Gale Warning 426, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
130 PM AKDT FRI JUN 28 2013

.ANALYSIS AND UPPER LEVELS...
THE OVERALL WEATHER PATTERN IS IN THE EARLY STAGES OF A MAJOR
TRANSITION. A CLOSED HIGH REMAINS OVER EASTERN SECTIONS OF INTERIOR
ALASKA...BUT IS BEING SLOWLY PUSHED INTO CANADA. WEAK DISTURBANCES
MOVING THROUGH THE EASTERLY FLOW AROUND THE PERIPHERY OF THE HIGH IS
HELPING TO MAINTAIN ISOLATED THUNDERSTORM ACTIVITY ACROSS THE COPPER
RIVER BASIN. EARLIER THIS MORNING A MORE SIGNIFICANT SHORTWAVE KICKED
OFF A SIGNIFICANT ROUND OF THUNDERSTORMS AND HEAVY RAIN AROUND PRINCE
WILLIAM SOUND. AT THE SURFACE...WEAK HIGH PRESSURE REMAINS IN PLACE
OVER THE NORTHERN GULF...WITH SOUTHWEST FLOW MAINTAINING COPIOUS
AMOUNTS OF LOW-LEVEL MOISTURE ACROSS SOUTHCENTRAL. MEANWHILE...WEAK
DIFFLUENT FLOW ALOFT IS GENERATING MINOR SYNOPTIC-SCALE LIFT ACROSS
UPPER COOK INLET. AS A RESULT...LOW CLOUDS AND DRIZZLE AROUND
ANCHORAGE AND THE MAT-SU VALLEY SHOW NO SIGNS OF BURNING OFF WITH
DIURNAL HEATING TODAY. OUT WEST...A LONGWAVE TROUGH OVER THE WESTERN
BERING IS GENERATING BROAD SOUTHWEST FLOW ALOFT OVER MOST OF THE
REGION. AS A RESULT...INCREASING AMOUNTS OF MOISTURE ARE STREAMING
INLAND ALL THE WAY TO THE KUSKOKWIM VALLEY. MEANWHILE...A RELATIVELY
WEAK FRONT IS IMPACTING THE EASTERN ALEUTIANS AND AKPEN TODAY WITH
RAIN AND WIND...BUT IS STRUGGLING TO MIX THE ATMOSPHERE ENOUGH TO GET
RID OF ENTRENCHED MARINE FOG. A MORE POTENT STORM IS TAKING SHAPE IN
THE NORTHWEST PACIFIC...PRIMED TO MOVE INTO THE WESTERN BERING EARLY
SATURDAY.

.MODEL DISCUSSION...
MODELS REMAIN IN GOOD OVERALL AGREEMENT ON THE EVOLUTION OF MAJOR
SYNOPTIC WEATHER FEATURES THROUGHOUT THE SHORT TERM FORECAST. NONE OF
THE MODELS ARE DOING PARTICULARLY WELL WITH THE AREAS OF CONVECTION
EAST OF THE ALASKA RANGE...WHICH IS LIKELY DUE TO THE FACT THAT THE
TRIGGER FOR THESE SHOWERS AND THUNDERSTORMS ARE VERY WEAK SHORTWAVES
THAT THE MODELS OFTEN STRUGGLE TO RESOLVE. OUT WEST...THERE ARE SOME
MODEL DISCREPANCIES THAT DEVELOP AS THE NEW UPPER LOW AND LONGWAVE
TROUGH BECOME ESTABLISHED OVER THE WEEKEND. THE NAM IS AN OUTLIER
KEEPING THE REMNANTS OF THE UPPER RIDGE OVER THE MAINLAND INTACT
LONGER...AND AS A RESULT THE UPPER LOW OVER THE BERING IS DISPLACED
FURTHER NORTH AND WEST. WHILE THE OTHER MODELS HAVE SOME
DIFFERENCES...ALL FLATTEN THE ANTECEDENT RIDGE A BIT FASTER...AND
THUS THE UPPER LOW (AND CORRESPONDING SURFACE LOW POSITION) MOVES
FURTHER EAST. THE HIGHER RESOLUTION OF THE NAM WAS USEFUL OVER THE
EASTERN DOMAIN TODAY...BUT THE NAM WAS REJECTED OVER THE WESTERN
DOMAIN DURING FORECAST PREP TODAY IN FAVOR OF AN ECMWF/GFS
COMBINATION.

.SHORT TERM FORECAST...
SOUTHCENTRAL...WEAK DIFFLUENT FLOW ALOFT SHOULD KEEP LOW CLOUDINESS
AROUND MUCH OF THE REGION UNTIL A HIGHLY AMPLIFIED RIDGE MOVES INTO
THE AREA FROM THE WEST ON SATURDAY. OVERALL FLOW WILL BECOME MUCH
MORE NORTHERLY AND OFFSHORE TOMORROW...BUT TRAPPED LOW-LEVEL MOISTURE
MAY CAUSE FOG/STRATUS TO LINGER INTO THE AFTERNOON HOURS. ASSUMING
SOME CLEARING SKIES...TEMPERATURES ACROSS THE AREA SHOULD REBOUND
NICELY TOMORROW WITH WARM AIR STILL IN PLACE FROM THE PAST FEW WEEKS.
BY SUNDAY...HIGH CLOUDS START TO OVERTAKE THE AREA FROM THE STORM
MOVING THROUGH THE BERING...WITH WIDESPREAD RAIN LIKELY BY SOMETIME
MONDAY AFTERNOON. WEAK AFTERNOON/EVENING SEA BREEZES ARE LIKELY BOTH
DAYS THIS WEEKEND ACROSS THE MAJORITY OF THE COASTAL AREAS.

SOUTHWEST...WIDESPREAD CLOUDINESS THIS MORNING IS BREAKING UP WITH
DIURNAL HEATING ACROSS PARTS OF BRISTOL BAY AND THE KUSKOKWIM VALLEY.
SOME SHOWER ACTIVITY WILL DEVELOP BY LATER THIS AFTERNOON...BUT WITH
THE THERMAL TROUGH RETREATING INTO THE INTERIOR OF THE STATE DO NOT
ANTICIPATE MUCH RISK OF THUNDERSTORMS TODAY OR FOR THE FORESEEABLE
FUTURE. BY MIDDAY TOMORROW STEADY RAIN AND GUSTY WINDS WILL HAVE
MOVED INTO THE DELTA...SPREADING INLAND OVERNIGHT AND INTO SUNDAY
MORNING. THIS WILL BRING SIGNIFICANT RELIEF TO THE HOT AND DRY
CONDITIONS THAT HAVE LED TO WIDESPREAD WILDFIRE ACTIVITY.

BERING SEA AND ALEUTIANS...WEAK FRONT BRINGING RAIN AND WIND TO THE
PRIBILOFS AND EASTERN ALEUTIANS/AKPEN WILL MEANDER TO THE NORTHEAST
AND BE ABSORBED BY TOMORROW MORNING BY A STRONGER FRONT ASSOCIATED
WITH THE DEVELOPING BERING STORM. WINDS ALONG THE FRONT ITSELF WILL
TOP OUT NEAR MIN-GALES. MEANWHILE...WINDS ASSOCIATED WITH THE LOW
CENTER ITSELF MOVING THROUGH THE BERING SATURDAY NIGHT AND SUNDAY
WILL BE SLIGHTLY STRONGER AND MUCH MORE WIDESPREAD COMPARED TO THE
FRONT. THE LOW WILL MOVE INTO THE NORTHERN BERING BY SUNDAY
NIGHT...SETTING THE REGION UP IN CONTINUED MOIST SOUTHWESTERLY FLOW
WITH PRECIPITATION BECOMING MORE SHOWERY BUT REMAINING UNSETTLED.

.LONG TERM FORECAST...
AS MENTIONED ABOVE...A MAJOR PATTERN CHANGE IS TAKING SHAPE THAT WILL
AFFECT VIRTUALLY THE ENTIRE STATE. BROAD SOUTHWEST FLOW ALOFT WILL
ALLOW AMPLE MOISTURE TO PENETRATE FAR INTO INTERIOR PORTIONS OF THE
STATE BY THE START OF NEXT WEEK. THIS NEW PATTERN FEATURING A
LONGWAVE TROUGH OVER THE BERING SEA WILL LIKELY REMAIN IN PLACE
THROUGH AT LEAST THE END OF NEXT WEEK. TEMPERATURES OVER THE MAINLAND
WILL DRAMATICALLY RETURN TO NEAR OR EVEN BELOW NORMAL AS WIDESPREAD
CLOUDINESS LARGELY LIMITS DIURNAL HEATING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 170 172 175 176 180
FIRE WEATHER...NONE

DIXON JUN 13