Small Craft Advisory 731, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM ADT THU SEP 6 2007

.ANALYSIS...
A LARGE LOW COMPLEX IS OVER THE BERING SEA JUST NORTHWEST OF ADAK. AN
ACCOMPANYING FRONT IS MOVING ONTO THE WEST COAST THIS AFTERNOON AS
WELL. THE WINDS AROUND THE LOW AND FRONT ARE STRONG. A WEAK LOW
PRESSURE SYSTEM IN THE GULF THIS MORNING MOVING TO THE PANHANDLE WITH
A SHORT WAVE RIDGE OVER SOUTH CENTRAL THIS AFTERNOON AND EVENING. THE
FRONT MOVING ONTO THE WEST COAST THIS AFTERNOON TO STRETCH OVER SOUTH
CENTRAL TONIGHT AND TOMORROW. WILL RAISE POPS AS A RESULT. THE LOW IN
THE GULF REMAINS STACKED WITH A STRONG SHORT WAVE TROUGH ROUNDING THE
BASE TONIGHT. IN ADDITION...A 150 KT JET IS ACCOMPANYING THIS WAVE. A
SECONDARY FRONT WITH THIS WAVE WILL PUNCH TO THE WEST COAST FRIDAY.

.MODEL DISCUSSION AND UPPER LEVELS...
NAM OFF WITH POSITION OF LOW IN THE BERING THIS MORNING. ALL OTHER
MODELS HAVE THIS POSITION WELL REPRESENTED. OTHER FEATURES ARE
REPRESENTED QUITE SIMILAR AS WELL. SYNOPTICALLY...THE EURO MODELS AND
THE GFS AGREE THROUGH MONDAY. BY TUESDAY...THE DIFFERENCES BECOME
LARGER WITH THE ECMWF MODEL PUSHING THE BERING LOW INTO THE STRAIT.
THE GFS HAS THE LOW SETTLED AROUND 60N 170W WHILE THE UKMET IS RIGHT
IN THE MIDDLE. AFTER THAT PERIOD...TIMING AND STRENGTH OF LOW SYSTEMS
IS VERY DIVIDED. CONFIDENCE IS QUITE LOW PAST TUESDAY.

A LARGE LOW IS SITUATED OVER THE WESTERN BERING WITH A RIDGE OVER THE
GULF CURRENTLY. THE LOW IN THE BERING TO MOVE SLOWLY EAST WITH MANY
SHORT WAVES ROTATING AROUND IT THE NEXT COUPLE DAYS. A STRONG JET
WILL ALSO ROUND THE LOW FRIDAY AND HELP LIFT IT NORTH TO ST LAWRENCE
ISLAND SATURDAY. IN THE MEANTIME...AN UPPER LOW TO MOVE OFF EASTERN
SIBERIA INTO THE NORTHWEST BERING. BY THIS TIME THE JET AXIS WILL
SHIFT FARTHER EAST WITH A STRONG MOIST SOUTHERLY FLOW OVER THE ENTIRE
MAINLAND. THE TWO FEATURES COMBINE INTO ONE LOW BY SUNDAY OVER THE
NORTHWEST BERING. THIS LARGE LOW TO REMAIN OVER THE NORTHERN BERING
THROUGH TUESDAY. HOW FAR NORTH AND WHEN IT EXITS THE REGION IS
DEFINING THE UNCERTAINTY OF THE FORECAST BEYOND TUESDAY. VERY
UNSTABLE AND UNCERTAIN AT THAT POINT.

.SHORT TERM FORECAST...
ALEUTIAN AND BERING...
THE LOW IN THE WESTERN BERING TO SLOWLY MOVE EAST OVER THE NEXT 48
HOURS. THE WINDS AROUND THE LOW WILL BE NEAR GALE FORCE THROUGH THIS
PERIOD WITH PLENTY OF PRECIPITATION. A FRONT IS MOVING TO THE WEST
COAST THIS EVENING WITH ANOTHER FRONT DEVELOPING ON THE SOUTHERN EDGE
OF THE LOW TONIGHT. THIS SECOND FRONT IS SUPPORTED BY A STRONG 150 KT
JET. THE FRONT WILL ROUND THE LOW AND PUSH THROUGH THE EASTERN BERING
FRIDAY AND INLAND FRIDAY NIGHT. STRONG GALE FORCE WINDS WILL BE THE
RULE WITH MODERATE TO HEAVY PRECIPITATION. THE LOW WILL ROTATE NORTH
WITH THE SHORT WAVE AS ANOTHER LOW DIVES INTO THE NORTHWEST BERING
SATURDAY. THE JET FROM THE FIRST SYSTEM MOVES INLAND SATURDAY NIGHT
AS THE TWO LOWS COMBINE OVER THE NORTHERN BERING BY SUNDAY AFTERNOON.
WINDS WILL DIMINISH IN THE TRANSITION TIME...BUT PICK BACK UP SUNDAY.

SOUTHWEST ALASKA...
A MOIST SOUTHWEST FLOW OVER THE AREA WITH A SOMEWHAT UNSTABLE AIR
MASS PROVIDING SOME SHOWERS INLAND. A FRONT IS MOVING ONSHORE THIS
AFTERNOON WITH RAIN INCREASING TONIGHT. WINDS WILL BE GUSTY ALONG THE
COAST. THE FRONT WILL QUICKLY EXIT THE AREA LATE TONIGHT WITH A BREAK
IN WINDS AND PRECIP BEFORE A STRONGER FRONT ARRIVES FRIDAY AFTERNOON.
THIS FRONT ACCOMPANIES A LOW MOVING NEAR SAINT PAUL THEN NORTH ALONG
170W SATURDAY. THIS PATH KEEPS THE VERY MOIST SOUTHWEST FLOW OVER THE
AREA THROUGH SATURDAY. AS THE LOW COMBINES WITH ANOTHER IN THE
NORTHERN BERING SUNDAY SOME OF THE PRECIP WILL TURN MORE SHOWERY.
ONE ADDITIONAL THING TO KEEP AN EYE ON IS THE STORM SURGE WITH THESE
SYSTEMS ESPECIALLY ON SATURDAY AS THE LOW LIFTS NORTH.

SOUTH CENTRAL...
A SHORT WAVE RIDGE HAS MOVED OVER THE AREA THIS AFTERNOON.
THEREFORE...NOT EXPECTING AS MUCH THUNDERSTORM ACTIVITY AS YESTERDAY.
IN ADDITION...MID LEVEL CLOUDINESS AROUND TO STUMP DIFFERENTIAL
HEATING SOURCE. STILL EXPECT SOME OVER THE HIGHER TERRAIN OF THE
TALKEETNAS AND ALASKA RANGE THOUGH. THE FRONT APPROACHING SOUTHWEST
ALASKA ALSO ENCROACHING UPON KODIAK THIS EVENING. THE FRONT WILL
BECOME MORE OF A WAVE MOVING OVER SOUTH CENTRAL LATE TONIGHT AND
TOMORROW MORNING. FEEL THERE IS ENOUGH LIFT WITH THIS WAVE FOR SOME
CHANCES OF RAIN OVER THE AREA ESPECIALLY THE COASTAL LOCATIONS AND
THE KENAI PENINSULA. A HIGH PRESSURE RIDGE WILL DEVELOP ALONG THE
NORTHERN COAST WITH THE PUSH OF THIS WAVE. SO...WE WILL EXPECT SOME
GAP WINDS THROUGH TURNAGAIN ARM LATER TONIGHT. THERE WILL BE A GAP
BETWEEN THIS FIRST FRONT AND A STRONGER FRONT TO REACH KODIAK LATE
FRIDAY AFTERNOON. THE STRONGER FRONT WILL ARRIVE TO THE COAST LATE
FRIDAY NIGHT. THIS WILL INCREASE THE GRADIENT FOR STRONGER GAP WINDS
FRIDAY NIGHT THROUGH SATURDAY. PRECIP WILL ALSO PICK UP OVER THE
ENTIRE SOUTH CENTRAL WITH INCREASED MOIST SOUTHERLY FLOW. THIS STRONG
MOIST SOUTHERLY FLOW TO CONTINUE THROUGH THE WEEKEND WITH PLENTY OF
PRECIP AND WINDS.

.LONG TERM FORECAST...
MOIST SOUTHERLY FLOW OVER THE ENTIRE MAINLAND THROUGH TUESDAY WITH
THE LARGE LOW OVER THE BERING. THE COMPLEX TO LEAVE THE AREA
WEDNESDAY. HOW FAST IT DOES AND WHAT THE STRENGTH OF THE NEXT SYSTEM
MOVING INTO THE WESTERN BERING ARE VERY UNDECIDED AT THIS TIME.
UP TO TUESDAY...RAIN WILL BE OVER MUCH OF THE MAINLAND AND THROUGHOUT
EASTERN AND CENTRAL BERING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 160 165 170 172 175 176 180
FIRE WEATHER...NONE

JN SEP 07