Gale Warning 509, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
220 PM AKDT WED JUL 22 2009

.ANALYSIS...
VERTICALLY STACKED LOW CONTINUES TO SPIN OVER THE ALASKA PENINSULA
WITH MULTIPLE SHORT WAVES ROTATING AROUND ITS PERIPHERY. THE MOST
OBVIOUS WAVE IS MOVING OUT OF THE NORTHERN BERING SEA WHICH WILL
EVENTUALLY BECOME THE NEW CENTER OF ROTATION A BIT FURTHER WEST.
ANOTHER POTENT SHORT WAVE IN THE NORTHERN GULF IS RESPONSIBLE FOR THE
ENHANCED RAINFALL ALONG THE COAST. A THIRD...AND MOST IMPORTANT FOR
THE FORECAST...IS CURRENTLY LOCATED OVER THE KAMCHATKA PENINSULA. AS
MENTIONED IN PREVIOUS DISCUSSIONS...THIS WILL HELP DIG THE TROUGH
DURING THE WEEKEND.

AT THE SURFACE...SURFACE RIDGING TAKING PLACE ALONG THE GULF COAST
RESULTING IN GUSTY WINDS THROUGH CHANNELED TERRAIN. A BROAD AREA OF
LOW PRESSURE IS LOCATED OVER THE ALASKA PENINSULA AND EASTERN BERING
SEA UNDER THE VERTICALLY STACKED LOW. THE THERMAL TROUGH IS LOCATED
WELL NORTH ALONG THE YUKON RIVER VALLEY WHICH IS HELPING TO INITIATE
THUNDERSTORM ACTIVITY EARLY THIS AFTERNOON.

.MODEL DISCUSSION...
MODELS CONTINUE RESOLVING LARGE SCALE FEATURES WELL AND ARE IN FAIR
AGREEMENT. THE TIMING AND EXACT LOCATION OF SHORT WAVES CONTINUE TO
CHANGE WITH EACH MODEL RUN...LEADING TO MINOR TWEAKS IN THE SHORT
TERM AND TRENDING THE FORECAST IN THE MEDIUM RANGE. ONE DIFFERENCE IS
THE DEVELOPING LOW MOVING OUT OF THE BASE OF THE TROUGH SATURDAY
MORNING INTO THE SOUTHWESTERN GULF. THE MODELS ARE TRENDING THIS
FEATURE FURTHER EAST TOWARD KODIAK ISLAND SATURDAY EVENING. THE
PREVIOUS LOCATION WAS NEAR CHIGNIK...SO A SIGNIFICANT SHIFT TO THE
EAST. HAVE NUDGED THE FORECAST TOWARD THIS NEW SCENARIO WHICH IS A
BLEND OF THE GFS AND NAM.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
NO SIGNIFICANT CHANGES EXPECTED IN THE SHORT TERM. SOUTHEASTERLY FLOW
WILL BECOMING MORE SOUTHERLY WITH THE PASSING OF A SHORT WAVE TONIGHT
INTO SOUTHCENTRAL INTERIOR. THIS WILL LEAD TO AN INCREASED CHANCE OF
RAIN OVER THE WESTERN KENAI AND ANCHORAGE BOWL FRIDAY AFTERNOON AND
THROUGH EARLY SATURDAY MORNING...THEN A BRIEF BREAK BEFORE THE
MOISTURE FROM THE KODIAK LOW ENCROACHES THE COAST AGAIN.

WE HAVE BEEN ADVERTISING A MORE SUBTROPICAL FETCH OF MOISTURE WITH
THIS NEXT SYSTEM AS A RESULT OF THE TROUGH BECOMING MORE AMPLIFIED
AND TAPPING THE LOWER LATITUDES. THIS IS EVIDENT BY THE CURRENT AND
FORECASTED PRECIPITABLE WATER FOR SOUTHCENTRAL. THE CURRENT ANCHORAGE
SOUNDING GIVES US .69 INCHES OF WATER WITH FORECASTED AMOUNTS NEAR
1.25 INCHES LATE IN THE WEEKEND AND INTO EARLY NEXT WEEK. COASTAL
AREAS ALREADY SEEING NEAR .75 INCHES OF PRECIPITABLE WATER COULD
REACH NEAR 1.5 INCHES BY MONDAY. THIS KIND OF DEEP TROPICAL MOISTURE
COULD FURTHER COMPLICATE FLOODING ISSUES ON THE KENAI RIVER THROUGH
THE WEEKEND. THEREFORE...THE FLOOD WATCH CONTINUES FOR THE ENTIRE
KENAI PENINSULA AND FLOOD ADVISORIES HAVE BEEN POSTED FOR THE KENAI
RIVER NEAR COOPER LANDING.

.WESTERN...
THE LOW CURRENTLY IN THE EASTERN BERING WILL CONTINUE TO RETROGRADE
AND WEAKEN. BY SATURDAY IT APPEARS ANOTHER LOW PRESSURE SYSTEM
ASSOCIATED WITH THE SAME LARGER UPPER LEVEL LOW WILL MOVE INTO THE
REGION AND BRING WITH IT SOME MORE RAIN AND POTENTIALLY
THUNDERSTORMS. WITH THE THE CURRENTLY RETROGRADING LOW EXPECT MORE
RAIN TO CONTINUE ALONG THE ALEUTIAN ISLANDS.

.LONG TERM FORECAST...
BY NEXT WORK WEEK IT APPEARS A RIDGE CURRENTLY MOVING INTO THE
PANHANDLE WILL MOVE TO THE NORTH AND WEST AND EVENTUALLY MOVE OVER
SOUTHCENTRAL ALASKA. AT THE SAME TIME THIS RIDGE BUILDS IN A LOW WILL
BE LOCATED OVER THE EASTERN ALEUTIANS...CREATING AN AMPLIFIED
PATTERN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD WATCH 121 125...FLOOD ADVISORY 121
MARINE...NONE
FIRE WEATHER...NONE

AB/TARALDSEN JUL 09