Small Craft Advisory 178, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
230 PM AKST SUN FEB 20 2011

.SHORT RANGE...
WEAKER ARCTIC HIGH OF ABOUT 1022 MB NEAR PAOH 14Z WILL BE FOLLWED BY
A MUCH STRONGER ARCTIC HIGH DVLPG FM THE NW MON.  WHAT SEPARATES THE
WEAK ARCTIC OUTFLOW FROM THE STRONGER OUTFLOW IS TROUGHS ALOFT AND
AN ASSOCIATED WEAK BARCLINIC WAVE TRACKING SE ALONG THE PNHDL
TONIGHT AND MONDAY MORNING. THE WAVE WILL EXIT ESE ACRS CZST BTWN
18Z MON AND 00Z TUE, AND AS IT IS EXITING WILL LEAVE AN INVERTED
TROUGH ALONG THE PNHDL THAT IN TURN WILL AID THE STRONGER ARCTIC
OUTBREAK DISCUSSED IN THE LONG RANG SXN BLO.

THE MODEL CONSENSUS IS GOOD.  (THE MAIN ISSUES FOR THE SHORT
RANGE OUR AOR IS THE LOW TRACKING SE ALONG THE PANHANDLE TONIGHT).
NAM 2012 WAS FITTED IN FOR PRES/WIND FIELDS FOR 12Z MON TO 00Z TUE.
WS WRF USED FOR SOME ADJUSTMENTS TO WIND DIRECTIONS IN INNER
CHANNELS A BLEND OF NMRS MODELS WAS USED FOR POPS AS THE OVERALL
CONSENSUS WAS GOOD.   NAM12 HAS HAD THE STRONGEST WINDS FOR THE
OUTER COAST FM POW ISLAND TO PASI, AND THE VALUES USED WERE BETWEEN
THE NAM AND THE CLUSTER OF THE OTHER MODEL SOLUTIONS.
&&

.LONG TERM...
COMING INTO DRY CLEAR WINDY AND COLD. STRONG SURFACE HIGH CELL WILL
DEFINITELY BUILD OVER THE YUKON BY 12Z TUE. USED 20/12Z AK-GFS-40
FROM 00Z TUE TO 00Z THU...LIKED THE STRONGER HIGH CELL.

ALL 20/12Z OPS MODELS AGREE THAT THE FLOW ALOFT OVER THE
PANHANDLE WILL BE WNW AT 00Z TUE WITH ONE LAST SHORTWAVE OVER THE
CENTRAL INTERIOR YET TO COME. BEST ESTIMATE IS THAT THERE WILL BE
HARDLY ANY MOISTURE IN THIS ONE SO WILL KEEP POPS ZERO WITH THIS
LAST GASP WITH MAYBE CIRRUS OVER THE NORTHERN END. THE UPPER
RIDGE AXIS WILL BE FROM THE WESTERN GULF THROUGH THE BERING
STRAIT AND TEMPS AT 500 HPA AROUND -40C OVER THE YUKON WITH VERY
COLD ALOFT OVER SIBERIA WHICH WILL MOVE THE UPPER RIDGE.

BAROCLINIC MODELS OFTEN BREAK DOWN BLOCKS TOO EARLY. PREDICTION
IS THAT WE WILL SEE THE MODEL FORECASTS BACK OFF ON MOVING THE
UPPER RIDGE TOO FAR EAST BEYOND FRI. GFS ENSEMBLES POINT TO THE
UPPER RIDGE AXIS OVER 152W BY 12Z THU WHICH AGREES WITH HPC AND
20/12Z ECMWF. BY 12Z FRI EVERYBODY TILTS THE RIDGE OVER THE YUKON
BUT FLOW ALF WILL STILL BE N OVER THE PANHANDLE FOR DRY COLD AND
LOCAL WINDZ. IF WE ACCEPT ECMWF/GFS/GFS ENSEMBLES YOU BRING A
SHORTWAVE FROM THE W SATURDAY THE 26TH. GONNA MAKE SOME POPS FOR
IT BUT WATCH AND SEE. CONFIDENCE HIGH THRU FRI...THEN LOW BEYOND.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMCR PKZ011>013-033-041>043-051-052.
&&