Areal Flood Advisory 21, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
500 AM AKDT THU OCT 4 2012

.ANALYSIS AND UPPER LEVELS...
EARLY THIS MORNING...A NEARLY STATIONARY FRONT OVER THE GULF
CONTINUES TO BRING SCATTERED SHOWERS ALONG THE GULF COAST AND
SOUTHCENTRAL. FURTHER SOUTH...RIDGING CONTINUES OVER THE PACIFIC
NORTHWEST. THE MAIN WEATHER FEATURE IS A BROAD UPPER LEVEL LOW THAT
SPANS ACROSS THE BERING SEA. THIS IS KEEPING SOUTHERLY FLOW ALONG
WITH SCATTERED RAIN ACROSS THE CENTRAL ALEUTIANS THROUGH SOUTHWESTERN
ALASKA. ON THE BACKSIDE OF THE LOW...NORTH TO WESTERLY FLOW IS NOTED
ACROSS THE WESTERN BERING. AS SEEN ON VISIBLE SATELLITE...PLENTIFUL
MOISTURE IS STREAMING NORTHWARD BETWEEN THE TWO SYSTEMS BRINGING LOW
AND MID LEVEL STRATUS ACROSS SOUTHERN ALASKA.

.MODEL DISCUSSION...
MODELS AGREEMENT IS GOOD THROUGH THE SHORT TERM FORECAST AND BOTH
THE GFS AND NAM WERE USED TO ADJUST THE CURRENT PACKAGE. FOR MID AND
LONG RANGE FORECASTS A BLOCKING PATTERN SETS UP THIS WEEKEND WITH THE
PACIFIC RIDGE MOVING FURTHER NORTH. MODELS SOLUTIONS BEGIN TO
SLIGHTLY DIVERGE FRIDAY NIGHT AS THEY AMPLIFY THE LONGWAVE TROUGH
OVER THE BERING. ON SATURDAY...A NEW CENTER FORMS AT THE BASE OF THE
LONGWAVE AND MODELS ARE IN BETTER AGREEMENT WITH FORMING A NEW LOW
SOUTH OF THE WESTERN ALEUTIANS.  THE NAM IS CURRENTLY THE OUTLIER
WITH A SLOWER PROGRESSION OF THIS LOW.

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
LIGHT SHOWERS THIS MORNING WILL CONTINUE ACROSS THE COASTAL AREAS AND
ALONG THE ALASKA RANGE. THROUGH TODAY A STRONG PRESSURE GRADIENT SETS
UP ACROSS SOUTHCENTRAL AND WILL BRING GUSTY WINDS ALONG THE TURNAGAIN
ARM AND HIGHER ELEVATIONS. IN ADDITION...WINDY CONDITIONS WILL OCCUR
ACROSS THE LOWER HILLSIDE AND ANCHORAGE AREAS. LATER THIS MORNING
ANOTHER SHORTWAVE AHEAD OF THE MAIN UPPER LOW WILL BRING MORE RAIN
ACROSS THE GULF AND ALL OF SOUTHERN ALASKA. WITH THE BLOCKING RIDGE
IN THE NORTH PACIFIC...THE BERING LOW WILL CONTINUE TO SEND WAVES OF
ENERGY THAT WILL GENERATE PERIODS OF RAIN THROUGH THE WEEKEND.

SOUTHWEST ALASKA...
WEDGED BETWEEN TWO SYSTEMS...ABUNDANT MOISTURE WILL CONTINUE TO
STREAM OVER SOUTHWEST ALASKA KEEPING SKIES MOSTLY CLOUDY. THE BERING
LOW WILL BRING GUSTY WINDS ACROSS THE COAST TODAY INTO FRIDAY
MORNING. SCATTERED RAIN WILL BE ONGOING THROUGH THE WEEKEND AS THE
BERING LOW SLOWLY MOVES NORTHWARD.

.ALEUTIANS/BERING SEA...
WITH THE EXPANSIVE LOW OVER THE BERING STRONG WINDS AND RAIN WILL
CONTINUE INTO THE WEEKEND. ON FRIDAY COLD AIR ADVECTION ALONG THE
BACKSIDE OF THE LOW WILL COOL TEMPERATURES ACROSS THE WESTERN
ALEUTIANS THROUGH THE WEEKEND.

.LONG TERM FORECAST...
THE RIDGE WILL MOVE FURTHER NORTH SUNDAY NIGHT. THIS WILL DIMINISH
THE WET PATTERN FOR A COUPLE OF DAYS. HOWEVER...THE RIDGE WILL START
ITS SHIFT BACK TO THE EAST MONDAY NIGHT. AT THE SAME TIME...THE UPPER
LOW THAT THE MODELS DEVELOP ON SATURDAY SOUTH OF THE ALEUTIAN
CHAIN...WILL BEGIN A NORTHWARD TRACK. THIS WILL BE A RESPECTABLE
SYSTEM WITH STRONG WINDS AND RAIN.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...120 155 160 165 170 171 172 175 176 179 180 185
FIRE WEATHER...NONE

KH OCT 12