000
FXAK67 PAJK 241445
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
645 AM AKDT FRI MAY 24 2013
.SHORT TERM...MOSTLY CLOUDY SKIES OVER THE PANHANDLE THIS MORNING,
WITH RAIN DEVELOPING IN MUCH OF SOUTHERN SOUTHEAST ALASKA BY THIS
AFTERNOON. RELATIVELY LIGHT WINDS WILL PERSIST, AND ONLY CROSS
SOUND HAS BEEN GIVEN A SMALL CRAFT ADVISORY. THIS SHORT RANGE
SECTION CONCLUDES WITH AN ANALYSIS OF A WARMING EVENT THAT TOOK
PLACE AT SKAGWAY EARLY THIS MORNING.
THE LARGEST ADJUSTMENTS TO THE SHORT RANGE FORECASTS ARE FOR
RAISING THE CLOUD COVER AMOUNTS FOR MOST OF THE AREA OF
RESPONSIBILITY. NOTE THE CLOUD COVER INCREASES ARE RAISED IN THREE
WAYS: FIRST, THE GOES VI SABLE IMAGERY THIS MORNING REVEALS AN
EXTENSIVE COVERAGE OF SEA STRATUS AND THE ONSHORE THE PANHANDLE.
SECOND, PATCHES OF FOG HAVE BEEN REPORTED AND PATCHY FOG WILL
DEVELOP TONIGHT. THIRD WE HAVE RAISED AMOUNTS OF MID AND UPPER
LEVEL DECK WITH CAUSES THAT ARE DISCUSSED IN THE NEXT PARAGRAPH.
CONFIDENCE IS AVERAGE.
A 500H LOW OVER THE SEATTLE VICINITY HAS A SYNOPTIC-SCALE FLOW
THAT EXTENDS AS FAR AS CENTRAL B.C. THE GOES IR LOOP DEPICTS THE
UPPER LEVEL EAST FLOW REACHING SOUTHERN SOUTHEAST ALASKA WITH
CLOUD COVER FROM THE WEAKENING OF SMALLER-SCALE CYCLONIC FEATURES.
A 500H RIDGE EXTENDS WSW FROM OVER GREAT BEAR LAKE AND OVER THE
CENTRAL PANHANDLE. WE SOMETIMES CALL A RIDGE ALOFT "DIRTY" IF
SHORT WAVES ARE ABLE TO TRAVEL THROUGH IT, EVEN IF THESE WAVES ARE
WEAKENING. IN THE PRESENT CASE, WE HAVE A DIRTY RIDGE THAT IS
WEAKENING THE SHORT WAVES ENOUGH TO LIMIT PRECIPITATION, HOWEVER
THE CLOUD MASS AT MID AND UPPER LEVELS WILL CONTINUE TO BE
CEILINGS.
MODELS: THE GFS MODEL RUN AT 24.00 WAS EASIER TO RECONCILE WITH
OBSERVABLE FEATURES ALOFT, AND THE MODEL HAS HAD A HIGHER POP
FIELD FARTHER WEST ACROSS THE SOUTHERN PANHANDLE. IN THIS WESTERN
EXTENT OF THE RAISED POPS AS WELL AS FOR CLOUD COVER, THE GFS WAS
AN OUTLIER, AND CORRECT.
THE YAKUTAT AND ANNETTE ISLAND RAOBS AT 12Z SHOW STRONG SUBSIDENCE
INVERSIONS. THE YAKUTAT RAOB INVERSION INCLUDES A MEASUREMENT OF
9C AT 900H, AND IF SUCH A VALUE IS ADIABATICALLY SUBSIDED TO NEAR
SEA LEVEL, WOULD BE 18C, OR 64F. A SIMILAR SUBSIDENCE EVENT RAISED
THE TEMPERATURES AT SKAGWAY THIS MORNING. THE SKAGWAY AIRPORT AT
3 AM REPORTED A TEMPERATURE OF 50F WITH CALM WINDS. BY 4 AM THAT
AIRPORT HAD WINDS FROM THE NORTH AT 7KT WITH GUSTS TO 14KT AND A
SURFACE TEMPERATURE OF 60F. DURING THE SAME TWO HOUR PERIOD THE
DEW POINT WENT DOWN FROM 37F TO 30F. THE NORTH WINDS AT SKAGWAY
PROVIDED THE DRY ADIABATIC PROCESS THIS MORNING.
.LONG TERM...AREA WILL REMAIN UNDER A GENERALLY E-SE FLOW ALOFT
OVER THE NEXT 5-7 DAYS...WITH UPPER RIDGE/HIGH REMAINING TO THE NE
OF THE AREA AND UPPER TROF TO THE SW. THIS PATTERN IS OFTEN NOT
HANDLED WELL BY THE MODELS AS FAR AS THE DETAILS GO. WILL PROBABLY
HAVE WEAK SHORTWAVE FEATURES MOVE ACROSS THE AREA FROM THE E
DURING THE PERIOD...BUT THE GFS AND ECMWF DO SUGGEST A SHARPER
LOBE OF THE UPPER RIDGE/HIGH TO THE NE WILL EXTEND INTO THE AREA
AT LEAST SUN-TUE...WHICH WOULD TEND TO WEAKEN THE SHORTWAVES.
ALSO...WILL HAVE A SMALL UPPER LOW LOOP AROUND THE ERN GULF SAT
THRU SUN THEN PULL NW AND OUT OF THE AREA BY EARLY NEXT WEEK.
AFTER COORD WITH WFO PAFC WENT WITH A BLEND OF THE 00Z GFS AND
ECMWF.
FOR SAT...WEAK SHORTWAVE WILL DRIFT NW ACROSS THE AREA WITH BANDS
OF MID-LEVEL CLOUDS AND POSSIBLY A LITTLE PRECIP. BEST CHANCES FOR
PRECIP APPEAR TO BE ALONG THE COAST MTNS WITH A WEAK ONSHORE FLOW
IN LOWER LEVELS AND SOME MID-LEVEL WARM ADVECTION OVER THE TOP.
FOR SAT NIGHT INTO SUN...UPPER LOW WILL DRIFT N THEN NW THRU THE
ERN GULF. THIS WILL INTERACT WITH THE LEFTOVER MOISTURE FROM THE
SAT SHORTWAVE AND MAY ORGANIZE PRECIP OVER THE NE GULF AND
ADJACENT COASTAL AREA. KEPT IN CHANCE POPS THERE TO HANDLE THIS
SYSTEM. FURTHER INLAND AND S...POPS SHOULD LOWER AS THE SHARPER
LOBE OF THE UPPER RIDGE/HIGH BEGINS TO AFFECT THE AREA. HAVE
LOWERED POPS SOME IN THESE AREAS. HAVE KEPT IN MOSTLY CLOUDY SKIES
THOUGH DUE TO WEAK ONSHORE FLOW KEEPING A STRATOCU LAYER IN.
FOR SUN NIGHT INTO TUE...SHARPER RIDGE LOBE SHOULD DOMINATE THE
AREA. THERE MAY BE SOME WEAK SHORTWAVE ENERGY DRIFTING ACROSS THE
FAR SERN AREA THOUGH...SO WILL KEEP IN LOW POPS THERE. OTHERWISE
SHOULD SEE MORE BREAKS IN THE CLOUDS ESPECIALLY MON. IF THE MODELS
MAINTAIN THE STRENGTH OF THE RIDGE LOBE OVER THE AREA...LATER
SHIFTS WILL LIKELY NEED TO DECREASE CLOUD COVER ESPECIALLY OVER
THE NRN AREA.
FROM MIDWEEK ON...LOOKS LIKE UPPER TROF TO THE SW WILL TRY TO
DRIFT CLOSER TO THE AREA AND THE RIDGE LOBE WILL WEAKEN. THIS
WOULD BRING IN A BETTER THREAT FOR PRECIP DUE TO INCREASED ELY
WAVE ACTIVITY. LEFT THE CHANCE POPS IN TO COVER THIS. PRECIP MAY
BE MORE SHOWERY AS WELL AS CONVECTION THAT FIRES OVER BC COULD
DRIFT WWD INTO THE AREA. THIS WILL NEED TO BE WATCHED CLOSELY.
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ022.
&&
$$
JBT/RWT
000
FXAK67 PAJK 232332
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
332 PM AKDT THU MAY 23 2013
.SHORT TERM...ANOTHER QUIET AND SUNNY DAY ACROSS THE AREA TODAY
WITH SCATTERED HIGH CLOUDS MOVING THROUGH. THE EXCEPTION WAS IN
THE GULF AND ALONG THE OUTER COAST THIS MORNING AS THE MARINE
LAYER CLOUDS MADE THEIR PRESENCE KNOWN PARTICULARLY IN YAKUTAT
WHICH JUST BROKE OUT OF THE CLOUDS A LITTLE AFTER NOON.
TEMPERATURES ARE WELL ON THEIR WAY TO THE UPPER 50S AND MID 60S
TODAY WITH THE SUNNY WEATHER. WINDS ARE GENERALLY LESS THEN 20 KT
IN MOST PLACES WITH SEA BREEZE CIRCULATIONS BEING THE MAIN
DRIVER. THE EXCEPTION TO THIS IS CROSS SOUND WHICH HAS A NW SMALL
CRAFT THIS AFTERNOON.
FOR TONIGHT INTO TOMORROW, THE NICE WEATHER CONTINUES WITH MOSTLY
CLEAR TO PARTLY CLOUDY SKIES MOST PLACES TONIGHT AND INCREASING
HIGH TO MID LEVEL CLOUDS TOMORROW. THE INCREASING CLOUDS IS DUE TO
THE REMAINS OF A FRONT IN THE UPPER TO MID LEVELS MOVING NW FROM
SOUTHERN BRITISH COLUMBIA. THIS MAY BRING SOME SCATTERED SHOWERS
TO THE SOUTHERN PANHANDLE AND COAST MOUNTAINS TOMORROW. THE REST
OF THE PANHANDLE SHOULD STAY DRY AS LOW LEVEL FLOW IS STILL
OFFSHORE AND DOWNSLOPE. ALONG THE OUTER COAST, THE MARINE LAYER
CLOUDS WILL RETURN TONIGHT BRINGING MORE OVERCAST SKIES BEFORE
THEY BURN OFF AGAIN TOMORROW MORNING.
WITH THE INCREASING CLOUDS TOMORROW, THE HIGHS WILL NOT BE QUITE
AS WARM AS THEY WERE TODAY ESPECIALLY IN THE SOUTH. GOING FOR
UPPER 50S TO LOW 60S DOWN SOUTH WHILE IN THE NORTH, WHERE THE
CLOUDS WILL NOT COME IN UNTIL LATER IN THE DAY, WILL GET INTO THE
LOW TO MID 60S.
FIRE WEATHER. FUEL CONDITIONS HAVE DRIED OUT IN MOST NORTHERN
PANHANDLE LOCATIONS ACCORDING TO AICC. HOWEVER, WIND HAS BEEN LOW
AND HUMIDITY VALUES HAVE NOT DROPPED MUCH LOWER THEN 30 TO 40
PERCENT. THE PLACE THAT HAS THE BEST CHANCE OF EXTREME FIRE DANGER
IS SKAGWAY WHERE THE HUMIDITY HAS FALLEN TO 24 PERCENT SO FAR
TODAY. DO NOT THINK THAT IT WILL REACH RED FLAG CRITERIA TODAY BUT
IT WILL GET CLOSE. TOMORROW AFTERNOON WILL LIKELY HAVE THE SAME
CONDITIONS BUT DEW POINTS MIGHT BE A BIT HIGHER THEN THEY ARE
TODAY SO DON`T ANTICIPATE A RED FLAG WARNING NEEDED TOMORROW
EITHER.
SHORT RANGE MODELS WERE IN GOOD AGREEMENT TODAY. DECIDED ON USING
THE NAM AND ECMWF AGAIN TODAY FOR THE DETAIL THAT THEY PROVIDED.
FORECAST CONFIDENCE IS A LITTLE ABOVE AVERAGE.
&&
.LONG TERM...THE RIDGE OVER THE GULF ALASKA REMAINS ONE OF PRIMARY
FEATURE AFFECTING SOUTHEAST ALASKA. EASTERLY FLOW TRYING TO SPREAD
CLOUDS AND LIGHT RAIN ACROSS THE COAST MOUNTAINS IN THE SOUTHEAST
PORTIONS OF THE PANHANDLE. FURTHER WEST AN OLD PARENT LOW OVER THE
SOUTHERN BERING SEA IS SPREADING A WEAKENING BAND/WEAK LOW ACROSS
THE SOUTHERN GULF. THINK THAT THE LOW WILL HEAD SOUTHEAST AND
THE FRONT WILL BE LIKELY SHEERING OUT OVER THE CENTRAL GULF. THERE
IS A SMALL VORTICITY LOBE THAT WILL BE ROTATING INTO THE NORTHERN
GULF AND THAT MAY TRY AND POP A FEW SMALL SHOWERS OVER THE
NORTHEAST PANHANDLE AREA LATE SATURDAY TO SUNDAY. IT SORT OF
DEPENDS AMOUNT OF MOIST THAT IS STREAMING ACROSS THE PANHANDLE.
HEADED INTO EARLY NEXT WEEK A LOW WILL LIKELY BE ESTABLISHING
ITSELF SOUTH OF KODIAK ISLAND AND THE RIDGE WILL BE LIMITED TO
PANHANDLE AND COAST MOUNTAIN AREA. THROUGH THE MIDDLE PART OF THE
WEEK EXPECT THE PANHANDLE AREA TO BE ABSORBED INTO A BROAD WEAK
AREA OF LOW PRESSURE THE PANHANDLE AREA IN THE CENTER OF THE
REGION. AS RESULT A LARGE PORTION OF THE EXTENDED FORECAST IS
MOSTLY CLOUDY, LIGHT WINDS AND POSSIBLY A CHANCE OF RAIN.
CONFIDENCE IN THE LATER PERIODS IS LOW OTHER THAN THE GENERALITY I
MENTIONED ABOVE, AS TO HOW MUCH IF ANY RAIN WILL FALL AND THEN HOW
MUCH. FOR THE MOST PART INTO THE HOLIDAY WEEKEND THE FORECAST
SEEMS TO BE BEHAVING RATHER WELL WITH AN AVERAGE TO ABOVE AVERAGE
CONFIDENCE FACTOR.
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ022-033.
SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ041-042.
&&
$$
EAL/BEZENEK
000
FXAK67 PAJK 231429
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
629 AM AKDT THU MAY 23 2013
.SHORT TERM...THIS WAS A TRICKY FORECAST DEFINED BY RELATIVELY
LIGHT FLOW AND POORLY DEFINED FEATURES IN THE MODELS AND ON OTHER
TOOLS LIKE SATELLITE. LET US START WITH WHAT WE KNOW. WE ARE IN A
WARM PATTERN WITH LOTS OF SOUTHEASTERLY FLOW ALOFT AND
TEMPERATURES WILL ONCE AGAIN WARM WELL INTO THE 60S ACROSS THE
REGION TODAY. A FEW INTERIOR LOCATIONS WILL LIKELY SEE THE 70S
LIKE DEEPER PARTS OF THE MENDENHALL VALLEY. THINK IN THE FAR
NORTH LIKE SKAGWAY AND HAINES, TEMPERATURES WILL RECOVER NOW THAT
CLOUDS HAVE MOVED NORTH. WITH WEAKENING HIGH PRESSURE OVER THE
GULF OF ALASKA AND A THERMAL TROUGH OF LOW PRESSURE EXTENDING
NORTHWEST, MOST WINDS WILL BE NORTHWESTERLY ACROSS THE PANHANDLE.
AS INTERIOR PARTS WARM RAPIDLY THIS AFTERNOON, WE SHOULD SEE
ANOTHER SURGE OF WESTERLIES INTO THE OCEAN ENTRANCES, SIMILAR TO
YESTERDAY AND THUS HAVE BUMPED UP CROSS SOUND AND SOUTHERN
CHATHAM INTO SCA WINDS THIS AFTERNOON, AND EMPHASIZED SOME 25 KT
WINDS IN SUMNER WITHOUT PLACING THEM IN SMALL CRAFT ADVISORY. SEA
BREEZES WILL DEVELOP LATE MORNING INTO THE AFTERNOON BEFORE
SHUTTING OFF IN THE EVENING. WE ALSO HAVE A LOT OF SEA STRATUS
OFFSHORE WITH SOME FOG BEING REPORTED BY MARINERS. THE SEA
STRATUS REACHED YAKUTAT, SITKA, AND CROSS SOUND AROUND MIDNIGHT.
THIS IS SOMETHING WE EXPECTED AND SEE NO REASON WHY THE PATTERN
WILL VARY MUCH TONIGHT. FOG WAS ADDED ACROSS THE OFFSHORE ZONES
USING NAM BOUNDARY LAYER HUMIDITY FIELDS AND THE FACT THAT
CONFIRMATION HAS BEEN REPORTED.
NOW FOR THE TRICKY PART: SKY COVER...A LOT MORE HIGH AND
MID-LEVEL CLOUDS ARRIVED INTO THE SOUTHERN PANHANDLE YESTERDAY
EVENING AND OVERNIGHT THAN PREVIOUSLY THOUGHT. CANNOT SAY THAT
MECHANISMS WEREN`T REVEALED: THERE WAS SOME WEAK VORTICITY
ADVECTION RIDING OVER THE RIDGE ALOFT OVERNIGHT COMING FROM THE
SOUTHWEST. BUT MOST OF THE MODELS DID NOT SUGGEST CLOUD COVER OF
ANY SIGNIFICANCE, WITH THE EXCEPTION OF THE ECMWF...WHICH SEEMED
TO OVERCOMPENSATE FOR THE LACK OF CLOUDS IN THE OTHER MODELS.
WHILE CLOUD COVER ON IR SATELLITE IMAGERY OVERNIGHT SEEMS TO
SUGGEST WEAKENING...CLOUDS LOOKED THICKER THAN THOUGHT ON WEBCAMS
AND WITH COORDINATION FROM ANNETTE WSO, ELECTED TO CALL THINGS
MOSTLY CLOUDY IN THE SOUTH. BUT FEEL AS THOUGH THEY WILL HAVE
SOME SUNSHINE THIS AFTERNOON. THE IMPORTANT THING IS DRY WEATHER
HERE. CLOUD COVER OVER THE CENTRAL PANHANDLE SEEMED THINNER AND
LESS SHADOW INHIBITING, SO CALLED FOR MAINLY SUNNY CONDITIONS
HERE AND TO THE NORTH. FOR THE NORTHEAST GULF COAST, WORRIED THAT
MID TO HIGH LEVEL CLOUDS FROM THE WEST MAY TAMPER WITH SUNSHINE
THIS AFTERNOON AS MARINE LAYER BREAKS UP...SO WENT WITH PARTLY
CLOUDY FOR THIS AFTERNOON FOR YAKUTAT. CLOUD COVER TONIGHT WAS
EQUALLY CHALLENGING. MODELS...ESPECIALLY GFS SHOWING A SURGE OF
MOISTURE MOVING IN FROM THE SOUTHEAST. MOS GUIDANCE CLOUD COVER
HAS BEEN UNHELPFUL AS IT HAS CARED LITTLE ABOUT THE CURRENT
CONDITIONS OVER THE SOUTH. THINK SOME DOWN-SLOPING WILL TEND
TOWARD CLEARER CONDITIONS THAN WHAT MODELS ARE INDICATING, AND SO
HAVE LEFT THINGS MAINLY CLEAR FOR MUCH OF THE INTERIOR PANHANDLE
OVERNIGHT. BUT PARTLY CLOUDY SKIES MAY HAVE BEEN THE SAFER
ALTERNATIVE.
THIS WEAK VORTICITY CENTER OVER THE SOUTHEAST GULF IS FORECAST
TO WEAKEN AND MOVE NORTH AND AS IT DOES IT WILL PUMP MORE WARM
AIR OVER THE REGION FROM THE SOUTHEAST, AND WITH THAT INEVITABLY
COMES MOISTURE AS WELL. THE MOISTURE WILL BEGIN TO WORK THROUGH
THE SOUTHERN COAST MOUNTAINS THIS AFTERNOON THAT MAY BRING THE
THREAT OF AN ISOLATED OR SCATTERED SHOWER NEAR HYDER. THINGS
DISSIPATE QUICKLY OVER THE EVENING, BUT A MORE SIGNIFICANT LOBE
OF MOISTURE ARRIVES LATE THAT WILL SPREAD SCATTERED SHOWERS OVER
HYDER TOWARD THE EARLY FRIDAY MORNING HOURS. FOR MORE ABOUT THIS
ONSET OF SOME WETTER WEATHER FOR THE SOUTHERN PANHANDLE SEE THE
LONG TERM SEGMENT.
ONE FINAL NOTE ABOUT TEMPERATURES, COOLED THEM A LITTLE FOR THIS
AFTERNOON GIVEN OUR THINKING AT THE TIME THAT SKIES WOULD BE A
LITTLE CLOUDIER, SO IT COULD GET WARMER THAN ADVERTISED...ESPECIALLY
OVER THE NORTH. WHITE PASS TEMPERATURES WERE WARMED TONIGHT
THINKING AN INVERSION MAY SET IN BELOW KEEPING TEMPERATURES AT
PASS LEVEL RELATIVELY MILD. RELIED ON NAM 925 MB TEMPS FOR
GUIDANCE.
MODELS WERE HAVING A DIFFICULT TIME WITH SOME OF THE POSITIONING
AND STRENGTH OF THE SURFACE HIGH OFFSHORE, AND ESPECIALLY CLOUDS
OVER THE REGION. SO INSTEAD CHOSE NOT TO CHANGE PRESSURE FIELD
AND CONFINED WIND CHANGES TO LOCAL EFFECTS. RELIED ON SATELLITE
INTERPRETATION FOR CLOUD COVER AND LOCAL KNOWLEDGE OF SEA BREEZES
FOR HELP ON WINDS. FORECAST CONFIDENCE AVERAGE TO GOOD, BUT FALLS
FOR SKY COVER...ESPECIALLY OVER THE SOUTHERN AND EVEN THE CENTRAL
ZONES. LUCKILY, IMPACTS OF MISSED FORECAST WILL BE MINIMAL.
&&
.LONG TERM...THE EXTENDED FORECAST PERIOD LOOKS LIKE IT WILL BE
DOMINATED BY HIGH PRESSURE ALOFT CENTERED OVER WESTERN CANADA AND
EASTERN AK. THE PACIFIC STORM TRACK WILL STAY WELL SOUTH OF THE
PANHANDLE. A COLD UPPER LEVEL LOW CENTER PRODUCING RAIN AND MTN SNOW
IS STUCK OVER THE PAC NW. CLOUDINESS IS CURVING AROUND THIS LOW
AND MOVING NW OVER BRITISH COLUMBIA TOWARD SE AK. THE PANHANDLE WILL
BE UNDER THIS SE FLOW ALOFT THROUGH THE MIDDLE OF NEXT WEEK. THE
MAIN FORECAST CHALLENGE WILL BE DETERMINING IF AND HOW MUCH RAIN
WILL SPILL OVER THE COASTAL MOUNTAINS FROM BRITISH COLUMBIA AND
INTO SE AK. THIS WEATHER PATTERN FAVORS A BIT HIGHER CHANCE OF
RAIN OVER THE SOUTHERN PANHANDLE AND DRIER BUT CLOUDY WEATHER OVER
THE NORTHERN PANHANDLE. THERE IS BETTER AGREEMENT IN NEARLY ALL
MODELS AND NATIONAL WPC GUIDANCE THAT MAINTAIN TEMPS WILL REMAIN
AT OR ABOVE NORMAL THROUGH THE EXTENDED RANGE.
THE GFS ENSEMBLE MEAN WAS USED TO UPDATE THE GRID FORECASTS. THE
DETERMINISTIC HEMISPHERIC MODELS SUCH AS THE GFS EC AND GEM HAD
VARIOUS SOLUTIONS SO THE ENSEMBLE MEAN WAS IS AN EFFECTIVE
COMPROMISE FOR DESCRIBING THE GENERAL LARGE SCALE FEATURES.
FORECAST CONFIDENCE REGARDING THE LOCATION AND TIMING OF
PRECIPITATION IS LOW.
THE FIRST SHOT OF POSSIBLE PRECIPITATION OVER SE AK APPEARS TO
BE DURING THE DAY ON FRI OVER THE SOUTHERN ZONES. DEFORMATION
ALOFT AND AN INCREASINGLY MOIST AIR MASS COULD LEAD TO LIGHT RAIN
ESPECIALLY N AND E OF KETCHIKAN. THIS WILL LIKELY DISSIPATE AND
DRY OUT AS IT MOVES NORTH FRIDAY NIGHT. ANOTHER BATCH OF RAIN
SHOWERS COULD DEVELOP SAT AND SAT NIGHT OVER THE CENTRAL AND
NORTHERN COASTAL MOUNTAINS. RELATED TO THIS I LOWERED DAYTIME MAX
TEMPS A BIT FROM PREVIOUS FCSTS THROUGH THE WEEKEND. THE CHANCE
OF PRECIP DOES APPEAR TO BE HIGHER AND MORE WIDESPREAD BY MON AND
TUES BUT RAIN AMOUNTS ARE NOT SIGNIFICANT...CERTAINLY LESS THAN
THE LAST TWO VERY WET WEEKENDS IN SE AK.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ022-033-041-042.
SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043.
&&
$$
JWA/TA
000
FXAK67 PAJK 222225
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
225 PM AKDT WED MAY 22 2013
.SHORT TERM...RATHER QUIET ALONG THE PANHANDLE TODAY AS MOSTLY
CLEAR SKIES AND DRY WEATHER REMAIN THE NORM. THE EXCEPTIONS TO
THIS RULE TODAY ARE SKAGWAY AND HAINES WHERE A MID LEVEL CLOUD
DECK HAS GIVEN THEM OVERCAST SKIES AND COOLER WEATHER TODAY. THE
CLOUD COVER THERE IS THE RESULT OF A MID LEVEL LOW THAT IS MOVING
NORTH JUST TO THEIR NE. THE LOW IS JUST FAR ENOUGH EAST THAT THE
NORTHERLY MID LEVEL FLOW IS DRAGGING THE CLOUDS OVER HAINES AND
SKAGWAY AND HAS PUSHED THE CLOUDS AS FAR SOUTH AS BERNER`S BAY
AND LENA POINT. AS THIS MID LEVEL LOW MOVES NORTH THIS EVENING
THE MID LEVEL FLOW SHOULD TURN MORE NW THEN W AND EVENTUALLY
CLEAR THE CLOUDS OUT OF THE AREA. THERE ALREADY IS EVIDENCE OF
THIS STARTING TO OCCUR ON RECENT SATELLITE IMAGES.
WINDS ARE BECOMING LESS OF A CONCERN AS THE INVERTED TROUGH OVER
THE PANHANDLE SLOWLY WEAKENS. CURRENTLY THE ONLY PLACES WITH
SMALL CRAFT WINDS ARE LYNN CANAL, STEPHENS PASSAGE, AND THE SE
GULF. THE FORMER TWO ARE ON A SLOW DECREASING TREND AT THE MOMENT
AND SHOULD DROP BELOW SMALL CRAFT BY THIS EVENING.
FOR TONIGHT AND TOMORROW, THE CLOUDS OVER THE EXTREME NORTH WILL
DIMINISH THIS EVENING AS THE MID LEVEL LOW MOVES NORTHWARD. SAME
FOR THE HIGH LEVEL CLOUDS THAT ARE SCATTERED OVER THE SOUTHERN
PANHANDLE. THESE WILL BE REPLACED ALONG THE OUTER COAST AND THE
GULF BY THE RETURN OF THE MARINE LAYER CLOUDS AS THE RIDGE THAT
IS IN THE GULF FLATTENS TONIGHT. SATELLITE IMAGES ALREADY SHOW
SOME MARINE LAYER CLOUDS STARTING TO FORM IN THE EASTERN GULF.
THESE CLOUDS SHOULD SPREAD ACROSS MOST OF THE GULF TONIGHT AND
MAY ENCROACH INTO YAKUTAT, CROSS SOUND, SITKA, AND THE EXTREME
WESTERN PARTS OF PRINCE OF WALES ISLAND. THESE CLOUDS WILL THEN
DO THEIR USUAL RETREAT OUT INTO THE GULF TOMORROW WITH THE DAY
TIME HEATING. OTHERWISE MOST AREAS WILL REMAIN DRY AND MOSTLY
CLEAR.
WINDS WILL NOT BE MUCH OF A CONCERN OVER THE PANHANDLE FOR THE
NEXT 24 HOURS. BESIDES THE USUAL SEA BREEZE PATTERNS MOST AREAS
WILL REMAIN BELOW 20 KT. THE SE GULF IS A DIFFERENT STORY, THE
CONTINUED INTERACTION BETWEEN THE GULF HIGH AND THE BRITISH
COLUMBIA LOW WILL CONTINUE TO CAUSE 25 KT NW WINDS IN THE SE GULF
THROUGH AT LEAST MIDDAY TOMORROW AS THE HIGH SLOWLY WEAKENS.
FIRE WEATHER. CLOUD COVER OVER THE EXTREME NORTHERN PANHANDLE
HAS SO FAR PREVENTED ANY DRASTICALLY LOW HUMIDITIES FROM
OCCURRING IN SKAGWAY TODAY. AIR TEMPERATURES AT SKAGWAY HAVE ONLY
RISEN INTO THE MID 50S AND WITH DEW POINTS HAVING RISEN OVERNIGHT
TO AROUND 30, THE RELATIVE HUMIDITY HAS BEEN HOLDING AROUND
40 PERCENT. WINDS HAVE ALSO BEEN 15 MPH OR LESS TODAY SO NO RED
FLAG WARNING WAS ISSUED. WE WILL CONTINUE TO MONITOR FIRE WEATHER
CONDITIONS IN THE AREA TOMORROW AS WITH CLEARER SKIES THE DAYTIME
TEMPERATURES ARE EXPECTED TO RISE AGAIN AND FUEL CONDITIONS
REMAIN DRY, BUT WITH INCREASING DEW POINT TEMPERATURES AND
CONTINUED LIGHTER WINDS IT IS BECOMING LESS OF A CONCERN THAT RED
FLAG CONDITIONS WILL BE REACHED TOMORROW. FUEL MOISTURE LEVELS
REMAIN TOO MOIST IN OTHER AREAS OF THE PANHANDLE FOR EXTREME FIRE
WEATHER CONDITIONS TO DEVELOP.
SHORT RANGE MODELS WERE IN GOOD AGREEMENT TODAY WITH FEW
DIFFERENCES NOTED. DECIDED ON STICKING WITH THE NAM AND A LITTLE
OF THE ECMWF FOR UPDATES TO GET MORE OF THE DETAILS THAT THOSE
MODELS PROVIDE. FORECAST CONFIDENCE IS ABOVE AVERAGE.
&&
.LONG TERM...HIGH PRESSURE RIDGE OVER THE AK GULF THAT HAS BEEN
PROVIDING SUNNY DRY WEATHER WILL BREAK DOWN THROUGH THE WEEK. LOW
PRESSURE SYSTEM OVER BRITISH COLUMBIA WILL TRACK NORTHWARD WITH
POTENTIAL FOR RAIN MOVING WESTWARD OVER THE COAST MOUNTAINS.
MARINE LAYER OVER THE AK GULF WILL MOVE EASTWARD BUT STILL
UNCERTAIN TO ITS EASTWARD EXTENT OVER THE PANHANDLE. LOW PRESSURE
SYSTEM MOVING ACROSS THE NORTH PACIFIC WILL INTERACT WITH A
BERING SEA LOW AS IT PASSES SOUTH OF THE ALEUTIAN CHAIN.
INTERACTION BETWEEN THESE TOW SYSTEMS ALONG WITH THE BREAK DOWN
OF THE RIDGE LEAD TO HIGH UNCERTAINTY IN EXTENDED FORECAST. BY
THE WEEKEND A SERIES OF RESULTING WEAK LOW PRESSURE SYSTEM WILL
MOVE INTO THE AK GULF. OVERALL THE STRONGER CENTERS LOOK TO NOW
TRACK SOUTHWARD SO OVERALL PRECIP SHOULD BE ALONG THE SOUTHERN
PANHANDLE STARTING ON SUNDAY AND FOR AREAS ALONG THE COAST
MOUNTAINS FROM THE BC LOW. KEEPING INCREASING CLOUD COVER THROUGH
THE WEEKEND WITH THE ADVANCING MARINE LAYER AND LOW PRESSURE
SYSTEMS. NOT MUCH IN THE WAY OF PRESSURE GRADIENTS OR FRONTAL
BOUNDARIES SO WINDS THROUGH THE LONG RANGE SHOULD BE LESS THAN
20 KTS. TEMPERATURES ARE ALSO LOOKING HIGHLY VARIABLE BETWEEN
MODELS. GFS IS BRINGING IN A WARMER AIR MASS WITH POSITIVE
TEMPERATURE ANOMALIES OVER THE REGION WHILE NAM/ECMWF ARE COOLER
BY 4 TO 8 DEGREES F. CLOUD COVER WILL BE ONE OF THE MAIN ISSUE
REGARDING DAY TIME HIGHS WITH THE TRACKING OF MID LEVEL AIR
MASSES ANOTHER.
HAD FAIR AGREEMENT BETWEEN MODELS FOR PRESSURE AND WINDS OVER
THE GULF. MORE VARIATION FOR THE INVERTED TROUGH OVER THE
PANHANDLE. BLENDED IN SOME NAM/GFS WITH INHERITED GRID BUT
OVERALL LITTLE CHANGE THROUGH DAY 4. NEW WPC WAS A BLEND OF
ENSEMBLES AS OPERATIONAL MODELS ARE SHOWING LARGE DISCREPANCIES
WHILE ENSEMBLE SPREAD IS FAIRLY LOW. UPDATED GRIDS THROUGH DAY
8 WITH NEW WPC, ALSO WITH LITTLE OVERALL CHANGE. FORECAST
CONFIDENCE IS LOW AT THIS TIME DUE TO THE LARGE VARIATIONS
BETWEEN MODELS IN POOR RUN TO RUN CONSISTENCY.
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ041-042.
SMALL CRAFT ADVISORY DUE TO SEAS FOR PKZ043.
&&
$$
EAL/PRB
000
FXAK67 PAJK 221418
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
618 AM AKDT WED MAY 22 2013
.SHORT TERM...THE NORTHERN, CENTRAL, AND SOUTHWESTERN PANHANDLE
ALL ENJOYED CLEAR SKIES OVERNIGHT. HOWEVER, AN UPPER LEVEL LOW
CENTERED OVER WASHINGTON STATE HAS BEEN DIRECTING SOME BACK-DOOR
MOISTURE INTO CENTRAL AND NORTHERN BC OVERNIGHT. AND SOME OF THIS
MOISTURE HAS MANAGED TO PENETRATE THE INTERIOR PARTS OF THE
PANHANDLE IN THE FORM OF MID TO HIGH LEVEL CLOUDS. WEBCAMS
CONFIRM THAT THERE ARE MORE CLOUDS IN THE SOUTHEASTERN PANHANDLE,
BUT SKAGWAY AND EVEN HAINES ARE SEEING SOME CLOUDS AT THIS HOUR
AS WELL. ALL MODELS AGREE THAT YESTERDAY`S BEAUTIFUL SUNNY SKIES
AND THE CLEAR ONES OVERNIGHT HAVE RESULTED FROM DRY NORTHWESTERLY
FLOW ALOFT. BUT IN BC, THE FLOW IS MORE SOUTHERLY, AND THEREFORE,
THERE IS A BAND OF DEFORMATION ACROSS THE INTERIOR PANHANDLE THAT
WILL ACT AS A WALL TO PREVENT CLOUDS FROM ENCROACHING MUCH TO THE
WEST. THIS DEFORMATION ZONE DEVELOPS SOME SPIN INTO THE AFTERNOON
AS A RIDGE ALOFT PUSHES IT TO THE NORTHEAST. THIS WILL DEFLECT
ANY SHOWER ACTIVITY AWAY FROM US. HOWEVER, A FEW OUTER LOCATIONS
MAY NOT ESCAPE THE MOISTURE COMPLETELY AS BOTH HYDER AND WHITE
PASS MAY EXPERIENCE AN ISOLATED SHOWER TODAY. A FEW CANADIAN
STATIONS IN INTERIOR BC REPORTED RAIN OVERNIGHT, AND PRINCE
RUPERT HAS SEEN RAIN EARLY THIS MORNING. SO SHOWERS ARE NOT OUT
OF THE QUESTION.
AS THIS UPPER LEVEL SPIN ZONE IS PUSHED NORTH AND EAST, THE
RIDGE ALOFT PROGRESSING EASTWARD ACROSS THE GULF WILL ALLOW THE
NORTHWESTERLY FLOW TO VEER TO MORE ONSHORE. THIS WILL WEAKEN THE
SURFACE HIGH OVER THE GULF, FLATTENING IT A BIT, AGAIN TO DIRECT
WINDS SLIGHTLY FROM NORTHWEST...MISSING THE SHORE...TO A BIT MORE
WEST. THIS COMBINED WITH DAYTIME HEATING IN THE 60S OVER MOST
PARTS OF THE PANHANDLE WILL BEGIN THE CHANGEOVER THIS AFTERNOON.
CHANGEOVER TO WHAT? WHILE NOT EVIDENCED ON YESTERDAY EVENING`S
VISIBLE, STILL THINK SOME STRATUS WILL DEVELOP OVER THE GULF AND
MOVE INTO OUR COASTAL COMMUNITIES LIKE YAKUTAT, PELICAN, SITKA,
AND CRAIG LATE TONIGHT...EVEN MOVING INTO ICY STRAIT CORRIDOR.
HOONAH AND GUSTAVUS COULD SEE A FEW STRATOCUMULUS LATE. THUS
RAISED OVERNIGHT LOW TEMPERATURES IN THIS REGION A BIT.
THIS UPPER LEVEL DEFORMATION ROTATING INTO A VORTICITY LOW ALOFT
THIS AFTERNOON WILL IN TURN WEAKEN HIGH PRESSURE OVER NORTHWEST
CANADA. WITH WEAKENING HIGH PRESSURE OVER CANADA AND WEAKENING
HIGH PRESSURE OVER THE GULF, THE GRADIENTS AROUND A THERMAL
TROUGH EXTENDING NORTHWEST OVER THE PANHANDLE FROM CENTRAL BC
WILL SLACKEN QUICKLY THROUGH THE REST OF TODAY. OUTFLOW WINDS,
ALTHOUGH DEVELOPED AT SHEEP MOUNTAIN, NEVER REACHED THE SURFACE
AT DOWNTOWN JUNEAU OVERNIGHT, JUST LIKE THE PREVIOUS NIGHT. BUT
WINDS IN NORTHERN LYNN CANAL, AND MOST RECENTLY AT SKAGWAY HAVE
BEEN SCA STRONG FROM THE NORTH. THE WEAKENING TREND FROM THE
SYNOPTIC GRADIENT WILL ALLOW MESOSCALE SEA BREEZES TO ASSUME
CONTROL OF LOCAL WIND PATTERNS THIS AFTERNOON. SO EXPECT SOME
TYPICAL CHANNEL BREEZES TO BEGIN DEVELOPING LATE THIS MORNING AND
AFTERNOON IN SPOTS.
IT IS A DEFINITE LUXURY TO SWEAT OVER PARTLY CLOUDY OR SUNNY SKY
ON A FORECAST SHIFT. BUT WHILE I WANTED TO FUDGE SKIES
TODAY...ESPECIALLY OVER THE INTERIOR PANHANDLE TO MOSTLY SUNNY OR
PARTLY CLOUDY IN SOME CASES, LONG TERM PARTNER CONVINCED ME THAT
FORECASTERS LOOK UP AND PEOPLE LOOK DOWN. IF PEOPLE SEE A SHADOW
IN SOUTHEAST ALASKA, IT MEANS A SUNNY DAY. SO TO A FORECASTER SKY
COVER MAY READ AS OPTIMISTIC, BUT TO THE PUBLIC, HOPEFULLY IT
WORKS JUST RIGHT. TO BE CLEAR I WILL STATE THAT THERE WILL BE
SOME ALTO-CUMULUS AND CIRRUS CLOUDS PASSING ACROSS THE SOUTHERN
AND INTERIOR PANHANDLE TO ADD TEXTURE TO TODAY`S SUNSHINE.
FIRE WEATHER...RELATIVE HUMIDITIES BOTTOMED OUT IN THE TEENS
YESTERDAY AFTERNOON AND EARLY EVENING IN SKAGWAY ALONG DRYING
NORTHEAST WINDS. AS FUELS WERE ALREADY DRY, THIS ALL SUPPORTED A
RED FLAG WARNING BEING ISSUED YESTERDAY AFTERNOON. FEEL THAT
WEAKENING WINDS THROUGH THE REST OF TODAY AND POSSIBLY A
SWITCHOVER TO SOUTH LATE THIS AFTERNOON MAY KEEP RH`S FROM
DROPPING AS LOW AS YESTERDAY. BUT THIS WILL BE WATCHED.
HYDROLOGY...THERE WILL BE NO ISSUES WITH HYDROLOGY FOR WEDNESDAY
AND WEDNESDAY NIGHT. DID EMPLOY ECMWF WITH SOME NAM AND RFC QPE
FOR QPF ACROSS THE FORECAST AREA AND WATERSHEDS OVER BC. MADE FEW
CHANGES.
MODEL OF CHOICE WAS THE NAM, WITH A LITTLE ECMWF THROWN IN FOR
POP AND QPF. BUT CHANGES WERE MAINLY LOCAL IN NATURE AND WERE
SMALL. CONFIDENCE IN FORECAST GOOD OVERALL.
&&
.LONG TERM.../THU THROUGH TUES/ THE CHALLENGE WITH THE LONG TERM
FORECAST IS DETERMINING WHEN THE CURRENT WARM AND DRY WEATHER WILL
END. IT NOW APPEARS TEMPS WILL REMAIN AT OR ABOVE MORMAL FOR MUCH
OF THE PANHANDLE THROUGH THE WEEKEND. BUT SOME LIGHT RAIN MAY
AFFECT THE REGION...ESPECIALLY THE SOUTHERN PANHANDLE...AS SOON AS
FRI. FORECAST CONFIDENCE IN THIS TRANSITION IS WEAK AS MODELS ARE
SHOWING DIFFERENT SOLUTIONS.
IN GENERAL SE AK IS UNDER THE INFLUENCE OF A SUMMER TIME WEATHER
PATTERN WITH HIGH PRESSURE...SURFACE AND ALOFT...TO THE WEST OVER
THE GULF AND LOWER PRESSURE EAST OF THE COASTAL MOUNTAINS.
SATELLITE IMAGERY THIS MORNING SHOWS A MOIST SE FLOW ALOFT OVER
BRITISH COLUMBIA ASSOCIATED WITH AN UNSEASONABLY COLD AND
UNSTABLE UPPER LOW OVER THE PAC NW. BY FRI THIS UPPER LOW IS
FORECAST BY THE GFS TO WEAKEN BUT DRIFT NORTH AND WEST AND
POSSIBLY STEER A BAND OF SHOWERS INTO THE SOUTHERN
PANHANDLE...ESPECIALLY NEAR THE COASTAL MOUNTAINS. MODEL RAINFALL
AMOUNTS DONT LOOK VERY HEAVY BUT CANADIAN RAOBS ARE ALREADY
SOMEWHAT MOIST AND STABILITY WILL BE DECREASING AS COOL AIR MOVES
IN ALOFT.
THIS CHANGE WILL ALSO FLATTEN THE OFFSHORE RIDGE SLIGHTLY AND
RESULT IN A BIT STRONGER WESTERLY ONSHORE FLOW. LOW MARINE
STRATUS CLOUDS ARE CURRENTLY OVER THE CENTRAL GULF UNDER THE
SURFACE RIDGE AXIS. THE NAM INCREASES LOW LEVEL BOUNDARY LAYER RH
ALONG THE COAST AS SOON AS THUR BUT THE RIDGE AXIS IS FORECAST TO
REMAIN OFFSHORE. THAT SUGGESTS THE LOW CLOUDS WONT MOVE INTO THE
INNER CHANNELS VERY QUICKLY. MOS GUIDANCE CONTINUES TO PREDICT AT
OR ABOVE AVERAGE TEMPS NEXT WEEK. MY GUT FEELING IS THAT THE
UPPER LEVEL LOW DRFTING NORTH AND SLOW BUT STEADILY INCREASING
ONSHORE FLOW WILL GRADUALLY INCREASE CLOUD COVER FRI AND SAT AND
EVENTUALLY LEAD TO WIDESPREAD CLOUDS AND CHANCES OF LIGHT RAIN
OVER THE PANHANDLE BY SUNDAY AND MONDAY.
&&
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...SMALL CRAFT ADVISORY FOR PKZ011>013-031-034-036-041>043.
&&
$$
JWA/TA
000
FXAK67 PAJK 212355
AFDAJK
SOUTHEAST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JUNEAU AK
355 PM AKDT TUE MAY 21 2013
.SHORT TERM...MOSTLY QUIET DAY ACROSS THE AREA AS WE ARE STILL
UNDER THE INFLUENCE OF AN INVERTED TROUGH OVER THE PANHANDLE WITH
A RIDGE OVER THE CENTRAL GULF. THE RESULT IS CLEAR SKIES AND DRY
CONDITIONS FOR MOST AREAS. THE EXCEPTION IS THE HYDER AREA WHICH
IS RECEIVING SOME CLOUDS FROM A UPPER LEVEL LOW THAT IS SLOWLY
PULLING NORTH THROUGH BRITISH COLUMBIA. WINDS ARE THE MAIN
CONCERN TODAY WITH NE TO NW SMALL CRAFTS IN LYNN CANAL, STEPHENS
PASSAGE, THE SOUTHERN OUTSIDE WATERS AND CROSS SOUND.
FOR TONIGHT INTO TOMORROW, DRY AND MOSTLY CLEAR CONDITIONS WILL
CONTINUE WITH SOME HIGH TO MID LEVEL CLOUDS TRYING TO FORCE THEIR
WAY OVER THE COAST MOUNTAINS. THEY WILL NOT GET FAR AS DOWN
SLOPPING WINDS ON THE WEST SIDE OF THE MOUNTAINS WILL RAPIDLY
CAUSE THE CLOUDS TO DIMINISH.
DUE TO THE CLEAR SKIES TEMPERATURES ONCE AGAIN WILL DROP
TONIGHT. OVERNIGHT LOWS ARE NOT EXPECTED TO GET AS LOW AS THE
PAST FEW NIGHTS WITH THE COLD UPPER TROUGH THAT HAS BEEN
SUSTAINING IT MOVING OFF TO THE EAST. STILL I THINK TEMPERATURES
WILL GET COLD ENOUGH IN YAKUTAT AND HOONAH TO WARRANT FROST
ADVISORIES FOR THOSE AREAS LATE TONIGHT. TEMPERATURES TOMORROW
WILL REBOUND INTO THE 50S AND 60S FOR DAY TIME HIGHS.
WINDS WILL CONTINUE TO BLOW ACROSS THE AREA INTO TONIGHT AS THE
NORTHERLY PRESSURE GRADIENT STAYS STRONG. THROUGH THE GRADIENT
WILL BE SOMEWHAT WEAKER THEN IT WAS TODAY. STILL EXPECT SMALL
CRAFT WINDS IN LYNN CANAL TONIGHT AND EARLY TOMORROW. IN THE
EASTERN GULF THE WINDS FROM THE INTERACTION BETWEEN THE INVERTED
TROUGH AND THE GULF HIGH WILL CONTINUE TO PRODUCE 25 KT NW WINDS
INTO TOMORROW.
FIRE WEATHER. A CALL WAS RECEIVED FROM THE SKAGWAY FIRE
DEPARTMENT STATING THAT THE BURNABLE FUELS IN THE AREA WERE
RATHER DRY. THIS COMBINED WITH THE 20 TO 30 PERCENT HUMIDITY AND
STRONG NE WINDS BLOWING AT SKAGWAY PROMPTED THE ISSUANCE OF A RED
FLAG WARNING FOR THE SKAGWAY FIRE ZONE FOR THIS AFTERNOON AND
EVENING. THE FIRE DANGER WILL LESSEN OVERNIGHT AS WINDS DIE OFF
AND THE HUMIDITY RISES INTO THE 40 TO 50 PERCENT RANGE. THE
HUMIDITY IS EXPECTED TO CREEP BACK DOWN TOMORROW AFTERNOON AS AIR
TEMPERATURES RISE AND THE WINDS ARE FORECAST TO COME BACK UP
THROUGH NOT AS STRONG AS TODAY. FIRE WEATHER CONDITIONS WILL
CONTINUE TO BE MONITORED CLOSELY.
SHORT RANGE MODELS WERE IN DECENT AGREEMENT TODAY BUT A FEW
DIFFERENCES WERE THERE. THOUGH THAT THE GFS HAD THE AXIS OF THE
INVERTED TROUGH TOO FAR OFFSHORE. DECIDED ON THE NAM FOR UPDATES
TO THE SHORT RANGE FORECAST TODAY. FORECAST CONFIDENCE IS ABOUT
AVERAGE.
.LONG TERM...DRY CONDITIONS AND ABOVE-NORMAL HIGH TEMPERATURES
WILL CONTINUE THROUGH THE START OF THE WEEKEND. CLOUDS AND
PRECIPITATION MAY CREEP BACK INTO THE PANHANDLE BY THE END OF THE
WEEKEND INTO EARLY NEXT WEEK.
DRY AND CLEAR SKIES WILL CONTINUE INTO THE LONG RANGE FORECAST
PERIOD. AN AREA OF HIGH PRESSURE WILL REMAIN OVER THE GULF OF
ALASKA, WHILE AN INVERTED TROUGH REMAINS ALONG THE COAST MOUNTAIN.
THE COMBINATION OF THESE WEATHER SYSTEMS WILL CONTINUE TO DRIVE
NORTHERLY OFFSHORE FLOW OVER THE PANHANDLE. THROUGH THE END OF THE
WORKWEEK, WIND SPEED SHOULD BE LESS THAN 15 MPH ACROSS THE INSIDE
WATERS AND ADJACENT LAND AREAS.
WITH CLEAR SKIES AND RELATIVE LIGHT WINDS, DIURNAL TEMPERATURE
RANGE WILL BE LARGE (UP TO 30 DEGREES IN SOME CASES) FOR THE NEXT
FEW DAYS. AS THE UNDERLYING CONTINENTAL POLAR AIRMASS CONTINUE TO
MODERATE, SOUTHEAST ALASKA WILL BE WARMING UP. THE THREAT OF
MORNING FROST SHOULD BE GOING AWAY. THE FORECASTED LOW
TEMPERATURES FOR WEDNESDAY AND THURSDAY NIGHT RANGE FROM 35 TO 45
DEGREES, WITH THE COLDEST CONDITIONS EXPECTED FROM YAKUTAT INTO
HOONAH AND GUSTAVUS AREAS. DAYTIME HIGH TEMPERATURES WILL RISE
INTO THE MID 60S STARTING THURSDAY. THE WARMEST LOCATIONS WILL BE
IN NORTH CENTRAL PANHANDLE, WITH SOME ISOLATED INLAND LOCATIONS SEEING
TEMPERATURES REACHING THE 70 DEGREE MARK. IN AREAS UNDER CLOUD
COVER OR INFLUENCED BY SEA BREEZES, HIGH TEMPERATURES MAY STRUGGLE
TO RISE INTO THE 60S. AFTERNOON SEA BREEZES AROUND 10 MPH ARE
EXPECTED ALONG COASTAL AREAS.
AREAS ALONG THE COAST AND NEAR THE COAST MOUNTAIN MAY NOT SEE AS
MUCH SUN AS OTHER AREAS ACROSS THE PANHANDLE IN THIS STRETCH OF
DRY WEATHER. MARINE STRATUS ARE EXPECTED TO MOVE TOWARDS THE
COASTAL AREA IN THE LATTER PART OF THIS WEEK. RIGHT NOW, NOT TOO
SURE ABOUT THE AERIAL EXTEND OF THE MARINE STRATUS. CLOUDS AND
SCATTERED RAIN SHOWERS WILL BE CREEPING INTO THE SOUTHEASTERN
PART OF THE PANHANDLE STARTING FRIDAY. THERE ARE ALSO
UNCERTAINTIES ON THE EXTEND OF THE CLOUD COVER AND PRECIPITATION.
THE NORTHERN AND CENTRAL PANHANDLE SHOULD REMAIN MOSTLY CLOUD FREE
THROUGH THE START OF THE WEEKEND. CLOUDS AND PRECIPITATION ARE
EXPECTED RETURN TO SOUTHEAST ALASKA BY THE END OF THE WEEKEND AND
EARLY NEXT WEEK AS ONSHORE FLOW RESUMES.
AS DISCUSSED IN THE SHORT TERM DISCUSSION ABOVE, FIRE WEATHER
CONDITIONS IN SKAGWAY ARE OF CONCERNED. HIGH TEMPERATURES THERE
ARE EXPECTED TO BE IN THE LOW TO MID 60S THROUGH EARLY NEXT WEEK.
AFTERNOON RH VALUE WILL BE AS LOW AS 40 PERCENT OR LOWER. WITH
AFTERNOON SEA BREEZES DEVELOPING, THE WIND SPEED MAY BE AS HIGH AS
15 TO 20 MPH IN THE AFTERNOON. NO PRECIPITATION IS EXPECTED, SO
FUEL CONDITIONS WILL CONTINUE TO BECOME DRIER. COMBINING THE
FACTORS OF LOW RH, WIND SPEED TO 20 MPH, AND DRY FUEL CONDITIONS,
FIRE DANGER WILL BE ELEVATED.
FORECAST CONFIDENCE IS ABOVE AVERAGE THROUGH SATURDAY, THEN
DECREASES TO AVERAGE AFTERWARDS. FAIRLY CONFIDENT ON THE DRY
CONDITIONS OVER MOST OF THE PANHANDLE THIS WEEK. THERE ARE
UNCERTAINTIES IN HOW MUCH CLOUDS AND PRECIPITATION WILL SPILL OVER
FROM THE EASTERN SIDE OF THE COAST MOUNTAIN INTO HYDER AND
KETCHIKAN AREA IN THE LATTER PART OF THE WORK WEEK. ALSO UNCERTAIN
ON HOW WIDESPREAD THE MARINE LAYER WILL SPREAD INTO THE COASTAL
AREAS. UTILIZES NUMERICAL GUIDANCE FROM ECMWF AND WPC TO REFRESH
THE PREVIOUS FORECAST PACKAGE.
.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...FROST ADVISORY FROM 1 AM TO 7 AM AKDT WEDNESDAY FOR AKZ017-021.
RED FLAG WARNING UNTIL MIDNIGHT AKDT TONIGHT FOR AKZ018.
MARINE...GALE WARNING FOR PKZ012.
SMALL CRAFT ADVISORY FOR PKZ011-013-021-022-031>034-041>043.
&&
$$
EAL/RCL
|
