Gale Warning 420, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT WED APR 22 2009

.ANALYSIS AND UPPER LEVELS...
A 990 MB LOW OVER THE NORTHWEST BERING IS WEAKENING WHILE MOVING
NORTHEAST. HIGH PRESSURE IS STILL ANCHORED OVER THE GULF OF ALASKA.
BETWEEN THESE TWO SYSTEMS...MOIST SOUTHWESTERLY FLOW IS EVIDENT ON
WATER VAPOR IMAGERY.

IN THE UPPER LEVELS...A RIDGE CENTERED OVER THE ALCAN IS MOVING EAST
INTO THE YUKON. A TROUGH IS OVER THE CENTRAL AND WESTERN
ALEUTIANS...WITH A WEAKENING UPPER LOW LOCATED OVER THE NORTHWESTERN
BERING. A SHORTWAVE OVER THE EASTERN ALEUTIANS IS ROTATING AROUND THE
BASE OF THE TROUGH...POISED TO MOVE INTO SOUTHWEST AND SOUTHCENTRAL
AK TONIGHT AND TOMORROW.

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT THROUGH SATURDAY. DIFFERENCES BEGIN TO
ARISE REGARDING POSITION AND INTENSITY OF THE NORTH PACIFIC LOW
APPROACHING THE WESTERN ALEUTIANS OVER THE WEEKEND. THE GFS WAS USED
TO CONSTRUCT THE AFTERNOON FORECAST PACKAGE DUE TO CONTINUED
CONSISTENCY.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
MOIST SOUTHWEST RETURN FLOW WILL BE PUSHING INTO SOUTHCENTRAL AS THE
RIDGE SLIPS EAST. A ROBUST SHORTWAVE AND SURFACE FRONT WILL ALSO MOVE
ACROSS THE AREA THURSDAY AFTERNOON THROUGH FRIDAY...BRINGING WITH IT
WIDESPREAD RAIN AND SNOW. ANOTHER SHORTWAVE WILL APPROACH THE AREA
FRIDAY AFTERNOON...ENHANCING PRECIPITATION POTENTIAL ONCE AGAIN AS WE
HEAD INTO THE WEEKEND.

.SOUTHWEST...
RAIN AND SNOW SHOWERS WILL PERSIST ACROSS SOUTHWEST IN RESPONSE TO
THE MOIST SOUTHWESTERLY FLOW. A SHORTWAVE PUSHING THROUGH WILL
REINFORCE CHANCES FOR PRECIP TONIGHT AND TOMORROW MORNING. THE UPPER
LOW OVER THE BERING WILL WEAKEN INTO AN OPEN WAVE WHILE MOVING
EAST...ONCE AGAIN ENHANCING SHOWER COVERAGE. RAIN AND SNOW WILL
INCREASE ACROSS THE AKPEN FRIDAY NIGHT AS A FRONT ASSOCIATED WITH THE
NORTH PACIFIC LOW MOVES INTO THE AREA.

.BERING SEA AND ALEUTIANS...
SCATTERED RAIN AND SNOW SHOWERS UNDER SOUTHERLY FLOW WILL CONTINUE
OVER THE NEXT SEVERAL DAYS AS THE UPPER LOW MOVES NORTHEAST.
PRECIPITATION WILL BECOME MORE WIDESPREAD OVER ALEUTIANS TOMORROW
NIGHT INTO FRIDAY AS A NORTH PACIFIC LOW CROSSES INTO THE BERING.

.LONG TERM FORECAST...
MOIST SOUTHWEST FLOW WILL CONTINUE OVER MAINLAND AK THROUGH THE FIRST
PART OF NEXT WEEK. EXPECTING A SERIES OF SLOW MOVING NORTH PACIFIC
LOWS TO CROSS INTO THE BERING SEA...THEN MOVE NORTHEAST WHILE
DISSIPATING. AS A RESULT...PRECIPITATION CHANCES WILL REMAIN HIGH
OVER THE MAINLAND AND ALEUTIANS THROUGH NEXT WEEK.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...155 175 176 411 AND 413.
FIRE WEATHER...NONE

NRH APR 09