Small Craft Advisory 527, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
116 PM AKDT WED JUL 9 2014

.ANALYSIS AND UPPER LEVELS...

THERE IS A LARGE UPPER LOW CENTERED OVER THE EASTERN BERING SEA.
THERE ARE SEVERAL SURFACE AROUND THE PERIMETER OF THIS UPPER
LOW. THE TWO MOST IMPORTANT OF THESE SURFACE LOWS ARE CURRENTLY
SPINNING UP...ONE JUST SOUTH OF KODIAK AND THE OTHER ABOUT 500
MILES SOUTH OF THE EASTERN ALEUTIANS. BOTH OF THESE CONTAIN A
DECENT AMOUNT OF MOISTURE...ESPECIALLY THE SECOND LOW. THERE IS A
WEAK SURFACE LOW JUST NORTH OF NUNIVAK ISLAND...AND ANOTHER TO THE
WEST OF THE PRIBILOFS IN THE CENTRAL BERING SEA. THERE IS A RIDGE
OF HIGH PRESSURE ALONG THE EASTERN BORDER OF ALASKA AND ANOTHER
ONE JUST NUDGING INTO THE WESTERN BERING SEA.

&&

.MODEL DISCUSSION...

THE FORECAST MODELS ARE STILL IN DISAGREEMENT IN THE SHORT TERM TO
A DEGREE THAT LOWERS CONFIDENCE IN THE FORECAST DETAILS. AT ISSUE
IS HOW THE MODELS HANDLE THE TWO MAIN LOWS THAT WILL AFFECT
SOUTHERN ALASKA OVER THE NEXT FEW DAYS. THE GFS AND CANADIAN GEM
HAS A STRONGER DIVISION BETWEEN THE TWO LOWS...WITH A DEFINITE
"TWO-SURGE" EVENT BEFORE THE LOWS CONSOLIDATE. THE ECMWF AND NAM
MERGE THE SYSTEMS MUCH FASTER...STILL A TWO-SURGE EVENT...BUT MUCH
LESS DEFINED BETWEEN THE EVENTS. AFTERNOON FORECAST LEANS TOWARDS
THE GFS/GEM SOLUTION BUT WITH A LOWER CONFIDENCE LEVEL THAN IS
OPTIMAL FOR A STRONG WEATHER SYSTEM EARLY IN THE FORECAST.

&&

.SHORT TERM FORECAST...

FOR SOUTH CENTRAL ALASKA...THE LOW SOUTH OF KODIAK ISLAND WILL
PUSH INTO SOUTHERN KODIAK TONIGHT AND STALL. THE WARM FRONT FROM
THIS SYSTEM IS PUSHING INTO SOUTH CENTRAL THIS EVENING...AND WILL
STALL AND BE ABSORBED BY THE NEXT FRONT (OCCLUSION) ON THURSDAY.
THIS OCCLUSION WILL BRING A PRETTY GOOD SHOT OF RAIN AND WINDS TO
THE GULF COAST AND AREAS NEARBY. LESS RAIN IS EXPECTED INLAND DUE
TO DOWN-SLOPE EFFECTS...BUT WITH FAIRLY DEEP MOISTURE SOME RAIN IS
EXPECTED...A "HIGH POP/LOW QPF" SCENARIO. WINDS WILL ALSO
INCREASE ALONG TURNAGAIN ARM.

THIS FIRST LOW WILL THEN DISSIPATE AS THE NEXT LOW (CURRENTLY
SOUTH OF THE EASTERN ALEUTIANS) MOVES INTO THE GULF AND
INTENSIFIES LATER THURSDAY. THIS NEXT SYSTEM WILL BRING EVEN MORE
RAIN AND STRONGER WINDS TO THE AREA THURSDAY NIGHT INTO FRIDAY
MORNING AS SOME OF THE MOISTURE WAS TAPPED FROM THE SUBTROPICS.
EXPECT DECENT RIVER RISES FOR AREAS AROUND PRINCE WILLIAM SOUND ON
FRIDAY...THOUGH FLOODING IS NOT EXPECTED AT THIS TIME. AGAIN THE
INLAND RAINFALL IS EXPECTED TO BE FAIRLY LIGHT...ANOTHER HIGH
POP/LOW QPF SITUATION.

THE WEATHER WILL SETTLE DOWN BY SATURDAY AS THE FRONT MOVES
INLAND AND DISSIPATES. THE MAIN UPPER LOW BY SATURDAY WILL BE
CENTERED OVER THE ALASKA PENINSULA. HOWEVER...CYCLONIC FLOW OVER
MUCH OF SOUTH CENTRAL ALASKA WILL BE WEAK AND PRECIPITATION WILL
BE SHOWERY...AND WINDS WILL SLACK OFF.

FOR SOUTHWEST ALASKA...IN GENERAL...CONDITIONS ARE EXPECTED TO BE
FAIRLY MOIST THROUGH SATURDAY WITH THE MAIN UPPER LOW OVER THE
AREA. THERE WILL BE SOME "SURGES" IN MOISTURE AS SOME SYSTEMS MOVE
ACROSS THE AREA. THE FIRST SURGE WILL MAINLY BE EAST OF THE
KUSKOKWIM DELTA..."WRAP AROUND" MOISTURE ASSOCIATED WITH THE LOW
MOVING INTO KODIAK ISLAND TONIGHT. THIS WILL THEN PUSH WESTWARD
ACROSS THE AREA ON THURSDAY...WITH PRECIPITATION DIMINISHING TO
SHOWERS. AS THE NEXT LOW MOVES INTO KODIAK ISLAND AND THE MAIN
UPPER LOW DIVES SOUTH TO THE ALASKA PENINSULA ON THURSDAY
NIGHT...ANOTHER SURGE OF "WRAP AROUND" RAIN WILL PUSH WESTWARD
ACROSS THE AREA THROUGH FRIDAY AFTERNOON. PRECIPITATION WILL AGAIN
SLACK OFF TO A MORE SHOWERY REGIME FRIDAY NIGHT AND SATURDAY.

FOR THE BERING SEA/ALEUTIANS...A COUPLE OF WEAK IMPULSES WILL
SLIDE AROUND THE MAIN LOW THROUGH THURSDAY NIGHT WILL BRING CHANCES
OF PRECIPITATION MAINLY TO AREAS FROM THE CENTRAL ALEUTIANS
EASTWARD. OTHERWISE THE HIGH OVER THE WESTERN GULF WILL SLOWLY
SLIDE EAST AS THE MAIN UPPER LOW SETTLES IN OVER THE ALASKA
PENINSULA.

&&

.LONG TERM FORECAST (SAT JULY 12 - TUE JULY 15)...

A LARGE TROUGH OF LOW PRESSURE CENTERED OVER THE ALASKA PENINSULA
WILL BE HEAVILY INFLUENCING THE WEATHER ACROSS ALASKA ON
SATURDAY...WITH NUMEROUS RAIN SHOWERS IMPACTING THE COAST...WITH
MORE SCATTERED RAIN SHOWERS INLAND. EXTENSIVE CLOUD COVER AND A
MARINE INFLUENCED AIR MASS WILL KEEP TEMPERATURES NEAR IF NOT
SLIGHTLY BELOW NORMAL BEFORE SLOWLY WARMING TO NORMAL MONDAY AND
TUESDAY. IN OTHER WORDS...NO DRAMATIC WARM...COOL...DRY...OR WET
PERIODS ARE EXPECTED THROUGH THE EXTENDED FORECAST.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING 119 120 125 129 130 131 138 139.
FIRE WEATHER...NONE.

&&

LUDWIG/AHSENMACHER JUL 14