Brisk Wind Advisory 61, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT THU APR 23 2009

.ANALYSIS AND UPPER LEVELS...
HIGH PRESSURE REMAINS FIRMLY ANCHORED OVER THE SOUTHERN GULF OF
ALASKA. A 999 MB LOW OVER THE NORTHERN BERING IS WEAKENING WHILE
MOVING NORTHWARD. A FRONT ASSOCIATED WITH THIS LOW IS MOVING ACROSS
SOUTHWEST ALASKA AND INTO SOUTHCENTRAL...WITH GOOD MOISTURE TRANSPORT
SEEN ON WATER VAPOR IMAGERY. A DEVELOPING 980 MB NORTH PACIFIC LOW
EVIDENT ON SATELLITE IMAGERY WILL BE THE MAJOR FORECAST PROBLEM OVER
THE NEXT SEVERAL DAYS.

IN THE UPPER LEVELS...A RIDGE CENTERED OVER THE ALCAN IS MOVING EAST
INTO CANADA. A BROAD LONGWAVE TROUGH IS CENTERED OVER THE EASTERN
BERING. AN UPPER LOW WITHIN THIS TROUGH HAS WEAKENED INTO AN OPEN
WAVE AND IS ALSO MOVING EASTWARD. VARIOUS SHORTWAVES ARE EMBEDDED
WITHIN THE TROUGH...WITH ONE SUCH DISTURBANCE CURRENTLY MOVING OVER
SOUTHWEST AND SOUTHCENTRAL ALASKA.

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT THROUGH SUNDAY. MODELS BEGIN TO DIVERGE
AT THIS POINT REGARDING THE EVOLUTION AND INTENSITY OF THE NORTH
PACIFIC LOW MOVING INTO THE BERING SEA. SUBSTANTIAL DIFFERENCES ALSO
EXIST BETWEEN SOLUTIONS NEXT WEEK DUE TO A POTENTIAL PATTERN CHANGE.
THE GFS WAS THE MODEL OF CHOICE FOR THIS AFTERNOON...DUE TO CONTINUED
CONSISTENCY.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
THE FRONT AND AN ATTENDANT SHORTWAVE WILL BE MOVING ACROSS
SOUTHCENTRAL TONIGHT...WITH ANOTHER UPPER DISTURBANCE MOVING INTO THE
AREA TOMORROW. THE HEAVIER PRECIPITATION MAKER WILL BE TONIGHT...WITH
MORE SCATTERED PRECIP EXPECTED ON FRIDAY. THE MAIN FORECAST CHALLENGE
FOR SOUTHCENTRAL TONIGHT CONCERNS PRECIP TYPE. MAINLY RAIN IS
EXPECTED ALONG THE IMMEDIATE COAST...WITH A RAIN SNOW MIX FOR OTHER
LOCATIONS. THE ONE EXCEPTION TO THIS IS FOR THE SUSITNA
VALLEY...MAINLY NORTH AND WEST OF TALKEETNA...WHERE SNOW IS EXPECTED
TO PREDOMINATE. AS IS TYPICAL IN THESE SCENARIOS PRECIP TYPE WILL
ULTIMATELY DEPEND HEAVILY ON INTENSITY...AS HEAVIER PRECIP CAN RESULT
IN PERIODS OF HEAVY SNOW. A FRONT ASSOCIATED WITH THE NORTH PACIFIC
LOW WILL MOVE INTO SOUTHCENTRAL ON SATURDAY...BRINGING WIDESPREAD
RAIN AND SNOW BACK TO THE AREA. THIS SYSTEM IS EXPECTED TO BE MUCH
WARMER THAN THE SYSTEM MOVING THROUGH TONIGHT.

.SOUTHWEST...
RAIN AND SNOW WILL BECOME MORE SHOWERY IN NATURE TONIGHT AS THE
SHORTWAVE AND FRONT MOVE TO THE EAST. SHOWERS WILL PERSIST ON FRIDAY
AS ANOTHER UPPER DISTURBANCE MOVES ACROSS THE AREA. RAIN AND SNOW
WILL BECOME MORE WIDESPREAD ONCE AGAIN ON SATURDAY AS A FRONT
ASSOCIATED WITH THE NORTH PACIFIC LOW PUSHES INTO SOUTHWEST.

.BERING SEA AND ALEUTIANS...
PRECIPITATION WILL BE OVERSPREADING THE ALEUTIANS AND PRIBILOFS
TONIGHT INTO TOMORROW...AS THE AFOREMENTIONED NORTH PACIFIC LOW MOVES
INTO THE BERING. EXPECTING MOSTLY RAIN WITH THIS SYSTEM ALTHOUGH SNOW
WILL MIX IN OCCASIONALLY...PARTICULARLY OVER THE PRIBILOFS. RAIN AND
SNOW SHOWERS WILL PERSIST AS WE HEAD INTO THE WEEKEND AS THE LOW
MOVES OUT OF THE AREA.

.LONG TERM FORECAST...
THE NORTH PACIFIC LOW MOVING INTO THE BERING WILL BE THE FOCUS OF THE
FORECAST THROUGH THE WEEKEND. MOIST SOUTHERLY FLOW WILL PERSIST
ACROSS THE SOUTHERN MAINLAND THROUGH THE FIRST PART OF NEXT
WEEK...KEEPING THE THREAT OF PRECIPITATION HIGH.

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

NRH APR 09