Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 242138
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
138 PM AKDT THU JUL 24 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW OVER THE NORTHWEST GULF OF ALASKA. AN
UPPER LEVEL TROUGH...ASSOCIATED WITH A LOW JUST NORTH OF THE
STATE...IS SITUATED NORTH/SOUTH ACROSS WESTERN ALASKA. A LARGE AND
STRONG UPPER RIDGE IS OVER THE WESTERN AND CENTRAL BERING
SEA/ALEUTIANS.

&&

.MODEL DISCUSSION...
THE NUMERICAL MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH 84
HOURS. THERE ARE SOME DISCREPANCIES ON HOW THEY HANDLE ENERGY
DROPPING SOUTH FROM THE WESTERN ALASKA TROUGH INTO THE GULF
LOW...BUT THE GLOBAL MODELS ARE CLOSE ENOUGH TO INSPIRE SOME
CONFIDENCE (NEAR TO ABOVE NORMAL) IN THE FORECAST.

&&

.SHORT TERM FORECAST...
THE LARGE SCALE PATTERN WILL REMAIN BASICALLY THE SAME THROUGH
SUNDAY WITH THE BERING RIDGE AND MAINLAND/GULF TROUGH/LOW. THE
MAIN CHANGE THAT WILL AFFECT THE WEATHER IS THAT AFTER THE FIRST
SYSTEM TRANSITIONS FROM THE TROUGH INTO THE GULF LOW...THE FLOW
SPLIT WILL WIDEN AND LEAVE SOUTHERN ALASKA UNDER A WEAK RIDGE
AND/OR "COL".

FOR SOUTH CENTRAL ALASKA...A WET DAY IS IN STORE FRIDAY AND INTO
SATURDAY FOR THE COOK INLET THROUGH THE MATANUSKA/SUSITNA VALLEY
AREA. THIS IS DUE TO THE ARRIVAL OF THE MAINLAND TROUGH...WHICH
WILL STALL OVER THE AREA AND "PINCH OFF" AN UPPER LOW THAT WILL
DIVE SOUTH...JOINING THE GULF LOW LATE SATURDAY. PRECIPITATION
AMOUNTS THROUGH SATURDAY AFTERNOON OF ONE HALF TO ONE INCH ARE
EXPECTED...WITH LOCALLY HIGHER TOTALS POSSIBLE. SOME PRECIPITATION
IS ALSO EXPECTED FURTHER EAST (COPPER RIVER/PRINCE WILLIAM SOUND)
BUT OF LOWER QUANTITIES THAN FURTHER WEST WHERE MORE OF THE
DYNAMICS ARE. MOST OF THE AREA WILL BE DRY SATURDAY NIGHT AND
SUNDAY AS WEAK RIDGING NUDGES IN FROM THE BERING HIGH. SOME
SHOWERS ARE STILL EXPECTED OVER THE COPPER RIVER BASIN AND PRINCE
WILLIAM SOUND...AREAS FURTHER FROM THE RIDGE AND CLOSER TO THE
GULF LOW.

FOR SOUTHWEST ALASKA...PRECIPITATION WILL END FROM THE WEST
TONIGHT AS THE UPPER TROUGH MOVES EASTWARD. DRY CONDITIONS ARE
EXPECTED FRIDAY THROUGH SUNDAY AS THE BERING RIDGE NUDGES
EASTWARD.

FOR THE BERING SEA/ALEUTIANS...THE RIDGE WILL SLOWLY MOVE EAST
THROUGH SUNDAY. ON SUNDAY THE RIDGE WILL HAVE MOVED FAR ENOUGH
EAST THAT A WEAK FRONT COULD SLIDE INTO THE WESTERN
ALEUTIANS...BRINGING CHANCES OF RAIN AND INCREASING SOUTHEASTERLY
WINDS.

&&

.LONG TERM FORECAST...
A HIGHLY AMPLIFIED PATTERN WILL EXIST ACROSS THE REGION ON
MONDAY...WITH A HIGH AMPLITUDE RIDGE OVER THE BERING SEA...AND A
LARGE UPPER LOW IN THE GULF OF ALASKA. A SHORTWAVE TROUGH WILL
DROP INTO SOUTHERN ALASKA LATE MONDAY INTO TUESDAY...SUPPORTING
SHOWERS ACROSS MOST OF SOUTHERN ALASKA. EVENTUALLY...THE LARGE LOW
IN THE GULF WILL LIFT NORTH INTO SOUTHERN ALASKA...WITH INCREASING
THREATS FOR EASTERLY WAVES TO ROTATE INTO THE MAINLAND...KEEPING
THE THREAT FOR SHOWERS AND PERIODS OF RAIN THROUGH THE END OF THE
WEEK. TEMPERATURES WILL GENERALLY HOVER AROUND NORMAL ACROSS THE
MAINLAND...WITH DAILY TEMPERATURE TRENDS HEAVILY MODULATED BY THE
TIMING OF INDIVIDUAL EASTERLY WAVES. ACROSS THE BERING...THE HIGH
AMPLITUDE RIDGE WILL GENERALLY SUPPORT WIDESPREAD FOG AND
STRATUS...WITH RAIN THREATS LARGELY REMAINING OVER THE WESTERN
BERING.

&&

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

$$

LUDWIG/JA JUL 14


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