Small Craft Advisory 156, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
414 PM AKST WED FEB 18 2015

.ANALYSIS AND UPPER LEVELS...

CONDITIONS THIS MORNING ACROSS MOST OF THE AOR ARE FAIRLY
TRANQUIL. VISIBLE SATELLITE IMAGERY DEPICTS A SWATH OF LOW CLOUDS
FROM THE EASTERN SUSITNA VALLEY SOUTH TO NEAR ANCHORAGE...WITH
A SECOND BATCH OF LOW CLOUDS OVER WESTERN COOK INLET AND THE
WESTERN SUSITNA VALLEY. LIGHT RAIN HAS BEEN REPORTED AT CORDOVA
AND THE VALDEZ AREA AND GLENNALLEN WILL LIKELY FALL ALONG THE
WESTERN EDGE OF THE SNOW FROM THIS SYSTEM TODAY.

THE WEATHER ROUNDUP ACROSS THE AOR THIS MORNING FEATURES THE
UPPER LEVEL LOW PULLING AWAY TOWARD NORTHWEST ALASKA AND A FAIRLY
WEAK SURFACE LOW MOVING ALMOST DUE NORTH OVER THE NORTHEASTERN
GULF. IN BETWEEN THESE TWO LOWS THE MAJORITY OF THE MAINLAND
REMAINS UNDER WEAK SOUTH TO SOUTHWESTERLY FLOW. UPPER LEVEL WINDS
ARE VERY LIGHT WITH THE ONLY SIGN OF JET ACTIVITY WELL TO OUR
SOUTH IN THE NORTH PACIFIC. THIS JET IS PROVIDING SOME SUPPORT TO
A BROAD LOW COMPLEX THAT WILL EVENTUALLY MAKE ITS WAY INTO THE
CENTRAL ALEUTIANS LATE TONIGHT INTO EARLY THURSDAY...AND THEN
MOVES INTO SOUTHWEST ALASKA AND KODIAK ISLAND LATE THURSDAY INTO
FRIDAY.

&&

.MODEL DISCUSSION...MODELS ARE ALL IN RELATIVELY GOOD AGREEMENT
THROUGH THE FIRST 48 HOURS (THU AFTERNOON) THEN CONTINUE TO
MAINTAIN THE SAME IDEA...EVEN THOUGH SOME OF THE DETAILS DIFFER.
FORECASTS THIS EVENING TRENDED TOWARDS A GFS/EC BLEND IN THE
SHORTER TERM AND THEN TRANSITIONED TO AN EC APPROACH WITH THE
FRONT MOVING UP FROM THE SOUTH THURSDAY THROUGH SATURDAY.

IN THE EXTENDED TIME FRAME...THE BLOCKING HIGH PRESSURE RIDGE OVER
THE PANHANDLE AND WESTERN CANADA WILL WEAKEN AND TRANSITION
RAPIDLY SOUTH AND EAST MONDAY...WITH ZONAL FLOW DEVELOPING ACROSS
THE REGION THROUGH MUCH OF THE WEEK BEFORE ANOTHER AMPLIFIED UPPER
LEVEL RIDGE BEGINS TO BUILD OVER THE STATE FROM THE SOUTH AND WEST
TOWARD THE END OF THE WEEK.

&&

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

THE PRIMARY FOCUS IN THE FORECAST TONIGHT CONTINUES TO REVOLVE
AROUND THE WEAK LOW THAT IS SLOWLY DISSIPATING SOUTH OF CORDOVA.
THIS LOW WILL BRING SNOW FROM THOMPSON PASS INTO THE EASTERN
COPPER RIVER BASIN INTO TOMORROW MORNING...WHILE THE CORDOVA AREA
SHOULD STAY WARM ENOUGH TO STAY MOSTLY RAIN WITH SOME SNOW MIXED
IN OVERNIGHT. AN UPPER TROUGH PASSING OVER THE AREA TONIGHT WILL
CAUSE THIS LOW TO SHIFT TO THE EAST AND ALLOW FOR WEAK RIDGING TO
BRIEFLY MOVE INTO THE AREA. THIS WILL LEAD QUIET WEATHER FOR MUCH
OF THE AREA...WITH THE ONLY FORECAST CONCERN BEING THE CHANCE OF
FOG AND LOW STRATUS DEVELOPMENT ON THURSDAY NIGHT INTO FRIDAY
MORNING. QUIET WEATHER WILL THEN CONTINUE FOR MOST OF THE DAY
FRIDAY IN MUCH OF SOUTHCENTRAL. KODIAK ISLAND ON THE OTHER HAND
WILL BEGIN TO BE IMPACTED WITH RAIN AND WIND FROM THE APPROACHING
NORTH PACIFIC FRONT STARTING LATE THURSDAY NIGHT...AND THEN SPREAD
INTO THE GULF COAST ON FRIDAY.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
COLD AIR ADVECTION WILL DIMINISH OVERNIGHT AS FLOW SHIFTS FROM
SOUTHWEST TO MORE DUE SOUTH AHEAD OF THE APPROACHING FRONT. AS THE
FRONT MOVES IN OVER THE SOUTHWEST EARLY ON THURSDAY PRECIPITATION
WILL START OFF AS SNOW BUT TRANSITION OVER TO RAIN. TEMPERATURES
SHOULD ALSO CONTINUE TO RISE THURSDAY NIGHT KEEPING THINGS RAIN.
ADDITIONALLY...STRONG WINDS WILL MOVE THROUGH WITH THE INITIAL
PASSAGE OF THE FRONT. THESE WARM CONDITIONS WILL LAST INTO THE
WEEKEND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE FRONT WILL PUSH THROUGH THE EASTERN ALEUTIANS AND ALASKA
PENINSULA TONIGHT BRINGING RAIN AND WINDS TO THE AREA. THE WARM
SOUTHERLY FLOW WILL CONTINUE INTO THE WEEKEND KEEPING THINGS
CLOUDY AND WET. OUT WEST WEAK NORTHERLY FLOW WILL KEEP COLDER AIR
OVER THE AREA. THIS WILL ALLOW FOR SNOW SHOWERS TO CONTINUE FOR
THE NEXT COUPLE OF DAYS.

&&

.LONG TERM FORECAST (SATURDAY THROUGH WEDNESDAY)...

THE INCURSION OF ANOMALOUSLY WARM TEMPERATURES TO ALASKA IS
EXPECTED TO CONTINUE AS A HIGHLY AMPLIFIED TROUGH OF LOW PRESSURE
EXTENDING FROM THE EAST COAST OF RUSSIA TO THE NORTHEASTERN GULF
CONTINUES TO BRING A SERIES OF LOW PRESSURE SYSTEMS TOWARD ALASKA
FROM THE NORTH PACIFIC. THE FIRST OF THESE LOWS WILL PUSH INTO THE
BERING SEA ON SATURDAY AND BRING WIDESPREAD RAINFALL AND ISOLATED
POCKETS OF SNOW TO MUCH OF ALASKA. PRECIPITATION ASSOCIATED WITH
THIS SYSTEM WILL GRADUALLY TAPER OFF MY MONDAY AS IT PUSHES NORTH
INTO THE BERING SEA. A POTENT WARM FRONT WILL MOVE INTO THE
SOUTHERN BERING SEA...BRINING ANOTHER PUSH OF WARM AIR TO THE
REGION. MODELS CONTINUE TO SHOW A RIDGE OVER SOUTHEAST ALASKA
BREAKING DOWN ON MONDAY AS A POTENT SHORTWAVE CLASHES WITH THE
RIDGE. THIS WILL ALLOW A LOW OVER THE SIBERIAN COAST TO MOVE OVER
THE BERING SEA AND BRING SLIGHTLY COOLER TEMPERATURES TO WESTERN
ALASKA.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GAES 132 150 155 165 172 175 176 177 180 352.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...CC
SOUTHCENTRAL ALASKA...DEK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DK
LONG TERM...MC