Small Craft Advisory 351, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
432 PM AKDT TUE APR 21 2015

.ANALYSIS AND UPPER LEVELS...
A PATTERN CHANGE IS JUST GETTING UNDERWAY AS THE COLD CORE ANCHOR
LOW WHICH HAS BEEN SITTING OVER THE BERING SEA LIFTS NORTHWARD UP
THE WEST COAST OF ALASKA. THE FLOW TO THE SOUTH IS BECOMING
PROGRESSIVE WITH THE MAIN BERING TROUGH TRACKING EASTWARD TOWARD
THE GULF AND A STRONG JET DRIVING A TROUGH AND DEVELOPING SURFACE
LOW ACROSS THE NORTHWEST PACIFIC AND TOWARD THE BERING SEA. THERE
ARE STILL A FEW UPPER LEVEL WAVES PINWHEELING AROUND THE DEPARTING
UPPER LOW HELPING TO FOCUS SHOWERS OVER THE SOUTHERN ALASKA
MAINLAND. THE DIGGING TROUGH OVER THE EASTERN BERING/NORTH-CENTRAL
PACIFIC HAS LED TO RAPID DEEPENING OF A LOW SOUTH OF THE ALASKA
PENINSULA. THIS LOW IS TRACKING NORTHEASTWARD TOWARD KODIAK ISLAND
AND THE WESTERN GULF WITH WINDS QUICKLY STRENGTHENING OUT AHEAD OF
IT. SHOWERS CONTINUE ACROSS MUCH OF THE CENTRAL AND EASTERN BERING
SEA AND ALEUTIANS...ALTHOUGH MORE STABLE AIR IS MOVING IN WITH A
SHORT-WAVE RIDGE...SO BOTH SHOWERS AND WINDS ARE ON A DOWNWARD TREND.

&&

.MODEL DISCUSSION...
THE LATEST NUMERICAL GUIDANCE IS IN EXCELLENT AGREEMENT WITH LARGE
SCALE FEATURES OVER THE NEXT COUPLE DAYS. THERE ARE STILL COME
CHALLENGES WITH DETAILS OF SHOWERS ASSOCIATED WITH WEAK UPPER
WAVES...BUT OVERALL FORECAST CONFIDENCE IS HIGH.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE ATMOSPHERE ACROSS THE KENAI PENINSULA AND SOUTH CENTRAL ALASKA
REMAINS MODERATELY UNSTABLE THIS EVENING THOUGH CONDITIONS WILL
BECOME MORE STABLE THROUGH WEDNESDAY AS WARMER AIR ALOFT MOVES IN
ACROSS THE REGION. AN INTENSIFYING LOW IS APPROACHING KODIAK
ISLAND FROM THE SOUTHWEST. THIS STORM IS EXPECTED TO REMAIN IN
THE GULF AND MOVE OFF TO THE EAST SOUTHEAST THROUGH WEDNESDAY. THE
STRONGEST WINDS WILL BE ACROSS KODIAK ISLAND ALONG WITH MODERATE
TO HEAVY PRECIPITATION TONIGHT AND WEDNESDAY IN ADVANCE OF THE
FRONT. THE FRONT IS EXPECTED TO REMAIN FAR ENOUGH SOUTH THUS THE
STORM FORCE WINDS WILL ONLY IMPACT THE KODIAK ISLAND WATERS AND
ARE NOT EXPECTED ALONG THE NORTH GULF COAST. WEAK RIDGING WILL
BUILD IN BEHIND THIS SYSTEM WEDNESDAY. ANOTHER STORM IS ON TAP FOR
THE BERING SEA THURSDAY. THIS WILL PUSH A FRONT ACROSS THE BERING
SEA INTO THE MAINLAND BY THURSDAY MORNING RE ESTABLISHING THE
CLOUDIER COOLER SOUTH TO SOUTHWEST FLOW ACROSS THE SOUTHERN
MAINLAND.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2...TUE AND WED)...THE
THE SNOW BAND ACROSS THE KUSKOKWIM DELTA AREA SHIFT EAST TONIGHT
ALONG AN UPPER LEVEL SHORT WAVE. SCATTERED SHOWER ACTIVITY WILL
CONTINUE THROUGH THURSDAY AS WEAK TROUGHING REMAINS OVER THE
KUSKOKWIM DELTA. TWO LOW PRESSURE CENTERS WILL BRING GUSTY WINDS
AND RAIN HEADING INTO MIDWEEK. THE FIRST SYSTEM WILL BE TONIGHT
DEVELOPING SOUTH OF THE ALASKA PENINSULA. THIS FRONT WILL MAINLY
BRING RAIN ALONG THE ALASKA PENINSULA AND ALEUTIAN RANGE. THE NEXT
FRONT TO BRING WIDESPREAD PRECIPITATION MOVES TO THE WEST COAST ON
THURSDAY MORNING. PRECIPITATION STARTS AS SNOW SPREADING EAST
THROUGH THE DAY CHANGING OVER TO RAIN IN THE AFTERNOON AS
TEMPERATURES WARM BEHIND THE FRONT.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND
2...)
A FRONT MOVES INTO THE WESTERN BERING TONIGHT BRINGING STRONG
SOUTHERLY WINDS AND A MIX OF RAIN AND SNOW. THIS FRONT MOVES INTO
THE CENTRAL BERING/ALEUTIANS BY WEDNESDAY MORNING WITH MAX GALE WINDS
ACROSS THE MARINE AREAS. THE SURFACE LOW ASSOCIATED WITH THIS
FRONT MOVES INTO THE SOUTHERN BERING WEDNESDAY NIGHT WITH STRONGER
NORTHWESTERLY FLOW RETURNING BEHIND THE SYSTEM WITH RAIN AND SNOW
SHOWERS CONTINUING THROUGH THURSDAY.

&&

.LONG TERM FORECAST (THURSDAY NIGHT THROUGH TUESDAY)...
A FRONT ASSOCIATED WITH A LOW OVER THE BERING SEA WILL DISSIPATE
OVER THE SOUTHWEST MAINLAND AND WESTERN GULF ON THURSDAY
EVENING...BRINGING RAIN AND SNOW TO THESE AREAS INTO FRIDAY
MORNING. THE BERING LOW WILL THEN MERGE INTO A DEVELOPING NORTH
PACIFIC LOW MOVING TOWARDS THE GULF WHERE IT WILL BECOME NEARLY
STATIONARY OVER THE SOUTHERN GULF THIS WEEKEND. AS THIS
OCCURS...THE JET WILL DIVE WELL SOUTH OF THE AOR AND ALLOW FOR
RIDGING TO DEVELOP FROM THE CENTRAL BERING SEA INTO THE MAINLAND.
THIS RIDGING WILL ALLOW FOR A PERIOD OF MUCH QUIETER WEATHER TO
DEVELOP OVER MOST OF THE STATE THAT SHOULD PERSIST INTO THE MIDDLE
OF NEXT WEEK. TEMPERATURES IN THIS PATTERN SHOULD REMAIN ABOVE
NORMAL WITH RAIN CHANCES LIMITED TO AFTERNOON AND EVENING
CONVECTIVE ACTIVITY.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...STORM 132 150
         GALE 119 120 130 131 138 155 170 172-179
FIRE WEATHER...NONE.

&&

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