Small Craft Advisory 737, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
245 PM ADT SUN SEP 9 2007

.ANALYSIS AND UPPER LEVELS...SATELLITE IMAGERY SHOWS A LARGE MATURE
VERTICALLY STACKED LOW SITTING OVER THE WESTERN BERING. A STRONG
SHORT-WAVE IS DROPPING SOUTHWARD ACROSS THE SOUTHWESTERN
BERING...BEGINNING TO AMPLIFY THE TROUGH AND PULL MOISTURE FROM
THE FORMER TYPHOON FITOW(AROUND 40N TO 45N LATITUDE) NORTHWARD.
THERE IS A DECENT UPPER JET (ESTIMATED 140KT) HELPING TO DRIVE THIS
SHORT-WAVE SOUTHWARD. A SURFACE LOW IS IN THE EARLY STAGES OF
DEVELOPMENT JUST AHEAD OF THE SHORT-WAVE NEAR 46N 175E. AREAS OF WIND
AND RAIN ASSOCIATED WITH THE BERING LOW CONTINUE ACROSS THE CENTRAL
TO WESTERN BERING.

HEADING EASTWARD...TWO WELL DEFINED SHORT-WAVES ARE ALMOST IN PHASE
ALONG 160W. THE NORTHERN ONE IS TRACKING NORTHEASTWARD ACROSS BRISTOL
BAY WHILE THE STRONGER SOUTHERN ONE IS SOUTH OF THE AKPEN ALSO
TRACKING OFF TO THE NORTHEAST. THE UPPER JET IS ALSO ALIGNED ALONG
THIS AXIS WITH UPPER RIDGE CENTERED TO THE EAST OVER THE NORTH
PACIFIC EXTENDING UP TO SOUTHEAST ALASKA. THE JET IS HELPING TO
TRANSPORT TROPICAL MOISTURE NORTHWARD. AT THE SURFACE THESE
SHORT-WAVES ARE PRODUCING SHOWERS OVER SOUTHWEST ALASKA...THE
AKPEN...AND KODIAK ISLAND. KENAI RADAR IMAGERY IS ALSO SHOWING AN
INCREASE IN RETURNS OVER COOK INLET. SHOWERS CONTINUE ACROSS THE
WESTERN PORTION OF SOUTHCENTRAL. FARTHER EAST...THE REMNANT COLD
FRONT THAT BROUGHT WIDESPREAD RAIN TO MUCH OF THE REGION ON FRIDAY
AND SATURDAY NOW LIES FROM THE CENTRAL GULF UP THROUGH PRINCE WILLIAM
SOUND INTO THE COPPER RIVER BASIN. RAIN...HEAVY AT TIMES CONTINUES
OVER EASTERN PRINCE WILLIAM SOUND AND THE COPPER RIVER BASIN.

.MODEL DISCUSSION...OTHER THAN CONTINUING PROBLEMS WITH NAM
INITIALIZATION ON LOW POSITIONS...MODEL SOLUTIONS ARE IN GOOD
AGREEMENT AND SHOW EXCELLENT RUN-TO-RUN CONSISTENCY THROUGH ABOUT
48 HOURS. THERE IS A BIT OF DIVERGENCE IN SOLUTIONS FROM 48 HOURS
TO 84 HOURS...BUT STILL IN THE SAME GENERAL AREA WITH SYNOPTIC
POSITIONS. WILL STICK WITH GFS THROUGH THIS PERIOD.

.SHORT TERM FORECAST...

SOUTHCENTRAL...EXPECT RAIN TO DEVELOP ACROSS WESTERN HALF OF
SOUTHCENTRAL THIS AFTERNOON INTO EARLY EVENING IN RESPONSE TO
UPPER SHORT-WAVES MOVING IN FROM SOUTHWEST. RAIN WILL TAPER OFF
TOWARD MORNING AS SHORT-WAVES MOVES PAST AND UPPER SHORT-WAVE
RIDGE BUILDS OVERHEAD. IF SKIES CLEAR BEFORE MORNING...EXPECT FOG
TO FORM. BASED ON CURRENT TIMING BEST CHANCE OF FOG LOOKS LIKE
KODIAK ISLAND UP TO THE WESTERN KENAI PENINSULA AND COOK INLET.
THINK CLOUDS WILL HOLD IN LONG ENOUGH ELSEWHERE TO HOLD OFF FOG.
FOR THE EASTERN HALF OF SOUTHCENTRAL...THE COLD FRONT WILL CONTINUE
TO SLOWLY PROGRESS EASTWARD...MOVING INTO THE YUKON MONDAY MORNING.
RAIN MAY LIGHTEN UP A BIT LATER THIS AFTERNOON ACROSS EASTERN
PORTION OF PRINCE WILLIAM SOUND AND WESTERN PORTION OF COPPER BASIN.
HOWEVER...UPPER SHORT-WAVES WILL NOT BE FAR AWAY. SO MODERATE TO
HEAVY RAIN WILL START UP AGAIN AND CONTINUE THROUGH MUCH OF THE
NIGHT. SOUTHCENTRAL WILL DRY OUT FROM WEST TO EAST ON MONDAY AND
REMAIN DRY MONDAY NIGHT. THIS WILL SET UP A GOOD RADIATIONAL COOLING
NIGHT WITH GOOD POTENTIAL FOR FOG. ON TUESDAY CONDITIONS WILL HEAD
BACK DOWN HILL FROM WEST TO EAST AS ANOTHER FRONT MOVES FROM BERING
TO SOUTHCENTRAL. LOW LEVEL FLOW THIS TIME AROUND LOOKS TO BE ORIENTED
SOUTH TO SOUTH-SOUTHEAST. SYSTEM DYNAMICS LOOK GOOD...SO EXPECT
WIDESPREAD RAIN...BUT HEAVIEST UPSLOPE RAIN WILL SHIFT A BIT. SURFACE
PRESSURE GRADIENT REALLY TIGHTENS UP BY LATE TUESDAY...BUT IT IS
TOO EARLY TO THINK ABOUT A HIGH WIND WATCH.

SOUTHCENTRAL HYDROLOGY...BASED ON AVAILABLE STREAM GAGE READINGS
RIVER AND STREAMS IN THE SUSITNA BASIN HAVE CRESTED BELOW FLOOD STAGE
LATE LAST NIGHT OR THIS MORNING AND HAVE BEEN HEADING DOWNWARD SINCE.
HOWEVER...MORE RAIN IS ON THE WAY FOR THIS AFTERNOON AND TONIGHT...SO
WATER LEVELS WILL RISE AGAIN. RAINFALL WILL BE LESS INTENSE THAN
YESTERDAY AND BRIEFER...SO AT THIS POINT WILL LIKELY CANCEL THE FLOOD
WATCHES. BUT RFC IS STILL WAITING FOR A COUPLE OBSERVATIONS TO COME
IN BEFORE MAKING A FINAL DECISION. WORST CASE...WOULD ISSUE A FLOOD
ADVISORY FOR SMALL STREAMS.

A FLOOD ADVISORY WAS ISSUED FOR THE VALDEZ AREA THIS MORNING. GREATER
THAN 4 INCHES HAD FALLEN THROUGH THIS MORNING AND MODERATE TO HEAVY
RAIN HAS CONTINUED SINCE. HIGH WATER LEVELS WERE ALSO OBSERVED ON
THE LOWE RIVER ALONG THE RICHARDSON HIGHWAY. WITH STEADY RAIN
EXPECTED THROUGH THE OVERNIGHT HOURS WILL LIKELY SEE ANOTHER 2 TO 4
INCHES BEFORE RAIN ENDS. THEREFORE...ADVISORY EXTENDS THROUGH 8 AM
MONDAY AND CONDITIONS WILL BE CLOSELY WATCHED TO MAKE SURE CONDITIONS
DO NOT GET ANY WORSE THAN MINOR FLOODING.

COPPER BASIN PRECIP HAVE BEEN LIGHT THUS FAR WITH MOST OF PRECIP
HANGING UP ON THE COASTAL RANGE. HOWEVER...MODELS HINT AT SIGNIFICANT
RAINFALL AMOUNTS TONIGHT THROUGH MONDAY MORNING AS UPPER SHORT-WAVES
COME THROUGH...ESPECIALLY FOR AREAS EAST OF THE RICHARDSON HIGHWAY.
WILL RIVERS AND STREAMS RUNNING LOW DO NOT EXPECT ANY FLOODING TO
OCCUR...BUT WILL KEEP AN EYE ON PRECIP AMOUNTS OVERNIGHT INTO MONDAY
MORNING.

BERING SEA/ALEUTIANS/SOUTHWEST ALASKA...SHOWERS OVER SOUTHWEST ALASKA
WILL TAPER OFF BY LATE EVENING AS BRISTOL BAY SHORT-WAVE MOVES TO
SOUTHCENTRAL. PARTIAL CLEARING AND UPPER SHORT-WAVE RIDGE BUILDING
OVERHEAD WILL PRODUCE AREAS OF FOG LATE TONIGHT INTO MONDAY MORNING.
THE WEAK LOW SOUTH OF THE WESTERN ALEUTIANS WILL RAPIDLY INTENSIFY
TONIGHT IN RESPONSE TO UPPER SHORT-WAVE AND STRONG UPPER JET. AS IT
TRACKS TO AROUND ADAK LATE TONIGHT EXPECT STORM FORCE WINDS TO
DEVELOP ALONG AND AHEAD OF THE FRONT WITH THE PEAK WINDS EXTENDING
FROM THE EASTERN ALEUTIANS TO THE PRIBILOFS. AS THE UPPER TROUGH
AMPLIFIES A SOUTHERLY JET WILL SET UP RIGHT THROUGH THIS
CORRIDOR...PROVIDING SUPPORT FOR EVEN STRONGER WINDS TO MIX DOWN TO
THE SURFACE. THEREFORE...THE HIGH WIND WATCH THAT WAS ISSUED FOR THE
EASTERN ALEUTIANS FOR LATE TONIGHT THROUGH MONDAY AFTERNOON WILL BE
UPGRADED TO A WARNING. WITH THE UPPER LEVELS CONTINUING TO
AMPLIFY...THE LOW WILL BE FORCED NORTHWARD TO THE NORTHCENTRAL
BERING. THE CURRENT LOW IN THAT REGION WILL BE ABSORBED INTO THIS NEW
LOW. COLD AIR WRAPPING AROUND THE BACK SIDE WILL PRODUCE GALE FORCE
WINDS MONDAY WHILE THE FRONT SLOWLY TRACKS TO THE EASTERN BERING AND
WEAKENS. ALL IN ALL...IT WILL BE VERY WET AND WINDY ACROSS THE BERING
SEA REGION THE NEXT COUPLE DAYS. THE FRONT WILL SPREAD INTO SOUTHWEST
ALASKA MONDAY NIGHT AND TUESDAY WHILE THE PARENT LOW LIFT TOWARD THE
NORTHERN BERING AND CONDITIONS APPROVE ACROSS THE SOUTHERN BERING.

.LONG TERM FORECAST...MODELS CONTINUE TO INDICATE A CHANGE IN THE
LARGE SCALE PATTERN AS UPPER RIDGE SHIFTS EASTWARD TOWARD WESTERN
CANADA AND UPPER TROUGH SHIFTS TOWARD MAINLAND ALASKA AND THE GULF.
IF THIS SOLUTION HOLDS...LOOK FOR A BREAK OVER THE BERING SEA THROUGH
NEXT WEEKEND WITH NO MAJOR SYSTEMS...WHILE THE EAST WOULD SET UP WITH
RAIN ALONG THE GULF COASTAL REGION AND SHOWERS INLAND AND OVER
SOUTHWEST ALASKA. FREEZING LEVELS WILL COME DOWN AS WE TRANSITION TO
THIS PATTERN...SO THERE IS A POTENTIAL FOR SNOW ON THE HIGHEST
MOUNTAINS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...HIGH WIND WATCH ZONE 185. FLOOD WATCH ZONE 111 145.
MARINE...STORMS 170 171 172 179 180 185. GALES 155 160 165 175 176.
FIRE WEATHER...NONE.

SEB SEP 07