Small Craft Advisory 324, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
354 PM AKDT MON MAY 14 2012

.SHORT TERM...1012 MB LOW 120 NM S OF PAMD SHOWS A OCFNT OF AT
LEAST TWO WRAPS THAT WILL REACH ITS GREATEST DEPTH OF ABOUT
1010 MB OVERNIGHT WHILE TRACKING ESE TOWARD PASI. THE NEAR-CORE
CONDITIONS INCLUDE ENOUGH BAROCLINICITY TO PERMIT THE ADDITIONAL
DEEPENING AS WELL AS GIVING GALE FORCE WINDS TO THE OFFSHORE
TONIGHT BEFORE THE CYCLONE EVOLUTION INCLUDES WEAKENING. THE COLD
AMS NEAR THE CORE ALSO HAS THICKNESSES AND 850 MB TEMPS LOW ENOUGH
TO HAVE SNOW MIXED INTO THE PRECIP TO SEA LEVEL FOR MOST LOCATIONS
NW OF A PASI-PAJN LN TONIGHT.

MOST IMPORTANT CHANGES TO SHORT-RANCE FORECASTS: FIRST IS FOR
WINDS 5-10 KT HIGHER INC SCA ADDED TO MOST MARINE ZONES IN INNER
CHANNELS FOR TUE. SECOND IS THE SNOW AT LEAST MIXED IN FOR SEVERAL
ZONES, ALBEIT THE ACCUMULATIONS WILL BE ONE INCH OR LESS NEAR SEA
LEVEL.

WARM BIAS 1000-975 MB WAS SHOWN ON GFS AND NAM BUFR SOUNDINGS
WHEN COMPARED TO THE ACTUAL RAOB. (NO MDCARS SINCE 02Z LAST
EVENING). INITIALIZATIONS OF SEVERAL FIELDS FAVORED THE EC.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...THE AFOREMENTIONED
LOW PRESSURE WILL HAVE WEAKENED BY TUESDAY NIGHT...HOWEVER THE
UPPER LEVEL LOW WILL STILL AFFECT WEATHER LOCALLY. A VORT MAX WILL
WRAP AROUND THE UPPER LEVEL LOW CAUSING SHOWERS TO CONTINUE
THROUGH TUES NIGHT INTO WEDNESDAY...TRACKING FROM NORTH TO SOUTH
AS THE LOW MOVES EAST THROUGH B.C. MOST OF THESE SHOWERS WILL BE
SCATTERED TO ISOLATED AND DIMINISHING BY WEDNESDAY NIGHT AS A
DRYER RIDGE OF HIGH PRESSURE BUILDS OVER THE GULF. THIS RIDGE WILL
HOLD IN PLACE THROUGH FRIDAY WITH A NWLY FLOW AT 850MB...HOWEVER A
FEW ISOLATED SHOWERS CANNOT BE RULED OUT WITH DAYTIME CONVECTION
AND ANOTHER UPPER LEVEL WAVE PASSING ON FRIDAY.

SATURDAY SEES A LOW PRESSURE SYSTEM MOVING INTO THE GULF FROM THE
WEST. MODELS DIFFER ON HOW THIS LOW TRACKS ACROSS THE GULF...HOWEVER
BOTH THE GFS AND ECMWF HAVE RAIN WITH THE ASSOC FRONTAL SYSTEM
EVENTUALLY REACHING THE PANHANDLE OVER THE WEEKEND. THE GFS SPLITS THE
LOW INTO TWO CENTERS AND GIVES MORE ENERGY TO THE NEW LOW WHICH IS
FURTHER SOUTH THAN THE ECMWF SOLUTION. THIS WOULD DELAY RAIN MOVING
INLAND UNTIL SUNDAY NIGHT WHILE THE ECMWF SOLUTION WOULD BRING RAIN
TO THE COAST BY SATURDAY AFTERNOON. THE ECMWF WAS FAVORED SLIGHTLY
MORE TODAY FOR ITS RUN TO RUN CONSISTENCY...HOWEVER MODEL DIFFERENCES
BRING FORECASTER CONFIDENCE DOWN A BIT. HAVE OPTED TO KEEP A
CHANCE OF RAIN FOR THE COASTAL AREAS ON SATURDAY THEN BRING LIKELY
RAIN INTO THE REST OF THE PANHANDLE FOR SUNDAY AND MONDAY.

PARTLY CLOUDY SKIES AND SUNSHINE ARE IN THE FORECAST MID WEEK WITH
THE RIDGE IN THE GULF. AS A RESULT HAVE TEMPERATURES INCREASING
SLIGHTLY EACH DAY AND GETTING BACK INTO THE UPPER 50S TO NEAR 60F BY
THE WEEKEND. PARTLY/MOSTLY CLEAR SKIES DURING OVERNIGHT PERIODS
HOWEVER WILL KEEP MINIMUM TEMPERATURES IN THE 30S. WINDS DURING THIS
TIME ARE EXPECTED TO BE FAIRLY LIGHT...SO THERE COULD BE SOME
FOG/FROST ISSUES DURING EARLY MORNING HOURS IN THE COOLER NORTHERN
VALLEYS.

OVERALL CHANGES TO THE GOING FORECAST WERE MINOR AS THINGS LOOKED ON
TRACK. MADE SOME SLIGHT TWEAKS IN WIND DIRECTIONS TO MATCH UP WITH
PRESSURE GRADIENTS...HOWEVER THESE COULD EASILY FLIP IN THE OTHER
DIRECTION AS WINDS ARE GENERALLY LIGHT. AFTERNOON SEA BREEZES
WILL ALSO PLAY A ROLE IN WIND SHIFTS ON THE DAYS WITH MORE
SUNSHINE.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-022-032>035-042-043-051-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041.

&&

JBT/HANNON