Small Craft Advisory 370, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
140 PM AKDT TUE MAY 6 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN TODAY HAS A LARGE LONGWAVE TROUGH
EXTENDING UP THE COAST OF NORTH AMERICA INTO THE YUKON AND A LARGE
LOW IN THE ARCTIC WITH A SHARP TROUGH EXTENDING OUT OF IT OVER
MOST OF THE MAINLAND PART OF THE STATE. THERE IS A SECONDARY
CENTER ALONG THIS TROUGH SOUTH OF KODIAK THAT IS BEGINNING TO CUT
OFF INTO A SEPARATE UPPER LEVEL LOW AS IT MOVES EASTWARD.
AN UPPER LEVEL TROUGH IS ALSO MOVING THROUGH SOUTHWEST ALASKA FROM
THE WEST TODAY. THIS IS ALSO HELPING TO CREATE SOME ADDITIONAL
MOISTURE AND LIFT TO THE MIX.
FARTHER WEST THERE IS ANOTHER UPPER LEVEL RIDGE THAT IS PUSHING
INTO THE ARCTIC LOW WITH THE RESULT BEING A FLATTENED RIDGE OVER
THE BERING SEA REGION PRODUCING ZONAL WESTERLY FLOW IN THAT
REGION. AT THE SURFACE THE LOW SOUTH OF KODIAK IS HEADING EASTWARD
BUT THE FRONT ASSOCIATED WITH IT IS MOVING ON SHORE ALONG THE
NORTH GULF COAST THIS AFTERNOON. THIS IS INCREASING WIND AND RAIN
FOR MOST OF SOUTH CENTRAL ALASKA WHILE PULLING IN NORTHWEST FLOW
TO SOUTHWEST ALASKA. THE STRONG SURFACE RIDGE SOUTH OF THE
ALEUTIANS WILL AMPLIFY IN THE EASTERN BERING SEA TOMORROW AND
BEGIN TO HAVE A MORE PRONOUNCED IMPACT ON THE WEATHER AS IT DOES.
&&

.MODEL DISCUSSION...
MODELS CONTINUE TO SHOW VERY GOOD AGREEMENT THROUGH THE FIRST FEW
DAYS. THE NAM HAS BEEN GOOD OVER MAINLAND PARTS OF THE STATE WITH
HIGHER DETAIL BUT IS THE MODEL THAT IS STRUGGLING WITH THE COMPLEX
LOW THAT WILL BE IN THE NORTHWEST BERING SEA WEDNESDAY THROUGH
FRIDAY. THE ECMWF AND GFS ARE HANDLING THIS SYSTEM FAIRLY WELL SO
THEY CAN BE USED IN THAT AREA WHERE THEN NAM APPEARS TO BE
STRUGGLING.
&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...RAIN...WITH GUSTY WINDS THROUGH CHANNELED
TERRAIN HAS BEEN THE STORY IN SOUTH CENTRAL ALASKA TODAY. THE
UPPER LEVEL FLOW HAS BEEN FROM THE DUE SOUTH INSTEAD OF SOUTHEAST
WHICH IS WHY THERE HAS NOT BEEN MUCH DOWNSLOPING TO CUT OFF THE
RAINFALL ON LEEWARD SIDES OF THE KENAI THROUGH TALKEETNA
MOUNTAINS. THE EXCEPTION IS IN THE COPPER RIVER BASIN WHERE THERE
IS DOWNSLOPING OFF THE CHUGACH AND WRANGELL MOUNTAINS. WHILE THERE
ARE GUSTY WINDS ALONG THE COPPER RIVER AND ONLY LIMITED RAINFALL
THERE IS STILL ENOUGH MOISTURE TO KEEP RELATIVE HUMIDITY VALUES UP
AND FIRE WEATHER CONCERNS DOWN EVEN IN THE COPPER RIVER BASIN.
THE SYSTEM MOVING THROUGH SOUTHCENTRAL WILL TAPER OFF THE RAINFALL
OVERNIGHT AND LEAVE SOME LINGERING SHOWERS WEDNESDAY BEFORE THE
HIGH PRESSURE BUILDING INTO SOUTHWEST ALASKA BEINGS TO ASSERT
ITSELF THURSDAY AND FRIDAY IN SOUTHCENTRAL BRINGING CLEARING SKIES
AND DRIER WEATHER AGAIN.

SOUTHWEST ALASKA...
THE TROUGH MOVING THROUGH THE KUSKOKWIM DELTA IS BRINGING IN
DRIER AND MORE STABLE AIR BEHIND IT. HOWEVER THIS STABLE AIR IS
ALSO BRINGING STRATUS FROM THE BERING SEA INTO THIS AREA. THIS
WILL PROBABLY PERSIST OVER A GOOD PART OF THE AREA OVERNIGHT BUT
WILL BEGIN TO CLEAR UP TOMORROW DURING THE DAY. THE BRISTOL BAY
REGION IS TRAPPED UNDER VERY MOIST AIR A JUST ENOUGH LIFTING TO
BRING LOW CLOUDS AND FOG TO A GOOD PORTION OF THE AREA. THIS WILL
BE THE CASE THROUGH THE NIGHT BUT WILL IMPROVE SLOWLY THROUGH THE
DAY TOMORROW. &&

.LONG TERM FORECAST...
AFTER THE CURRENT SYSTEM MOVES EAST OF THE REGION THE HIGH
PRESSURE BUILDING INTO SOUTHWEST ALASKA WILL BRING CLEAR SKIES TO
A LARGE PORTION OF MAINLAND ALASKA AGAIN. TEMPERATURES WILL ALSO
LIKELY RISE ABOVE NORMAL BY THE END OF THE WEEK...BUT ARE UNLIKELY
TO SET RECORD HIGH TEMPERATURES LIKE LAST WEEK.
&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 119.
FIRE WEATHER...NONE.
&&

MAY 14