Gale Warning 622, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKDT SUN SEP 29 2013

.ANALYSIS AND UPPER LEVELS...
A NEARLY STATIONARY UPPER-LVL LOW NEAR THE AK PANHANDLE IS FILLING.
THIS LARGE UPPER-LVL CIRCULATION HAS SOME MINOR SENSIBLE IMPACTS
ACROSS SOUTHCENTRAL AK. THIS GENERALLY FEATURES WEAK DISTURBANCES
PINWHEELING AROUND THE NORTHERN PERIPHERY OF THAT LOW THAT SPREADS
SOME CLOUDS AND SOME LIGHT PRECIP TO INTERIOR AREAS. THE SOUTHERN
REACHES OF A WEAK DEFORMATION AREA IN CENTRAL AK DOES POKE A BIT INTO
THE LOWER KUSKOKWIM VALLEY...WITH THICKER CLOUDS AND LIGHT SNOWS
FALLING THERE AS WELL. FURTHER WEST...UPPER-LVL RIDGING MOVES THROUGH
THE BERING SEA AND ALEUTIANS SUPPORTING A SURFACE HIGH PRESSURE
CENTER NEAR ADAK. IN BETWEEN THIS BROAD RIDGING AND THE LINGERING FAR
SE GULF LOW...THE PRESSURE GRADIENT REMAINS SUBSTANTIALLY SQUEEZED TO
SUPPORT WIDESPREAD NORTH TO WEST GALES WITH STORM FORCE WINDS THROUGH
FAVORED GAPS/PASSES FROM THE NW GULF BACK THROUGH THE AKPEN. THIS HAS
BEEN CORROBORATED BY NUMEROUS SHIP OBSERVATIONS TODAY. ALSO OF NOTE
IS A SHORTWAVE TROUGH BEGINNING TO EJECT OFF EASTERN SIBERIA TOWARDS
SW AK. THERE IS ALSO A SURFACE LOW FORMING OVER THE KAMCHATKA
PENINSULA WHICH IS TRACKING EAST TOWARDS THE WESTERN ALEUTIAN CHAIN.

.MODEL DISCUSSION...
IN THE EAST...THE UPPER-LOW IN THE PANHANDLE SHOULD CONTINUE FILLING
WITH TIME AS THE SUPPORTING UPPER JET OUTRUNS IT BY FURTHER INTO
BRITISH COLUMBIA AND THE THE NW CONUS. THE SHORTWAVE EJECTING FROM
EASTERN SIBERIA QUICKLY SWINGS THROUGH SW AK ON MON AND DOWN PAST THE
SOUTHERN GULF ON TUE. THIS LOBE OF ENERGY SHOULD CONSOLIDATE WITH THE
LAST VESTIGES OF THE OLD UPPER-LOW AND FINALLY PUSH IT AWAY FROM THE
AOR MID WEEK. MODELS SHOW THE RIDGING IN THE BERING SEA NOSING EAST
TOWARDS SW AK BUT FALLING SHORT OF MOVING INTO SOUTHCENTRAL AK OR THE
GULF. THIS SEEMS TO OCCUR BECAUSE A SHEAR LOBE ON THE DOWNSTREAM SIDE
SHARPENS INTO A RESPECTABLE SHORTWAVE TROUGH ON TUE AS ENERGY FROM NW
AK DIGS SOUTHWARD TOWARDS THE AOR. THE GFS/ECMWF/GEM ACTUALLY CARVE
OUT AN UPPER LOW CENTER NEAR THE KUSKOKWIM VALLEY BY EARLY WED. WHILE
THE NAM DOES NOT SHOW THIS CUT OFF LOW ALOFT..IT DOES REFLECT A
STRONG TROUGH AND IS SIMILAR IN THE QPF FIELDS OF THE OTHER MODELS
SPREADING PRECIPITATION BACK THROUGH PORTIONS OF UPPER COOK INLET AND
PRINCE WILLIAM SOUND.

FURTHER WEST...THE LOW FORMING OVER THE KAMCHATKA PENINSULA IS
DEPICTED MOVING TO AROUND 400 MILES NW OF ATTU AT 997 MB MON
MORNING...THEN MOVING TO NEAR ATKA AT 985 MB PEAK INTENSITY TUE
AFTERNOON. THE LOW THEN SLOWLY FILLS AS IT TRACKS TO AROUND 200 MILES
SOUTH OF UNALASKA ON WED. THERE IS REASONABLY GOOD AGREEMENT WITH
THIS TREND...THOUGH THE NAM DEPICTS THE WEAKEST SYSTEM IN THE
SOLUTION ENVELOPE. THE GFS SEEMS TO HAVE GOOD CONSISTENCY WITH THIS
LOW...SUPPORTED STRONGLY BY THE ECMWF AND HAVE LEANED THE FORECAST
PACKAGE IN THAT DIRECTION.

.SHORT TERM FORECAST...
SOUTHCENTRAL/GULF...
LITTLE SUBSTANTIVE CHANGE TO THE FORECAST EXPECTED THE NEXT 24 HOURS
AS THE DOMINANT WEATHER FEATURES ARE SLOW MOVING. THE APPROACH OF THE
SHORTWAVE THAT MOVES THROUGH SW AK MON TO THE WESTERN GULF WILL BRING
SOME ADDED ENERGY TO ALLOW WINDS TO LINGER THE LONGEST IN MARINE
AREAS AROUND THE BARREN ISLANDS AND KODIAK ISLAND. ANY LINGERING
GALES SHOULD DIMINISH RAPIDLY BY EARLY TUE AS THE CONSOLIDATED
UPPER-LOW FINALLY CLEARS THE GULF. IN THE INTERIM...THE LION'S SHARE
OF AREAS SHOULD REMAIN PRECIPITATION FREE WITH SUNNY BREAKS AS
AVAILABLE LIFT FOR PRECIPITATION IS WEAK AND THE LOW-LVLS STAY RATHER
DRY IN OFF-SHORE FLOW (INCLUDING KODIAK ISLAND). CAVEATS WOULD BE FOR
HIGHER ELEVATION SPOTS OF THE COPPER RIVER BASIN (SUCH AS NEAR
EUREKA) AND NEAR THE TALKEETNA AND ALASKA RANGES WHERE SOME LOCALIZED
UPSLOPE WILL SUPPORT SOME LIGHT SNOW AS WEAK EMBEDDED UPPER
DISTURBANCES PINWHEEL THROUGH.

SOUTHWEST/AKPEN...
EXPECT SOME PERIPHERAL LIGHT SNOW TONIGHT WITH THE WEAKENING
DEFORMATION AREA IN THE LOWER KUSKOKWIM VALLEY...OTHERWISE COOL AND
BRISK CONDITIONS TO PERSIST ACROSS THE SW MAINLAND. THE ENERGY WITH
THE SHORTWAVE SLIPPING OUT OF E SIBERIA WILL BRUSH COASTAL AREAS ON
MON...BUT AS IT IS RATHER FAST MOVING AND STARVED OF DEEP MOISTURE
ANY PRECIP SHOULD BE ON THE LIGHT SIDE. A SLOW WEAKENING OF THE
PRESSURE GRADIENT BETWEEN THE GULF LOW AND BERING HIGH WILL TREND
GALE FORCE WINDS TO SMALL CRAFTS OR LESS FROM WEST TO EAST BY MON
NIGHT.

BERING SEA/ALEUTIANS...
HIGH PRESSURE NEAR ADAK RETREATS SOUTHEAST THROUGH EARLY MON. THE
LOW TRACKING FROM THE KAMCHATKA PENINSULA WILL OVERSPREAD RAIN
THROUGH THE WESTERN TO CENTRAL CHAIN THE LATTER PART OF MON. GALES
WILL ONCE AGAIN BECOME COMMON THROUGH THE BERING/CHAIN WITH THE LOW
STILL IN DEEPEING STAGES THROUGH EARLY TUE.

.LONG TERM FORECAST...
THE BERING SEA LOW LOOKS TO PUSH A FRONT INTO THE GULF ON WED...WITH
THE RESIDUAL LOW FOLLOWING SUIT ON THU. THERE IS CONSIDERABLE MODEL
SPREAD ON WHERE A TRIPLE POINT LOW WILL FORM ALONG THE FRONT (EASTERN
GULF VS WESTERN GULF) ALONG WITH MAGNITUDE OF WINDS (GALES VS
STORMS). IN GENERAL THOUGH...MODELS AGREE THAT THE SOUTHERN MAINLAND
WILL REMAIN IN A TROUGH THROUGH LATE WEEK THUS KEEPING THINGS RATHER
UNSETTLED WITH ELEVATED CHANCES OF PRECIPITATION. OUT WEST...
INITIALLY THERE IS RIDGING BUILDING ACROSS THE BERING/CHAIN IN THE
WAKE OF THE LOW MOVING TOWARDS THE GULF MID WEEK. ANOTHER POWERFUL
960S MB LOW IS DEPICTED IMPACTING THE AREA BY FRI INTO THE WEEKEND.
SIZABLE TRACK AND SPEED DIFFERENCES EXIST WITH THIS FEATURE...WITH
THE GFS AND GEM TENDING TO BRING IT UP TOWARDS THE BERING
STRAIT...WHILE THE ECMWF MEANDERS THE LOW OUT OVER THE NW BERING SEA.
A GFS/GEM VERIFIED SOLUTION WOULD LIKELY BRING MUCH STRONGER WINDS
AND HIGHER SWELLS THROUGH THE BERING SEA AND TOWARDS THE SW MAINLAND.
AVERAGE TO LOW CONFIDENCE EXISTS IN THE LONG TERM FORECAST PERIOD.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE...130 132 138 150 155 160 172 176 351 352 413
FIRE WEATHER...NONE

MALOY