Small Craft Advisory 422, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
438 PM AKDT SAT MAY 16 2015

.ANALYSIS AND UPPER LEVELS...
THE BLOCKING RIDGE OVER NORTHWEST CANADA AND EASTERN ALASKA
CONTINUES TO BE THE DOMINANT FEATURE ON THE WEATHER MAP. THERE IS
AN UPPER LOW OVER THE SOUTHERN BERING SEA THAT IS MAKING THE TURN
FROM EASTWARD MOVING TO NORTHWARD MOVING AS IT BEGINS TO NUDGE UP
AGAINST THE BLOCKING RIDGE. HIGHER MOISTURE AND PRECIPITATION
CONTINUES THROUGH KODIAK AND SOUTHWEST ALASKA...WHILE VERY DRY
CONDITIONS REMAIN OVER THE COPPER RIVER BASIN. ANOTHER LOW OVER
THE SOUTHERN SEA OF OKHOTSK (BETWEEN KAMCHATKA AND JAPAN) THAT
WILL PLAY A ROLE IN THE FORECAST FOR THE ALEUTIANS TOWARD THE END
OF THE SHORT TERM.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN GOOD AGREEMENT FOR THE SHORT TERM
PORTION OF THE FORECAST. PREFERENCE TOWARD THE HI-RES MODELS (NAM
AND REGIONAL GEM) FOR THEIR BETTER DETAIL. FORECAST CONFIDENCE IS
HIGHER THAN NORMAL FOR THE AFTERNOON PACKAGE.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
HIGH PRESSURE WILL DOMINATE THE SOUTHCENTRAL FOR THE NEXT COUPLE
DAYS. THIS WILL LEAD TO CLEAR SKIES AND WARM TEMPERATURES.
ADDITIONALLY...THIS WILL BRING IN DIURNAL WINDS WITH PLACES AROUND
COOK INLET AND PRINCE WILLIAM SOUND SEEING SEA BREEZES IN THE
AFTERNOON ON SUNDAY AND MONDAY. THESE WARM CONDITIONS WILL HELP IN
DROPPING RH VALUES BELOW 30 PERCENT IN THE AFTERNOON HOURS IN
SEVERAL LOCATIONS AROUND THE SOUTHCENTRAL. THE DRIEST CONDITIONS
WILL BE IN THE COPPER RIVER BASIN WHERE TEMPERATURES AROUND 70
WILL ALLOW RH VALUES TO DROP BELOW 15 PERCENT ON SUNDAY AND TO
NEAR 15 ON MONDAY. LIGHT WINDS ARE EXPECTED THROUGHOUT THE BASIN
BUT SOUTH WINDS WILL PICK UP IN THE AFTERNOON ALONG THE COPPER
RIVER GETTING AS HIGH AS 15 MPH. RECOVERIES FOR THESE AREAS WILL
BE IN THE 60S TO 70S OVERNIGHT.

THE EXCEPTION TO THE CLEAR SKIES WILL BE AROUND KODIAK ISLAND.
THE FRONT APPROACHING THE ISLAND WILL STALL OUT THERE BRINGING
SOUTHEAST WINDS AND RAIN TO THE AREA INTO EARLY NEXT WEEK. SOME OF
THE RAIN AND CLOUD COVER WILL MAKE IT OVER THE SOUTHERN PARTS OF
THE KENAI PENINSULA.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
LOW PRESSURE OVER THE CENTRAL BERING IS STATIONARY TONIGHT AS IT
ELONGATES ITS CENTER TOWARD SAINT MATTHEW ISLAND. RIDGING ACROSS
THE GULF BLOCKS THE FRONT ACROSS THE SOUTHWEST THEREFOR MOIST
SOUTHERLY FLOW ENSUES ACROSS THE SOUTHWEST MAINLAND THROUGH
MONDAY. A STRONGER SHORTWAVE MOVES INTO THE EASTERN BERING TONIGHT
BRINGING STEADY RAIN TO THE ALASKA PENINSULA AND THE WEST COAST
SPREADING SLOWLY EAST OVERNIGHT. GUSTY WINDS CONTINUE THROUGHOUT
THE EVENT AS THE PRESSURE GRADIENT REMAINS TIGHT BETWEEN THE LOW
IN THE BERING AND THE RIDGE OVER THE GULF. STRONG WINDS ACCOMPANY
THE SHORTWAVE TONIGHT WITH GALES CONTINUING ALONG THE WEST COAST.
WINDS TAPER DOWN A LITTLE ON SUNDAY...HOWEVER THEY REMAIN GUSTY
THROUGH MONDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...

LOW PRESSURE ACROSS THE SOUTHERN BERING ELONGATES TONIGHT AND THEN
SHIFTS NORTH THROUGH SUNDAY. GUTSY SOUTHERLY WINDS WILL CONTINUE
ACROSS THE EASTERN BERING THROUGH MONDAY MORNING WITH GUSTY
NORTHWESTERLY FLOW ACROSS THE WESTERN BERING. RAIN BECOMES
WIDESPREAD ACROSS THE EASTERN BERING TONIGHT WITH SHOWERS ACROSS
THE WESTERN AREAS ON THE BACKSIDE OF THE LOW. ON MONDAY
MORNING...THE NEXT FRONT MOVES FROM THE NORTH PACIFIC INTO THE
CENTRAL ALEUTIANS. THIS SYSTEM IS EXPECTED TO BRING GALE STRENGTH
WINDS ALONG THE FRONTAL BOUNDARY WITH RAIN SPREADING INTO THE
SOUTHERN BERING AND EASTERN ALEUTIANS MONDAY NIGHT.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7...TUESDAY THROUGH
SATURDAY)...

ON TUESDAY...A GALE FORCE NORTH PACIFIC LOW WILL BE MOVING INTO
THE BERING SEA...WITH THE BRUNT OF THE PRECIPITATION STREAMING
NORTHEAST INTO WESTERN ALASKA. THE DOMINANCE OF THE NORTH AMERICAN
RIDGE WILL CONTINUE TO KEEP A BULK OF THE MOISTURE AND
PRECIPITATION OVER WESTERN ALASKA THROUGH THE WEEK. ABOVE AVERAGE
TEMPERATURES WILL ALSO BE THE NORM ACROSS
SOUTHCENTRAL...ESPECIALLY ACROSS THE COPPER BASIN. THERE
ARE...HOWEVER...STRONGER INDICATIONS THAT THIS WILL BE A RATHER
"DIRTY" RIDGE IN THAT EXTENSIVE MID AND HIGH CLOUDS WILL PASS
THROUGH THE RIDGE AT TIMES AS THE ACTIVE AND AMPLIFIED UPPER LEVEL
JET STREAM REMAINS IN PLACE.

ON THURSDAY...THE REMNANT REMAINS OF RECURVING TYPHOON DOLPHIN
WILL BEGIN TO IMPACT THE FAR SOUTHWEST BERING SEA. THE ECMWF AND
GFS DETERMINISTIC GUIDANCE ARE NOW RELATIVELY CLOSE WITH THAT
FEATURE...AND DEPICT A DEEP 960 TO 970 HPA LOW IMPACTING THE
WESTERN BERING. THE OTHER IMPACT WILL BE WITH RESPECT TO ENERGY
RELEASE INTO THE NORTH AMERICAN PATTERN ALOFT AS THIS SYSTEM
UNDERGOES EXTRATROPICAL TRANSITION. THE INDIVIDUAL DETERMINISTIC
MODELS HAVE CONSISTENTLY TRIED TO FORM A STRONG HIGH LATITUDE
BLOCK OVER ALASKA NEAR THE WEEKEND...BUT CONTINUE TO STRUGGLE
WITH TIMING AND STRENGTH OF ANY POTENTIAL BLOCKING PATTERN. FOR
NOW THIS IS A LOW CONFIDENCE SCENARIO...BUT IF IT WERE TO
HAPPEN...MUCH OF SOUTHERN ALASKA WOULD EXPERIENCE RATHER
SIGNIFICANT POSITIVE TEMPERATURE ANOMALIES BY THE END OF THE
WEEKEND. BUT ONCE AGAIN...THIS IS A LOW CONFIDENCE POTENTIAL
PATTERN GIVEN THE INTRICACIES INVOLVED WITH TYPHOON DOLPHIN.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...BL
SOUTHCENTRAL ALASKA...DWK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KH
LONG TERM...AHSENMACHER