Small Craft Advisory 861, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
510 AM AKDT FRI OCT 31 2014

.ANALYSIS AND UPPER LEVELS...
THE MAIN FEATURE OF INTEREST THIS MORNING IS A STORM FORCE LOW
TRACKING EASTWARD THROUGH THE BERING SEA...BRINGING RAIN AND
STRONG WINDS TO MUCH OF THE REGION. THE LOW CENTER IS CURRENTLY
LOCATED SOUTHWEST OF THE PRIBILOF ISLANDS WITH AN ASSOCIATED FRONT
ARCING SOUTH AND EASTWARD ACROSS THE PRIBILOFS AND THE ALASKA
PENINSULA ACCOMPANIED BY RAIN AND STRONG SOUTHEASTERLY WINDS.
BEHIND THE FRONT...WESTERLY STORM FORCE WINDS ARE IMPACTING THE
CENTRAL AND EASTERN ALEUTIANS ON THE SOUTHERN PERIPHERY OF THE
LOW. MEANWHILE...FAIRLY BENIGN CONDITIONS PERSIST ACROSS THE
SOUTHERN MAINLAND BENEATH CYCLONIC FLOW ALOFT...WITH WEAK LOW
PRESSURE OVER THE NORTHERN GULF HELPING TO SUPPORT MODEST GAP
WINDS THROUGH FAVORED AREAS ALONG THE GULF COAST. A WEAK UPPER
DISTURBANCE IS ALSO BRINGING A FEW SNOW SHOWERS TO EASTERN
PORTIONS OF THE COPPER RIVER BASIN.

&&

.MODEL DISCUSSION...
MODELS HAVE FINALLY STARTED TO SHOW SOMEWHAT BETTER AGREEMENT WITH
RESPECT TO THE LOW IN THE BERING AFTER THE SIGNIFICANT POSITIONAL
SPREAD OF THE PAST FEW DAYS. THE EC IS STILL ON THE WESTERNMOST
EDGE OF THE GUIDANCE BUT HAS SHOWN A LARGE EASTWARD JUMP IN THE
12Z RUN TO COME INTO BETTER AGREEMENT WITH THE NAM/GEM/GFS
SOLUTIONS. THERE IS ALSO GENERALLY GOOD AGREEMENT REGARDING THE
DEVELOPMENT OF A TRIPLE POINT LOW EAST OF KODIAK ISLAND LATER THIS
AFTERNOON AND THEN THE TIMING OF THE FRONT AS IT APPROACHES THE
GULF COAST FRIDAY NIGHT INTO SATURDAY. MAINLY USED THE GEM
SOLUTION FOR THE FORECAST AS IT HAS DISPLAYED THE MOST CONSISTENCY
OVER THE PAST SEVERAL RUNS.

&&

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...
GAP FLOWS WILL BE TRENDING DOWNWARD THIS MORNING IN RESPONSE TO
THE WEAKENING PRESSURE GRADIENT BEFORE ATTENTION QUICKLY TURNS TO
THE IMPACTS OF THE FRONT AS IT MOVES INTO THE GULF. PRECIPITATION
WILL OVERSPREAD KODIAK ISLAND LATER THIS MORNING WITH THE ARRIVAL
OF THE FRONT AS A TRIPLE POINT LOW FORMS JUST EAST OF THE ISLAND.
IT APPEARS TEMPERATURES WILL BE COLD ENOUGH TO SUPPORT ALL SNOW AT
THE ONSET OF PRECIPITATION BEFORE A QUICK TRANSITION TO RAIN WHICH
WILL MITIGATE THE POTENTIAL FOR MUCH IN THE WAY OF ACCUMULATING
OR BLOWING SNOW. THE FRONT WILL THEN REACH THE COAST
TONIGHT...BRINGING A MIX OF RAIN AND SNOW TO AREAS ALONG THE
COAST. AREAS FARTHER INLAND WILL REMAIN MOSTLY DRY AS A RESULT OF
DOWNSLOPING OFF OF THE CHUGACH RANGE INTO THE DAY ON SATURDAY
BEFORE CROSS BARRIER FLOW WEAKENS AND ALLOWS A FEW SHOWERS TO MAKE
IT OVER THE MOUNTAINS. ONE AREA THAT LOOKS TO REMAIN ALL SNOW
WILL BE PORTAGE VALLEY AS NORTHEASTERLY FLOW AT THE SURFACE HELPS
TO KEEP COLDER AIR IN PLACE AND ALSO SUPPORTS LOCALIZED AREAS OF
BLOWING SNOW.

SOUTHWEST ALASKA...
THE FRONT ASSOCIATED WITH THE BERING LOW WILL REACH THE COAST
LATER THIS MORNING...BRINGING SNOW TO COASTAL PORTIONS OF BRISTOL
BAY INTO THE AFTERNOON BEFORE SPREADING INLAND TONIGHT AND
SATURDAY. THE BEST CHANCE FOR ACCUMULATING SNOW WILL BE OVER
INTERIOR PORTIONS OF BRISTOL BAY WHERE 3 TO 5 INCHES OF SNOW WILL
BE POSSIBLE BY SATURDAY MORNING. ACCUMULATIONS SHOULD BE MORE
LIMITED ALONG THE COAST AS PRECIPITATION BEGINS TO CHANGE OVER TO
RAIN TONIGHT WITH WARMER AIR MOVING NORTHWARD. PRECIPITATION WILL
BEGIN TO WIND DOWN LATER SATURDAY AS THE FRONT SLIDES OFF TO THE
EAST AND THE LOW WEAKENS OVER THE EASTERN BERING...WITH NORTHERLY
FLOW TAKING HOLD OVER THE SOUTHWEST MAINLAND.

BERING SEA/ALEUTIANS...
STRONG WINDS WILL CONTINUE TO IMPACT THE BERING SEA INTO THE
WEEKEND AS THE POWERFUL LOW TRACKS EASTWARD TOWARDS BRISTOL BAY.
STORM FORCE WINDS WILL PERSIST INTO TONIGHT OVER THE COASTAL
WATERS OF THE EASTERN AND CENTRAL ALEUTIANS BEFORE GRADUALLY
DIMINISHING FROM WEST TO EAST AS THE LOW BEGINS TO WEAKEN...WITH
GALE FORCE WINDS CONTINUING ALONG THE ENTIRE CHAIN AND OVER MOST
OF THE BERING THROUGH THE DAY ON SATURDAY. RAIN WILL CONTINUE
ALONG THE FRONT TODAY AS IT MOVES TOWARDS THE SOUTHWEST
MAINLAND...FOLLOWED BY A TRANSITION TO A MORE SHOWERY REGIME AS
NORTHWEST FLOW COMMENCES ON THE BACKSIDE OF THE SYSTEM. COLD
ADVECTION WILL ALLOW FOR A CHANGEOVER TO SNOW LATER TODAY FOR THE
PRIBILOF ISLANDS...WITH A COUPLE INCHES OF ACCUMULATION POSSIBLE
BY SATURDAY MORNING. PRECIP TYPE LOOKS TO REMAIN MOSTLY RAIN ALONG
THE ALEUTIANS...ALTHOUGH SOME SNOW WILL START TO MIX IN DURING THE
DAY ON SATURDAY.

&&

.LONG TERM FORECAST (MON THROUGH THU)...
THE MID-LONG RANGE MODELS CONTINUE TO STRUGGLE WITH THIS PATTERN
AS WE REMAIN IN THE FALL TRANSITION SEASON. THE DETAILS ARE QUITE
MESSY FROM START TO FINISH...THOUGH THE GENERAL IDEA REMAINS
ALMOST A "RINSE AND REPEAT" PATTERN COMPARED WITH THE END OF THIS
WEEK.

REMNANT LOW PRESSURE NEAR BRISTOL BAY SLIDES INTO THE WESTERN
GULF OF AK EARLY IN THE WEEK. THIS LOW LOOKS TO SLOWLY WEAKEN AND
BROADEN ACROSS THE GULF THROUGH WED. MEANWHILE OUT WEST...A SHARP
RIDGE OF HIGH PRESSURE WILL MOVE QUICKLY ACROSS THE BERING TO
START THE WEEK. THIS WILL SPELL DRY CONDITIONS FOR A BRIEF
PERIOD...BUT COULD ALSO MAKE FOR SOME TIGHTER GRADIENTS LEADING TO
GUSTIER WINDS. ANOTHER LOW TRACKS OFF THE KAMCHATKA PENINSULA BY
MID-WEEK. AS OF NOW...THE GENERAL CONSENSUS IS THAT THIS FEATURE
SHOULD BE FILLING AND ELONGATING BY THAT TIME AND THUS...HAVE
LIMITED WINDS TO GALE-FORCE.

THE RINSE AND REPEAT PORTION OCCURS TOWARDS THE END OF THE LONG-
TERM. SPRAWLING LOW PRESSURE ACROSS THE BERING BEGINS TO INTERACT
WITH WEAK LOW PRESSURE IN THE GULF. THE DETAILS REMAIN VERY
HAZY...BUT THERE LOOKS TO BE SIGNS OF ANOTHER TRIPLE POINT LOW
FORMING VERY NEAR WHERE THE ONE FOR TOMORROW IS PROGGED TO FORM.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE
MARINE...STORM WARNING 170 172 174 176 413 414
		 GALE WARNING 119 132 150 155 160 165 173 175 177 178 179
					  180 181 185 352 411 412
FIRE WEATHER...NONE

&&

CB/MO OCT 14