Small Craft Advisory 594, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 PM AKDT WED AUG 7 2013

.MODEL DISCUSSION...
GENERAL SYNOPTIC TRENDS THROUGH THE SHORT TERM ARE IN REASONABLE
AGREEMENT. THE FORECAST CHALLENGE WILL BE IN THE MESOSCALE DETAILS
AND EXACT POSITIONING OF THE MAIN FEATURES. THE NAM OVERALL IN THE
EAST ALONG WITH THE GEM HAS A MORE REPRESENTATIVE SOLUTIONS...WHERE
THERE SEEMS TO BE SMALL CONCERNS OUT WEST WHERE THE GFS IS OVERALL
PREFERRED.

.ANALYSIS AND UPPER LEVELS...
.500 MB...
THE BROAD UPPER TROUGH CONTINUES TO BE THE DOMINATE FEATURE. SEVERAL
WAVES ARE EMBEDDED IN THE GENERAL TROUGH AXIS WITH BROAD SOUTHERLY
FLOW OVER MUCH OF THE MAINLAND. THE MEAN POSITION OF THE LOW OVER THE
EASTERN BERING UNDERGOES LITTLE CHANGE CHANGE THROUGH FRI. THIS
CENTER ACTS AS PIVOT POINT FOR SHORT WAVES ROTATING NORTH INTO THE
GULF AND SOUTHERN MAINLAND. SIGNIFICANT WAVES OF NOTE ARE THE ONE
MOVING INTO SOUTHCENTRAL TONIGHT AND A SECONDARY WAVE WHICH ROUNDS
THE BASE OF THE TROUGH AS IT HEADS TOWARD THE WESTERN GULF FRIDAY.
THIS WAVE SETS UP A SOMEWHAT DEEPER SLOWLY FETCH ACROSS
SOUTHCENTRAL/GULF INTO SAT.

.SURFACE...
A BROAD FRONTAL BOUNDARY OVER THE EASTERN AND NORTH GULF OF ALASKA
PRODUCED WIDESPREAD RAIN ACROSS THE EASTERN KENAI...ANCHORAGE BOWL
AND SOUTHERN SUSITNA VALLEY. SHOWERS ASSOCIATED WITH A BROAD UPPER
TROUGH AND NORTHWEST MOVING LOW NEAR BRISTOL BAY WERE EVIDENT ACROSS
SW ALASKA.

.SHORT TERM FORECAST...
.SOUTHCENTRAL ALASKA...
THE FRONTAL BAND OVER THE GULF OF ALASKA WILL MOVE OVER THE NORTH
GULF COAST LATE TONIGHT/FRI MORNING THEN WEAKEN AS IT MOVES INLAND
FRI AFTERNOON. WIDESPREAD RAIN IS EXPECTED TO MOVE ALONG THE GULF
COAST TONIGHT. RAIN/SHOWERS WILL ACCOMPANY THE FRONT AS IT MOVES
INLAND...BUT WILL NOT BE AS WIDESPREAD AS ALONG THE COASTS...HOWEVER
THE ANCHORAGE BOWL WILL GET STEADY RAIN AS THE DOWNSLOPE DIMINISHES
TONIGHT. GAP FLOWS WILL DIMINISH OVERNIGHT AS PRESSURE GRADIENTS
WEAKEN ACROSS MUCH OF SOUTHCENTRAL. PRESSURE RISES ON THE BACKSIDE
NORTH MOVING FRONT WILL PRODUCE SOME LOCALLY GUSTY SOUTH WINDS ACROSS
THE COPPER RIVER BASIN THU AFTERNOON.

A DEVELOPING FRONT MOVING INTO THE WESTERN GULF OF ALASKA WILL
INCREASE PRESSURE GRADIENTS AND GAP FLOWS ACROSS SOUTHCENTRAL ON FRI.
THE FRONT WILL ALSO HAVE A DEEPER SOUTHERLY FETCH AND BRING MORE
SIGNIFICANT RAIN TO THE KENAI PEN AND GULF COAST.

SOUTHWEST ALASKA...BROAD SOUTHERLY FLOW ALOFT CONTINUES THE ACTIVE
WEATHER PATTERN OVER SW ALASKA. THE LOW OVER OVER BRISTOL BAY THIS
MORNING MOVES NORTHWEST AND WEAKENS. A COUPLE CENTERS ASSOCIATED WITH
THE UPPER LOWS WILL FORM OVER THE EASTERN BERING SEA OVER THE NEXT 24
HRS AND HOLD THROUGH SAT. SHOWERS OR RAIN WILL SPREAD NORTH ACROSS
THE DELTA TONIGHT AS THE FIRST WAVE PUSHES NW. A SECONDARY LOW WHICH
MOVES TO BRISTOL BAY THU WILL BRING IN ANOTHER BATCH OF RAIN AND WIND
TO THE REGION.

BERING SEA AND ALEUTIANS...A SHORTWAVE TROUGH DROPPING DOWN THE
WESTERN BERING WILL REINFORCE THE CURRENT UPPER LOW OVER THE AREA
BRINGING RAIN TO THE ALEUTIANS THIS AFTERNOON. RAIN WILL BECOME MORE
SHOWERY AND SPORADIC OVERNIGHT TONIGHT AND CONTINUE THROUGH
FRIDAY...MAINLY FOR THE EASTERN BERING SEA.

.LONG TERM FORECAST...
THE SEASONABLE FALL PATTERN LOOKS TO CONTINUE FOR THE EXTENDED
PERIOD. AN UPPER LOW WILL BE PRESENT IN THE BERING SEA SENDING
PERIODIC WAVES AND FRONTS TOWARD THE MAINLAND MUCH LIKE THE CURRENT
PATTERN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALES 150.
FIRE WEATHER...NONE.

RMC AUG 13