408
FXAK68 PAFC 130149 CCA
AFDAFC
SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
550 PM AKDT MON AUG 12 2013
CORRECTED ISSUANCE TIME
.ANALYSIS AND UPPER LEVELS...
THE LONG WAVE TROUGH AND ASSOCIATED 500 MB LOW NORTH OF THE WESTERN
ALEUTIANS IS SLOWLY LIFTING NORTH INTO THE WESTERN BERING SEA. THE
JET STREAM OVER WESTERN ALASKA IS SHEARING APART WITH ANOTHER MAXIMUM
SOUTH OF THE ALEUTIANS ROUNDING THE BASE OF THE TROUGH.
WEAK HIGH PRESSURE OVER THE YUKON-KUSKOKWIM DELTA AND WESTERN ALASKA
IS HELPING TO BREAK UP CLOUD COVER BETWEEN THE BERING SEA LOW AND THE
MOIST PACIFIC AIR FLOWING OVER SOUTHCENTRAL ALASKA. IN THIS
AREA...FOG HAS BEEN AN ISSUE WITH NO MAJOR WEATHER FEATURE TO CLEAR
AWAY THE LOW LEVEL MOISTURE.
LIGHT RAIN IS SLOWLY ENDING OVER THE KENAI PENINSULA AND COOK INLET
REGION AS A LONG FETCH OF MOISTURE TRAVELS FROM THE SUBTROPICS...OVER
THE ALASKA RANGE...TO THE ARCTIC COAST.
DRIER AIR SITS JUST EAST OF THE PLUME... KEEPING THE COPPER RIVER
BASIN AND EASTERN PRINCE WILLIAM SOUND MOSTLY CLEAR AND DRY.
.MODEL DISCUSSION...
THE NAM IS THE MODEL OF CHOICE TODAY AND TAKES THE SURFACE LOW FROM
THE WESTERN ALEUTIANS NORTH ALONG 180W THROUGH TUESDAY WHERE THE
STORM DEEPENS TO 984MB. WEDNESDAY THE STORM FILLS SLIGHTLY WHILE
REMAINING NEARLY STATIONARY.
THE UPPER LEVEL COMPLEX OVER THE WESTERN BERING TO CONSOLIDATE OVER
THE NEXT 48 HOURS. AS THIS TAKES PLACE...THE CLOSED LOW OVER EASTERN
RUSSIA TO LIFT NORTH TONIGHT AND TOMORROW TEARING APART THE FETCH OF
MOISTURE FROM 30N TO THE ARCTIC. THE CLOSED LOW IN THE GULF OF ALASKA
TO MOVE TO THE PACIFIC NORTHWEST AS WELL. THE REMAINING LARGE SCALE
LOW OVER THE BERING TO DOMINATE THE PATTERN THROUGH THE END OF THE
WEEK. HOW THIS LOW INTERACTS WITH THE HIGH OVER THE YUKON AND WHEN
THE LOW PROGRESSES EASTWARD ARE THE DETERMINING FACTORS FOR THE
REMAINDER OF THE WEEK.
AS IT STANDS...THE NAM IS THE SLOWER PROGRESSION OF THE LOW COMPARED
TO THE EC AND GFS. THE GFS ENSEMBLES HINT AT THE SLOWER PROGRESSION
AS WELL AND THAT IS WHY WE LEANED TOWARD THE SLOWER NAM AT THIS TIME.
MOISTURE WILL RETURN TO SOUTHWEST ALASKA WEDNESDAY AND TO
SOUTHCENTRAL ALASKA BY LATE WEEK AS SOUTHWESTERLY WINDS RETURN IN
ADVANCE THE BERING SEA LOW.
.SHORT TERM FORECAST...
SOUTHCENTRAL...AS THE DEEP FEED OF MOISTURE CUTS OFF... PERSISTENT
RAIN WILL BECOME SPOTTY AND MORE SHOWERY THROUGH MIDWEEK. A COUPLE
WEAK DISTURBANCES TO MOVE THROUGH THE AREA TOMORROW NIGHT AND
WEDNESDAY NIGHT FOR A CHANCE AT A FEW SHOWERS. MORNING FOG BECOMES
THE PREDOMINANT WEATHER ISSUE ALONG THE COAST AND INLAND. CLOUDS WILL
REMAIN OVER THE REGION WITH OCCASIONAL BREAKS HELPING TO KEEP
TEMPERATURES AT OR SLIGHTLY ABOVE NORMAL.
SOUTHWEST...WITH THE MAIN STORM TO WEST AND WEAK PRESSURE
DEVELOPING...SHOWERS AND WINDS ALONG THE ALASKA AND THE ALEUTIAN
RANGE WILL DIMINISH. A FRONT MOVING OUT AHEAD OF THE MAIN LOW IN THE
WESTERN BERING WEDNESDAY WITH BRING SOME RAIN TO THE COAST AND
MODERATE WINDS. AS THE FRONT WORKS INLAND WEDNESDAY AFTERNOON AND
EVENING...RAIN AND WINDS WILL DIMINISH. THE NEXT THREAT WILL BE WHEN
THE LOW SWINGS INTO THE EASTERN BERING THURSDAY. PATCHY FOG WILL BE
AN ISSUE EACH MORNING.
BERING SEA AND ALEUTIANS...THE LOW OVER THE WESTERN BERING PUSHING A
FRONT ACROSS THE BERING AND ALEUTIAN CHAIN TODAY AND TONIGHT.
MODERATE RAINFALL AND GALE FORCE WINDS WILL ACCOMPANY THE FRONT AND
AROUND THE LOW INTO TOMORROW WITH GOOD UPPER LEVEL SUPPORT FROM THE
JET AND THERMAL GRADIENTS AT MID LEVELS. THE LOW WILL WRAP UP
TOMORROW IN THE WESTERN BERING WITH MODERATE PRECIP NEAR THE LOW. THE
LOW WILL FILL A BIT INTO WEDNESDAY AND THURSDAY WITH PRECIP BECOMING
MORE SHOWERY AND WINDS DIMINISHING.
.LONG TERM FORECAST...
BY MID TO LATE WEEK...STACKED LOW OVER THE EASTERN BERING WITH RIDGE
OVER THE YUKON IN ADDITION TO A STACKED LOW NEAR VANCOUVER ISLAND.
STACKED LOW OVER THE EASTERN BERING TO SWING TO THE EAST THURSDAY
INTO FRIDAY AND INTO THE GULF BY SUNDAY MORNING. A RIDGE WILL BUILD
OVER THE BERING. IN GENERAL...SHOWERS WILL FOLLOW THE LOW ACROSS
SOUTHWEST ALASKA THURSDAY AND FRIDAY AND INTO THE GULF FOR THE
WEEKEND. THE BERING WILL EXPERIENCE INCREASING STRATUS UNDER THE
RIDGE.
.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD ADVISORY 121
MARINE...GALE 155 170 171 172 175 176 179 185
FIRE WEATHER...NONE
NELSON/SNIDER AUG 13