760
FXAK67 PAJK 230123
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
523 PM AKDT MON OCT 22 2018
UPDATE
COOLER TEMPERATURES NEAR WHITE PASS TODAY AND INTO
TONIGHT PROMPTED THE UPDATED TO LOWER TEMPERATURES. WEB CAMS FROM
RWIS (ROAD WEATHER INFORMATION SYSTEM) SITE NEAR THE PASS IS
SHOWING SNOW FALLING AND IT SHOULD CONTINUE THROUGH THE EVENING
WITH A FEW INCHES OF ACCUMULATION NEAR THE PASS. WARM AIR
ADVECTION FROM THE SOUTH WILL SPREAD A WARM LAYER NORTH, HOWEVER
NEAR THE SURFACE, A LIGHT NORTH WIND SHOULD CONTINUE INTO EARLY
TUESDAY. THINK THE SNOW WILL MELT TO RAIN, AND WILL FALL THROUGH
THE COOLER AIR AND MAY START FREEZING ON SURFACES NEAR THE PASS.
AS A RESULT HAVE ISSUED A WINTER WEATHER ADVISORY FOR SNOW AND
FREEZING RAIN OVERNIGHT. INTENSITY OF THE WARMING COULD WIPE OUT
THE COLD LOWER AIR LAYER NEAR SURFACE EARLIER, SO THE WILL NEED
TO MONITOR FOR THE CONTINUATION OF THIS WINTER WEATHER.
PREV DISCUSSION......ISSUED AT
246 PM AKDT OCT 22 2018
SHORT TERM...A VERY DYNAMIC SYSTEM CONTINUES TO DEVELOP OVER THE
GULF THIS AFTERNOON, AND A VERY ACTIVE PATTERN IS EXPECTED TO
CONTINUE THROUGH THIS SHORT TERM FORECAST PERIOD. AN EVEN STRONGER
LOW IS THEN EXPECTED TO DEVELOP AND TAKE A SIMILAR TRACK TO OUR
CURRENT SYSTEM BEGINNING THIS WEDNESDAY.
ACCORDING TO CURRENT WV SATELLITE IMAGERY, A BROAD UPPER LEVEL
TROUGH EXTENDS SOUTH THROUGH THE ALEUTIAN ISLANDS AND WESTERN
GULF, EXTENDING EVEN DEEPER INTO THE PACIFIC. A STRONG UPPER
LEVEL RIDGE OVER THE WESTERN CONUS PUSHES EVEN FURTHER NORTH INTO
BRITISH COLUMBIA, ANSWERING THE DEEPENING RIDGE. THE TIGHTENING
PRESSURE GRADIENT BETWEEN THESE TWO FEATURES HAS ALLOWED A
RELATIVELY STRONG JET TO FORM, WHICH CONTINUES TO ADVECT LARGE
AMOUNTS OF MOISTURE INTO THE ALASKAN PANHANDLE. MANY LOCATIONS
AUTOMATED SURFACE OBSERVING SYSTEMS CONTINUE TO REPORT MODERATE
RAINFALL THIS AFTERNOON, WITH HOURLY OBSERVATIONS BETWEEN A TENTH
AND TWO TENTHS OF AN INCH. RAIN, HEAVY AT TIMES, WILL CONTINUE
THROUGH TONIGHT FOR AREAS IN THE NORTHERN PANHANDLE AS THE STREAM
OF MOISTURE PIVOTS NORTH WITH THE DEVELOPING SHORTWAVE. THIS
SHORTWAVE CAN ALSO BE SEEN ON SATELLITE EMBEDDED WITHIN THE MAIN
TROUGH AND BEGINNING TO LIFTING NORTH AND STRENGTHEN. IN ADDITION
TO THE UPPER LEVEL JET MENTIONED PREVIOUSLY, IT ALSO LIES WITHIN
THE LEFT EXIT REGION OF AN ADDITIONAL JET STREAK, PROVIDING
DIVERGENCE ALOFT AND ALSO HELPING TO STRENGTHEN THIS FEATURE. AS
THIS LOW FURTHER DEVELOPS TUESDAY, THE DYNAMICS WILL BECOME
FAVORABLE FOR THUNDERSTORM DEVELOPMENT, ESPECIALLY OVER THE
EASTERN GULF WATERS, BUT LIGHTNING STRIKES CANNOT BE DISCOUNTED ON
LAND, ESPECIALLY FOR AREAS SUSCEPTIBLE TO TERRAIN ENHANCEMENT.
BOTH GFS AND NAM FORECAST SOUNDINGS FOR KLAWOCK AND SITKA SHOW
SFC-3KM LAPSE RATES GREATER THAN 7 DEGREES C/KM AND CAPE IN EXCESS
OF 300 J/KG. THERE WILL BE DECENT INSTABILITY AS THE LOW FURTHER
LIFTS NORTH TUESDAY EVENING.
MODELS CONTINUE TO COME INTO BETTER AGREEMENT ON ANOTHER STRONG
LOW IMPACTING SE ALASKA BEGINNING WEDNESDAY. THIS WILL TAKE A
SOMEWHAT SIMILAR TRACK TO THE LOW IMPACTING US TOMORROW, BUT
STRONGER JET DYNAMICS WILL MAKE THIS A STRONGER CONTENDER. THE
BIGGEST CONCERNS WITH BOTH THE SYSTEM FOR TUESDAY AND THIS
DEVELOPING SYSTEM FOR WEDNESDAY WILL BE THE WINDS. AT ISSUE FIRST
WILL BE A HIGH WIND EVENT FOR THE SOUTHERN OUTER COAST TONIGHT.
925MB STREAMLINES AND ISOTACHS INDICATING 65 KTS OF WIND ALONG THE
COAST OF PRINCE OF WALES ISLAND WITH AS MUCH AS 55 KTS OF WIND
OVER NORTHERN KUIU ISLAND - MORE THAN ENOUGH TO PRODUCE 60 MPH
WIND GUSTS AT THE SURFACE. HIGH WIND WARNING FOR WESTERN PORTIONS
OF ZONE 26 - TO INCLUDE KAKE AND POINT BAKER - ZONE 27, AND
SOUTHERN BARANOF ISLAND. MAIN FOCUS ON BARANOF WILL BE THE EASTERN
SHORE AND THE COMMUNITIES OF PORT ALEXANDER, PORT WALTER, AND PORT
ARMSTRONG. DO NOT THINK HIGH WIND GUSTS WILL MAKE IT AS FAR NORTH
AS SITKA, BUT THE LOW LEVEL JET SETUP IS VERY SIMILAR TO THE LAST
STRONG WIND EVENT, WHEN SITKA HARBOR RECORDED A 70 MPH WIND GUST.
AS THE FRONT ASSOCIATED WITH THESE HIGH WINDS TRACKS NORTH,
YAKUTAT WILL SEE HIGH WINDS BEGINNING TOMORROW MORNING AND A HIGH
WIND WARNING HAS BEEN ISSUED FOR THERE AS WELL. STREAMLINE FLOW
HAS ENOUGH OF AN OFFSHORE COMPONENT THAT WIND GUSTS IN ZONE 22
SHOULD REMAIN BELOW 60 MPH. STRONG WIND HEADLINES THERE, AS WELL
AS VARIOUS OTHER PLACES ON THE INSIDE. MARINE WINDS TONIGHT AND
TOMORROW OVER THE EASTERN GULF WILL BE AT THE HIGH END OF GALE,
POSSIBLY HIGHER. HIGH CONFIDENCE IS A STORM FORCE BARRIER JET
BETWEEN ICY BAY AND CAPE SUCKLING TOMORROW MORNING. THERE WILL BE
A BRIEF BREAK IN THE WIND ACTION TUESDAY NIGHT AND WEDNESDAY IN
THAT THERE WILL BE NO WIND WARNINGS, BUT ANOTHER STORM FORCE LOW
IS FORECAST TO ENTER THE GULF FROM THE SOUTH WEDNESDAY AFTERNOON,
TAKING A SIMILAR TRACK AS THE LOW RESPONSIBLE FOR HIGH WINDS
TONIGHT & TOMORROW. HIGH HINDS POSSIBLE ONCE AGAIN FOR ZONES 23,
26, AND 27 WEDNESDAY AFTERNOON AND OVERNIGHT. IF MODELS REMAIN
CONSISTENT, ANOTHER HIGH WIND WATCH MAY BE ISSUED ONCE THE CURRENT
STORM IS OUT OF THE PICTURE. WE'RE NOT IN KANSAS ANY MORE.
LONG TERM.../ THURSDAY TO MONDAY AS OF 10 PM SUNDAY / THE ACTIVE
WEATHER PATTERN WILL PERSIST FROM THE MIDDLE OF THE WEEK THROUGH
THE WEEKEND AS A PARADE OF LOWS AND WEATHER FRONTS CONTINUE TO
MOVE THROUGH THE GULF ON A SIMILAR TRACK. OVERALL THE LONG RANGE
PATTERN HAS NOT CHANGED THROUGH THIS TIMEFRAME.
SHOWERS ACROSS THE GULF AND PANHANDLE FOR FRIDAY INTO SATURDAY.
THE NEXT SYSTEM APPROACHING OUT OF THE NORTH PACIFIC MOVES TO THE
SOUTHERN GULF BY SATURDAY MORNING. MODELS HAVE CONTINUED
CONSISTENCY ISSUES OF POSITION ON THIS AND WILL STRENGTHENING SOME
THOUGH SUNDAY. FORECAST CONFIDENCE IS AVERAGE IN THE LATE TIME
FRAMES.
TEMPERATURES FROM THURSDAY TO SATURDAY WERE WERE COOLED SLIGHTLY
BEHIND THE BIG THURSDAY FRONT AND SNOW LEVELS AS A RESULT LOWERED
SLIGHTLY TOO, ALTHOUGH ONLY THE HIGHER ELEVATION SHOULD EXPECT TO
SEE ANY SNOW.
AJK WATCHES/WARNINGS/ADVISORIES
PUBLIC...HIGH WIND WARNING FROM 10 PM THIS EVENING TO 6 AM AKDT TUESDAY
FOR AKZ023-026-027.
STRONG WIND FROM 1 AM AKDT TUESDAY THROUGH TUESDAY MORNING FOR
AKZ021-022.
STRONG WIND FROM 10 PM AKDT THIS EVENING THROUGH LATE TONIGHT
FOR AKZ028.
WINTER WEATHER ADVISORY UNTIL 1 PM AKDT TUESDAY FOR AKZ018.
HIGH WIND WARNING FROM 6 AM TO 4 PM AKDT TUESDAY FOR AKZ017.
MARINE...STORM WARNING FOR PKZ052.
GALE WARNING FOR PKZ022-033-035-036-041>043-051-053.
SMALL CRAFT ADVISORY FOR PKZ021-031-032-034.
BEZENEK/FRITSCH/VOVERIS/BEZENEK
VISIT US AT HTTP://WWW.WEATHER.GOV/JUNEAU
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page