Small Craft Advisory 598, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
134 PM AKDT FRI AUG 8 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS A LARGE UPPER LOW CENTERED OVER THE ALASKA PENINSULA. AN
OCCLUDED FRONT ASSOCIATED WITH THIS LOW IS SITUATED ALONG THE
NORTH GULF COAST. THERE IS A WEAK UPPER HIGH OVER NORTHEAST ALASKA
AND ANOTHER RIDGE OVER THE CENTRAL AND WESTERN BERING SEA. AN
UPPER LOW OVER THE SEA OF OKHOTSK IS MOVING TOWARDS THE WESTERN
BERING SEA FROM THE WEST.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH 84
HOURS. THERE ARE SOME SMALL DIFFERENCES ON THE LOCATIONS OF FRONTS
AND UPPER LEVEL DISTURBANCES...BUT WELL WITHIN "ACCEPTABLE" RANGE.
THE FORECAST CONFIDENCE FOR THE AFTERNOON PACKAGE IS A LITTLE
ABOVE NORMAL.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...THE FRONT OVER THE NORTH GULF COAST
WILL ESSENTIALLY REMAIN THERE THROUGH SATURDAY AFTERNOON WITH
OCCASIONAL "SURGES" IN WIND AND PRECIPITATION AS VARIOUS EMBEDDED
SYSTEMS ARE PUSHED INTO THE AREA FROM THE MAIN UPPER LOW. THE
HEAVIEST RAIN WILL HIT THE EASTERN KENAI PENINSULA. THE FRONT WILL
BREAK APART LATE SATURDAY WITH THE MAIN MOISTURE PUSHING EAST INTO
THE PANHANDLE. LESS PRECIPITATION IS EXPECTED INLAND WITH
UNFAVORABLE FLOW ALOFT...MOST OF THE PRECIPITATION WILL BE "WRUNG
OUT" BY THE COASTAL MOUNTAINS.

THE MAIN UPPER LOW WILL SLIDE EAST INTO THE GULF TONIGHT THROUGH
SATURDAY NIGHT. ON SUNDAY AND MONDAY THE LOW WILL MOVE INTO THE
NORTHERN GULF AND SLOWLY BREAK APART AS ANOTHER SYSTEM ARRIVES
FROM THE WEST. SHOWERY CONDITIONS ARE EXPECTED OVER MOST OF SOUTH
CENTRAL ALASKA WITH THE RESIDUAL MOISTURE AND CYCLONIC FLOW ALOFT.

FOR SOUTHWEST ALASKA...SHOWERY CONDITIONS WILL CONTINUE FOR THE
NEXT COUPLE OF DAYS WITH THE RESIDUAL MOISTURE AND PROXIMITY OF
THE PENINSULA/GULF LOW...THOUGH DIMINISHING OVER TIME. A BRIEF
BREAK IS POSSIBLE FOR SOME AREAS SUNDAY NIGHT WITH BRIEF RIDGING
AHEAD OF THE NEXT SYSTEM APPROACHING FROM THE WEST. PRECIPITATION
ASSOCIATED WITH THE NEXT SYSTEM WILL PUSH INTO SOUTHWEST ALASKA ON
SUNDAY.

FOR THE BERING SEA/ALEUTIANS...MUCH OF THE AREA WILL BE IN BETWEEN
SYSTEMS TONIGHT WITH WEAK RIDGING SLIDING EASTWARD. PRECIPITATION
AND WINDS ASSOCIATED WITH THE SEA OF OKHOTSK LOW WILL RAPIDLY
PUSH ACROSS THE FAR WESTERN BERING TONIGHT...INTO THE WESTERN
ALEUTIANS SATURDAY MORNING THEN INTO THE CENTRAL BERING BY
SATURDAY EVENING. THE UPPER LOW ITSELF WILL REACH THE WESTERN
ALEUTIANS SUNDAY AFTERNOON AND THE SOUTH CENTRAL BERING BY MONDAY
AFTERNOON. THIS WILL DEVELOP INTO A STRONG AND LARGE LOW...BECOMING
THE DOMINANT LOW IN THE AREA BY MONDAY AND TAKING UP ALL OF THE
BERING SEA AND ALEUTIANS.

&&

.LONG TERM FORECAST...

THE MAIN WEATHER FEATURE IN THE AOR STILL LOOKS TO BE THE BERING
SEA/ALEUTIAN LOW SLIDING EASTWARD EARLY TO MID NEXT WEEK. THE GFS
AND ECMWF SHOW SOME BETTER AGREEMENT THAT THE PARENT UPPER-LOW
CENTERED JUST NORTH OF ADAK MON NIGHT WILL MOVE TO NEAR THE
ALASKA PENINSULA LATE WED NIGHT/THU. AT A COMMENSURATE TIME...THE
GEM MOVES THE UPPER FEATURE TO THE FAR SW REACHES OF THE GULF OF
AK...SO THERE IS STILL SOME SPREAD IN THE SOLUTIONS. THE LARGE
SCOPE (ALBEIT WEAKENING) OF THIS FEATURE COUPLED WITH THE
INCREASINGLY CLOSER PROXIMITY TO THE SOUTHERN MAINLAND AS TIME
WEARS ON LOOKS TO KEEP THINGS CLOUDY AND WET OVER MOST
LOCALES...PARTICULARLY COASTAL AREAS.

AT PRESENT THERE IS STILL SOME QUESTION AS TO HOW MUCH IMPACT THE
TROPICAL SYSTEMS IN THE CENTRAL TO WESTERN PACIFIC WILL HAVE ON
THE FORECAST AREA. THE REMNANT ENERGY OF TYPHOON HALONG IMPACTING
JAPAN THIS WEEKEND WILL BE MOVING UP TOWARDS THE WESTERN SEA OF
OKHOTSK BY TUE AS A SHEARED UP EXTRATROPICAL SYSTEM. TYPHOON
GENEVIEVE PASSING EAST OF WAKE ISLAND IN THE CENTRAL PACIFIC WILL
ALSO BE INCHING NORTHWESTWARD TO NEAR 35N 165E AROUND TUE AND BE
SUBSTANTIALLY WEAKER. THE POSSIBLE IMPACT FROM THESE FEATURES
WOULD BE MANIFESTED IN THEIR RESIDUAL ENERGY GETTING CAUGHT UP
INTO THE JET STREAM AND FUSING CONSIDERABLE MOISTURE INTO ANY
LINGERING OR DEVELOPING ALASKA STORM SYSTEM. WHILE THERE IS NO
OMINOUS SIGN OF THIS OCCURRING...MODELS DO NOT TYPICALLY PERFORM
WELL IN THESE TYPES OF SCENARIOS AND THESE TROPICAL FEATURES ARE
OUT THERE AT PRESENT SO THEY BEAR WATCHING. FOR NOW WILL SAY THE
THREAT IS LOW FOR IMPACT TO FORECAST AREA...STIPULATED ALSO THAT
CONFIDENCE IN THE LONG TERM FORECAST IS AVERAGE TO LOW.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 119 125 129 130.
FIRE WEATHER...NONE.

&&

LUDWIG/JAM AUG 14