781
FXAK69 PAFG 122317
AFDAFG
NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
317 PM AKDT MON AUG 12 2013
.DISCUSSION...
UPPER LEVEL RIDGE BUILDING FROM SOUTHEAST OVER CANADA AND EXTENDING
ACROSS CENTRAL ALASKA TO THE WEST COAST TOMORROW. AN UPPER LEVEL
LOW WILL CONTINUE TO SLOWLY MOVE EASTWARD ACROSS THE SOUTHERN
BERING SEA THROUGH THE WEEK WITH A WEAK IMPULSE MOVING NORTHWARD
UP OVER THE RIDGE BETWEEN THE TWO SYSTEMS ON WEDNESDAY MORNING AND
EXPECTED TO BE OVER THE YUKON DELTA. THERE ARE SOME DIFFERENCES IN
THE TIMING OF THIS UPPER LEVEL SHORTWAVE WITH THE GFS ROUGHLY 6
HOURS SLOWER THAN THE ECMWF. IN EITHER CASE THIS FEATURES WILL
BRING PRECIPITATION BACK TO SOUTHERN PORTIONS OF WESTERN ALASKA ON
LATE TUESDAY NIGHT INTO WEDNESDAY MORNING. FINALLY THE UPPER LEVEL
LOW OVER THE CHUKCHI SEA WILL WEAKEN INTO AN UPPER LEVEL TROUGH AS
IT MOVES EASTWARD FROM THE CHUKCHI SEA TO THE BEAUFORT SEA ON
WEDNESDAY AFTERNOON.
AT THE SURFACE...THE 1025 MB HIGH PRESSURE 400 NM NORTHEAST OF
BARROW WILL CONTINUE TO TO MOVE EAST TOWARDS BANKS ISLAND. HIGH
PRESSURE ALONG THE BERING STRAIT WILL MOVE NORTHEAST AND BE 114 NM
NORTHWEST OF BARROW BY WEDNESDAY. THE THERMAL TROUGH WILL CONTINUE
TO BUILD INTO THE EASTERN INTERIOR. FINALLY THE 986 MB LOW LOCATED
NORTH OF THE CENTRAL ALEUTIANS WILL MOVE TO 225 NM WEST OF THE
PRIBILOFS BY TUESDAY EVENING BEFORE WEAKENING AND MOVING TO THE
SOUTHEAST.
NORTH SLOPE...EXPECT SCATTERED RAIN SHOWERS AS THE UPPER LEVEL
LOW WEAKENS TO AN UPPER LEVEL TROUGH AND MOVES EAST ACROSS THE
ARCTIC COAST TONIGHT THROUGH TUESDAY. EXPECT SOME ISOLATED
THUNDERSTORMS TO DEVELOP IN THE NORTHWEST BROOKS RANGE ASSOCIATED
WITH THE UPPER LEVEL LOW DYNAMICS. DENSE FOG DEVELOPED THIS
MORNING AND ANTICIPATE REDEVELOPMENT FOR AREAS LIKE DEADHORSE
OVERNIGHT. BARTER ISLAND HAS ALREADY DEVELOPED QUARTER OF A MILE
VISIBILITIES IN FOG AND HAVE ISSUED DENSE FOG HEADLINE TO CONTINUE
THROUGH MORNING. COULD POTENTIALLY NEED ONE AS WELL FOR PUBLIC
ZONE 203. SHOULD STARTED TO HAVE CLEARING BY TUESDAY AND TUESDAY
AFTERNOON FOR THE NORTH SLOPE.
WESTERN ALASKA...LOOKS LIKE CLEARING FROM SOUTHWARD TO NORTH FOR
MUCH OF THE WESTERN COAST. THIS WILL BE A DECENT BREAK IN
PRECIPITATION AS HIGH PRESSURE BUILDS OVER THE AREA.
HOWEVER...THERE IS ANOTHER WEAK SHORTWAVE THAT WILL BRING SHOWERS
ACROSS THE AREA ON LATE TUESDAY NIGHT INTO WEDNESDAY PRIMARILY FOR
AREAS FROM SEWARD PENINSULA AND YUKON DELTA. THERE IS A STRONG
UPPER LEVEL LOW JUST NORTH OF THE CENTRAL ALEUTIANS THAT WILL
BRING SOME STRONGER WINDS ACROSS MARINE ZONE 210 AND GUSTY WINDS
FOR ST LAWRENCE ISLAND. THIS LOW WILL THEN SLOWLY DRIFT SOUTHWARD
BY THURSDAY.
CENTRAL AND EASTERN INTERIOR...WARM AND DRY CONDITIONS PERSISTING
ONCE AGAIN. THE BAND OF SHOWERS THAT WAS EXPECTED FOR MONDAY ENDED
UP MAINLY BEING IN THE FORM OF CLOUD COVER WHICH HAS STAYED WEST
OF FAIRBANKS MAINLY IN A NORTH SOUTH DIRECTION BETWEEN GALENA AND
MANLY HOT SPRINGS. LATEST SATELLITE IMAGERY SHOWS MAJORITY OF
CLEAR SKIES ACROSS EASTERN INTERIOR AS HIGH PRESSURE IS ALREADY
BUILDING ACROSS THE AREA. EXPECT REMAINING CLOUD COVER OVER
CENTRAL INTERIOR TO CLEAR OUT TONIGHT FOR MOSTLY CLEAR SKIES
TOMORROW. THERE MAY BE SOME ISOLATED SHOWER THAT DEVELOP JUST WEST
OF EAGLE...BUT IT LOOKS LIKE THAT MAY STRUGGLE THIS EVENING WITH
THE HIGH PRESSURE BUILDING. AS FOR CONVECTION...IT LOOKS BLEAK
ACROSS THE INTERIOR WITH WARMING AND DRIER CONDITIONS ON TAP.
THERE WAS A VERY SLIGHT CHANCE OF THUNDERSTORM DEVELOPMENT ON
WEDNESDAY AFTERNOON MAINLY ALONG THE CANADIAN AND UPPER TANANA
VALLEY AREA WITH SOME WEAK INSTABILITY. HOWEVER THE KEY WILL BE
HOW MUCH OF IT WILL BE NEEDED TO OVERCOME THE RIDGE AND MAY BE
CAPPED. FOR NOW HAVE MENTIONED SOME ISOLATED THUNDERSTORMS. ON
THURSDAY NIGHT CONFIDENCE IS NOT EVEN WORTH MENTIONING IN
FORECAST.
COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE
&&
.FIRE WEATHER...
WITH THE RIDGE BUILDING BACK OVER THE AREA THIS WEEK EXPECT
WARMER AND DRIER CONDITIONS ACROSS THE CENTRAL AND EASTERN
INTERIOR. NOT ONLY WILL THERE BE LITTLE RECOVERY OF THE RELATIVE
HUMIDITY VALUES EACH DAY...THE FUELS WILL ALSO REMAIN DRY. THERE
IS A VERY ISOLATED CHANCE OF THUNDERSTORMS ALONG THE CANADIAN AND
UPPER TANANA VALLEY AND FORTYMILE COUNTRY ON WEDNESDAY AFTERNOON.
OTHERWISE NOT MUCH IN WAY OF THUNDERSTORM DEVELOPMENT EXPECTED.
ALSO...DO NOT ANTICIPATE WINDS ANY GUSTY WINDS TO BE ABOVE 20 MPH
DURING THE MID TO LATE AFTERNOON THROUGH THE WEEK AS WELL. TO BE
STRONGER THAN GUST TO 20 MPH DURING THE AFTERNOONS THROUGH MID
WEEK.
&&
.HYDROLOGY...
NONE.
&&
.AFG WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR PKZ210.
&&
$$
MAK/JL AUG 13