Area Forecast Discussion
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FXAK67 PAJK 071350
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
550 AM AKDT TUE JUL 7 2015

.SHORT TERM...EARLY MORNING SATELLITE IMAGE SHOWS A PERSISTING
RIDGE OF HIGH PRESSURE OVER THE EASTERN GULF AND A WEAKENING
INVERTED TROUGH OF LOW PRESSURE ACROSS THE SOUTHERN PANHANDLE. A
COLD FRONT ASSOCIATED WITH A PARENT LOW IN THE BERING SEA MOVE
NORTHWARD ALONG THE WESTERN EDGE OF THE CENTRAL GULF. MAIN
MOISTURE STREAM IS HEADING TOWARD THE NORTHERN GULF...BUT MID TO
HIGH LEVEL CLOUDS OUTSKIRT FROM THE RAIN BANDS THEN RIDE THE TOP
OF THE RIDGE AND STREAMING SOUTHEASTWARD ACROSS THE NORTHERN
PANHANDLE. AS THE RIDGE OF HIGH WEAKENS A BIT...MARINE STRATUS ARE
NOT AS EXTENSIVE AS PREVIOUS DAY. AREAS OF LOW CLOUDS AND FOG
MOVED ONSHORE OVERNIGHT ALONG THE NORTHEASTERN GULF
COAST...ENTERED CROSS SOUND INTO THE MOUTH OF GLACIER BAY AND
SOUTH TO THE BARANOF ISLAND INTO SITKA AREA. SMALL CRAFT LEVEL
WEST TO NORTHWEST WINDS PREVAIL OVER ICY STRAIT AND SOUTHERN
OUTSIDE WATERS. OVERNIGHT TEMPERATURES RANGE FROM THE LOWER TO MID
50S OVER THE NORTHERN PANHANDLE TO THE LOWER TO 60S ACROSS THE
SOUTHERN ZONES.

MODELS REMAIN IN GENERAL AGREEMENT FOR THE RIDGE OF HIGH PRESSURE
CONTINUES TO WEAKEN AND MOVES SOUTHWARD THROUGH LATE TONIGHT. THE
WEAKENING INVERTED TROUGH OF LOW PRESSURE OVER THE SOUTHERN
PANHANDLE WILL DISSIPATE BY EARLY THIS AFTERNOON. THE LOW IN THE
BERING SEA WILL CONTINUE TO PUSH RAIN BANDS INTO THE EASTERN GULF
THIS AFTERNOON THEN OVER THE NORTHEASTERN GULF COAST BY LATE
TONIGHT. REFRESHED THE INHERITED FORECAST WITH THE ECMWF AND GEM
GLOBAL FOR THEIR GOOD CONSENSUS FOR PRESSURE AND WIND FIELDS. USED
ENSEMBLE APPROACH FOR POPS AND QPF FIELDS FOR THE RAIN BANDS
MOVING OVER YAKUTAT AREA THIS AFTERNOON...THEN SPREAD EAST TO
SOUTHEAST TO THE NORTHERN PANHANDLE.

DUE TO THE DISTANT PARENT LOW IN THE BERING SEA...THE RAIN BANDS
WILL LIKELY TO DISORGANIZE AS THEY MOVE ONSHORE OVER THE NORTHERN
PANHANDLE. DAYTIME HIGH WILL BE LESS WARM THAN YESTERDAY DUE TO
INCREASING CLOUDS AND A COOLING TREND ALOFT WITH INCOMING RAIN
BANDS...EXPECTING MOSTLY IN THE MID TO UPPER 60S ALONG THE COASTAL
SECTIONS TO THE MID 70S INLAND LOCATIONS. HYDER WILL BE THE
WARMEST TO THE MID TO UPPER 80S. THE SMALL CRAFT LEVEL WINDS
ACROSS THE SOUTHERN OUTSIDE WATERS AND CLARENCE STRAIT WILL
DIMINISH LATE THIS MORNING OR EARLY IN THE AFTERNOON. SOUTHERLY
PRESSURE GRADIENT WILL BECOME TIGHT ENOUGH TO PRODUCE SMALL CRAFT
LEVEL WINDS OVER NORTHERN LYNN CANAL BY MID MORNING AND CONTINUE
THROUGH TONIGHT. OVERNIGHT TEMPERATURES WILL BE MOSTLY IN THE
50S...EXCEPT AROUND 60 FOR HYDER AREA.

.LONG TERM...WEDNESDAY WILL MARK THE CONTINUATION OF THE BREAKDOWN OF
THE UPPER RIDGE AND A GRADUAL CHANGE IN THE WEATHER PATTERN TO
COOLER/MORE MOIST FOR THE REST OF THE WEEK AND WEEKEND. 850 MB
FLOW WILL BE WEAK ONSHORE...A BIT STRONGER ON THE SOUTHERN
PANHANDLE SIDE WED. LOW- AND MID-LEVEL FLOW REMAINS WEAK BUT
MOSTLY ONSHORE FOR THE REST OF THE WEEK. WEDNESDAY WILL BE A
MOSTLY CLOUDY DAY FOR THE PANHANDLE WITH AREAS OF LIGHT RAIN OVER
ALL BUT THE EXTREME SOUTH WITH A BIT MORE SIGNIFICANT RAIN
POSSIBLE FOR YAKUTAT AND EAST-CENTRAL PORTIONS OF THE PANHANDLE
WED PM. DO NOT HAVE ENOUGH CONFIDENCE TO INCREASE POPS FOR THE
REST OF THE FORECAST AREA...IE. SOME AREAS WILL LIKELY ESCAPE
MEASURABLE RAIN THROUGH THIS FIRST WAVE OF MOISTURE. WINDS WILL BE
GENERALLY LIGHT THROUGH THE REGION THROUGH THE REST OF THE WEEK
WITH 20KTS OF FLOW ONLY AFFECTING EXTREME SOUTHERN AREAS ON
WEDNESDAY AND OCCASIONALLY IN NORTHERN LYNN CANAL WED THROUGH
FRI...WITH DIURNAL ACCELERATIONS CONTINUING OVER THE CAPE DECISION
AREA LATE ON WED AND THU. THURSDAY AND FRIDAY LOOK TO HAVE A BREAK
FROM RAIN CHANCES IN GENERAL BUT WITH MOSTLY CLOUDY SKIES...THEN
WENT WITH A CHANCE OF RAIN FOR MOST AREAS FROM SATURDAY ONWARDS.
GUIDANCE INDICATES NO ORGANIZED FRONTS/WAVES THROUGH SATURDAY AND
LOW QPF...THUS DID NOT HAVE ENOUGH CONFIDENCE TO CHANGE THE
"CHANCE" POP APPROACH CURRENTLY ENTRENCHED FOR THE PERIOD.

STRONGER SYSTEMS APPEAR LIKELY TO WAIT UNTIL AT LEAST LATE WEEKEND TO
TAKE AIM AT THE PANHANDLE....ALTHOUGH GFS/EC DETERMINISTIC RUN
DIVERGENCE SETS IN BY MONDAY. BEST GUESS IS THAT BY EARLY NEXT
WEEK AT THIS POINT THE FRONTS COMING OUT OF THE GULF WILL BE
STRENGTHENED BY JET ENERGY ENTERING THE WESTERN GULF IN
EARNEST...MORE ORGANIZED FRONTS/WAVES ARE LIKELY IN STORE FOR
EARLY WEEK WITH INCREASED WINDS. DETAILS...ON SUNDAY PM THE GFS
BECOMES MORE ROBUST WITH THE POTENTIAL FOR HIGHER RAIN AMOUNTS
OVER THE PANHANDLE. MEANWHILE THE EC CONTINUES TO SPLIT THE FLOW
WITH THE SOUTHEASTERN GULF CLOSED LOW FURTHER SOUTH...SOUTH OF
HAIDA GWAII...BUT WITH A WAVE/FRONT INFRINGING ON THE PANHANDLE
WITHIN WEAK BUT CYCLONIC FLOW ALOFT. BOTH MODELS AGREE ON
SIGNIFICANT WAVE ENERGY ENTERING THE WESTERN GULF AT THIS TIME.
THE GEM APPEARS TO BE THE OUTLIER ON SUNDAY PLACING THE LONGWAVE
BERING TROUGH FURTHER WEST AND A CLOSED LOW OVER THE NORTHERN GULF
AND A RAIN/SHOWER SCENARIO FOR THE PANHANDLE ON THAT DAY. BY
MONDAY THE OVERALL SIGNAL IN THE GFS AND EC UPDATES IS FOR
SIGNIFICANT RAINS RETURNING TO THE PANHANDLE FORCED BY FRONTAL
DYNAMICS AND TERRAIN FORCING.

WENT WITH INHERITED DYNAMIC GRIDS (WITH LOCAL WIND TWEAKS) FOR WED-FRI
ALONG WITH BLENDING THE NEW EC/GFS RUNS WITH INHERITED THERMODYNAMIC
GRIDS. FOR SATURDAY-SUNDAY EVENING PERIOD, BLENDED THE FIELDS DERIVED
FROM WPC GUIDANCE WITH THE NEW EC 00Z GRIDS. THEN MIGRATED ON TO
EXISTING WPC GUIDANCE FOR REMAINDER OF EXTENDED PERIOD. TWEAKED
TEMPERATURES THROUGHOUT UTILIZING MOS GUIDANCE. OVERALL UPDATES
WERE MINOR AND MODEL CONFIDENCE WAS ABOVE AVERAGE THROUGH THE
WEEKEND.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-021-036-041-042.

&&

$$

AHN/WESLEY

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