Dense Fog Advisory 21, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT FRI AUG 22 2008

.MODEL DISCUSSION...
MODELS INITIALIZED WELL TODAY AND ARE IN GENERAL AGREEMENT THROUGH
THE SHORT TO MEDIUM TIME FRAME TODAY. BETTER DAY THAN THE LAST COUPLE
WITH MODEL CONTINUITY. LAST NIGHT...THE 00Z EC AND NAM WERE THE
PREFERRED SOLUTIONS. EVERY MODEL VERY SIMILAR TO THESE SOLUTIONS
THROUGH THE NEXT FEW DAYS. SOME DIFFERENCES START TO APPEAR WITH THE
SPEED OF THE NEXT LOW SOUTH OF THE ALEUTIANS IN DAY 2. BEST SOLUTION
FOR TODAY WAS TO USE THE PREVIOUS GRIDS AND PICK UP SOME OF THE NEW
DETAILS IN THE SHORT TERM. THE 12Z GFS WAS VERY SIMILAR TO THE 00Z EC
THROUGH THE FIRST 5 DAYS AS WELL.

.ANALYSIS...
SURFACE LOW IN THE EASTERN GULF WITH A BROAD AREA OF LOW PRESSURE
THROUGH THE EASTERN BERING. LOTS OF LOW CLOUDS AND FOG THROUGH EARLY
THIS AFTERNOON FROM YESTERDAYS PRECIPITATION AND STRATUS THROUGHOUT
THE BERING. TRANSITIONAL HIGH PRESSURE OVER THE WESTERN BERING. AN
EASTERLY WAVE ROTATING THROUGH THE KENAI PENINSULA TODAY WITH
SHOWERS. WEAKER WAVES WILL CONTINUE TO ROTATE AROUND THE UPPER LOW IN
THE GULF THROUGH TONIGHT. THE AIR MASS CONTINUES TO BE UNSTABLE...SO
ANY BREAKS IN CLOUDS CREATES AN AREA CONDUCIVE TO RAPID THUNDERSTORM
DEVELOPMENT. THIS WAS EVIDENT YESTERDAY WHEN HAIL AND HEAVY
PRECIPITATION MOVED OVER ANCHORAGE.

.UPPER LEVELS...
A LOW AMPLITUDE RIDGE OVER THE WESTERN BERING WITH A STRONG JET
RUNNING FROM THE WESTERN ALEUTIANS WRAPPING AROUND THE LOW IN THE
GULF TOWARD THE PANHANDLE. THE LOW IN THE GULF TO COMBINE WITH AN
UPPER LOW MOVING OUT OF BRISTOL BAY TONIGHT TO FORM A LARGE LOW IN
THE CENTRAL GULF SATURDAY. THE LOW TO DEEPEN OVER THE NORTHEAST GULF
THROUGH SUNDAY. A GOOD EASTERLY WAVE TO PUSH THROUGH SOUTH CENTRAL
SATURDAY. IN THE MEANTIME...THE RIDGE IN THE BERING EVAPORATES AS
ANOTHER LOW MOVES INTO THE WESTERN BERING WITH A BROAD AREA OF LOW
PRESSURE OVER THE EASTERN BERING ASSOCIATED WITH THE GULF LOW. WAVE
WILL CONTINUE TO RUN AROUND THE GULF LOW THROUGH THE WEEKEND AS THE
LOW IN THE BERING SPINS UP A BIT. THIS LOW PUSHES OUT THE GULF LOW
MONDAY AS IT MOVES TO THE EASTERN ALEUTIANS. MEANWHILE...A POLAR LOW
DROPS INTO THE CHUKCHI SEA. A LONG WAVE TROUGH THEN DEVELOPS OVER
THE EASTERN BERING WITH A RIDGE OVER THE WESTERN BERING AND MOIST
SOUTHWEST FLOW OVER THE MAINLAND AND PANHANDLE TO REMAIN THROUGH
WEDNESDAY.

.SHORT TERM FORECAST...
ALEUTIANS AND BERING...
THE BROAD AREA OF LOW PRESSURE IN THE EASTERN BERING COMBINED WITH A
WEAK HIGH IN THE WESTERN BERING TO KEEP LIGHT WINDS AND STRATUS AND
FOG OVER THE AREA THROUGH MUCH OF TOMORROW. THE WESTERN BERING TO BE
AFFECTED BY A LOW STARTING LATE TOMORROW WITH GALE FORCE WINDS AND
PRECIPITATION. THE LOW CENTER TO REMAIN SOUTH OF THE CHAIN...BUT
PRECIPITATION AND STRONGER WINDS TO WORK TO THE EAST THROUGH THE
WEEKEND. THE LOW TO STRETCH AND WEAKEN ON SUNDAY INTO MONDAY SOUTH OF
CENTRAL AND EASTERN ALEUTIANS.

SOUTHWEST ALASKA...
BROAD AREA OF LOW PRESSURE TO REMAIN OVER THE AREA THROUGH EARLY NEXT
WEEK. INLAND AREAS WILL SEE SOME CONVECTION AS THE AIR MASS IS
UNSTABLE AND ANY BREAKS IN CLOUD COVER WILL ALLOW THUNDERSTORM
DEVELOPMENT THROUGH TODAY. AIR MASS TO BECOME A BIT MORE STABLE OVER
THE NEXT COUPLE DAYS AS THE AIR ALOFT WARMS. STILL ENOUGH FOR SHOWERS
AND A FEW THUNDERSTORMS. THERE MAY BE A GOOD EASTERLY WAVE ON SUNDAY
FOR POSSIBLE INCREASE IN THUNDERSTORM ACTIVITY.

SOUTH CENTRAL ALASKA...
UPPER LOW IN THE GULF WITH A FEW EASTERLY WAVES TO PUSH AROUND THE
NEXT COUPLE DAYS. THE FIRST ONE IS TODAY THAT IS MOVING THROUGH THE
KENAI PENINSULA. COMBINED WITH THE COOLER AIR MASS ALOFT...ANY BREAKS
IN CLOUD COVER WILL ALLOW FOR RAPID THUNDERSTORM DEVELOPMENT THIS
AFTERNOON AND EVENING. MUCH IN THE SAME MANNER AS YESTERDAY. THE NEXT
WAVE IS EXPECTED SATURDAY AS THE LOW IN THE EASTERN GULF ROTATES TO
THE NORTHERN GULF BEFORE COMBINING WITH THE ANOTHER UPPER LOW IN THE
CENTRAL GULF. THIS WAVE HAS A DECENT SURFACE REFLECTION IN THE WIND
FIELD AS WELL. THEREFORE...EXPECT GALE FORCE WINDS ALONG THE NORTHERN
GULF COAST AND EAST WEST GAPS OF SOUTH CENTRAL. ANOTHER WAVE TO WORK
TO THE COPPER BASIN SUNDAY...BUT STOPPED SHORT OF ROTATING FARTHER
EAST SINCE THE UPPER LOW GETS PUSHED OUT OF THE AREA LATE SUNDAY INTO
MONDAY. THEREFORE...SHOWER ACTIVITY TO BE LESS ON SUNDAY EXCEPT NEAR
THE NORTHERN GULF COAST.

.LONG TERM FORECAST...
COLD FRONT TO PUSH THROUGH THE BERING MONDAY NIGHT AND TUESDAY AND
DIG A LONG WAVE TROUGH OVER THE EASTERN BERING. THIS WILL PUSH THE
LOW SOUTH OF THE EASTERN ALEUTIANS INTO THE GULF AND DEEPEN.
ESSENTIALLY...THERE WILL BE A COLD AIR MASS OVER THE BERING WITH A
WARMER MOIST AIR MASS OVER SOUTH CENTRAL AND THE PANHANDLE THROUGH
THE END OF NEXT WEEK.

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

NELSON AUG 08