Small Craft Advisory 322, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
500 AM ADT THU APR 5 2007

.DISCUSSION...

ANALYSIS...THE MAIN FEATURE VISIBLE ON IR IMAGERY THIS MORNING
CONTINUES TO BE THE LARGE MATURE LOW CENTERED WELL SOUTH OF KODIAK
ISLAND NEAR 50N WITH A BROAD OCCLUDED FRONT EXTENDING ACROSS THE GULF
OF ALASKA. OBS SHOWING BROAD SWATH OF GALES ACROSS THE GULF WITH THIS
FRONT ALONG WITH A BROAD SWATH OF STRATIFORM PRECIP AS IT MOVES NORTH
ACROSS THE GULF WITH KODIAK OBSERVING A RAIN SNOW MIX ATTM THOUGH IT
SHOULD CHANGE OVER TO RAIN WITHIN THE NEXT COUPLE OF HOURS. AREAS OF
SHOWERS ARE MOVING ACROSS BRISTOL BAY THIS MORNING AS THE REMNANT
MOISTURE FROM THE OLD FRONTAL BOUNDARY OF YESTERDAY MOVES OVERHEAD.
NORTHEAST FLOW AND COLD ADVECTION ALONG WITH AN UPPER LEVEL LOW
DROPPING DOWN IS GENERATING A BROAD AREA OF SNOW SHOWERS ACROSS MUCH
OF THE CENTRAL AND WESTERN BERING SEA.

MODEL DISCUSSION...MAIN DIFFERENCES IN SHORT TO MEDIUM RANGE BETWEEN
THE MODELS LIE WITH LOCATION OF LOW THAT RIDES UP INTO THE EASTERN
GULF ON FRI AND HOW FAR EAST THE LOW MOVES. THE ECMWF AND UKMET FAVOR
A SLIGHTLY MORE WESTERLY TRACK SOLUTION WITH THIS LOW DUE IN PART TO
THE INFLUENCE OF A STRONGER RIDGE DOWNSTREAM THAN INDICATED IN THE
GFS OR NAM. HOWEVER WE ARE STICKING WITH THE GFS AS IT HAS CONTINUED
TO SHOW GOOD CONSISTENCY FROM RUN TO RUN ON THE TRACK OF THIS SYSTEM.
OTHERWISE GOOD AGREEMENT OVERALL UNTIL SUNDAY WHERE THE GFS DEVELOPS
A LOW OVER THE CENTRAL ALEUTIANS FROM A PRE-EXISTING SURFACE TROUGH
THAT INTERACTS WITH AN UPPER LOW THAT IS ROTATING ACROSS THE BERING
SEA AT THAT TIME PERIOD. THE LATEST GFS RUN DEVELOPS THIS LOW MORE
STRONGLY THAN THE OTHER MODELS OR THE PREVIOUS RUN OF THE GFS...SO
WILL TAKE A WAIT AND SEE APPROACH REGARDING THAT SYSTEM.  FORTUNATELY
IT MOVES OUT OF THE FORECAST AREA AS IT STRENGTHENS SO THE IMPACT OF
THIS ANOMALY IS NOT TOO DRAMATIC.

SOUTHCENTRAL ALASKA FORECAST...THE FRONT CONTINUES NORTH OVER THE
GULF WITH STRONG GALES IN THE MARINE ZONES MOVING NORTH ALONG WITH
THE FRONT UNTIL IT MAKES LANDFALL ALONG THE NORTH GULF COAST THIS
AFTERNOON BRINGING WET AND BREEZY WEATHER. LOOK FOR PRECIP TO BE
MOSTLY IN THE FORM OF RAIN WITH HIGHEST QPF VALUES ACROSS KODIAK
ISLAND AND THE EASTERN KENAI PENINSULA. THE FRONT STALLS ONCE IT
MAKES LANDFALL AS IT BECOMES REMOVED FROM ITS SOURCE OF UPPER LEVEL
SUPPORT. PRECIP WITH THIS SYSTEM WILL BE LIMITED TO COASTAL AREAS
ALONG THE GULF AS THE FRONT WILL BE TOO WEAK TO PENETRATE INLAND. THE
NEXT SYSTEM ORIGINATES FROM A POWERFUL UPPER LEVEL SHORTWAVE THAT
ROTATES AROUND THE OLD UPPER LEVEL CENTER AND UP INTO THE
NORTHEASTERN GULF BRINGING MAX GALES WITH POSSIBLE STORM FORCE WINDS
INTO MARINE ZONE 120 FRIDAY EVENING. THIS LOW SHOULD BRING HEAVIER
PRECIP TO THE NORTHEASTERN GULF COAST...INCLUDING CORDOVA...THAN THE
PREVIOUS SYSTEM ALONG WITH WARMER TEMPERATURES WITH PRECIP STAYING
ALL RAIN. THIS LOW CUTS ACROSS THE SOUTHERN TIP OF THE KENAI LATE
FRIDAY NIGHT WITH THE ANCHORAGE BOWL AND MATSU HAVING A BETTER CHANCE
OF RECEIVING SOME PRECIP...THOUGH DOWNSLOPING SHOULD KEEP PREIP
TOTALS PRETTY LIGHT. STRONG WINDS THROUGH TURNAGAIN ARM MAY ALSO
OCCUR WITH THIS LOW. YET ANOTHER LOW THAT IS ALREADY FORMING ON THE
LEFT EXIT REGION OF A JETMAX SOUTH OF THE ALEUTIANS IS PROGGED TO
ROTATE NORTH AROUND THE MAIN UPPER LOW CENTERED NEAR THE AKPEN AND
ACROSS KODIAK ISLAND SAT NIGHT BRINGING YET MORE EASTERLY GALES TO
THE GULF AND RAIN TO THE GULF COAST SAT NIGHT INTO SUN.

SOUTHWEST ALASKA AND THE BERING SEA/ALEUTIANS...EXPECT SCATTERED
SHOWERS TO CONTINUE ACROSS THE BERING SEA WITH MORE STRATIFORM PRECIP
AND HIGHER POPS OCCURRING ACROSS THE EASTERN BERING AND PRIBILOFS
THROUGH TONIGHT CLOSER TO THE ISENTROPIC UPLIFT ASSOCIATED WITH THE
WARM ADVECTION FROM THE LOW SOUTH OF THE AKPEN. PRECIP OVER THE
MAINLAND SHOULD CONSIST MAINLY OF ISOLATED SHOWERS IN THE KUSKOKWIM
DELTA WITH SCATTERED SHOWERS AROUND BRISTOL BAY AMD CATEGORICAL POPS
ALONG THE AKPEN...PARTICULARLY ALONG THE SOUTH SIDE. SHOULD ALSO SEE
A SLIGHT WARMING TREND ACROSS MAINLAND SOUTHWEST AK OVER THE NEXT FEW
DAYS AS A WARMER MARITIME AIRMASS OVERSPREADS THE REGION. LOOK FOR
SCATTERED SHOWERS TO CONTINUE ACROSS THE CENTRAL AND WESTERN BERING
THROUGH FRI WITH POPS INCREASING FRI NIGHT AS A SURFACE TROUGH MOVES
THROUGH IN CONJUNCTION WITH AN UPPER LOW AS PREVIOUSLY MENTIONED.
AFTER THAT SNOW SHOWERS SPREAD ACROSS THE WESTERN AND CENTRAL BERING
IN NORTH TO NORTHWESTERLY CYCLONIC FLOW. OVER THE MAINLAND...
NORTHEASTERLY FLOW SHOULD KEEP THINGS DRY ALBEIT CLOUDY WITH
OVERSPREADING MID TO HIGH LEVEL CLOUDS FROM THE STORMS IN THE GULF ON
FRI. THE LOW THAT MOVES ACROSS THE SOUTHERN KENAI FRI NIGHT OPENS UP
INTO A TROUGH ON THE OTHER SIDE OF THE ALEUTIAN RANGE BRINGS A CHANCE
OF RAIN/SNOW INTO MAINLAND SOUTHWEST AK ON SAT AS DOES THE NEXT LOW
THAT FOLLOWS THAT LOW UP SUN NIGHT.

EXTENDED...LITTLE CHANGE IN THE OVERALL PATTERN INTO NEXT WEEK WITH A
THREE-WAVE HEMISPHERIC PATTERN AND THE LONGWAVE TROUGH/UPPER LOW
REMAINS ENTRENCHED OVER ALASKA WITH THE MID LATITUDE JET REMAINING
NEARLY ZONAL ALONG 40N THROUGH THE MIDDLE OF NEXT WEEK. THINGS QUIET
DOWN SOME ALONG THE GULF COAST AFTER THE LAST STORM MAKES LANDFALL
SUNDAY...BUT KEPT CHANCE POPS GOING ACROSS MUCH OF THE EAST WITH
AVERAGE TO ABOVE AVERAGE TEMPS AS THE REGION REMAINS UNDER GENERAL
SOUTHERLY FLOW WITH ABUNDANT MOISTURE ON THE EAST SIDE OF THE
LONGWAVE TROUGH. LATEST GFS RUN HAS A LOW MOVING INTO THE GULF ON
TUESDAY...HOWEVER CONFIDENCE IN THIS LOWS PRESENCE IS LOW ATTM AS IT
HINGES ON WHETHER THE LOW DEVELOPS OVER THE CENTRAL ALEUTIANS ON
SAT...SOMETHING THAT THE MODELS ARE NOT IN TOTAL AGREEMENT ON.
NORTHERLY FLOW ACROSS THE BERING SEA ON THE OTHER SIDE OF THE
LONGWAVE TROUGH IN ADDITION TO THE PRESENCE OF THE REMNANTS OF THE
GULF LOWS SHOULD ALLOW FOR SHOWERS TO CONTINUE ACROSS MUCH OF THE
BERING INTO MID WEEK WHILE THE MAINLAND MAY SEE A DRYING TREND
STARTING MONDAY NIGHT AS WEAK RIDGING MOVES OVERHEAD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 120 130 132 138 150 155 165 185
FIRE WEATHER...NONE.

WOOD APR 07