Area Forecast Discussion
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FXAK67 PAJK 061345
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
545 AM AKDT MON JUL 6 2015

.SHORT TERM...EARLY MORNING SATELLITE IMAGE SHOWS A PERSISTING
RIDGE OF HIGH PRESSURE OVER THE CENTRAL AND EASTERN GULF WITH AN
INVERTED TROUGH OF LOW PRESSURE EXTENDING NORTHWESTWARD FROM
VANCOUVER ISLAND TO THE SOUTHERN PANHANDLE. MARINE STRATUS MAINLY
REMAINS OFFSHORE OVER THE SOUTHERN OUTER WATERS...BUT MOVES
NEARSHORE FROM CAPE EDGECUMBE NORTHWEST TO THE NORTHERN GULF
COAST WITH AREAS OF FOG. NORTHWESTERLY SMALL CRAFT LEVEL WINDS
CONTINUE ACROSS THE CENTRAL AND SOUTHERN OUTSIDE WATERS. OVERNIGHT
TEMPERATURES RANGE FROM THE UPPER 40S TO THE MID 50S OVER THE
NORTHERN AND CENTRAL PANHANDLE TO THE LOWER TO MID 60S ACROSS THE
SOUTHERN AREAS.

MODELS REMAIN IN GENERAL AGREEMENT WITH THE RIDGE OF HIGH
PRESSURE REMAINS OVER THE EASTERN GULF AND THE INVERTED TROUGH OF
LOW PRESSURE OVER THE SOUTHERN PANHANDLE THROUGH TONIGHT.
REFRESHED THE INHERITED PRESSURE AND WIND FIELDS WITH THE ECMWF
AND GEM GLOBAL FOR THEIR GOOD CONSENSUS ON HANDLING THE INVERTED
TROUGH. USED AN ENSEMBLE APPROACH FOR POPS AND QPF FIELDS FOR RAIN
BANDS MOVING NORTH ACROSS THE OFFSHORE WATERS.

MOSTLY CLEAR SKIES AND WARM WEATHER WILL CONTINUE AND TEMPERATURES
MAY SOAR UP TO BRING RECORD BREAKING DAYTIME HIGHS ON SOME LOCATIONS.
THE MARINE STRATUS WILL RETURN ONSHORE LATE TONIGHT ALONG THE
PANHANDLE COAST FROM YAKUTAT BAY SOUTHEAST TO BARANOF ISLAND WITH
AREAS OF LOW CLOUDS AND FOG...POSSIBLY EXTEND INTO CROSS SOUND TO
THE MOUTH OF GLACIER BAY. DUE TO TIGHTENED PRESSURE GRADIENT
BETWEEN THE HIGH PRESSURE AND INVERTED TROUGH...SMALL CRAFT LEVEL
WINDS WILL REMAIN OVER THE SOUTHERN TWO OUTSIDE MARINE ZONES
THROUGH TONIGHT...INCLUDING SOUTHERN CHATHAM STRAIT. WEST TO
SOUTHWEST WINDS WILL BE ENHANCED OVER CROSS SOUND AS WELL LATE
THIS AFTERNOON AND EARLY EVENING HOURS. WITH A LOW
CONFIDENCE...DUE TO THE INVERTED TROUGH TO THE SOUTH...EXPECT
INCREASING NORTHEAST WIND UP TO 20 MPH WITH OCCASIONAL HIGHER
GUSTS TO 30 MPH FOR DOWNTOWN JUNEAU AND DOUGLAS THIS AFTERNOON.

.LONG TERM...TUES MORNING SHOULD BEGIN WITH WIDESPREAD MARINE
STRATUS AND FOG POSSIBLY EDGING WELL INTO CROSS SOUND...THOUGH NOT
COMPLETELY CONFIDENT AS THIS WILL DEPEND ON THE EFFECTS OF INCREASING
MID- AND UPPER CLOUDS FROM THE WEST AT THIS TIME AND WHETHER THE
DIURNAL CYCLE WILL BE WEAKENED. IN THE MEANTIME THIS PERIOD WILL
LIKELY CATCH THE TAIL END OF GRADIENT NNW FLOW OVER ZONES 41/42
WITH POTENTIAL OF GREATER THAN 25KTS THROUGH ABOUT NOON AND 20KTS+
OVER THE EXTREME SOUTH OCEAN ENTRANCES. GRADIENT BEGINS TO WEAKEN
BY MIDDAY TUE. DESPITE THE INCREASING CLOUD COVER MUCH ABOVE
AVERAGE HIGH TEMPS WILL CONTINUE OVER THE PANHANDLE WITH 70S
COMMON AND EVEN POTENTIALLY CLOSE TO 90F FOR A HIGH IN HYDER AS
850MB TEMPS GET UP TO 18-19C...SOUTH END OF THE PANHANDLE WILL
CONTINUE WITH PARTLY CLOUDY SKIES AT WORST AND VERY WARM TEMPS.
MODELS IN AGREEMENT WITH INCREASING RAIN CHANCES FOR THE AFTERNOON
IN THE YAKUTAT VICINITY TO LIKELY FOR TUES NIGHT AND THIS SHOULD
SPREAD EAST INTO THE NORTHERN/CENTRAL PANHANDLE LATE ON TUE
NIGHT/WED. LIGHT QPF AMOUNTS ARE EXPECTED WITH THIS FIRST ROUND AS
THERE IS NO ORGANIZED FRONT OR STRONG FORCING ALOFT...JUST A WEAK
WAVE WITH INCREASING MOIST MID- LEVEL SWLY FLOW. THIS WILL MARK
THE BEGINNING OF A COOLING TREND THROUGH THE PANHANDLE THIS WEEK.
AT THIS POINT EXPECT AREAS OF LIGHT RAIN ON WED OVER THE NORTHERN
HALF OF THE PANHANDLE. CHANCES OF RAIN WILL THEN INCREASE OVER THE
SOUTHERN PANHANDLE ON WEDNESDAY NIGHT AS THE WAVE PROCEEDS
EASTWARD. SOME AREAS MAY GET MISSED ENTIRELY...HENCE STAYED AWAY
FROM THE LIKELY RAIN CATEGORY FOR THE MOST PART ON WED.

AT THIS POINT EXPECT A BREAK IN MOST OF THE RAIN ACTIVITY ON
THURS BUT CLOUDINESS AND COOLER TEMPS WILL CONTINUE...WEAK
SHORTWAVE RIDGING ALOFT IS PROGGED. FRIDAY LOOKS MOSTLY DRY AT
THIS POINT AND THEN RAIN CHANCES INCREASE AGAIN ON SAT/SUN
PANHANDLE-WIDE AS TEMPS ALOFT CONTINUE TO COOL AND WEAK CYCLONIC
FLOW PREVAILS...STILL NO ORGANIZED/STRONG FORCING BUT THE MOISTURE
IS THERE AND DETAILS SHOULD GET HAMMERED OUT IN THE NEXT FEW DAYS.
MODEL AGREEMENT IS GENERALLY GOOD THROUGH FRIDAY WITH THIS
SCENARIO BUT BEGINNING SAT SOME DIFFERENCES ARE EVIDENT WITH THE
GEM SHOWING A CLOSED LOW WEST OF HAIDA GWAII WHILE THE EC/GFS HAVE
A WEAKER CUTOFF SOUTH OF THE GEM POSITION. ON SUN THE GFS IS MORE
AGGRESSIVE WITH A PHASED GULF UPPER TROUGH ORIENTED NW-SE WHILE
THE EC MAINTAINS THE STRONG BERING UPPER LOW SPLIT AWAY FROM THE
WEAK LOW SOUTH OF HAIDA GWAII WITH RIDGING BETWEEN. THIS IS
FOLLOWED UP WITH PROGRESSION OF THE BERING LOW BEGINNING EARLY
NEXT WEEK...NOT EXPECTING THIS PROGRESSION TO HAPPEN THOUGH AS
THE LONGWAVE PATTERN MAINTAINS THE BERING/ALEUTIAN LOW FROM NOW
THROUGH DAY 7 ON THE EC. WENT WITH AN EC/GFS/INHERITED BLEND ON
THERMODYAMIC FIELDS THROUGH DAY 3 WITH THE INHERITED DYNAMIC
FIELDS. CONTINUED WITH THIS APPROACH ON DAY 4 EXCEPT UPDATED
DYNAMIC FIELDS WITH UPDATED EC/GEM COMBO AND THE T/D GRIDS WITH AN
EC/INHERITED COMBO. THEN MIGRATED TO WPC GUIDANCE AFTER DAY
4...WHICH USED A WHOLESALE ENSEMBLE APPROACH FROM THE 00/06 RUNS
FROM A DAY AGO. GOOD CONFIDENCE ON THROUGH THE WEEKEND WITH THIS
APPROACH AS THE NEW EC DID NOT CONTRADICT ITS LAST 2 RUNS DURING
THIS PERIOD.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ022-033-041-042.

&&

$$

AHN/WESLEY

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