Small Craft Advisory 44, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
528 AM AKST THU JAN 15 2015

.ANALYSIS AND UPPER LEVELS...
THE AMPLIFIED UPPER LEVEL NEGATIVE TILTED RIDGE REMAINS POSITIONED
THROUGH THE PACIFIC NORTHWEST...EXTENDING NORTHWEST UP THROUGH
SOUTHEAST ALASKA INTO THE NORTH SLOPE REGION. UPSTREAM THERE IS A
CLOSED LOW AT 500 MB NEAR THE SHUMAGIN ISLANDS WITH AN INVERTED
TROUGH EXTENDING INTO THE GULF. AT THE SURFACE THERE IS A STORM
FORCE LOW LOCATED SOUTHEAST OF SAND POINT. THE WEATHER FRONT
ASSOCIATED WITH THIS LOW WILL BE PUSHING THROUGH THE NORTHERN GULF
INTO THE INLAND AREAS THIS MORNING. THIS WILL CONTINUE TO BRING
MORE WARM AIR ADVECTION WITH WIDESPREAD RAIN TO THE NORTHERN GULF
COASTLINE AND INLAND AREAS. THE MIDDLETON RADAR IMAGERY IS SHOWING
MODERATE TO HEAVY PRECIPITATION THROUGH THE NORTHERN GULF
EXTENDING ALONG THE EASTERN KENAI PENINSULA. THE SURFACE
TEMPERATURES FOR SOUTHCENTRAL ALASKA WILL REMAIN IN THE UPPER 30S
TO LOWER 40S WITH THE CONTINUED SOUTHERLY FLOW IN THE GULF. THE
ANCHORAGE BOWL WILL CONTINUE TO HAVE DOWNSLOPE DRYING CONDITIONS.
THE UPPER LEVEL CLOSED LOW NEAR SAND POINT WILL PRODUCE SEVERAL
SHORTWAVES ROTATING AROUND THE LOW. THIS WILL RESULT IN PERIODS OF
RAIN THROUGH SOUTHWEST ALASKA AND THE EASTERN BERING SEA THROUGH
THE AFTERNOON HOURS. THERE WILL BE PERIODS OF LIGHT FREEZING RAIN
BY LATE THIS MORNING THROUGH THE LATE AFTERNOON FOR THE KUSKOKWIM
DELTA BEFORE DIMINISHING AS THE SHORTWAVE PASSES THROUGH THE
REGION. THE BRISTOL BAY INTERIOR WILL CONTINUE TO HAVE
TEMPERATURES IN THE UPPER 30S TO LOWER 40S WITH DOWNSLOPING ALONG
THE ALEUTIAN RANGE AND ISOLATED POCKETS OF LIGHT FREEZING RAIN
NORTH OF DILLINGHAM WITH THE COOLER TEMPERATURES IN THE VALLEY
THROUGH THE MORNING HOURS. THE EASTERN ALEUTIANS WILL BE ON THE
BACKSIDE OF THE SURFACE LOW LOCATED JUST SOUTH OF CHIGNIK
RESULTING IN NORTHWESTERLY WINDS WITH SHOWERY PRECIPITATION. THE
TEMPERATURES ALONG THE EASTERN ALEUTIANS WILL REMAIN IN THE LOWER
40S PRODUCING ALL RAIN THROUGH THE REGION.

&&

.MODEL DISCUSSION...
THE MODELS ARE IN OVERALL GOOD AGREEMENT EXCEPT FOR SOME UNCERTAINTY
BY FRIDAY AFTERNOON WITH A NORTH PACIFIC LOW DEVELOPING BEFORE
MOVING INTO THE GULF BY LATE FRIDAY EVENING. IN THE BRISTOL BAY
REGION THE MODELS KEEP THE SURFACE LOW NEARLY STATIONARY FOR THE
NEXT FEW DAYS. THE PREFERRED MODELS OF CHOICE WERE THE NAM AND EC
THROUGH THE SHORT TERM. THE FORECAST CONFIDENCE REMAINS ABOVE
AVERAGE THROUGH FRIDAY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...

FOR THE THIRD DAY IN A ROW A WARM FRONT IS MOVING ONSHORE ALONG
THE NORTH GULF COAST. THE PATTERN WILL SUBTLY SHIFT AFTER THIS
FRONT AND ALLOW COOLER AIR ALOFT TO FILTER BACK INTO SOUTHCENTRAL
TONIGHT. THIS WILL ALLOW SOME SNOW TO MIX IN WITH THE RAIN AT
LOWER ELEVATIONS AND TURN HIGHER ELEVATION PRECIPITATION TO ALL
SNOW.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...THU AND
FRI)...ANOTHER VERY TRICKY PRECIPITATION TYPE FORECAST. BOTTOM
LINE IS THAT THE ATMOSPHERE HAS NOT CHANGED MUCH OVER THE PAST FEW
DAYS AND THERE REMAINS THE POSSIBILITY OF MIXED PRECIPITATION
THROUGHOUT THE AREA. NORTHEAST FLOW CONTINUES AT THE SURFACE OVER
THE KUSKOKWIM DELTA...BUT IT HAS NOT BEEN ENOUGH TO GET RID OF
THE WARM NOSE LOCATED FROM ABOUT 1000 FT AGL TO ABOUT 4000FT AGL.
WITH THIS SET-UP AND SEVERAL MOIST IMPULSES PRIMED TO MOVE IN FROM
THE SOUTH TODAY...WE OPTED TO ISSUE ANOTHER FREEZING RAIN ADVISORY
THROUGH THIS EVENING. AND UNFORTUNATELY...AS THE SURFACE LOW MAKES
IT WAY INTO BRISTOL BAY TONIGHT...THE PATTERN DOES NOT CHANGE
SIGNIFICANTLY. THIS WILL LEAVE MANY PLACES VULNERABLE TO A WINTRY
MIX...THE MOST LIKELY SPOTS BEING THE COLDER LOCATIONS NORTH OF
DILLINGHAM...THE INLAND KUSKOKWIM DELTA...AND THE LOWER KUSKOKWIM
VALLEY WEST OF SLEETMUTE. BUT THERE ARE SIGNS THAT ARCTIC AIR WILL
START TO WORK INTO THE DELTA FROM THE EASTERN BERING BY LATE
FRIDAY NIGHT. THIS SHOULD HOPEFULLY TURN PRECIPITATION TO ALL SNOW
FROM WEST TO EAST IN THIS AREA BY SAT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2...THU AND
FRI)...FOR MID JANUARY...IT IS ABOUT AS QUIET AS IT GETS ACROSS
THIS DOMAIN. AS THE PREVIOUSLY MENTIONED LOW SETS UP OVER BRISTOL
BAY LATE TONIGHT INTO FRI...MORE WIDESPREAD RAIN AND SNOW WILL
DEVELOP FROM THE PRIBILOFS TOWARDS UNALASKA BAY. THIS LOW WILL
ALSO BE QUICK TO TAP INTO THE COLDER AIR OVER EASTERN SIBERIA AND
PULL IT SOUTH ACROSS THE CENTRAL BERING. THIS WILL LEAD TO
WIDESPREAD COLD AIR ADVECTION SNOW AND RAIN SHOWERS WITH SOME
ACCUMULATING SNOW LIKELY FOR THE PRIBILOF ISLANDS. IT SHOULD ALSO
BRING A WIDESPREAD AREA OF GALES FROM ST MATTHEW ISLAND DOWN
THROUGH THE PRIBILOFS INTO FRI. THE COLD AIR MIXED WITH THESE
STRONGER WINDS SHOULD ALSO BRING SOME OF THE MOST EXTENSIVE HEAVY
FREEZING SPRAY WE HAVE SEEN YET THIS WINTER.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

MODELS ARE IN AGREEMENT THAT THE UPPER LOW WILL BECOME BRIEFLY
ENTRENCHED NEAR THE BERING STRAIT SAT AND SUN BEFORE EJECTING
NORTH. AN ASSOCIATED SURFACE LOW AND FRONT WILL BRING COLDER
SIBERIAN AIR INTO WESTERN AK THAT WILL PERSIST INTO THE BEGINNING
OF NEXT WEEK. THIS WILL RETURN SNOW TO WESTERN AK. A CORRESPONDING
SURGE OF WARMER AIR ALONG THE EASTERN FLANK OF THE UPPER LOW WILL
BRING ANOTHER FRONT INTO THE GULF COAST WITH COASTAL RAIN AND AN
INTERIOR MIX THROUGH MON.

AT THIS POINT MODELS DIVERGE AS A PATTERN CHANGE BEGINS. WPC
ENSEMBLE GUIDANCE INDICATES THAT MON INTO TUE AN UPPER LOW
TRAVELING ALONG THE JET WILL MOVE TO THE CENTRAL ALEUTIANS. A
FRONTAL SYSTEM WILL THEN BRING WARMING TEMPERATURES AND RAIN
ACROSS THE ALEUTIANS...WITH MORE FREEZING RAIN POSSIBLE FOR SW AK.
AS THE FRONTAL SYSTEM MOVES EAST...ANOTHER SURGE OF RAIN INTO THE
GULF COAST AND MIX INLAND IS POSSIBLE ON WED.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...HEAVY FREEZING SPRAY 180 181 185
         GALES 119-20 130 179 181 185.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...PD
SOUTHCENTRAL ALASKA...EZ
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MSO
LONG TERM...DS