Weather Service Report


475 
FXAK67 PAJK 161352
AFDAJK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
552 AM AKDT WED APR 16 2014

.SHORT TERM...THERE HAS BEEN LITTLE CHANGE IN THE GOVERNING
WEATHER PATTERN OVER SEAK THE PAST 24 HRS. AN ELONGATED UPPER
LEVEL TROUGH EXTENDS FROM THE CENTRAL PANHANDLE WEST TO A LOW
CENTER OVER THE CENTRAL GULF. SATELLITE AND RADAR IMAGERY SHOWS 
MOISTURE AT VARIOUS LEVELS STREAMING INTO THE SRN PANHANDLE THEN
CURVING NW AROUND THE UPPER TROUGH. WIDELY SCATTERED LIGHT RAIN
WAS OBSERVED OVERNIGHT FARTHER NORTH THAN IT WAS ON TUES
INCLUDING ANGOON...JUNEAU...HAINES...SKAGWAY...AND YAKUTAT. THE
SOUTHERN PANHANDLE WAS TRENDING TO DRIER WEATHER AND DECREASING
CLOUDS THIS MORNING. 

 THAT TREND WILL BE SHORT LIVED AS AN AREA OF LOW PRESSURE
CURRENTLY LOCATED AT 52N 140W CONTINUES TO SHOW SIGNS OF
STRENGTHENING. WATER VAPOR SATELLITE IMAGERY SHOWS A DRY SLOT
PUNCHING INTO THE SW SIDE OF THIS SYSTEM IN THE VICINITY OF
ACCELERATING WINDS ALOFT. ALL MODELS DEEPEN THE SURFACE LOW
CENTER TO A GALE FORCE 990 MB LOW BY THUR MORNING. THERE IS SOME
VARIATION ON THE EXACT TRACK OF THE SYSTEM BUT IT LOOKS SAFE TO
SAY IT WILL BE CENTERED OFF THE SRN OR CENTRAL PANHANDLE COAST
THU MORNING. THE MODEL CONSENSUS IN THE SHORT TERM IS TO MOVE THE
LOW CENTER EAST OF 130W. THIS PROXIMITY TO THE COAST TOGETHER WITH
INCREASING PRESSURE GRADIENT AROUND THE LOW CENTER CONVINCED ME
TO BUMP UP THE SURFACE WINDS SLIGHTLY WED NIGHT FROM ROUGHLY
DIXON ENTRANCE TO CAPE DECISION...INCLUDING CLARENCE STRAIT. GALE
WARNINGS AND STRONG WIND HEADLINES WERE ADDED TO THE SOUTHWESTERN
PANHANDLE ZONES. 

 THE BULK OF THE HEAVY WEATHER ASSOCIATED WITH THIS SYSTEM WILL
AFFECT THE SOUTHERN HALF OF THE PANHANDLE THROUGH THUR MORNING.
IN ADDITION TO WINDY WEATHER...RAINFALL AMOUNTS WILL BE ONE HALF
TO ONE INCH BY THUR MORNING AND CONTINUE THURS AS THE RAIN SHIELD
SPREADS NORTHWARD. 

 CONSENSUS OF THE NAM AND HI RESOLUTION WRF MODEL SUPPORTED THE
EXISTING GRID FORECASTS. ONLY SLIGHT ADJUSTMENTS WERE MADE TO THE
WIND AS MENTIONED ABOVE. FORECAST CONFIDENCE IN THE APPROACHING
LOW...IN PARTICULAR WIND SPEEDS AND RAINFALL AMOUNTS...IS AVE. 

 && 

 .LONG TERM...ACTIVE WEATHER PATTERN THROUGH THE WEEKEND WITH A
SECOND STRONGER LOW PRESSURE SYSTEM MOVING INTO THE AK GULF AFTER
REMNANTS OF THE WEDNESDAY NIGHT LOW TRACK NORTHWARD INTO THE
YUKON. SPREAD WITH SURFACE DETAILS AMONG THE VARIOUS MODELS
CONTINUES HOWEVER MANY MODELS ARE NOW SHOWING GOOD RUN TO RUN
CONSISTENCY.  

 THE WEDNESDAY NIGHT LOW WILL WEAKEN TO AN OPEN WAVE TROUGH
THROUGH THURSDAY WITH A SECONDARY WRAP HITTING THE SOUTHERN
PANHANDLE FOR ANOTHER ROUND OF GUSTY WINDS. WINDS WILL DROP OFF
THROUGH THE DAY AS THE LOW MOVES NORTHWARD. PRECIP WILL MOVE
NORTHWARD ALONG WITH THE TRACKING LOW AND WILL MOSTLY SWITCH TO
SHOWERS WHILE WINDS SHIFT TO THE SOUTH THURSDAY NIGHT INTO FRIDAY
AS A HIGH PRESSURE RIDGE BUILDS OVER THE PANHANDLE. 

 THE NEXT LOW CURRENTLY DEVELOPING IN THE CENTRAL PACIFIC WILL
DEEPEN AS IT TRACKS EASTWARD. COUPLED WITH A 130 KT JET STREAM BY
FRIDAY NIGHT THE FAST MOVING LOW CENTER WILL DEEPEN TO AROUND
976 MB AS IT REACHES 50N/140W. CURRENT MODEL DEPICTIONS HAVE THE
LOW MOVING INTO THE SOUTHERN AK GULF WITH THE CENTER ROTATING
COUNTER CLOCKWISE WHILE WEAKENING AND EVENTUALLY EXITING THE AREA
TO THE SOUTHEAST. WINDS WILL SHIFT TO THE NORTH AS THE GRADIENT
FLIPS. EXPECTING STRONGER WINDS WITH THE WEEKEND SYSTEM WITH
850 MB WINDS IN THE 50 TO 60 KT RANGE. STILL SOME UNCERTAINTY
WITH THE POSITION OF THE LOW CENTER DUE TO THE MODEL SPREAD. 

 MEANWHILE ANOTHER LOW IS MOVING TOWARD THE WESTERN TIP OF THE
ALEUTIANS, THE AN ASSOCIATED FRONT MOVING INTO THE WESTERN GULF
WITH DEVELOPING WAVES. HIGH UNCERTAINTY AT THIS TIME WITH THIS
NEXT FEATURE.  

 KEPT WITH THE EC/NAM SOLUTION THROUGH 84 HOURS WITH LITTLE
CHANGE AS A BLEND OF THE NEW MODELS MATCHED UP WELL WITH THE
PREVIOUS FORECAST. MAIN CHANGE WAS FOR LATE SATURDAY INTO SUNDAY
WHERE 00Z ECMWF/GFS WERE IN GOOD AGREEMENT AND MOVES THE LOW
FURTHER TO THE SOUTH AND WEST. LEFT WPC GRIDS THE REMAINDER OF
THE FORECAST PACKAGE DUE TO HIGHER UNCERTAINTY AND SPREAD WITH
THE OPERATIONAL MODELS. FORECAST CONFIDENCE IS ABOVE AVERAGE FOR
OVERALL SYNOPTIC PATTERN BUT STILL BELOW AVERAGE FOR EXACT
DETAILS. 

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...STRONG WIND THIS EVENING FOR AKZ027.
         STRONG WIND FROM THIS EVENING THROUGH LATE TONIGHT FOR AKZ023.
MARINE...GALE WARNING FOR PKZ036-041-042. 
         SMALL CRAFT ADVISORY FOR PKZ021-022-033-035-043-051-052. 

&&

$$

TA/PRB




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