Small Craft Advisory 955, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
438 PM AKST MON NOV 30 2015

.ANALYSIS AND UPPER LEVELS...
THE MAIN SURFACE AND UPPER LEVEL LOW NEAR SAND POINT WILL SLOWLY
MOVE TO THE SOUTHERN GULF OF ALASKA THROUGH WED. THE UPPER AND
SURFACE LOW OVER THE NORTHWEST BERING SEA WILL SLOWLY WEAKEN AND
DISSIPATE OVER THE NEXT COUPLE OF DAYS. THE NEXT SYSTEM THAT WILL
IMPACT THE ALEUTIANS AND SOUTHERN BERING SEA IS FORMING OVER
NORTHERN JAPAN.

&&

.MODEL DISCUSSION...
THE MAIN ISSUE TODAY IS THE MODELS NOT RECOGNIZING THE LOW THAT
FORMED ALONG THE FRONT NOW IN THE GULF OF ALASKA. THE ECMWF HINTS
AT THIS LOW WITH A SHORT WAVE IN THE UPPER LEVELS. THE GFS DOES
APPEAR TO RECOGNIZE AND FORM A SECOND LOW ALONG THE FRONT IN THE
SOUTHERN GULF OF ALASKA AND IS BRINGING THIS LOW NORTH TOWARD
PRINCE WILLIAM SOUND AND THE KENAI PENINSULA TUESDAY. OTHERWISE
THE MODELS ARE IN GOOD SYNOPTIC AGREEMENT HANDLING THE LOW NEAR
SAND POINT AND THE NEXT STORM MOVING INTO THE WESTERN ALEUTIANS BY
MID WEEK. THE MODELS HAVE CONVERGED ON THE CENTRAL PRESSURE AND
LOCATION OF THE LOW MOVING FROM SAND POINT TO SOUTH OF THE GULF
HAVING IT ABOUT 480 NM SOUTH OF YAKUTAT AROUND 975 MB BY WED
AFTERNOON. THE STORM MOVING INTO THE WESTERN ALEUTIAN ENDS UP
IN THE SAME GENERAL LOCATION WED JUST WEST SOUTHWEST OF SHEMYA.
HOWEVER THE CENTRAL PRESSURE VARIES SIGNIFICANTLY WITH THE ECMWF
COMING IN AROUND 960 MB WHILE THE NAM IS AT 975 AND THE GFS IS IN
THE MIDDLE AROUND 970 MB BY WED. THE PRESSURE GRADIENT IN ADVANCE
OF THE FRONT IS RESOLVED SIMILARLY BY THE MODELS. AT THIS POINT WE
ARE USING THE NAM FOR THIS SYSTEM.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
A FRONT PUSHING INTO THE NORTHERN GULF COAST THIS EVENING WILL
STALL OVER THE AREA AS THE UPPER LOW SOUTH OF THE ALASKA PENINSULA
SLOWLY TRACKS EASTWARD. THIS WILL KEEP PRECIPITATION MAINLY OVER
THE NORTHERN GULF...WITH SOME SHOWERS OVER THE SOUTHERN PORTION OF
THE EASTERN KENAI PENINSULA AND KODIAK ISLAND. INLAND AREAS WILL
REMAIN MOSTLY DRY AS NORTHERLY FLOW INCREASES OVER THE AREA THIS
EVENING THROUGH TOMORROW MORNING. A SURFACE LOW WILL DEVELOP ALONG
THE FRONT ON TUESDAY...AND PUSH WESTWARD INTO THE NORTHERN GULF BY
TUESDAY AFTERNOON. THIS WILL PUSH SOME MOISTURE INLAND FROM EAST
TO WEST TUESDAY EVENING THROUGH WEDNESDAY AFTERNOON...BRINGING
INCREASED CHANCES OF PRECIPITATION TO PARTS OF THE SOUTHCENTRAL
INTERIOR.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
SCATTERED RAIN AND SNOW SHOWERS WILL CONTINUE ACROSS BRISTOL BAY
WITH ISOLATED SHOWERS TO THE NORTH THROUGH TUESDAY. THE LOW SOUTH
OF THE ALASKA PENINSULA WILL START TO SLOWLY TRACK TO THE
SOUTHEAST LATE TUESDAY WHICH SHIFTS EASTERLY FLOW TO THE NORTH.
THIS FLOW CHANGE WILL ALLOW COLD AIR ADVECTION TO FILTER IN WITH
DRIER CONDITIONS ACROSS THE SOUTHWEST INTO WEDNESDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
NORTHERLY FLOW INCREASES ACROSS THE EASTERN ALEUTIANS THIS EVENING
AS RIDGING BUILDS INTO THE WESTERN BERING TIGHTENING THE GRADIENT
WITH LOW PRESSURE HOLDING SOUTH OF THE ALASKA PENINSULA.
NORTHWESTERLY WINDS ARE EXPECTED TO GUST BETWEEN 50 TO 65 MPH
BEFORE TAPERING OFF LATER TUESDAY AFTERNOON WHEN THE LOW MOVES TO
THE SOUTHEAST. THE NEXT FRONT WILL QUICKLY MOVE INTO THE WESTERN
ALEUTIANS TUESDAY EVENING WITH MAX GALES TO STORM FORCE WINDS
ALONG THE BOUNDARY. THE FRONT MAKES IT TO THE CENTRAL BERING AND
EASTERN ALEUTIANS WEDNESDAY AFTERNOON.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
BEGINNING THE EXTENDED PERIOD ON WEDNESDAY EVENING...A LONGWAVE
TROUGH WILL EXIST OVER THE NORTH PACIFIC EXTENDING INTO THE
SOUTHERN GULF OF ALASKA WITH A DEEP WARM SECLUSION CYCLONE OVER
THE FAR WESTERN BERING SEA AND ALEUTIANS. SHORTWAVE RIDGING WILL
EXIST OVER THE EASTERN BERING WITH ANOTHER OVER SOUTHCENTRAL
ALASKA. INLAND SHOWERS ACROSS SOUTHCENTRAL WILL BE IN THE PROCESS
OF DIMINISHING WITH RAIN AND SNOW SHOWERS MAINLY IMPACTING THE
COAST.

WITH TIME...THE DEEP BERING CYCLONE WILL MOVE EAST AND TAP THE
NORTH PACIFIC...WITH A DEEP LOW FORMING SOMEWHERE ACROSS THE
CENTRAL OR EASTERN GULF OF ALASKA. THERE IS MUCH UNCERTAINTY WITH
THE TRACK AND STRENGTH OF THIS LOW FRIDAY THROUGH SATURDAY...BUT
MOST OF THE IMPACTS WILL BE OVER THE MARINE WATERS AS STRONG
EASTERLY FLOW ALOFT AND OFFSHORE FLOW IN THE LOW LEVELS WILL KEEP
INLAND LOCATIONS LARGELY DRY.

THEREAFTER...THE NORTH PACIFIC JET BECOMES HIGHLY ACTIVE AND
VOLATILE...WITH THE MAIN BRUNT OF ENERGY IMPACTING THE BRITISH
COLUMBIA COAST TO THE PANHANDLE OF ALASKA...KEEPING SOUTHCENTRAL
UNDER THE INFLUENCE OF WEAKER LOWS EJECTING OUT OF THE STRONG JET
STREAM INTO THE GULF OF ALASKA. ONCE AGAIN...THIS PATTERN TENDS TO
FAVOR A GENERAL DOWNSLOPE FLOW SIGNATURE WITH PRECIPITATION.
HOWEVER...WITH A CONTINUED OFFSHORE PRESSURE GRADIENT WITH THE
STRONG ARCTIC HIGH TO THE NORTH TEMPERATURES SHOULD NOT MOVE TOO
FAR AWAY FROM NORMAL EVEN UNDER THE INFLUENCE OF STRONG CROSS
BARRIER FLOW.

BY EARLY TO MID NEXT WEEK THERE ARE HINTS THAT A SERIES OF
TROUGHS WILL INTERACT WITH THE COLD ARCTIC TROUGH OVER THE BERING
SEA...ADVECTING COLDER AIR INTO SOUTHCENTRAL BY MIDWEEK...AND
POSSIBLY BRINGING INCREASED SNOW CHANCES AS WELL. HOWEVER...FOR
THE TIME BEING STORMINESS WILL REMAIN FAR TO THE SOUTH OF THE
REGION WITH THE GENERAL PATTERN OF COASTAL SHOWERS AND LARGELY
DRY CONDITIONS INLAND LASTING INTO THE WEEKEND BEFORE UNCERTAINTY
ARISES BY EARLY NEXT WEEK.

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM WARNING 170 171 172 173.
         GALE WARNING...120 130 131 138 139 155 165
                        175 176 177 178 179.

&&

SYNOPSIS AND MODEL DISCUSSION...SA
SOUTHCENTRAL ALASKA...TP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...JA