Freeze Warning 1, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
250 PM AKDT SUN MAY 15 2011

.SHORT TERM...MAIN ISSUE IN THE SHORT TERM FORECAST PERIOD WILL
BE ANOTHER COLDER THAN NORMAL NIGHT FOR THE NORTHERN PANHANDLE.
ISSUED FROST ADVISORIES FOR THE NORTHERN HALF, LESS ZONE 22.
BELIEVE THERE IS A VERY GOOD CHANCE OF A HARD FREEZE IN AND
AROUND GUSTAVUS AS WELL AS THE MENDENHALL VALLEY, SO ISSUED A
FREEZE WARNING FOR THESE TWO ZONES. HARD FREEZE CONDITIONS FOR
ZONE 25 WILL BE LIMITED IN SCOPE, ENCOMPASSING PARTS OF THE
MENDENHALL VALLEY AND OTHER ISOLATED, WIND SHELTERED LOCATIONS.
AREAS NEAR THE WATER, SUCH AS DOWNTOWN JUNEAU MAY NOT EVEN GET
DOWN FREEZING, BUT IT WOULD PROBABLY BE BEST TO TAKE TEMPERATURE
SENSITIVE PLANTS INDOORS REGARDLESS.

 AM BEGINNING THE SHORT TERM FORECAST WITH SMALL CRAFT WINDS OVER
THE SOUTHERN COASTAL MARINE ZONES AS WELL AS THE SOUTHERN/WESTERN
PORTIONS OF SOUTHERN CHATHAM STRAIT AND SUMNER STRAIT. THESE
CONDITIONS WILL DIMINISH SLOWLY THROUGH THE NIGHT.
ELSEWHERE...TYPICAL LAND/SEA BREEZES WILL PREVAIL TONIGHT AND
TOMORROW.

 AFTER ANOTHER NIGHT OF CLEAR SKIES AND NORTHWEST WINDS, TOMORROW
SHOULD BRING DECREASING NORTHWESTERLY FLOW ALONG THE OUTER COAST,
INCREASING CLOUDS OVER THE SOUTHERN ZONES, AND SHOWER ACTIVITY
MOVING INTO THE SOUTHEASTERN PORTION OF THE PANHANDLE. FORECAST
CONVECTIVE PARAMETERS AS WELL AS 700 MB OMEGA AND SATURATED
THETA-E SUGGEST A WEAKLY CONVECTIVE ENVIRONMENT IN THE LOWER
LEVELS, SO CHARACTERIZED PRECIP AS SHOWERS. MOST PRECIPITATION
WILL FALL OVER THE HIGHER TERRAIN NEAR THE COAST MOUNTAINS.

 USED NAM FOR PRESSURE AND WIND. UPDATED POP WITH A BLEND OF GFS
AND SREF. FORECAST CONFIDENCE IS ABOVE AVERAGE.

 &&

 .LONG TERM...A RETURN TO WET WEATHER OVER SE ALASKA FOR THE LONG
TERM. MAIN FEATURES: A LOW PRESSURE SYSTEM OF BRITISH COLUMBIA
WITH EXTENDED TROUGH MOVING NORTH OVER THE PANHANDLE THROUGH THE
WEEK. AS THIS TROUGH MOVES NORTH IT WILL BRING INCREASING CLOUDS
AND PRECIP OVER THE COASTAL MOUNTAINS STARTING IN THE
SOUTHEASTERN REGIONS. WEAKENING RIDGE OVER THE AK GULF WILL
CONTINUE TO TRACK EAST. TO THE WEST A 500H LOW WITH ASSOCIATED
SURFACE LOW OVER KODIAK WILL TRACK TO THE EAST INTO THE GULF AS
SURFACE FRONT MOVES INTO THE WESTERN GULF. THIS FIRST WEATHER
FRONT WILL DISSIPATE AS IT TRACKS EAST TUE INTO WED. THIS
FEATURES WILL BE FOLLOWED BY ANOTHER SURFACE LOW. MODELS HAVE
BEEN SHOWING THE FRONT ASSOCIATED WITH THIS LOW SHEARING APART
JUST AS IT HITS THE PANHANDLE COAST THU WITH A MID LEVEL RIDGE
BUILDING OVER THE PANHANDLE. HOWEVER AS MODELS BY THIS TIME ARE
NOT IN GOOD AGREEMENT HAVE KEPT CHANCE PRECIP FOR THE PANHANDLE.

 WINDS OVER THE PANHANDLE GENERALLY AT OR BELOW 15 KT. HOWEVER
MAY SEE SMALL CRAFT WINDS OVER NORTHERN LYNN CANAL WITH
INCREASING PRESSURE GRADIENT WAS HIGH PRESSURE RIDGE MOVES EAST
OVER THE AREA. AK GULF AND COASTAL WATERS WILL SEE INCREASE WINDS
AND SEA HEIGHTS WITH EAST FRONTAL BAND AS THEY TRACK EAST THROUGH
THE WEEK.

 MODELS BEGAN IN FAIR AGREEMENT AND EACH INITIALIZED WELL. RUN TO
RUN CONSISTENCY HOWEVER HAS NOT BEEN GREAT. GFS ESPECIALLY
SHOWING LARGE CHANGES IN POSITION OF GULF LOWS. WHILE EC IS
BETTER BY COMPARISON AND IS HANDLING POSITION OF LOW A BIT
BETTER. DID FEEL AN ENSEMBLE SOLUTION BY MID WEEK WAS THIS WAY TO
GO. UPDATED GRIDS TO DAY 4 USING A BLEND OF INHERITED GRIDS AND
00Z ECMWF FOR PRESSURE AND WINDS. POP WAS UPDATED WITH A BLEND OF
SREF, ECMWF AND SOME NAM. FOR THE REMAINDER USED UPDATED HPC
GRIDS TO BLEND WITH INHERITED FORECAST. OVERALL ONLY MINIMAL
CHANGES. FORECAST CONFIDENCE IS ABOUT AVERAGE WITH SOME INCREASED
UNCERTAINTY THROUGH THE WEEK.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...HARD FREEZE WARNING FROM 10 PM THIS EVENING TO 7 AM AKDT MONDAY
     FOR AKZ020-025.
         FROST ADVISORY FROM 10 PM THIS EVENING TO 7 AM AKDT MONDAY FOR
     AKZ017>019-021.
MARINE...SMALL CRAFT ADVISORY FOR PKZ033-035-036-041-042.

&&

FRITSCH/PRB