Gale Warning 162, NWS Juneau, AK

SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
353 PM AKDT SAT MAR 22 2014

.SHORT TERM...SHORTWAVE TROUGH THAT BROUGHT LIGHT PRECIPITATION
TO SRN PORTIONS OF THE PANHANDLE FRI NIGHT IS MOVING EWD ACROSS
BC THIS AFTERNOON. MEANWHILE...OFFSHORE FLOW AND A SUBSIDENT
LARGE- SCALE REGIME ARE AIDING IN CLEARING SKIES AND GENERALLY
PLEASANT CONDITIONS ACROSS THE FORECAST AREA. BESIDES THE CLEAR
SKIES...PRIMARY WEATHER STORY DURING THE SHORT-TERM WILL BE
STRONG WINDS IN THE LYNN CANAL AS WELL AS JUNEAU/DOUGLAS. THE
SURFACE PRESSURE GRADIENT BETWEEN SKAGWAY AND JUNEAU IS FORECAST
TO WEAKEN THIS AFTERNOON AND EVENING...AND THEN RESTRENGTHEN SUN
MORNING. THUS...EXPECT SMALL CRAFT TO NEAR GALE FORCE WINDS TO
PERSIST DURING THE NEXT 30 HRS OVER THE LYNN CANAL. IN
ADDITION...MODEST CROSS BARRIER FLOW WILL CONTINUE ACROSS THE
SALISBURY RIDGE THROUGH SUN EVENING. THESE WINDS COMBINED WITH
THE DEVELOPMENT OF A NOCTURNAL INVERSION SUN MORNING AND AGAIN
SUN EVENING WILL SUPPORT OCCASIONALLY GUSTY CONDITIONS FOR
DOWNTOWN JUNEAU AND DOUGLAS.

 FORECAST CONFIDENCE THROUGH SUN NIGHT IS ABOVE AVERAGE. MINOR
CHANGES TO THE PREVIOUS FORECAST WERE MADE USING A GFS/ECMWF
BLEND.

.LONG TERM...SUNNY DAYS AND CLEAR COOL NIGHT FOR THE NORTHERN AND
CENTRAL PANHANDLE. PRECIPITATION POTENTIAL CONFINED TO SOUTHERN
PANHANDLE. POTENTIALLY STRONG OUTFLOW WIND EVENT FOR JUNEAU AND
DOUGLAS MONDAY NIGHT INTO TUESDAY.

 GENERAL SYNOPTIC PATTERN FEATURES A YUKON HIGH AND A NORTH
PACIFIC LOW. THE COMBINED SYSTEMS WILL DRIVE NORTHEASTERLY OUTFLOW
WIND ACROSS THE PANHANDLE. THIS WILL BRING IN COOLER AND DRIER
CONTINENTAL AIRMASS OVER THE PANHANDLE. THUS GIVING NORTHERN
PANHANDLE MINIMAL SKY COVER. FOR SOUTHERN AREAS, THERE WILL BE
CLOUD COVER AND PRECIPITATION POTENTIAL FROM THE LOW PRESSURE
SYSTEM THAT WILL BE HEADING TOWARDS THE PANHANDLE. HOWEVER, THE
CONTINENTAL AIRMASS WILL BE STRONG ENOUGH TO PREVENT THE LOW FROM
INTRUDING THE PANHANDLE.

 THIS WEATHER PATTERN IS VERY SLOW-MOVING AND VERY BLOCKY. THERE
IS A REX BLOCK OVER ALASKA/NORTH PACIFIC REGION. BESIDES, THERE
ARE THREE OMEGA BLOCKS WITH CENTER OF ACTIONS OVER EAST ASIA,
INTERNATIONAL DATELINE, AND THE WEST COAST OF NORTH AMERICA. THIS
IS A HIGHLY BLOCKY SITUATION, AND THIS BLOCK IS UNLIKELY TO
BREAKDOWN FOR THE NEXT WEEK. THUS, SOUTHEAST ALASKA WILL
EXPERIENCE AN ELONGATED PERIOD OF COOL, DRY, AND BREEZY WEATHER.

 WITH CLEAR SKIES AND CALM WIND OVERNIGHT, TEMPERATURES WILL DROP
INTO THE TEENS FOR THE NORTHERN AREAS. FOR WHITE PASS AND HAINES
CUSTOMS, OVERNIGHT MINIMUM TEMPERATURES WILL BE AROUND 0 DEGREES.
LOWS WILL BE IN THE UPPER 20S TO LOW 30S IN THE SOUTHERN AREAS.
WITH ABUNDANT SUNSHINE, HIGH TEMPERATURES FOR THE PANHANDLE WILL
RISE TO THE UPPER 30S TO LOW 40S. FOR SKAGWAY AND YAKUTAT, THERE
WILL BE SOME COMPRESSIONAL HEATING FROM DOWNSLOPING, DAILY DIURNAL
TEMPERATURE RANGE WILL BE PRETTY LARGE.

 THE BIG WEATHER STORY WILL BE THE POTENTIAL OUTFLOW WIND EVENT
FOR JUNEAU AREA. THE LAST 4 RUNS OF THE NAM MODEL SHOW THE 70 KT
CROSS BARRIER FLOW NEAR THE SURFACE FROM MONDAY EVENING UNTIL
TUESDAY AFTERNOON. INVERSION WILL PERSIST DURING THE SAME TIME.
CRITICAL LAYER WILL BE AROUND 500 MB. THESE FACTORS ALL POINT TO A
POTENTIAL WIND EVENT IN JUNEAU AREA. RIGHT NOW, PUT IN HIGHER
GUSTS FOR DOWNTOWN JUNEAU AND DOUGLAS AREA. RIGHT NOW, STILL NEED
TO DETERMINE THE EXACT MAGNITUDE OF THE EVENT. ANOTHER THING THAT
NEED TO BE DETERMINED IS WHETHER IT WILL BE A WIDESPREAD OR LOCAL
(DOWNTOWN JUNEAU AND DOUGLAS) WIND EVENT. FOR FURTHER INFORMATION,
PLEASE REFER TO THE SPECIAL WEATHER STATEMENT.

 MODEL OF CHOICE IS ECMWF, THEN GOES INTO WPC FOR DAY 4 AND BEYOND.
ECMWF IS THE SUPERIOR MODEL WHEN DEALING WITH BLOCKING SITUATION.
GFS AND OTHER NUMERICAL WEATHER MODELS TEND TO BE TOO QUICK IN THE
BREAKDOWN OF BLOCKING PATTERN. FORECAST CONFIDENCE IS ABOVE
AVERAGE FOR THE GENERAL SYNOPTIC PATTERN OF COOL, DRY, AND WINDY
PATTERN OVER SOUTHEAST ALASKA. HOWEVER, THERE ARE STILL
UNCERTAINTIES IN THE MAGNITUDE OF THE WIND EVENT FOR MONDAY NIGHT
INTO TUESDAY AND BEYOND.

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALE WARNING FOR PKZ012.
         SMALL CRAFT ADVISORY FOR PKZ011-013-021-022-031-035-043-051.
         SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042-052.

&&

JMG/RCL