Small Craft Advisory 109, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
425 PM AKST SUN JAN 31 2016

.ANALYSIS AND UPPER LEVELS...

THE MAJORITY OF MAINLAND ALASKA IS UNDERNEATH UPPER LEVEL HIGH
PRESSURE AGAIN TODAY. THE UPPER LEVEL LOW RUNS ACROSS THE BERING
SEA AND INTO THE WESTERN GULF OF ALASKA. THIS IS WHERE THE LOW
TRACK RESIDES AND THE GOES SATELLITE SHOWS THE LATEST IN A SERIES
OF LOWS MOVING THROUGH THE ALASKA PENINSULA AND INTO THE BERING
SEA. THE FRONT ASSOCIATED WITH THIS LOW IS ALSO EASILY SEEN ON
SATELLITE AND IT WILL WEAKEN AS IT PUSHES NORTHWARD AND INTO THE
HIGH PRESSURE OVER THE MAINLAND PART OF THE STATE.

&&

.MODEL DISCUSSION...

MODELS HAD A DIFFICULT TIME LOCKING ONTO THE LOW THAT IS NEAR THE
ALASKA PENINSULA THIS AFTERNOON. SATELLITE SHOWED IT AS A STRONGER
FEATURE THAN DID ANY MODEL UNTIL THE 18Z RUNS BEGAN COMING IN
WHEN THEY STARTED TO MAKE IT A MORE PRONOUNCED LOW. THIS DOES
THROW SOME INCREASED UNCERTAINTY INTO THE EARLIER PART OF THE
FORECASTS FOR THE BRISTOL BAY AND ALASKA PENINSULA AREAS. MODELS
ALSO CONTINUE A WEAKENING TREND FOR THE FRONT THAT WILL MOVE TO
THE NORTH GULF COAST TOMORROW INTO MONDAY NIGHT. ALL THE MODELS
WANT TO DEVELOP A SECONDARY LOW SOMEWHERE ALONG THE FRONT BUT FOUR
DIFFERENT MODELS GIVE FOUR DIFFERENT SOLUTIONS THAT VARY OVER A
600 MILE LONG ARC. THE GOOD NEWS IS THAT THE LOW WILL NOT BE
STRONG AND THE MAJORITY OF THE AREAS WILL NOT BE IMPACTED BY THIS
UNCERTAINTY. AFTER THAT THE MODELS ARE IN GOOD AGREEMENT WITH A
STRONG LOW THAT WILL DEVELOP IN THE NORTH PACIFIC AND MOVE SOUTH
OF THE GULF OF ALASKA TUESDAY NIGHT. THE UNCERTAINTY IN THIS
SYSTEMS LIES IN THE STRENGTH OF THE RIDGE OVER THE STATE AND HOW
MUCH IT SLOWS THE PROGRESSION OF THE LOW AS IT MOVES NORTHWARD.

&&

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

MODELS HAVE COME INTO BETTER AGREEMENT WITH FRONTAL TIMING AND
ORIENTATION OVER THE NEXT COUPLE OF DAYS. THE BIGGEST CHANGE TO
THE PREVIOUS FORECAST IS THAT THE FRONT MOVING ACROSS THE WESTERN
GULF OF ALASKA LOOKS TO GET SHEARED APART MUCH QUICKER THAN
ORIGINALLY ANTICIPATED AND IS ORIENTED MORE EAST TO WEST VS
SOUTHEAST TO NORTHWEST. THIS WILL KEEP THE PRESSURE GRADIENT LESS
FAVORABLY ORIENTED TO PRODUCE STRONG GAP WINDS THROUGH PORTAGE
VALLEY AND ALONG TURNAGAIN ARM...THUS HAVE LOWERED WIND SPEED
THROUGH THESE LOCATIONS. CURRENT OBSERVATIONS BACK UP THIS
WEAKENING TREND AS GRADIENTS HAVE BEEN SLOW TO TIGHTEN AND MODELS
CONTINUE TO OVERPERFORM ON THE WIND GUSTS. THE EAST TO WEST
ORIENTATION OF THE FRONT WILL KEEP MUCH OF THE SOUTHCENTRAL ALASKA
DRY OUTSIDE OF KODIAK ISLAND AND THE SOUTHERN TIP OF THE KENAI
PENINSULA. THE NORTHERN GULF COAST MAY SEE A FEW SCATTERED SHOWERS
LATE MONDAY BUT WITH THE FRONT DISSIPATING AS QUICKLY AS THE
MODELS SUGGEST...OVERALL CONFIDENCE IS PRETTY LOW. FOG WILL REMAIN
AN ISSUE ACROSS THE COPPER RIVER BASIN WHERE IT HAS STRUGGLED TO
BURN OFF UNDER THE AFTERNOON SUN. WITH MAX DIURNAL HEATING AND
MIXING ALREADY PAST US...AREAS OF FOG WITH LOCALLY DENSE FOG WILL
LIKELY SET UP FOR THE OVERNIGHT PERIOD. OTHERWISE...STILL NO
SIGNIFICANT CHANGE IN THE OVERALL PATTERN IS EXPECTED OVER THE
NEXT SEVERAL DAYS WITH TEMPERATURES BRIEFLY RETURNING TO NEAR
NORMAL TEMPERATURES THROUGH TUESDAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
AN UPPER LEVEL WAVE RIDING ALONG THE FRONTAL BOUNDARY CURRENTLY
STALLED ALONG THE COAST WILL HELP TO ENHANCE GUSTY WINDS THROUGH
THIS EVENING ACROSS BRISTOL BAY AND THE KUSKOKWIM DELTA AND ALSO
SERVE TO SHIFT THE FRONT FARTHER INLAND LATER TONIGHT. THE FRONT
WILL THEN LINGER OVER INTERIOR PORTIONS OF BRISTOL BAY THROUGH
TUESDAY MORNING...KEEPING THE BULK OF THE PRECIPITATION FOCUSED
ALONG A RELATIVELY NARROW NORTHWEST TO SOUTHEAST ORIENTED
CORRIDOR NORTH OF DILLINGHAM AND WEST OF THE ALEUTIAN RANGE. THE
WARM AIR CURRENTLY IN PLACE WILL KEEP PRECIPITATION AS A MIX OF
RAIN AND SNOW AND HELP TO HOLD DOWN SNOW AMOUNTS THROUGH TONIGHT
BEFORE COLD ADVECTION FACILITATES A CHANGE TO ALL SNOW FOR MONDAY
AND MONDAY NIGHT...WITH SEVERAL INCHES OF ACCUMULATION POSSIBLE BY
TUESDAY MORNING AS THE BOUNDARY GRADUALLY WEAKENS. A COOLING AND
DRYING TREND WILL THEN BEGIN TO TAKE HOLD ACROSS THE SOUTHWEST
MAINLAND AS OFFSHORE FLOW INCREASES AHEAD OF THE NEXT NORTH
PACIFIC LOW MOVING TOWARDS THE AKPEN.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
RELATIVELY BENIGN SHOWERY CONDITIONS WILL CONTINUE ACROSS THE
BERING SEA THROUGH TUESDAY IN THE ABSENCE OF ANY STRONGLY DEFINED
SURFACE OR UPPER LEVEL FEATURES AS THE LOW OVER THE NORTHERN
BERING DEPARTS TOWARDS THE KAMCHATKA PENINSULA. THE FRONT
ASSOCIATED WITH THE NEXT NORTH PACIFIC LOW WILL APPROACH THE
AKPEN BY TUESDAY AFTERNOON ACCOMPANIED BY HEAVIER PRECIPITATION
AND STRONG EASTERLY WINDS.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
ANOTHER STRONG LOW APPROACHES THE AKPEN AND KODIAK FROM THE SOUTH
TUESDAY EVENING...PUSHING A FRONT NORTHWARD INTO MUCH OF THE
SOUTHERN MAINLAND THROUGH WEDNESDAY NIGHT. A TRIPLE POINT LOW
WILL THEN QUICKLY DEVELOP ALONG THE SOUTHEASTERN SIDE OF THE
PARENT SYSTEM WEDNESDAY EVENING...AND TRACK NORTHWARD INTO THE
WESTERN GULF BY LATE THURSDAY MORNING. THE FRONT ASSOCIATED WITH
THIS TRIPLE POINT LOW WILL TRACK THROUGH THE GULF THURSDAY MORNING
AND PUSH INTO THE NORTHERN GULF COAST BY THURSDAY AFTERNOON...
BRINGING ANOTHER ROUND OF WET AND WINDY WEATHER TO THE SOUTHERN
MAINLAND. THE ACTIVE PATTERN WILL CONTINUE WITH A THIRD SYSTEM
TRACKING UP FROM THE NORTH PACIFIC SATURDAY NIGHT...TAKING A VERY
SIMILAR PATH TO THE INITIAL SYSTEM MENTIONED ABOVE AND BRINGING
MORE WET AND WINDY CONDITIONS TO THE SOUTHERN MAINLAND THROUGH
NEXT WEEKEND. PRECIPITATION TYPE WILL BE THE PRIMARY CONCERN FOR
MUCH OF SOUTHERN ALASKA...WITH THE POTENTIAL FOR LIQUID
PRECIPITATION AS FAR NORTH AS ANCHORAGE AT TIMES WITH CONTINUED
WARM TEMPERATURES. GUSTY WINDS WILL ALSO REMAIN A CONCERN FOR
SOUTHERN ALASKA...AS THESE SYSTEMS PUSH INTO THE AREA WITH GALE TO
STORM-FORCE WINDS WITH A POTENTIAL BARRIER JET FORMING ALONG THE
NORTHERN GULF COAST.

THE MODELS SEEM TO BE IN FAIR AGREEMENT OVERALL WITH THE
AFOREMENTIONED SYSTEMS...WITH SOME SMALL TIMING AND STRENGTH
ISSUES AS THESE SYSTEMS APPROACH THE SOUTHERN COAST. THUS FORECAST
CONFIDENCE IN THE LONG TERM IS SLIGHTLY HIGHER AS MODELS REMAIN IN
FAIR AGREEMENT WITH THE OVERALL SYNOPTIC PATTERN.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE 130 131 132 180 352 411
         STORM 150 160.

&&

SYNOPSIS AND MODEL DISCUSSION...EZ
SOUTHCENTRAL ALASKA...MC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...CB
LONG TERM...TP