Storm Warning 213, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT MON NOV 1 2010

.MODEL DISCUSSION...GFS AND ECMWF MODELS ARE IN AGREEMENT QUITE WELL
THROUGH WEDNESDAY. NAM SEEMS TO BE AN OUTLIER TODAY. AFTER THIS TIME
FRAME...THERE ARE SOME DISCREPANCIES IN TIMING OF THE LOW PRESSURE
SYSTEMS MOVING THROUGH THE BERING AND DIGGING INTO THE GULF. THE EC
AND GFS COME TOGETHER ONCE THINGS SETTLE INTO 2 SYSTEMS DOMINATING
THE PICTURE BY FRIDAY.

.ANALYSIS AND UPPER LEVELS...LARGE SCALE TROUGH OVER THE MAINLAND OF
ALASKA. THIS HAS BROUGHT COLD AIR TO THE STATE WITH A 190KT JET
WORKING SOUTH OVER THE WESTERN ALEUTIAN CHAIN. THIS WILL ACT TO DIG
THE TROUGH OVER THE NEXT 24 HOURS INTO THE NORTHERN PACIFIC. SOME
RIDGING MOVING INTO THE WESTERN ALEUTIANS TONIGHT AS THE TROUGH MOVE
A BIT. AT THE SURFACE...A 960 LOW IS WORKING UP THE COAST WITH GALE
TO STORM FORCE WINDS. GOOD GAP WINDS THROUGH NORTH-SOUTH GAPS IN
SOUTH CENTRAL. THE LOW WILL WEAKEN AS IT REACHES THE KENAI PENINSULA
BY TOMORROW MORNING AS THERE IS NO UPPER LEVEL SUPPORT. PRECIPITATION
WILL WORK UP THE COAST TONIGHT AND CROSS SOUTH CENTRAL TOMORROW AS
THE LOW LIFTS INLAND. OVER THE WEST...STRONG NORTHWEST FLOW WITH LOW
CLOUDS AND SNOW SHOWERS OVER THE CENTRAL AND EASTERN BERING WITH HIGH
PRESSURE MOVING THROUGH THE WESTERN BERING SEA. IFR TO VFR CHANGING
CONDITIONS CONTINUALLY IN THIS FLOW.

THE JET CORE WILL WEAKEN OVER THE NORTHERN PACIFIC WITH THE TROUGH
OVER THE STATE. THIS JET CORE WILL ACT TO SWING THE TROUGH EAST
WEDNESDAY INTO THURSDAY. THE TROUGH WILL WEAKEN WITH AN UPPER LOW
REMAINING OVER THE MAINLAND. THE FLOW BEHIND THE TROUGH WILL BECOME
MORE ZONAL WITH THE JET REMAINING SOUTH OF THE STATE FRIDAY THROUGH
EARLY NEXT WEEK. THIS WILL USHER IN A STRONG UPPER LOW INTO THE
WESTERN BERING THIS WEEKEND WITH A SHORT WAVE RIDGE JUST AHEAD OF THE
LOW. COLD AIR WILL HAVE SETTLED OVER MUCH OF THE STATE THEN.

.SHORT TERM FORECAST...
EAST OF THE ALEUTIAN RANGE...LOW PRESSURE SYSTEM MOVING UP THE COAST
TO SWING INTO THE AREA LATER TONIGHT WITH SNOW SPREADING ACROSS THE
AREA. HEAVIEST SNOW SHOULD BE EAST OF ANCHORAGE. ANCHORAGE TO SEE
SOME SNOW TOMORROW MORNING THROUGH MUCH OF THE DAY. EXPECTING 1 TO 4
INCHES WITH HIGHEST AMOUNTS ALONG THE HILLSIDE. IF THE SURFACE TEMP
HOVERS AROUND FREEZING MAY NOT SEE ANY ACCUM ON THE WEST SIDE OF TOWN
AGAIN. THE LOW WILL LIFT INLAND TUESDAY WITH A BREAK FOR TUESDAY
NIGHT BEFORE THE NEXT STRONG LOW ASSOCIATED WITH GOOD UPPER LEVEL
SUPPORT MOVES INTO THE AREA. STORM FORCE WINDS WITH AN ACTIVE FRONT
TO MOVE IN WEDNESDAY. POSSIBLE HURRICANE GUSTS FOR THE FRONT ALONG
THE NORTHERN GULF COAST AS WELL. WARMER AIR MASS WITH THIS FRONT...SO
PRECIP AT THE VALLEY LOCATIONS WILL BE ALL RAIN. STRONG WINDS WILL
MAKE IT THROUGH THE EAST-WEST AND NORTH-SOUTH GAPS OF SOUTH CENTRAL.

SOUTHWEST ALASKA...STRONG NORTHWEST FLOW IN AN UNSTABLE ENVIRONMENT
MAKING FOR SOME LOW CLOUD AND SCATTERED SNOW SHOWERS. THESE
CONDITIONS TO REMAIN AS THE LOW CONTINUES IN THE GULF AND HIGH
PRESSURE REMAINS OVER THE WESTERN BERING. THE HIGH PRESSURE TO MOVE
INTO THE CENTRAL BERING TUESDAY AND THE GULF LOW MOVES INLAND. WINDS
WILL DIMINISH A BIT OVER THE MAINLAND BUT PICK UP OVER THE EASTERN
BERING WITH CONTINUED INSTABILITY SHOWERS. GRADIENT WEAKENS WEDNESDAY
AS THE HIGH PRESSURE MOVES OVER THE EASTERN BERING AND THE LOW INLAND
DISSIPATES. THERE WILL BE ENOUGH INSTABILITY REMAINING FOR ISOLATED
SNOW SHOWERS.

BERING SEA...HIGH PRESSURE CURRENTLY OVER THE WESTERN BERING WITH
STRONG NORTHERLY FLOW IN THE CENTRAL BERING. THE AIR MASS IS UNSTABLE
ENOUGH IN THE LOWEST LAYERS FOR SNOW SHOWERS. THE HIGH PRESSURE TO
MOVE EAST AS A FRONT MOVES TO SHEMYA TUESDAY. GALE FORCE WINDS TO
ACCOMPANY THIS FRONT AT FIRST. HOWEVER...THE FRONT WEAKENS AS IT
MOVES INTO THE CENTRAL BERING WEDNESDAY WITH LOW CENTERS WRAPPING
AROUND EACH OTHER NEAR THE KAMCHATKA PENINSULA.

.LONG TERM FORECAST...EC AND GFS NOT IN GOOD TIMING FROM WEDNESDAY
THROUGH FRIDAY AS THE FLOW CHANGES FROM MORE MERIDIONAL TODAY TO MORE
ZONAL SATURDAY. HOWEVER...BY SATURDAY 2 SYSTEMS BECOME DOMINANT FOR
THE WEATHER PATTERN. A LOW SITUATES ITSELF IN THE GULF WHILE THE
KAMCHATKA LOW DOES NOT MOVE MUCH. A REASON FOR THIS IS THAT THE JET
CORE IS WELL SOUTH OF THE FORECAST AREA BY THIS TIME. THEREFORE...WE
HAVE STACKED LOW WITH LITTLE MOVEMENT FOR A COUPLE DAYS.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...120 172 175 176 180 185
FIRE WEATHER...NONE

JN NOV 10