Area Forecast Discussion - SouthCentral and SouthWest


FXAK68 PAFC 011311
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
511 AM AKDT WED JUL 1 2015
.ANALYSIS AND UPPER LEVELS...
THE UPPER LEVEL LOW THAT HAD BEEN CENTERED SOUTHWEST OF KODIAK
OVER THE LAST TWO DAYS HAS SHIFTED EASTWARD SLIGHTLY. WELL SOUTH
OF THIS LOW...A WAVE IS DEVELOPING OVER THE NORTHEAST PACIFIC AND
HEADING TOWARDS THE GULF. THIS WILL DEVELOP INTO A SURFACE LOW AND
MOVE TOWARD THE PANHANDLE THIS EVENING. AT THE SAME TIME OVER THE
COPPER RIVER BASIN...THE EASTERLY WAVE IS BEGINNING TO SHOW ITS
FIRST SIGNS OF DEVELOPMENT. THIS WILL CONTINUE DEVELOPING OVER THE
COURSE OF THIS MORNING AND BE THE DRIVER OF WIDESPREAD RAINFALL
OVER SOUTHCENTRAL BEGINNING THIS EVENING. THE RIDGING THAT HAD
ENCOMPASSED MUCH OF THE BERING SEA EARLIER THIS WEEK HAS NOW
SHIFTED TO THE EAST IN ADVANCE OF A BROAD FRONTAL SYSTEM THAT
STRETCHES FROM THE CENTRAL ALEUTIANS TO ITS PARENT LOW OVER THE
KAMCHATKA PENINSULA. THIS FRONT IS BRINGING RAIN AND CLOUD COVER
TO MUCH OF THE ALEUTAINS WEST OF DUTCH HARBOR...WHILE FOG AND
STRATUS PREVAILS UNDER RIDGING TO THE EAST.

&&
.MODEL DISCUSSION...
SYNOPTIC AGREEMENT BETWEEN THE MODELS REMAIN IN VERY GOOD
AGREEMENT INTO THE END OF THE WORK WEEK. THERE STILL REMAINS SOME
UNCERTAINTY AS TO THE EXACT PLACEMENT TIMING OF THE RAINFALL FROM
THE EASTERLY WAVE THAT WILL SET UP THIS MORNING...BUT THERE IT
ENOUGH AGREEMENT IN THE PLACEMENT OF THE WAVE THAT THERE IS GOOD
CONFIDENCE THAT MOST AREAS OF SOUTHCENTRAL WILL SEE STEADY
RAINFALL THIS EVENING. BY FRIDAY...THE MODELS BEGIN TO DISAGREE
WITH THE POSITION AND INTENSITY OF AN UPPER LEVEL TROUGH OVER THE
WEST COAST...WHICH BRING SOME UNCERTAINTY ON THE POSSIBLY OF
CONVECTION OVER THE INTERIOR. THE GFS WAS USED FOR THIS
FEATURE...WHICH IS A GOOD MIDDLE OF THE ROAD SOLUTION FOR BOTH
POSITION AND INTENSITY.

&&
.FIRE WEATHER...
SOUTHCENTRAL...THE EASTERLY WAVE SETTING UP OVER THE COPPER RIVER
BASIN WILL BRING MOIST AND CLOUDY CONDITIONS TO MUCH OF THE AREA
TODAY. WINDS IN MOST AREAS WILL REMAIN LIGHT...THOUGH GAP WINDS
ALONG TURNAGAIN ARM WILL CONTINUE INTO THIS EVENING...WITH
SOUTHERLY WINDS ALONG THE COPPER RIVER BASIN EXPECTED AGAIN THIS
AFTERNOON/EVENING. STARTING ON THURSDAY...MID LEVEL RIDGING WILL
MOVE INTO THE AREA...ALLOWING FOR CLEARING SKIES AND DRIER WEATHER
TO MOVE IN FOR THE REMAINDER OF THE WORK WEEK...THOUGH CRITICAL
FIRE WEATHER CONDITIONS ARE NOT EXPECTED.

SOUTHWEST...A WEAK THERMAL TROUGH WILL AID IN THE DEVELOPMENT OF
ISOLATED WET THUNDERSTORM ACTIVITY OVER THE KUSKOKWIM VALLEY AND
INTERIOR BRISTOL BAY THIS AFTERNOON/EVENING. THIS THUNDERSTORM
ACTIVITY WILL ONCE AGAIN BE THE PRIMARY FIRE WEATHER CONCERN TODAY
AS MOIST AND RELATIVELY COOL CONDITIONS WILL PREVAIL. STARTING ON
THURSDAY...RIDGING FROM THE BERING SHOULD PROVIDE ENOUGH STABLE
AIR BRING AN END TO ANY THUNDERSTORM ACTIVITY THROUGH FRIDAY.
THIS RIDGE WILL CREATE WARMER AND DRIER CONDITIONS THAN OVER THE
PAST FEW DAYS...HOWEVER RH VALUES ARE EXPECTED TO REMAIN WELL
ABOVE RED FLAG CONDITIONS.

&&

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

AN EASTERLY WAVE MOVES INTO SOUTHCENTRAL TODAY AND DRIFTS EAST AND
WEAKENS THU AS THE UPPER LOW MOVES INTO WESTERN CANADA. IT APPEARS
THAT WETTING RAINS WILL OCCUR OVER THE NORTHERN SUSITNA VALLEY AS
WELL AS THE WESTERN AND NORTHERN COPPER RIVER BASIN TODAY. MODELS
HAVE ACTUALLY PUSHED THE MOISTURE FURTHER WEST IN THE SUSITNA
VALLEY FOR THIS EVENING AND SLOWED THE EASTWARD PROGRESSION OF THE
RAIN TONIGHT FROM PREVIOUS RUNS. RAIN SHOULD SPREAD TO THE LOWER
SUSITNA VALLEY...MATANUSKA VALLEY...AND THE ANCHORAGE BOWL THIS
EVENING AND THEN MOVE EAST ACROSS THE COPPER RIVER BASIN ON THU.
LINGERING SHOWERS WILL CONTINUE TO THE WEST. NORTH TO WEST OUTFLOW
WINDS ARE EXPECTED TO DEVELOP ACROSS THE EASTERN KENAI PEN THU
MORNING WITH HIGHER PRESSURE BUILDING IN FROM THE WEST AND
GENERALLY LOWER PRESSURE ACROSS THE EASTERN GULF. OUTFLOW WINDS
SHOULD DIMINISH IN INTENSITY LATE THU AFTERNOON.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE SHOWERY PATTERN IS EXPECTED TO REMAIN OVER SOUTHWESTERN ALASKA
THROUGH THURSDAY EVENING WITH MOST OF THE PRECIPITATION REMAINING
EAST OF THE KILBUCK/AHKLUN MOUNTAINS. ISOLATED THUNDERSTORMS ARE
EXPECTED TODAY OVER THE MIDDLE KUSKOKWIM VALLEY AND THE BRISTOL
BAY REGION NORTH OF DILLINGHAM AS THE ATMOSPHERE WILL REMAIN
UNSTABLE ENOUGH FOR THUNDERSTORM DEVELOPMENT. CONDITIONS WILL BE
LESS FAVORABLE FOR THUNDERSTORMS ON THURSDAY WITH CONFIDENCE IN
ANY CONVECTIVE DEVELOPMENT LOW ENOUGH TO PRECLUDE THE INCLUSION IN
THE FORECAST...ALTHOUGH IT IS POSSIBLE FOR THE DEVELOPMENT OF A
ISOLATED THUNDERSTORM OR TWO OVER THE BRISTOL BAY REGION.

AS WITH PREVIOUS DAYS...AREAS OF SMOKE...MAINLY INLAND...WILL
CONTINUE THROUGH THE PERIOD. THE WORST CONDITIONS WILL AGAIN BE DURING
THE OVERNIGHT AND EARLY MORNING HOURS AS NIGHTTIME INVERSIONS WILL
PREVENT ADEQUATE MIXING.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
WIND...FOG...AND RAIN ARE THE MAIN FEATURES OF NOTE IN THE SHORT
TERM FORECAST FOR THE REGION. WINDS WILL CONTINUE TO INCREASE TO
JUST BELOW GALE FORCE FOR THE SOUTHERN BERING AND EASTERN
ALEUTIANS AS THE LOW REMAINS JUST SOUTH OF THE CENTRAL ALEUTIANS.
WINDS WILL INCREASE EAST OF ADAK TODAY AND MOVE EASTWARD OVER THE
ALASKA PENINSULA AND NORTH INTO THE SOUTHERN BERING AS THE FRONT
ASSOCIATED WITH THE LOW ROTATES NORTHWARD AND ELONGATES FROM EAST
TO WEST OVER THE ALEUTIAN CHAIN. THIS FRONT WILL BRING RAINFALL
ALONG MOST OF THE ALEUTIAN ISLANDS THROUGH THE PERIOD. THIS SYSTEM
WILL HAVE A FAIRLY MOIST AIRMASS FLOWING FROM THE SOUTH AND THE
EXPECTED POSITION OF THE LOW WILL SETUP A FAIRLY PERPENDICULAR
MOISTURE FLOW INTO THE EASTERN ALEUTIANS ON THURSDAY...THUS
BRINGING THE CHANCE FOR A MODERATE TO POSSIBLY HEAVY RAIN EVENT TO
UNALASKA.

ELSEWHERE...WITH HIGH PRESSURE REMAINING OVER A GOOD PORTION OF
THE REGION...MARINE STRATUS AND AREAS OF DENSE FOG WILL REMAIN
OVER MUCH THE BERING SEA REGION THROUGH THURSDAY.

&&

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

THURSDAY NIGHT INTO FRIDAY A LONGWAVE TROUGH DIGS FROM THE
NORTHWEST COAST. THIS WILL KEEP LIGHT RAIN CHANCES ACROSS THE
SOUTHERN MAINLAND FOR THE END OF THE WEEK. MOST OF THE
PRECIPITATION WILL BE LIGHT WITH HIGHER AMOUNTS ALONG MOUNTAIN
RANGES. TO THE WEST...A LOW PRESSURE SYSTEM ACROSS THE CENTRAL
ALEUTIANS MOVES A FRONT INTO THE SOUTHERN BERING THURSDAY NIGHT
WHICH EXTENDS TOWARD THE ALASKA PENINSULA. THIS FRONT MOVES INTO
THE EASTERN AND NORTHERN BERING BY FRIDAY NIGHT.

LONG TERM FORECAST FOR SATURDAY INTO THE BEGINNING OF NEXT WEEK
REMAINS HIGHLY UNCERTAIN AS MODELS CONTINUE TO HAVE A LARGE SPREAD
IN SOLUTIONS. THE MODEL CHOICE FOR THE EXTENDED RANGE WAS THE
ECMWF WITH ONLY MINOR CHANGES MADE. THE GENERAL PATTERN INTO THE
NEXT WEEK KEEPS DIURNAL SHOWERS ALONG THE MOUNTAINS AND GENERALLY
WEAK SURFACE FLOW. THE MAIN CHALLENGE FOR THE UPCOMING WEEKEND
WILL BE A FRONT THAT MOVES INTO THE SOUTHERN GULF ON SATURDAY. THE
ECMWF PUSHES THIS FRONT INTO THE COAST SATURDAY NIGHT AND THE GFS
DIMINISHES IT...WHILE THE GEM TRENDED WITH A MIDDLE RANGE
SOLUTION. THE GFS CONTINUES TO PRESENT THE WARMEST SOLUTION FOR
THE BEGINNING OF NEXT WEEK...BUT WILL CONTINUE TO BE CONSERVATIVE
WITH FORECAST INFLUENCES AS THE OTHER OPERATIONAL MODELS REMAIN
RELATIVELY COOLER.

&&


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

&&

$$

SYNOPSIS AND MODEL DISCUSSION...DEK
SOUTHCENTRAL ALASKA...RMC
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...RF
LONG TERM...KH