Area Forecast Discussion
Issued by NWS Anchorage, AK

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
000
FXAK68 PAFC 211329
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
529 AM AKDT THU AUG 21 2014

.ANALYSIS AND UPPER LEVELS...

NO DRAMATIC CHANGE IN THE LARGE SCALE UPPER AIR PATTERN FROM
YESTERDAY...WITH A CLOSED LOW OVER THE WESTERN BERING...AND AN
EASTERN PACIFIC RIDGE CENTERED OVER 40N. AN ACTIVE SUBTROPICAL JET
STREAM IS WRAPPING AROUND THE AFOREMENTIONED UPPER TROUGH...WITH
THE FIRST OF MANY SHORTWAVE DISTURBANCES TRACKING INTO THE
SOUTHWEST GULF OF ALASKA. ACROSS THE MAINLAND...SHORTWAVE RIDGING
IS TRANSITING THE NORTHERN GULF OF ALASKA...WITH WEAK UPPER LEVEL
MIGRATORY WAVES TRACKING THROUGH SOUTHWEST ALASKA. THIS WEAK FLOW
PATTERN/PRESSURE GRADIENT PATTERN ACROSS THE MAINLAND IS PROMOTING
AREAS OF FOG AND STRATUS...ESPECIALLY ACROSS PORTIONS OF THE
NORTHERN GULF AND COOK INLET. WITH TIME...THE PATTERN WILL BEGIN
TO TRANSITION TO A MORE ACTIVE ONE AS THE WESTERN BERING TROUGH
MOVES EAST...WITH THE SUBTROPICAL JET STREAM TRACKING INTO
SOUTHERN ALASKA LATE THIS WEEKEND.

&&

.MODEL DISCUSSION...

THE NUMERICAL GUIDANCE IS IN GOOD AGREEMENT WITH THE GENERAL
SYNOPTIC PATTERN HEADING INTO NEXT WEEK...BUT IS IN POOR
AGREEMENT WITH THE TIMING AND STRENGTH OF A SUBTROPICAL WARM FRONT
EXPECTED TO IMPACT SOUTHERN ALASKA THIS WEEKEND. ALL THE NUMERICAL
GUIDANCE IS STRUGGLING MIGHTILY WITH THE PHASING OF A WEAK LOW
NEAR KAMCHATKA WITH THE LARGER SCALE TROUGH...AND THE EVENTUAL
DEVELOPMENT OF THE SURFACE LOW AS IT TRACKS INTO THE EASTERN
BERING SEA. THE ECMWF IS THE MOST AGGRESSIVE AND FAST...WHILE THE
GFS AND NAM ARE SLOWER. FOR NOW...THE FORECAST WILL TAKE A MIDDLE
GROUND APPROACH WITH A BLEND TO THE GFS AND ECMWF TO ACCOUNT FOR
THE UNCERTAINTY.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
WEAK FLOW ALOFT WILL CONTINUE TO SUPPORT DIURNAL AFTERNOON AND
EVENING MOUNTAIN SHOWERS...WITH A WEAK SOUTHWESTERLY COMPONENT
ALOFT HELPING TO PUSH SOME OF THOSE SHOWERS INLAND...ESPECIALLY
NEAR THE TALKEETNA AND WRANGELL MOUNTAINS. MARINE FOG AND LOW
STRATUS CONTINUES TO LINGER ACROSS PORTIONS OF COOK INLET...AND IT
HAS MADE FURTHER PROGRESS INTO THE SOUTHERN SUSITNA VALLEY AND THE
ANCHORAGE BOWL. MOST FOG WILL DIMINISH WITH DAYTIME HEATING...BUT
THE POSSIBILITY EXISTS FOR A RETURN TO FOG OVERNIGHT...ESPECIALLY
ACROSS THE NORTHERN KENAI ALONG THE INLET. ON FRIDAY...A
DISTURBANCE WILL SPREAD CLOUDS AND MORE WIDESPREAD SHOWERS INTO
MUCH OF SOUTHCENTRAL BEFORE RETURNING TO LARGELY PLEASANT LATE
SUMMER CONDITIONS SATURDAY.

SOUTHWEST ALASKA...
WEAK DISTURBANCES ALOFT MOVING IN FROM THE SOUTH WILL CONTINUE TO
SUPPORT EXTENSIVE CLOUDS AND ISOLATED TO SCATTERED RAIN SHOWERS
ACROSS PORTIONS OF THE KUSKOKWIM DELTA AND BRISTOL BAY REGION.
AFTERNOON AND EARLY EVENING CONVECTIVE SHOWERS WILL CONTINUE TO
DEVELOP ALONG THE ALASKA AND ALEUTIAN RANGE TODAY AND AGAIN FRIDAY
BEFORE A WARM FRONT MOVES IN LATE SATURDAY INTO SUNDAY...SPREADING
RAIN ACROSS ALL OF SOUTHWEST ALASKA.

BERING SEA/ALEUTIANS...
THE WESTERN BERING LOW WILL BEGIN TO TRACK EAST FRIDAY...WITH
SHOWERS MOVING ACROSS THE WESTERN AND CENTRAL ALEUTIANS. ON
SATURDAY...A MORE STOUT WARM FRONT WILL MOVE INTO THE EASTERN
BERING AND ALEUTIANS...WITH WIDESPREAD RAIN IMPACTING THOSE
LOCATIONS.

&&

.LONG TERM FORECAST (MONDAY AUG 25 - THU AUG 28)...

AN ACTIVE WAVE PATTERN WILL BE UNDERWAY MONDAY AS THE REMNANTS OF
THE BERING TROUGH WILL BE TRANSITING ACROSS SOUTHERN ALASKA...WITH
CLOUDS AND RAIN SHOWERS LINGERING INTO TUESDAY. A BRIEF BREAK MAY
DEVELOP LATE TUESDAY INTO WEDNESDAY BEFORE ANOTHER BERING
LOW...PHASING WITH A LARGE COLD UPPER VORTEX OVER NORTHERN
ALASKA...MOVES INTO SOUTHERN ALASKA...WITH MORE RAIN AND CLOUDS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FLOOD ADVISORY...121
         DENSE FOG ADVISORY 101 121.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

$$

AHSENMACHER AUG 14


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.