Small Craft Advisory 734, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 PM ADT FRI SEP 7 2007

.ANALYSIS...
LARGE STACKED LOW PRESSURE SYSTEM OVER THE SOUTH CENTRAL BERING WITH
A STRONG FRONT MOVING TO THE ALASKA PENINSULA THIS AFTERNOON. THE
FRONT IS SUPPORTED BY A STRONG VORT MAX AND 140 KT JET. THERE ARE
ALSO STRONG WINDS ALONG THE FRONT WITH MODERATE PRECIPITATION. THE
FRONT WILL LIFT ACROSS SOUTHWEST AND SOUTH CENTRAL ALASKA TONIGHT AND
TOMORROW. STRONG WINDS WILL MOVE ACROSS MANY AREAS TONIGHT AND
TOMORROW WITH THE FRONT. A RIDGE OF HIGH PRESSURE WILL REMAIN ALONG
THE NORTHERN GULF COAST THROUGH TOMORROW MORNING. A MOIST SOUTHWEST
FLOW WILL REMAIN BEHIND THE FRONT.

.MODEL DISCUSSION AND UPPER LEVELS...
LOOKS AS THOUGH THE GFS AND NAM A BIT SLOW ON THE SHORT WAVE IN THE
BASE OF THE BERING LOW NEAR ADAK. UKMET A BIT FASTER WITH THIS
FEATURE. THE 18Z NAM SEEMS TO BE CATCHING UP TO THE FEATURE A BIT.
SO...THIS FORECAST LOOKS TO BE REASONABLE FOR THE SHORT TERM. EARLY
FORECASTS ARE LEANING TO THIS SOLUTION AS WELL. AFTER THE INITIAL 48
HOURS GFS AND NAM DIFFER ON THE POSITIONS OF A LOW DROPPING INTO THE
NORTHWEST BERING AND THE HANDLING OF THE DISSIPATING TYPHOON FITOW
INTO THE BERING. THE GFS AND ECMWF MATCH UP WELL THROUGH TUESDAY AS
WELL AS THE ENSEMBLE MEAN. THE GFS THEN IS PREFERRED ESPECIALLY
DEALING WITH THE INFUSION OF THE DISSIPATING TYPHOON FITOW SUNDAY
NIGHT INTO MONDAY OVER THE SOUTH CENTRAL BERING.

FAIRLY CONSISTENT MEAN PATTERN THROUGH THE WEEK WITH A TROUGH OVER
THE BERING AND A RIDGE OVER THE PANHANDLE AND WESTERN CANADA. AN
UPPER LOW IS LOCATED NEAR ADAK WITH A BROAD TROUGH OVER THE GULF. A
STRONG WAVE WITH AN ASSOCIATED 130 KT JET WILL MOVE AROUND THIS LOW
AND ROTATE A FRONT AROUND THIS LOW AND EVENTUALLY PULL THE LOW NORTH
TO THE BERING STRAIT SATURDAY. ANOTHER LOW TO DROP INTO THE NORTHWEST
BERING SATURDAY AND DROP INTO THE WESTERN BERING SUNDAY. THE
DISSIPATING TYPHOON TO INTERACT WITH THIS LOW ON SUNDAY NIGHT AND
INTENSIFY THE LOW OVER THE SOUTHERN BERING. THIS LOW TO REMAIN IN THE
BERING THROUGH TUESDAY. MEANWHILE...A MODERATE TO STRONG MOIST
SOUTHWEST FLOW TO REMAIN OVER THE MAINLAND. UNCERTAINTY STARTS TO
CREEP IN AFTER TUESDAY WITH HOW THIS LOW MOVES OUT OF THE BERING. THE
RIDGE TO BREAK DOWN MID WEEK INTRODUCING THE UNCERTAINTY.

.SHORT TERM FORECAST...
ALEUTIANS...
THE LARGE LOW WILL MOVE TOWARD SAINT PAUL AND DISSIPATE SATURDAY WITH
A LOW DEVELOPING ALONG THE FRONT MOVING TO THE STRAIT. GALE FORCE
WINDS TO ACCOMPANY THE FRONT AND DEVELOPING LOW TONIGHT INTO TOMORROW
MORNING WITH MODERATE PRECIPITATION. THERE WILL BE A BRIEF PERIOD OF
DRY WEATHER FOR THE WESTERN BERING BEHIND THE LOW TONIGHT THROUGH
TOMORROW AND OVER THE CENTRAL BERING SATURDAY NIGHT. ANOTHER LOW WILL
DROP INTO NORTHWEST BERING AT THIS TIME THEN DROPS INTO THE WESTERN
BERING AND MERGES WITH THE REMNANTS OF TYPHOON FITOW SUNDAY NIGHT.
THIS WILL BRING VERY STRONG WINDS TO THE BERING AS THE LOW BOMBS. MAX
GALES TO STORM FORCE WINDS ARE ANTICIPATED WITH THIS LOW ON SUNDAY
NIGHT INTO MONDAY.

SOUTHWEST ALASKA...
STRONG FRONT MOVING ONSHORE THIS EVENING WITH RAIN AND WINDS
BEGINNING TO SPREAD OVER THE ALASKA PENINSULA. THE WINDS AND RAIN TO
SPREAD ACROSS THE ENTIRE AREA TONIGHT. WILL INCLUDE STRONG WIND
HEADLINES FOR BRISTOL BAY AS A RESULT. SOME WIND SHEAR PROBLEMS ALSO
POSSIBLE WITH THIS FRONT TONIGHT. A MODERATE SOUTHERLY MOIST FLOW TO
REMAIN BEHIND THE FRONT SATURDAY. ENOUGH FLOW TO PRODUCE HIGH SEAS
OVER THE EASTERN BERING AND COMBINED WITH MAX TIDES HAVE PROMPTED A
HIGH SURF ADVISORY FOR WESTERN BRISTOL BAY THROUGH THE COAST OF THE
KUSKOKWIM DELTA FOR SATURDAY NIGHT. AS THE LOW LIFTS INTO THE BERING
STRAIT SUNDAY RAIN WILL TURN TO SHOWERS AND BECOME LESS WIDESPREAD.
SHOWERS WILL DIMINISH EVEN FURTHER MONDAY EVEN THOUGH WE REMAIN UNDER
A MOIST SOUTHWEST FLOW BUT JUST IN BETWEEN SYSTEMS WITH A LARGE LOW
OUT IN THE CENTRAL/WESTERN BERING.

SOUTH CENTRAL...
RIDGE OF HIGH PRESSURE ALONG THE NORTHERN GULF COAST WITH ENCROACHING
WARM FRONT ENTERING THE GULF THIS AFTERNOON. WINDS ARE BEGINNING TO
INCREASE ACROSS THE GULF AS A RESULT. THE GRADIENT OVER THE TURNAGAIN
ARM HAS INCREASED AS WELL. THIS GRADIENT TO BECOME QUITE STRONG
TONIGHT INTO TOMORROW MORNING. COMBINED WITH THE FRONT AND STRONG
WINDS AT 850 MB AND 925 MB AND PROXIMITY OF THE JET...WILL MOST
LIKELY UPGRADE THE HIGH WIND WATCH TO A WARNING WITH THE AFTERNOON
PACKAGE FOR SATURDAY. THE FRONT TO REACH THE COAST THIS EVENING AND
SPREAD PRECIP AND MODERATE TO STRONG WINDS ACROSS SOUTH CENTRAL. THE
FRONT WILL MOVE INLAND LATE TONIGHT AND FARTHER INLAND TOMORROW. WITH
THE STRONG SOUTHEAST FLOW ALOFT...EXPECT ANCHORAGE AND PALMER AND
PORTIONS OF THE WESTERN KENAI TO EXPERIENCE SOME DOWNSLOPE FOR LESS
PRECIP. AS THE FRONT PUSHES THROUGH TOMORROW...RAIN WILL SPREAD OVER
THE DRIER AREAS. THE FRONT TO DISSIPATE INLAND SATURDAY NIGHT BUT A
MODERATE SOUTHERLY FLOW TO REMAIN. THEREFORE SHOWERS TO REMAIN OVER
MANY AREAS SATURDAY NIGHT AND SUNDAY. GALES TO END OVER THE MARINE
AREA BY TOMORROW AFTERNOON. WILL BE BETWEEN WAVES FOR MONDAY FOR ONLY
ISOLATED TO SCATTERED SHOWERS.

.LONG TERM FORECAST...
THE OVERALL UPPER LEVEL PATTERN OF A LOW IN THE BERING AND A RIDGE
OVER EASTERN ALASKA LOOKS TO HOLD THROUGH TUESDAY. THE RIDGE TO BREAK
DOWN IN MID WEEK. THIS WOULD GENERALLY KEEP UNSETTLED WEATHER OVER
MUCH OF THE AREA WITH WINDS DECREASING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WARNING ZONE 101
         HIGH SURF ADVISORY ZONE 155 AND 161
MARINE...GALE 120 130 132 150 160 165 170 175 176 180
FIRE WEATHER...NONE

JN SEP 07