN BERING SEA WILL BE THE DOMINATE FEATURE DURING
THE MEDIUM RANGE.
500 MB HEIGHTS AND 850 MB TEMPS ARE IN THE 90TH PERCENTILE THROUGH 
THE MIDDLE OF NEXT WEEK AT NOME AND KOTZEBUE...BUT SHY OF RECORD 
LEVELS.  THIS WILL MEAN ABOVE AVERAGE TEMPERATURES AND LITTLE THREAT 
OF PRECIPITATION ALONG THE WEST COAST...THO SFC TEMPS WILL BE
TEMPERED IN ONSHORE AREAS. DOWNSTREAM...MOST OF THE INTERIOR WILL BE IN
N-NW FLOW ALOFT WITH SEASONABLE TEMPERATURES. SHORTWAVES SPILLING
OVER THE TOP OF THE RIDGE WILL PRODUCE CLOUDS AND ISOLATED SHOWERS
AT TIMES...BUT THE MODELS SEEM OVERDONE ON THE AMOUNT OF QPF.
THE PATTERN BECOMES LESS PREDICTABLE LATE NEXT WEEK. IT APPEARS THAT 
A STRONGER SHORTWAVE MAY BREAK DOWN THE RIDGE AND BEING SOME COOLER 
AIR INTO NORTHERN AK WITH THE RIDGE REBOUNDING AGAIN NEXT 
WEEKEND...BUT DETAILS VARY FROM MODEL TO MODEL AND RUN TO RUN MAKING 
THE PREDICTABILITY BELOW AVERAGE. 
NORTH SLOPE...TEMPS MODERATING NEXT 36 HOURS AS COOL AIRMASS EXITS
TO THE EAST. SOME WARM ADVECTION SNOW OVER WESTERN ZONES SAT
NIGHT/SUNDAY BUT OTHERWISE VERY LITTLE PRECIP. WINDS ALSO
INCREASING WESTERN ZONES BUT MOSTLY FAIRLY LIGHT IN THE EAST.
WEST COAST...FORECAST ISSUE HERE IS HOW MUCH OF THE MILD AIR ALOFT
WILL BE REALIZED AT THE SURFACE. WITH SURFACE HIGH REMAINING NEAR
OR SOUTH OF ST MATTHEW ISLAND FOR THE FORESEEABLE FUTURE...AREAS
WHERE W-SW WINDS ARE ONSHORE WILL LIKELY MOSTLY STAY IN THE ST AND
OCNL FOG...WHILE INLAND AREAS WILL BE MILDER. THE HIGH ALOFT MAY
BE STRONG ENOUGH TO EVENTUALLY START TO ERODE THE MARINE ST FROM
ABOVE BUT WITH STILL PLENTY OF ICE COVER ON THE BERING ODDS ARE
NOT HIGH FOR WHOLESALE CLEARING.
INTERIOR...REASONABLY FAST FLOW ALOFT WILL MEAN VARIABLE MID-HIGH
CLOUDS BUT LIMITED PRECIP. 00Z ECMWF HAS MUCH STRONGER SHORTWAVE
DROPPING SOUTH ALONG THE ALCAN BORDER BY MID-WEEK. THIS WILL HAVE
TO BE WATCHED.
&&
.FIRE WEATHER...
NONE..AND WITH COOLER TEMPS NONE EXPECTED. HOWEVER...WITHOUT
SIGNIFICANT PRECIP ANYTIME SOON IN MOST OF THE INTERIOR...SLOW
DRYING CONTINUES.
&&
.HYDROLOGY...
MAJOR PROBLEM REMAINS THE YUKON RIVER BETWEEN ABOUT FORT YUKON AND
THE DALTON HIGHWAY BRIDGE. AS OF FRI EVENING...AIRCRAFT RECON
INDICATED THE BREAK-UP FRONT JUST DOWNRIVER OF BEAVER. DEPENDING
ON JUST WHERE AND HOW LONG ICE JAMS FORM AND LAST...SIGNIFICANT
FLOODING IS A REAL POSSIBILITY AT THIS WEEKEND AT BOTH BEAVER AND
STEVENS VILLAGE. FLOOD WARNING ALSO VCNTY RUBY DUE TO LOCAL JAMS. 
FLOOD WATCHES REMAIN IN EFFECT FOR BUCKLAND RIVER AT BUCKLAND AND
KUSKO AT MCGRATH...
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH FOR AKZ210-AKZ227.
BRISK WIND ADVISORY FOR PKZ220-PKZ225-PKZ230.
&&
$$
RT/CB MAY 09