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FXAK68 PAFC 162115
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
115 PM AKDT TUE SEP 16 2014

.ANALYSIS AND UPPER LEVELS...
LINGERING SHOWERS ACROSS SOUTHCENTRAL ALASKA ASSOCIATED WITH A
BROAD UPPER TROUGH MOVING NORTH HAVE BECOME MORE ISOLATED THIS
AFTERNOON. AN EASTWARD MOVING LOW JUST NORTH OF THE WESTERN AK
PEN WAS SLOWLY INTENSIFYING. ITS ASSOCIATED FRONTAL SYSTEM
EXTENDS EAST AND NORTH TOWARD BRISTOL BAY AND SOUTH ACROSS THE AK
PEN SPREADING RAIN TO MUCH OF THE BRISTOL BAY COAST AND THE AK
PEN. RAIN WAS ALSO ENCROACHING ON KODIAK ISLAND. A DEVELOPING LOW
SOUTH OF THE ALEUTIANS WAS MOVING RAPIDLY EAST UNDER A STRONG
NORTH PACIFIC JET.

&&

.MODEL DISCUSSION...
MODELS ARE IN FAIRLY GOOD AGREEMENT ON SYNOPTIC FEATURES. SOME
DIFFERENCES HOWEVER SHOW UP WITH THE INITIAL TRACK OF THE
DEVELOPING LOW MOVING RAPIDLY ACROSS THE NORTH PACIFIC. THE MAIN
DIFFERENCE IS THE TIMING OF THE LOW MOVING TO THE NORTHERN GULF
AND HOW FAR IT MOVES EAST BEFORE RECURVING NORTH. THE GEM
REGIONAL/GLOBAL SEEM TO HAVE A FAIRLY GOOD HANDLE ON THIS SYSTEM
INITIALLY WITH THE CENTER WELL SOUTH OF KODIAK ISLAND WED
AFTERNOON. SECONDARY DEVELOPMENT ALONG THE FRONTAL BOUNDARY TO THE
NORTH SEEMS LIKELY WITH THE PARENT CENTER REMAINING FURTHER SOUTH
AND EAST. FOR NOW IT LOOKS LIKE A COMPOSITE FORECAST OF THE MODELS
WITH SOME OFFICIAL THROWN IN IS REASONABLE.

&&

.SHORT TERM FORECAST...
SOUTHCENTRAL ALASKA...
THE OCCLUDED FRONT APPROACHING KODIAK ISLAND THIS AFTERNOON MOVES
TO THE NORTHERN AND EASTERN GULF WED AND SHOULD STALL. THE
DEVELOPING LOW SOUTH OF THE AK PEN MOVES RAPIDLY EAST ALONG THE
TRAILING BAROCLINIC ZONE ACROSS THE NORTH PAC AND RECURVES INTO
THE GULF WED/WED NIGHT. THE FRONT ASSOCIATED WITH THIS FEATURE
THEN PUSHES TO THE NORTHERN GULF THU.

SHOWERS ACROSS THE GULF COASTS WILL SHIFT TO MORE STEADY RAIN
TONIGHT WITH THE APPROACH OF THE FIRST FRONT NEAR KODIAK. RAIN
WILL LIKELY CONTINUE MAINLY ALONG THE COASTS AS CROSS BARRIER
BARRIER FLOW SHOULD MINIMIZE RAIN INLAND. THE CROSS BARRIER
COMPONENT OF THE WIND AT 850 MB WILL DIMINISH ON THU AFTER THE
NEXT FRONT ROLLS NORTH INTO THE GULF. THE BROAD EASTERLY 700 MB
FLOW COMBINED WITH INSTABILITY OVER THE GULF AND THE WESTWARD
MOVING UPPER WAVE ALONG THE GULF SHOULD BRING A SHOT AT STEADY
RAIN WEST OF THE CHUGACH ON THU. EAST TO SOUTHEAST GALES ARE
EXPECTED TONIGHT ACROSS THE NORTH GULF AHEAD OF THE FIRST FRONTAL
SYSTEM. GALES WILL LIKELY BE REINFORCED OVER THE NORTH GULF WED
NIGHT AS THE NEXT FRONT AND LOW ROLL NORTH. BRISK GAP FLOWS ACROSS
SOUTHCENTRAL CAN BE EXPECTED TONIGHT.

SOUTHWEST ALASKA...
RAIN WILL CONTINUE TO SPREAD NORTH AND EAST WITH THE FRONT AND LOW
TONIGHT. RAIN WILL GIVE WAY TO SHOWERS ACROSS MUCH OF SW ALASKA
WED AS THE LOW BECOMES NEARLY STATIONARY IN BRISTOL BAY AND THE
FRONT WEAKENS. BRISK GAP WINDS ARE EXPECTED ALONG MUCH OF THE
ALEUTIAN RANGE FROM KING SALMON NORTH TONIGHT...WINDS SHOULD
WEAKEN ON WED. GUSTY NORTH WINDS ON THE BACK SIDE OF THE LOW IN
BRISTOL BAY WILL IMPACT THE AK PEN TONIGHT AND WED. THESE WINDS
ARE EXPECTED TO BE BELOW GALE STRENGTH.

BERING SEA/ALEUTIANS...

NORTH TO NORTHWEST WINDS RETURN ACROSS THE BERING AND ALEUTIANS AS
LOW PRESSURE SHIFTS ITS CENTER INTO THE GULF OF ALASKA. A SHOWERY
PATTERN WITH PATCHY FOG REMAINS OVER THE FORECAST AREA AS WEAK
WAVES MOVE AROUND THE BACKSIDE OF THE LOW. COOLER TEMPERATURES
ACROSS THE BERING WILL WARM SLIGHTLY ON FRIDAY ACROSS THE WESTERN
BERING AS RIDGING BUILDS IN BEHIND THE LOW.

&&

.LONG TERM FORECAST...
A GENERALLY WET PATTERN LOOKS TO CONTINUE INTO THE WEEKEND AS THE
LONGWAVE TROUGH CENTERED OVER THE EASTERN BERING AND WESTERN
MAINLAND SHIFTS TO THE WESTERN GULF LATE THIS WEEK AND THEN
GRADUALLY WEAKENS THROUGH EARLY NEXT WEEK. THIS WILL RESULT IN
MORE RAIN FOR LOCATIONS ALONG THE NORTHERN GULF COAST AND SHOWERY
WEATHER FARTHER INLAND AS A SERIES OF DISTURBANCES ROTATE
NORTHWARD TOWARDS SOUTHCENTRAL AK. MEANWHILE...HIGH PRESSURE
BUILDING OVER THE CENTRAL BERING LATER THIS WEEK WILL BE SHORT
LIVED AS ANOTHER LOW PRESSURE SYSTEM APPROACHES THE WESTERN
ALEUTIANS THIS WEEKEND.

&&

AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 119 120 125 130 131 132.
FIRE WEATHER...NONE.

&&

$$

RMC/CB SEP 14




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