Area Forecast Discussion
Issued by NWS Anchorage, AK

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FXAK68 PAFC 070001
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
401 PM AKDT MON JUL 6 2015

.ANALYSIS AND UPPER LEVELS...
A NEGATIVELY TILTED UPPER TROUGH EXTENDS SOUTHEAST FROM AN UPPER
LOW OVER THE NORTHERN BERING SEA TO A SECONDARY CENTER APPROACHING
THE ALASKA PENINSULA. AT THE SURFACE A WEAKENING 980S LOW IS
EVIDENT OVER THE CENTRAL BERING SEA WITH A SECONDARY LOW CENTER
SOUTH OF THE AK PEN. AN OCCLUDED FRONT EXTENDS ACROSS COASTAL SW
ALASKA TO JUST SOUTH OF KODIAK ISLAND. RAIN IS FALLING OVER MUCH
OF SOUTHWEST ALASKA ...HEAVIEST ALONG BRISTOL BAY...TO OVER KODIAK
ISLAND. THE KENAI NEXT NEXRAD RADAR SHOWED RETURNS ACROSS THE
KENAI PEN AND WESTERN COOK INLET. INLAND AREAS OF SOUTHCENTRAL
ALASKA WERE GENERALLY WARM WITH A FAIRLY THIN LAYER OF HIGH CLOUDS
(CIRRUS). CLOUDS HOWEVER WERE STARTING TO THICKEN UP ACROSS THE
KENAI PEN AND COOK INLET IN ADVANCE OF THE NORTH MOVING OCCLUDED
FRONT. EASTERLY GAP WINDS WERE STRENGTHENING ALONG TURNAGAIN ARM
AND PORTAGE VALLEY THIS AFTERNOON. GAP FLOWS ARE EXPECTED TO
INCREASE THROUGH KNIK ARM AND ACROSS THE COPPER RIVER BASIN
THROUGH THE REMAINDER OF THIS AFTERNOON WITH BUILDING PRESSURES
ALONG THE COAST AND LOWER PRESSURE INLAND ASSOCIATED WITH THE
THERMAL TROUGH. THE BERING SEA AND ALEUTIANS WERE GENERALLY CLOUDY
WITH AREAS OF LIGHT RAIN AND PATCHY FOG. GUSTY SOUTH WINDS WERE
EVIDENT ACROSS THE AK PEN WITH BRISK WESTERLY WINDS ACROSS THE
CHAIN.

&&

.MODEL DISCUSSION...
MODELS OVERALL HAVE A SIMILAR HANDLING OF THE SYNOPTIC PRESSURE
CENTERS...UPPER LEVEL FEATURES...AND THE GENERAL PRECIPITATION
PATTERN. MINOR DIFFERENCES DO EXIST WITH THE COMPLEX LOW OVER THE
BERING SEA. FOR NOW WILL LEAN TOWARD THE GFS WITH THIS FEATURE. IN
THE EAST...THE HIGHER RESOLUTION NAM WILL BE USED TO CAPTURE
MESOSCALE WINDS.

&&

.FIRE WEATHER...
WIDESPREAD WETTING RAIN WILL CONTINUE ACROSS THE SOUTHWEST
MAINLAND THROUGH TONIGHT AS THE FRONT CONTINUES TO PUSH THROUGH
THE AREA AND A POTENT UPPER LEVEL WAVE TRACKS INLAND THROUGH THE
BRISTOL BAY REGION INTO THE LOWER KUSKOKWIM VALLEY. PRECIPITATION
WILL THEN BECOME MORE SHOWERY IN NATURE ON TUESDAY WITH A COOLER
AND WETTER PATTERN CONTINUING INTO THE MIDDLE OF THE WEEK IN
PERSISTENT ONSHORE FLOW.

RED FLAG CONDITIONS WILL LINGER THROUGH LATE THIS EVENING IN THE
COPPER RIVER BASIN AS A TIGHTENING PRESSURE GRADIENT IN ADVANCE
OF THE APPROACHING FRONT SUPPORTS GUSTY SOUTHERLY WINDS COMBINED
WITH MINIMUM RH VALUES IN THE 25-30 PERCENT RANGE. CONDITIONS
WILL THEN IMPROVE TONIGHT INTO TUESDAY AS RAIN SPREADS OVER
SOUTHCENTRAL AK FROM THE SOUTHWEST...WITH AN UPPER LEVEL
DISTURBANCE PUSHING THROUGH THE COOK INLET REGION HELPING TO BRING
AN END TO DOWNSLOPE FLOW ACROSS THE CHUGACH AND TALKEETNA
MOUNTAINS AS GAP WINDS GRADUALLY DIMINISH THROUGH TURNAGAIN ARM
AND THE KNIK RIVER VALLEY.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE RIDGE OF HIGH PRESSURE WHICH HELPED BRING DRIER AND WARMER
CONDITIONS OVER SOUTHCENTRAL TODAY WILL BEGIN TO PUSH EASTWARD
THIS EVENING...AS A FRONT CURRENTLY PRODUCING RAIN OVER KODIAK
ISLAND AND SOUTHERN KENAI PENINSULA CONTINUES TO TRACK TOWARD THE
NORTHERN GULF COAST. WIDESPREAD RAINS OVER MUCH OF SOUTHCENTRAL
ARE EXPECTED TO PERSIST THROUGH TOMORROW AS THE FRONT TRACKS INTO
THE NORTHERN GULF COAST AND FURTHER INLAND BY TUESDAY AFTERNOON.
CONDITIONS WILL BECOME MORE SHOWERY IN THE WAKE OF THE FRONT BY
TUESDAY EVENING...AND LINGER AROUND THROUGH WEDNESDAY AFTERNOON.
STRONGER GAP WINDS ALONG TURNAGAIN ARM AND THE COPPER RIVER THAT
DEVELOPED TODAY WILL BEGIN TO DIMINISH THIS EVENING...AS THE
GRADIENT OVER THE AREA BEGINS TO SLACKEN AND WINDS DIE DOWN BY THE
LATE MORNING.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
RAINFALL HAS ESTABLISHED ACROSS SOUTHWEST ALASKA AS EXPECTED AS A
FRONT CONTINUES TO PUSH ACROSS SOUTHWEST ALASKA. THE FRONT IS IN
THE PROCESS OF OCCLUDING AND WILL CONTINUE TO DO SO THROUGH THIS
EVENING AS IT SLOWLY PUSHES FURTHER INLAND. THE FRONTAL OCCLUSION
WILL PROVE SOMEWHAT IMPORTANT IN THE COMING DAYS AS SOME COLDER
AIR ALOFT WILL BE FILTERING IN BEHIND THE "COLD OCCLUSION"...WHICH
WILL HELP TO USHER IN SOME COOLER TEMPERATURES. IN ADDITION...THE
COLDER TEMPERATURES ALOFT WILL HELP STEEPEN THE MID-LEVEL LAPSE
RATES WHICH WILL KEEP RAIN SHOWERS IN THE FORECAST BEHIND THE
FRONTAL PASSAGE. AT THIS TIME HOWEVER...THE LACK OF INSTABILITY
BOTH AT THE SFC AND ALOFT LOOKS MARGINAL AT BEST SO THUNDERSTORMS
ARE NOT ANTICIPATED AT THIS TIME. THE STREAM OF SUBTROPICAL
MOISTURE THAT HAS BROUGHT AN ANOMALOUSLY HIGH PRECIPITABLE WATER
AIR MASS TO SOUTHWEST ALASKA WILL BE SHIFTING EAST THIS EVENING
AND ALSO WILL BE GETTING CUT OFF FROM THE SUBTROPICS WHICH WILL
TAPER THE AMOUNT OF PRECIPITATION AND COVERAGE OF SHOWERS THAT
DEVELOP POST- FRONTAL. A SERIES OF UPPER LEVEL WAVES ASSOCIATED
WITH UPPER LEVEL LOW ENCOMPASSING THE VAST MAJORITY OF THE BERING
SEA WILL TRAVERSE SOUTHWEST ALASKA THROUGH THE SHORT TERM...WHICH
WILL HELP TO LOCALLY ENHANCE SHOWER ACTIVITY AND COVERAGE AT
TIMES. TEMPERATURES WILL FALL TO NEAR NORMAL TO SLIGHTLY BELOW
NORMAL STARTING TUESDAY AND CONTINUING THROUGH WEDNESDAY AND
LIKELY INTO THE WEEKEND.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
AN AREA OF LOW PRESSURE WILL CONTINUE TO QUICKLY PUSH INTO THE
WESTERN BERING SEA THIS EVENING. AN UPPER LEVEL LOW ENCOMPASSING
THE VAST MAJORITY OF THE BERING SEA WILL BEGIN INTERACTING WITH
THE SFC LOW AND HELP PRODUCE DECENT RAIN CHANCES ACROSS THE BERING
SEA. THE BEST RAIN CHANCES WILL BE IN THE PROXIMITY OF THE SURFACE
LOW (LIFTING MECHANISM) AND THE PACIFIC SIDE OF THE ALEUTIAN
ISLANDS (UPSLOPE ALSO ACTING AS A LIFTING MECHANISM). MULTIPLE
UPPER LEVEL DISTURBANCES WILL TAKE A RIDE ALONG THE PERIPHERY OF
THE UPPER LOW...LEADING TO MULTIPLE ROUNDS OF RAIN THROUGH THE
FORECAST PERIOD.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...
A PERSISTENT LARGE AREA OF LOW PRESSURE WILL REMAIN CENTERED OVER
THE BERING THROUGH AT LEAST NEXT WEEKEND WHILE UPPER LEVEL RIDGING
REMAINS WEAK OVER THE EASTERN INTERIOR OF ALASKA AND WESTERN
CANADA. THE NET RESULT WILL PUT THE SOUTHERN ALASKA MAINLAND INTO
A PERSISTENT COOL AND SHOWERY PATTERN...WITH NO STRONG FRONTS
ANTICIPATED MOVING INLAND FROM THE PACIFIC AND GULF...AND A
SURFACE RIDGE ALONG THE EASTERN GULF AND NORTH GULF COAST
SUPPORTING LOW LEVEL ONSHORE FLOW. SHORTWAVE TROUGHS WILL
ROUTINELY ROTATE UP FROM THE WESTERN GULF AND EASTERN BERING
KEEPING SKIES MOSTLY CLOUDY AND BRINGING SCATTERED
SHOWERS...PERIODS OF RAIN AND NEAR NORMAL TEMPERATURES TO MUCH OF
SOUTHWEST AND SOUTH CENTRAL ALASKA. A WEAK FRONT MAY MOVE NORTH
AND EAST TOWARD THE SOUTHERN MAINLAND TOWARD SUNDAY AND MONDAY OF
NEXT WEEK AND BRING A MORE SUSTAINED PERIOD OF RAIN ESPECIALLY
ALONG THE COAST...BUT CONFIDENCE IN THIS PARTICULAR FEATURE IS LOW
RIGHT NOW.

THE SYNOPTIC PATTERN THROUGH AT LEAST THE NEXT 7 DAYS AND
POTENTIALLY WELL INTO NEXT WEEK WILL CONTINUE TO BE DICTATED BY
DYNAMIC FORCING FROM INTENSE TROPICAL CONVECTION OVER THE
EQUATORIAL PACIFIC...WHICH IS IN A FAIRLY STATIC STATE RIGHT NOW.

AS FAR AS IMPACTS...THE MILDER AND COOLER CONDITIONS MEAN FIRE
WEATHER CONDITIONS WILL BECOME MORE PERSISTENTLY AND CONSISTENTLY
FAVORABLE FOR WILDFIRE SUPPRESSION EFFORTS.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...NONE.
FIRE WEATHER...RED FLAG WARNING 141.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...RC
SOUTHCENTRAL ALASKA...TP
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...MC
LONG TERM...CC



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