Brisk Wind Advisory 60, NWS Anchorage, AK

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

.ANALYSIS AND UPPER LEVELS...
THE ALASKAN DOMAIN IS UNDER THE INFLUENCE OF A LARGELY ZONAL UPPER
LEVEL PATTERN...WITH THE JET REMAINING SOUTH OF THE ALEUTIANS AND
GULF OF ALASKA. AS IS TYPICAL WITH A HIGH ZONAL INDEX THERE ARE
MULTIPLE FAIRLY WEAK DISTURBANCES MOVING THROUGH THE PATTERN. A
DE-AMPLIFYING UPPER LEVEL TROUGH IS LIFTING NORTHEASTWARD INTO THE
GULF...WITH A WEAK SURFACE LOW BEGINNING TO DEVELOP SOUTH OF KODIAK
ISLAND WHERE LIGHT RAIN HAS BEGUN TO FALL. WHILE THIS TROUGH IS
BRINGING WIDESPREAD CLOUDINESS TO THE REST OF SOUTHCENTRAL THERE IS
VERY LITTLE PRECIPITATION FALLING AT THIS TIME AS THE JET ENERGY IS
ALREADY BEGINNING TO SHUNT MOST OF THE UPPER LEVEL ENERGY EASTWARD
INTO THE PANHANDLE. HOWEVER...RIDGING AND RELATIVELY WEAK FLOW AHEAD
OF THIS TROUGH HAVE ALLOWED AREAS OF STRATUS AND FOG TO DEVELOP AND
PERSIST FROM COOK INLET TO PRINCE WILLIAM SOUND AND EVEN THE COPPER
RIVER BASIN. FURTHER WEST...A NEGATIVELY TILTED TROUGH IS SUPPORTING
THE DEVELOPMENT OF A SURFACE LOW OVER THE SOUTHERN BERING WITH GUSTY
WINDS AND LIGHT RAIN OCCURRING FROM THE CENTRAL ALEUTIANS TO THE
ALASKA PENINSULA.

.MODEL DISCUSSION...
THE MODELS ALL SHOW AN AMPLIFICATION OF THE UPPER LEVEL PATTERN OVER
THE NEXT 24-48 HOURS AS THE JET STREAM BUCKLES OVER THE CENTRAL
ALEUTIANS AND ALLOWS A MUCH MORE SUBSTANTIAL LOW TO FORM SOMEWHERE IN
THE VICINITY OF THE ALASKA PENINSULA ON TUESDAY. HOWEVER...EVEN SOME
OF THE BASIC DETAILS OF THIS TRANSITION ARE UNCLEAR. THE NAM IS
FURTHER EAST THAN ANY MODEL WITH THIS DEVELOPING LOW...NOT SURPRISING
GIVEN THE ZONAL JET BRINGING FEATURES IN FROM OUTSIDE THE MODEL
DOMAIN (A KNOWN WEAKNESS). AS A RESULT...THE NAM CAN BE TOSSED OUT
TODAY. SEVERAL RUNS OF THE GEMGLB HAVE BEEN EXTREMELY FAST AND
FURTHER NORTH THAN THE OTHER MODELS...SO DESPITE A 12Z SOLUTION THAT
MAY BE FINALLY COMING INTO LINE...IT CANNOT BE TRUSTED. THE GFS AND
EC HAVE EACH BEEN A BIT MORE CONSISTENT...BUT HAVE SOME DIFFERENCES
WITH HOW QUICKLY MULTIPLE PIECES OF ATMOSPHERIC ENERGY COMBINE INTO A
SINGLE UNIFIED LOW CENTER. THESE DIFFERENCES LIKELY STEM FROM A
DIFFERENCE IN HOW DEVELOPED THE UPPER LOW WILL BECOME OVER THE
CENTRAL BERING ON MONDAY. THE GFS KEEPS THIS UPPER FEATURE
STRONGER...WHICH DELAYS HOW QUICKLY THE ENERGY TRANSFERS AND
CONSOLIDATES OVER THE EASTERN BERING. AS A RESULT...THE SURFACE LOW
KICKS EASTWARD TOWARD SHELIKOF STRAIT BEFORE RE-CURVING INTO BRISTOL
BAY TUE EVENING. THE ECMWF HAS BEEN A BIT MORE CONSISTENT DEVELOPING
A UNIFIED LOW CENTER EARLIER THAN THE GFS...INSTEAD TRACKING A LOW
NORTHWARD DIRECTLY ACROSS THE ALASKA PENINSULA. THIS SOLUTION (ECMWF)
IS THE PREFERRED SOLUTION TODAY BASED ON BOTH RUN-TO-RUN CONSISTENCY
AND A DESIRE TO MAINTAIN SOME CONTINUITY WITH THE EXISTING FORECAST.

.SHORT TERM FORECAST...
SOUTHCENTRAL...MULTIPLE SURFACE LOWS WILL DEVELOP IN THE GULF OVER
THE NEXT 24 HOURS AS UPPER TROUGH LIFTS INTO THE AREA. THE FIRST IS
CURRENTLY DEVELOPING SOUTH OF KODIAK ISLAND WHERE LIGHT RAIN HAS
BEGUN WITH SHOWERS BEGINNING TO SPREAD NORTHWARD TOWARD THE GULF
COAST. A GALE-FORCE BARRIER JET WILL FORM ALONG THE NORTH GULF COAST
AND THE COAST OF THE EASTERN KENAI PENINSULA THIS EVENING AS THE
AFOREMENTIONED LOWS STRENGTHENS AND MOVES TOWARD THE CENTRAL GULF.
GENERALLY LIGHT PRECIPITATION WILL SPREAD TO MOST OF THE COASTLINES
THIS EVENING...FALLING MAINLY AS SNOW WITH MINIMAL ACCUMULATIONS. BY
LATE TONIGHT A NEW LOW WILL FORM OVER THE EASTERN GULF AND QUICKLY
PULL PRECIP TOWARD THE PANHANDLE. ANOTHER FAST-MOVING SHORTWAVE WILL
JAZZ UP THE LINGERING LOW IN THE GULF ON MONDAY AFTERNOON...THOUGH
THE MAIN IMPACT WILL SIMPLY BE A CONTINUATION OF SCATTERED SHOWERS
ALONG THE COASTLINES AND ACROSS THE GULF.

SOUTHWEST...BROAD SOUTHEAST FLOW WITH MULTIPLE UPPER WAVES MOVING
THROUGH WILL KEEP SCATTERED TO NUMEROUS SHOWERS ACROSS THE AREA
THROUGH MONDAY AFTERNOON. PRECIPITATION TYPE WILL BE SNOW NORTH OF A
LINE FROM KING SALMON TO CAPE NEWENHAM...WITH MINOR SNOW
ACCUMULATIONS EXPECTED THROUGH TOMORROW. A MUCH MORE SIGNIFICANT
STORM WILL AFFECT THE REGION ON TUESDAY WITH STRONG WINDS AND HEAVY
PRECIPITATION. THE EXACT STORM TRACK WILL DETERMINE HOW MUCH WARM AIR
IS PULLED OVER THE ALEUTIAN RANGE AND INTO THE AREA...WITH THE
POTENTIAL FOR STRONG CHINOOK WINDS POSSIBLE AT MANY LOCATIONS. ALSO
DEPENDENT ON THE TRACK OF THE LOW IS DETERMINING POTENTIAL FOR VERY
STRONG WINDS TO DEVELOP OVER A MORE WIDESPREAD PORTION OF INTERIOR
BRISTOL BAY ZONE...WHERE HEAVY SNOW OR A RAIN/SNOW MIX IS ALSO A
POSSIBILITY.

BERING SEA AND ALEUTIANS...MULTIPLE FAIRLY WEAK LOW PRESSURE CENTERS
WILL CONTINUE OVER THE NEXT 24-48 HOURS...BRINGING PERIODS OF RAIN
AND NEAR GALE-FORCE WINDS TO MUCH OF THE ALEUTIAN CHAIN. UNSETTLED
WEATHER WILL GRADUALLY SHIFT EASTWARD OVER THE NEXT SEVERAL DAYS AS
THE DOWNSTREAM JET AMPLIFIES. AS THIS HAPPENS...COLD AIR WILL SLOWLY
BLEED BACK IN FROM THE NORTH AND WEST...RETURNING TEMPERATURES TO
MORE SEASONABLE LEVELS.

.LONG TERM FORECAST...
EXTENDED MODELS SUGGEST A RESURGENCE OF A RIDGE OVER THE EASTERN
PACIFIC AND GULF OF ALASKA BY NEXT WEEKEND AS A DEEP UPPER TROUGH
DEVELOPS OVER BOTH EASTERN RUSSIA AND CENTRAL NORTH AMERICA. THIS
WOULD KEEP ABOVE NORMAL TEMPERATURES ACROSS SOUTHERN ALASKA...WITH A
POTENTIALLY ACTIVE STORM TRACK INTO THE EASTERN BERING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE
MARINE...GALE 119 120 131 150 155 172 174 177 178
FIRE WEATHER...NONE

AMD DEC 13