Small Craft Advisory 200, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
238 PM AKDT SUN MAR 11 2012

.SHORT TERM...A BROAD AREA OF LOW PRESSURE OVER THE EASTERN GULF
AND SOUTHEAST ALASKA REMAINS IN PLACE THROUGH THE SHORT TERM
FORECAST PERIOD. MULTIPLE WEAK LOW LEVEL CIRCULATIONS ARE VISIBLE
IN SATELLITE IMAGERY WITH THE MOST SIGNIFICANT CIRCULATION
IMMEDIATELY OFF THE COAST JUST SOUTH OF SITKA, WHICH WILL BE
RESPONSIBLE FOR SMALL CRAFT WINDS OVER THE CENTRAL OUTER COAST
THROUGH LATE EVENING. UPPER LEVEL SUPPORT FOR THIS LOW IS NOT
OVERLY STRONG, BUT IT HAS BEEN ENOUGH TO SUPPORT STEADY SHOWER
ACTIVITY THROUGH THE DAY OVER THE SOUTHERN PANHANDLE. TRAINING
SHOWERS HAVE PRODUCED AS MUCH AS 2 INCHES OF SNOW OVER PORTIONS
OF ZONE 28 NEAR KETCHIKAN TODAY. FARTHER NORTH OVER ZONE 26,
TEMPERATURES HAVE BEEN WARMER AND PRECIP HAS BEEN MOSTLY LIQUID.
DECIDED NOT TO ISSUE A WINTER WEATHER ADVISORY FOR THE SOUTHERN
ZONES, BUT DID INCLUDE UP TO 2 INCHES FOR TONIGHT.

 VERY COLD AIR IS ALSO EVIDENT IN SATELLITE IMAGERY WITH A LARGE
AREA OF OPEN CELL CUMULUS THE FLOWS SOUTHEAST OFF THE ALASKA
PENINSULA, THEN EAST ACROSS THE SOUTHERN GULF, THEN NORTHEAST AS
IT BECOMES ENTRAINED IN THE SURFACE FLOW ASSOCIATED WITH THE LOW
NEAR SITKA. BELIEVE THIS WILL PRODUCE OVERNIGHT LOWS ACROSS THE
PANHANDLE THAT WILL BE ABOUT 5 DEGREES COLDER TONIGHT THAN LAST
NIGHT. BELIEVE THIS COLDER AIR HAS ALREADY ARRIVED OVER THE
SOUTHWESTERN PANHANDLE, AS EVIDENCED BY THE DROP IN ASOS
TEMPERATURES EARLY THIS AFTERNOON AT KLAWOCK. HAVE SOME BREAKS IN
THE CLOUD COVER SHOWING UP THIS AFTERNOON AND WENT WITH MOSTLY
CLOUDY IN THE SKY GRIDS OVER MUCH OF THE SOUTHERN PANHANDLE.
THESE BREAKS WILL ALSO AIDE IN COOLING TEMPS DOWN TONIGHT.

 A RIDGE OF HIGH PRESSURE WILL PRESS SOUTH FROM THE INTERIOR AND
YUKON TOMORROW AS A LOW APPROACHES THE PANHANDLE FROM THE SOUTH.
RESULTANT OFFSHORE FLOW OVER THE CENTRAL PANHANDLE WILL PRODUCE
SOME CLEARING TOMORROW. HAVE PARTLY TO MOSTLY CLOUDY SKIES FOR
TOMORROW, BUT DO NOT EXPECT SIGNIFICANT WARMING DUE TO THE LOW
LEVEL COLDER AIR MOVING IN PLACE TONIGHT. TO THE NORTH, NORTHERLY
WINDS WILL INCREASE TOMORROW. HAVE SOME GUSTY IN SKAGWAY TOMORROW
WITH A SMALL CRAFT ADVISORY FOR NORTHERN LYNN. TO THE SOUTH, HAVE
A SMALL CRAFT ADVISORY FOR CLARENCE STRAIT AND COASTAL MARINE
ZONE 41 LATE IN THE DAY.

 MINOR CHANGES TO EXISTING GRIDS APART FROM ADDING MORE SNOW TO
ZONES 27 AND 28. FORECAST CONFIDENCE IS AVERAGE.

.LONG TERM...UPPER TROF WILL REMAIN OVER THE GULF AND ERN PAC
INTO NEXT WEEKEND. TROF WILL HAVE A NEGATIVE TILT MUCH OF THIS
TIME WITH THE MOST NEGATIVE TILT LATER IN THE WEEK. THIS WILL
GENERALLY MEAN SYSTEMS WILL BE WEAKENING AS THEY MOVE INTO THE
AREA FROM THE S OR SE. MODELS STILL HAVING ISSUES WITH TIMING
SYSTEMS INTO THE AREA ESPECIALLY LATER ON. ENDED UP USING THE 12Z
EC FROM 06Z TUE TO 06Z WED...THEN THE REMAINING PERIOD AS LEFT
MOSTLY AS IS.

 MAIN FACTOR IN THE CHANGES EARLY ON WAS MODELS SPEEDING UP
TIMING OF LOW MOVING IN FROM THE S MON NIGHT. THIS LOW WILL BE
FAIRLY STRONG WELL S OF THE AREA BUT WILL BE WEAKENING RAPIDLY AS
IT MOVES INTO THE SRN AREA MON NIGHT. THIS WILL BRING IN PRECIP
FASTER THAN PREVIOUSLY FORECASTED TO THE S. RAISED POPS UP TO
LIKELY FOR THE SRN INNER CHANNELS LATER MON NIGHT INTO TUE.
CLOUDS WILL INCREASE A BIT MORE QUICKLY OVER THE NRN AREA TUE
THAN PREVIOUSLY FORECASTED AS LEFTOVERS OF LOW MOVE BY ALONG THE
OUTER  COAST AND FLOW TURNS MORE SLY. NUDGED TEMPS UP A FEW
DEGREES OVER THE S MON NIGHT DUE TO CLOUDS MOVING BACK IN FASTER.

 BEYOND 12Z WED...ONLY SIGNIFICANT CHANGE WAS TO USE THE PREVIOUS
HPC POPS. THE POPS THAT WERE IN THERE LOOKED TOO MESOSCALE AS FAR
AS COVERAGE GOES GIVEN MODEL UNCERTAINTY ON SYSTEM TIMING INTO
THE AREA. DID LIMIT POPS ON HIGH END TO LIKELY. SNOW LEVEL WAS
TWEAKED TO ACCOUNT FOR ANY TEMPS OF 32 OR LESS...LOWERING THOSE
AREAS TO ZERO.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ012-036-041-043-052.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ042-051.

&&

FRITSCH/RWT