Small Craft Advisory 288, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
119 PM AKDT MON APR 7 2014

.ANALYSIS AND UPPER LEVELS...
A LOOK AT THE MORNING SATELLITE IMAGE SHOWS A HIGHLY AMPLIFIED
UPPER LEVEL TROUGH IN PLACE ALONG THE WEST COAST OF ALASKA.
SOUTHERLY FLOW AHEAD OF THE TROUGH IS STEERING A 981 MB LOW INTO
THE NORTHERN PANHANDLE NEAR YAKUTAT WITH STEADY SNOW SPREADING
INTO EASTERN SECTIONS OF THE COPPER RIVER BASIN. A SLOW-MOVING
SHORTWAVE TROUGH OVER THE SOUTHWEST MAINLAND CONTINUES TO GRIND
SLOWLY EAST...WITH ASSOCIATED INSTABILITY HELPING TO PRODUCE
SHOWERS AROUND MUCH OF THE COOK INLET REGION THIS MORNING.
MODERATE MID-LEVEL INSTABILITY HAS HELPED SOME OF THESE SHOWERS
PRODUCE LOCALIZED AREAS OF HEAVY SNOW...BUT WITH TEMPERATURES NEAR
OR ABOVE FREEZING ACCUMULATION HAS BEEN MINIMAL. THE MUCH-
ANTICIPATED REINFORCING SHOT OF COLD AIR IS MOVING ACROSS THE
KUSKOKWIM DELTA AND INTO THE BASE OF THIS TROUGH. SKIES ARE MOSTLY
CLEAR IN THE COLD AND DRY NORTHERLY FLOW...WITH INSTABILITY
SHOWERS CONTINUING OVER THE OPEN WATER OF THE EASTERN BERING. OUT
WEST...A STALLED FRONT IS DISSIPATING IN PLACE OVER THE PRIBILOF
ISLANDS WHILE A MORE SUBSTANTIAL SECOND FRONT IS MOVING INTO THE
WESTERN ALEUTIANS WITH RAIN AND GALE-FORCE WINDS.

&&

.MODEL DISCUSSION...
MODELS REMAIN IN THE SAME GOOD SYNOPTIC AGREEMENT AS PREVIOUS
DAYS. THE NAM HAS TRENDED TOWARD THE ECMWF SOLUTION IN A SLIGHTLY
SHARPER/STRONGER TROUGH AXIS PASSING THROUGH THE ANCHORAGE BOWL
AND SOUTHCENTRAL ALASKA. THE MODELS ARE KNOWN TO DOWNPLAY SNOW
AMOUNTS ACROSS THE AREA IN PATTERNS LIKE THIS...THUS WITH ALL THE
KEY INGREDIENTS FOR SNOW (MID-LEVEL TROUGH...LOW-LEVEL COLD AIR
ADVECTION...AND A WEAK LOW IN PRINCE WILLIAM SOUND) WILL CONTINUE
TO ADVERTISE GENERALLY MODEST ACCUMULATIONS OF SNOW ACROSS THE
AREA TONIGHT. BY WEDNESDAY...THE PARENT UPPER LOW ASSOCIATED WITH
THE TROUGH CURRENTLY AFFECTING THE AREA WILL DROP DOWN THE FRONT
OF A BERING SEA RIDGE AND HEAD TOWARD THE COPPER RIVER BASIN. THE
GFS IS ALONE IN KEEPING THIS FEATURE UP OVER THE EASTERN INTERIOR.
OVERALL THE ECMWF REMAINS THE MOST CONSISTENT WITH THE TOTALITY
OF THE MAJOR ATMOSPHERIC FEATURES IN THE NEXT FEW DAYS...AND
REMAINS THE PREFERRED MODEL.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
THERE IS A COMPLEX EVOLUTION OF MANY FEATURES HAPPENING ACROSS THE
AREA CURRENTLY. LOWER PRESSURES AT THE SURFACE HAVE SPREAD FROM
THE LOW NEAR THE PANHANDLE TOWARD PRINCE WILLIAM SOUND...AND GAP
WINDS FROM WHITTIER TO THOMPSON PASS HAVE RESPONDED WITH
INCREASING OFFSHORE FLOW. AT THE SAME TIME...GENTLE COLD AIR
ADVECTION FROM THE NORTHWEST WILL RAMP UP SIGNIFICANTLY THIS
EVENING ACROSS ALL OF COOK INLET. THE BIGGEST QUESTION MARK
REMAINS HOW EXACTLY THE UPPER LEVEL TROUGH WILL RESPOND TO THE
REINFORCING SHOT FROM UPSTREAM...AND HOW QUICKLY DYNAMIC LIFT WILL
MOVE INTO THE SOUTHERN MAINLAND TO ENHANCE THE LIFT FROM THE
IMMINENT AIRMASS REPLACEMENT. THE TREND TODAY HAS BEEN TOWARD A
SLOWER ARRIVAL OF THIS DYNAMIC LIFT...WHICH COULD LEAD TO A
LIGHTER BUT MORE PROLONGED SNOWFALL EVENT FOR THE POPULATION
CENTERS AROUND UPPER COOK INLET. WILL GENERALLY STICK WITH CURRENT
FORECAST SNOW AMOUNTS...BUT ADD IN SOME ADDITIONAL ACCUMULATIONS
DURING THE DAY TOMORROW AS THE UPPER TROUGH FINALLY ARRIVES.

SOUTHWEST ALASKA...
CLEARING SKIES AND DRY OFFSHORE FLOW WILL SPREAD ALL THE WAY TO
THE ALEUTIAN RANGE THIS EVENING AS THE REGION COMES UNDER THE
INFLUENCE OF STRENGTHENING HIGH PRESSURE ALOFT OVER THE EASTERN
BERING SEA. BELOW-NORMAL TEMPERATURES WILL BEGIN TO MODERATE AS
EARLY AS TUESDAY AS THE COLD SURGE OF AIR RETREATS NORTHEAST INTO
THE INTERIOR OF THE STATE.

BERING SEA/ALEUTIANS...
TWO BASIC WEATHER FEATURES WILL AFFECT THE AREA OF THE NEXT FEW
DAYS. THE FIRST IS THE FRONT CURRENTLY MOVING INTO THE WESTERN
ALEUTIANS. THIS FRONT WILL SLOWLY WEAKEN AS IT TRAVERSES ALL THE
WAY TO THE ALASKA PENINSULA BY TUESDAY AFTERNOON. THE FRONT WILL
STRETCH OUT SO MUCH THAT EVENTUALLY A NEW LOW WILL FORM NEAR THE
INTERSECTION WITH A ZONAL JET SOUTH OF THE ALASKA PENINSULA
TUESDAY EVENING. THIS LOW WILL THEN RACE INTO THE SOUTHERN GULF.
BEHIND THIS FRONT...THE LARGE AND COMPLEX PARENT LOW WILL AMBLE
INTO THE WESTERN BERING BY MIDWEEK WITH ANOTHER ROUND OF GUSTY
WINDS AND MORE SHOWERY PRECIPITATION.

&&

.LONG TERM FORECAST...
THE HIGH PRESSURE MENTIONED ABOVE WILL SPREAD EASTWARD INTO THE
MAINLAND BY MIDWEEK AND BRING SEVERAL DAYS OF SUNNIER AND WARMER
CONDITIONS TO MOST AREAS. BY NEXT WEEKEND THE EXTENDED MODELS
CONTINUE TO SUGGEST AN AMPLIFICATION OF THE LONGWAVE TROUGH OVER
THE BERING WITH HIGH PRESSURE CONTINUING OVER THE INTERIOR. THIS
WILL GENERALLY STEER MORE ACTIVE WEATHER INTO MUCH OF SOUTHERN
ALASKA FOR THE START OF NEXT WEEKEND WITH TEMPERATURES REBOUNDING
TO NEAR NORMAL.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 130 131 173 174 175 179
         HEAVY FREEZING SPRAY 180 185
FIRE WEATHER...NONE.

&&

AMD APR 14