Small Craft Advisory 724, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
146 PM AKDT FRI SEP 19 2014

.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL PATTERN HAS A HIGH AMPLITUDE LONGWAVE TROUGH THAT
EXTENDS FROM A LOW NEAR KODIAK ISLAND SOUTHWARD TO AROUND 35N.
WEST OF THAT THERE IS A FAIRLY HIGH AMPLITUDE RIDGE OVER THE
BERING SEA WITH ANOTHER UPPER LEVEL LOW NEAR THE SOUTHERN TIP OF
KAMCHATKA. THE JET STREAM IS RUNNING SOUTH OF THESE FEATURES AT 135KT
TO 155KT AT THE 250 MB LEVEL.
THE SURFACE LOW IN THE GULF IS NEAR SEWARD AND PROCEEDING TO THE
NORTHWEST AS IT SLOWLY WEAKENS. THE NEXT LOW TO MOVE INTO THE GULF
IS BEGINNING TO FORM AROUND 40N 155W IN THE HIGH AMPLITUDE TROUGH.
THE BERING SEA IS SEEING HIGH PRESSURE AT THE SURFACE IN
CONJUNCTION WITH THE RIDGE ALOFT WITH A STRONG SURFACE LOW WELL TO
THE WEST NEAR KAMCHATKA.

&&

.MODEL DISCUSSION...
MODELS ARE DOING FAIRLY WELL OVERALL WITH THE SYNOPTIC SCALE
FEATURES. THE NAM HAS BEEN EXCELLENT IN ITS HANDLING OF THE LOW
CURRENTLY NEAR THE NORTH GULF COAST. THE ONE AREA THAT IS STILL AN
ISSUE IS THE SERIES OF LOWS MOVING INTO THE EASTERN GULF THIS
WEEKEND. THE FIRST ONE SHOULD MOSTLY BE IN THE FAR EASTERN GULF
AND MAINLY IMPACT THE PANHANDLE REGION. THE SECOND AND STRONGER
LOW WILL MOVE RAPIDLY TOWARD THE GULF ON A DUE NORTH TRACK
SATURDAY NIGHT THROUGH SUNDAY NIGHT AND THEN MOVE MORE
NORTHWESTERLY AS IT MAKES ITS WAY CLOSE TO CORDOVA MONDAY
AFTERNOON. WHILE THE GFS AND ECMWF MODELS SEEM TO DO THE BEST JOB
MOVING THIS LOW AS IT PROCEEDS NORTHWARD THE ECMWF SEEM TO HAVE
THE BEST OVERALL SOLUTION. THE NAM IS TOO SLOW IN ITS NORTHWARD
PROGRESSION AND DOES NOT CATCH UP UNTIL THE END OF ITS RUN MONDAY
AFTERNOON AFTER THE LOWS FORWARD PROGRESS HAS SLOWED. THE GEM
GLOBAL DOES NOT HAVE A HANDLE ON THIS SYSTEM AT ALL AND IS NOT
EVEN WORTH LOOKING AT.

&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
THE LOW MOVING THROUGH THE NORTHERN KENAI PENINSULA IS BRINGING A
LOT OF RAINFALL TO MUCH OF SOUTH CENTRAL AS WELL AS LOW CEILING
FOR AVIATION OVER MUCH OF THE COOK INLET REGION. THESE CONDITIONS
WILL BE SLOW TO CHANGE OVERNIGHT AS THE LOW TREKS ACROSS THE AREA.
AS THIS LOW MOVES THROUGH THE AREA TOWARD THE NORTHWEST THERE WILL
BE PRESSURE RISES BEHIND THE LOW. THESE PRESSURE RISES WILL CAUSE
SOME GUSTY SOUTHEAST WINDS IN THE PRINCE WILLIAM SOUND AREA THIS
EVENING WHICH THEN MOVE ALONG THE COPPER RIVER AND TURNAGAIN ARM
AFTER THAT. THE GUSTY WINDS FROM PRESSURE RISES OFTEN DO NOT LAST
MORE THAN A COUPLE OF HOURS BUT THEY CAN BE STRONG AND THE EVENT
CAN BEGIN AND END ABRUPTLY.

SOUTHWEST ALASKA...
NORTHWEST FLOW OVER THE AREA WILL KEEP A FEW SHOWERS IN THE AREA
WITH FOG ONCE AGAIN DEVELOPING AFTER MIDNIGHT. AREAS NEAR THE
ALASKA RANGE WILL LIKELY SEE SOME PRECIPITATION OVERNIGHT FROM THE
LOW MOVING INTO SOUTHCENTRAL ALASKA BUT THE REST OF THE REGION
WILL JUST HAVE SOME PASSING SHOWERS.

BERING SEA/ALEUTIANS...
NORTHWEST FLOW OVER MOST OF THE BERING SEA IS BRINGING SOME
SHOWERS BUT ALSO SOME BREAKS IN THE CLOUDS. THERE IS AN AREA OF
STRATUS DEVELOPING IN THE CENTRAL BERING SEA WHICH MAY INCREASE IN
SIZE AS IT MOVES EASTWARD.
THE EASTERN ALEUTIANS AND ALASKA PENINSULA WILL SEE SOME RAIN
SHOWERS IN THE NORTHWEST FLOW BUT THESE SHOULD SLOWLY TAPER OFF
THROUGH TOMORROW NIGHT.

&&

.LONG TERM FORECAST...
A TROUGH OF LOW PRESSURE WILL EXIST ACROSS THE WESTERN
BERING...WITH A WEAKENING UPPER LOW IN THE VICINITY OF THE COPPER
BASIN STRETCHING SOUTHWARD TO THE CENTRAL GULF OF ALASKA. HIGH
PRESSURE ALOFT WILL BE CENTERED OVER THE EASTERN BERING AND
SOUTHWEST ALASKA. LINGERING CLOUDS AND SHOWERS OVER THE COPPER
BASIN AND ALONG THE CHUGACH MOUNTAINS WILL RAPIDLY DIMINISH AS
OFFSHORE FLOW DEVELOPS THROUGH MIDWEEK. THIS WILL SET THE STAGE
FOR A SOMEWHAT UNUSUAL EXTENDED PERIOD OF DRY WEATHER...AND
COOLING TEMPERATURES...ESPECIALLY DURING THE NIGHT TIME PERIODS.
THE DRY AND PLEASANT WEATHER WILL LIKELY PERSIST INTO AND POSSIBLY
THROUGH NEXT WEEKEND AS THE MAIN STORM TRACK REMAINS ACROSS THE
NORTH PACIFIC.

&&

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

SEP 14