AREA FORECAST DISCUSSION
NWS MARQUETTE MI
422 PM EDT MON MAR 12 2007
.DISCUSSION...
SHORT TERM...TONIGHT THROUGH 00Z WED...
UPPER AIR PATTERN CONSISTS OF A 500 MB CLOSED IN SE NEW MEXICO WITH
A TROUGH OVER THE LOWER GREAT LAKES AND RIDGING ACROSS THE DESERT
SW. 500 MB FLOW IS ZONAL ACROSS THE NORTHERN U.S. WITH A SHORTWAVE
ALONG THE AL/B.C. BORDER. THERE IS ALSO A STATIONARY FRONT THAT IS
ACROSS NORTHERN LAKE SUPERIOR AND THIS SHOULD SLOWLY HEAD NORTH
TONIGHT AS THE SHORTWAVE IN CANADA HELPS TO PUSH IT NORTH AS A WARM
FRONT.
NAM SHOWS THE ALBERTA/B.C. SHORTWAVE HEADING EAST TONIGHT AND TUE
AND THIS REMAINS NORTH ACROSS ONTARIO FOR TUE. WHAT THIS SHORTWAVE
WILL DO IS HELP TO PUSH A COLD FRONT ACROSS THE AREA ON TUE. BASED
ON 1000-500 MB THICKNESS PACKING...IT IS HARD TO PICK OUT THE COLD
FRONT ON THE NAM. NAM IS SHOWING 850-500 MB Q-VECTOR CONVERGENCE
MOVING INTO THE CWA TUE AFTERNOON AND EVENING WITH RRQ OF UPPER JET
PASSING BY LATE IN THE AFTERNOON. NAM ALSO IS PRODUCING SOME QPF IN
THE AFTERNOON WHICH LOOKS GOOD WITH MID LEVEL MOISTURE ON
I295K-I305K SURFACES. THE LIFT ON THESE SURFACES IS NOT VERY STRONG.
GFS IS SIMILAR TO THE NAM AND WILL USE A BLEND OF THE TWO MODELS FOR
THIS FORECAST. WILL CONTINUE WITH LOW CHANCE POPS FOR TUE LATE
MORNING THROUGH AFTERNOON ACROSS THE CWA AS MOISTURE WILL BE LIMITED
AND WILL BE IN THE MID LEVELS.
PROBLEM FOR TONIGHT IS CLOUD COVER. LATEST TAMDAR SOUNDINGS FROM
KSAW SHOWS AN INVERSION UP TO 800 MB WITH MOISTURE TRAPPED BELOW THE
INVERSION FROM 850 MB DOWNWARDS. THE LOW CLOUDS ARE SLOWLY ERODING
ALONG THE WI BORDER THIS AFTERNOON AND WILL TAKE THEIR TIME TO ERODE
FROM MOST OF THE CWA. NAM RH FIELDS FROM 850 MB AND BELOW SHOWS THIS
TREND WELL AND WILL FOLLOW. NAM SHOWING WITH WESTERLY WINDS
TONIGHT...LOW CLOUDS SHOULD CONTINUE TO PUSH EAST. ONLY PROBLEM
COULD BE A SOUTH WIND THAT DEVELOPS AT THE SFC TONIGHT AND COULD
BRING IN SOME STRATUS FROM LAKE MICHIGAN FROM KESC TO KSAW EASTWARDS
AND WILL KEEP MOSTLY CLOUDY THERE BECAUSE OF THAT POSSIBILITY AND
THIS WILL ALSO BE THE AREA WHERE FOG HAS ITS BEST CHANCE TO FORM.
ADDED IN PATCHY FOG INTO THE FORECAST TONIGHT AND EARLY TUE MORNING
WITH DEW POINTS NOT DROPPING MUCH AND WINDS WILL BE LIGHT OVERNIGHT
FOR THE MOST PART. THINGS SHOULD NOT GET TOO OUT OF HAND THOUGH WITH
WINDS PICKING UP ACROSS THE WEST AND THERE IS STRONGER WINDS ABOVE
900 MB THAT BOTH THE NAM AND GFS ARE SHOWING FOR TONIGHT WHICH
SHOULD GO OVER THE TOP OF THE BOUNDARY LAYER. WHERE WINDS DO
DECOUPLE WITH THE SNOWMELT THAT HAS TAKEN PLACE ADDING TO THE LOW
LEVEL MOISTURE...FOG IS DEFINITELY POSSIBLE. STRATUS COULD MAKE A
RETURN TONIGHT WITH THE LIGHT WINDS AND WILL INCREASE CLOUD COVER
BACK INTO THE CWA FOR THIS REASON.
FOR TEMPERATURES...WENT CLOSE TO GFS TONIGHT AND WENT CLOSE TO
ADJMAV FOR TUE. THINK THERE WILL BE MORE CLOUDS THAN PREVIOUSLY
THOUGHT WITH A MID DECK AND THIS WILL CUT THE HEATING POTENTIAL WITH
THE COLD FRONT MOVING ACROSS THE AREA LATE IN THE DAY. LOWERED HIGHS
ABOUT 5-6 DEGREES EVERYWHERE AND THERE WILL STILL BE SOME MID 40S TO
LOWER 50S POSSIBLE WHICH IS STILL WARM.
&&
LONG TERM (TUESDAY NIGHT THROUGH NEXT MONDAY)...
TUESDAY NIGHT INTO WEDNESDAY...INCREASING UPR DIV IN RRQ OF 140 KT
3H OVER ONTARIO AND ASSOC 700-600 MB FRONTOGENESIS ALONG AND NORTH
OF FRONTAL BOUNDARY COULD SUPPORT SOME LINGERING RAIN/SNOW SHOWERS
OVER SCNTRL COUNTIES TUE NIGHT PER NAM/GFS AND UKMET. LOOK FOR STILL
A SLIGHT OF RAIN OVER SCNTRL COUNTIES ON WED AS FGEN FORCING WEAKENS
SOME WITH FRONTAL BOUNDARY SAGGING A BIT FARTHER S. LOOK FOR COOLER
TEMPS ON WED AS FLOW BECOMES NE ON BACKSIDE OF SFC TROF/FRONTAL
BOUNDARY.
WEDNESDAY NIGHT...MODELS IN PRETTY GOOD AGREEMENT THAT DIFFLUENT
FLOW ALOFT WILL NOW SET UP OVER REGION WED NIGHT AS SFC HIGH BUILDS
IN FROM ONTARIO PUSHING STATIONARY BOUNDARY WELL S OF WI AND MI.
THUS...HAVE REMOVED SLIGHT CHC OF SNOW FOR WED NIGHT.
THURSDAY INTO FRIDAY...APPROACH OF SHORTWAVE AND DEVELOPMENT OF
INVERTED TROF PER 12Z GFS/UMKET/CANADIAN AND ECMWF WILL WARRANT
KEEPING CHC POPS FOR LIGHT SNOW ON THU. MODELS SHOW ENOUGH COLD AIR
BEHIND THIS SYSTEM (850 MB TEMPS FALLING TO -12 TO -14C ON FRI PER
ECMWF AND GFS) AND CYCLONIC NE FLOW THAT THERE COULD BE SOME LES OFF
LAKE SUPERIOR AS WELL THU NIGHT INTO FRI. SINCE MODELS STILL DIFFER
SOMEWHAT ON HOW DEEP THIS SYSTEM/TROF WILL BE AND DEGREE OF COLD AIR
BEHIND IT...WILL CONTINUE THE LOW CHCS POPS FOR SNOW AT THIS POINT.
HOWEVER...WE MAY NEED TO BUMP UP POPS FOR NE UPSLOPE AREAS ALONG
LAKE SUPERIOR ESPECIALLY IF MODELS TREND DEEPER WITH SYSTEM ON LATER
RUNS.
SATURDAY INTO MONDAY...MODELS NOT IN GOOD AGREEMENT ON DETAILS FOR
WEEKEND INTO EARLY NEXT WEEK. GFS AND CANADIAN DEVELOP DEEPER SYSTEM
FOR LATE WEEK AND SHOW CYCLONIC NRLY LINGERING INTO SAT NIGHT WHILE
ECMWF SHOWS WEAKER SYSTEM DEPARTING QUICKER WITH SFC HIGH BUILDING
INTO REGION BY SAT. GIVEN UNCERTAINTY WILL STICK WITH LOW CHC POPS
FOR LAKE SUPERIOR COUNTIES THROUGH SAT NIGHT...AND EVEN KEEP IN
ISOLD POPS OVER KEWEENAW AND ERN COUNTIES SUN INTO MON AS WEAK NW
FLOW PERSISTS AND 850 MB TEMPS FCST AROUND -13/-14C OVER LAKE
SUPERIOR.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...NONE.
&&
$$
SHORT TERM...MICHELS
LONG TERM....VOSS
AREA FORECAST DISCUSSION
NWS SEATTLE WA
845 AM PDT SUN MAR 11 2007
.SYNOPSIS...A STRONG AND WET PACIFIC STORM SYSTEM WILL AFFECT THE
AREA TODAY AND TONIGHT. THIS SYSTEM WILL BRING STRONG SOUTHWEST FLOW
ALOFT AND A HIGH SNOW LEVEL. A WEAKER SYSTEM WILL BRUSH ACROSS THE
AREA TUESDAY FOLLOWED BY WEAK RIDGING LATER IN THE WEEK.
&&
.SHORT TERM...RAINFALL AMOUNTS COPIOUS ON THE COAST AND IN THE
MOUNTAINS...RELATIVELY LIGHT OVER MOST OF THE INTERIOR LOWLANDS. SO
FAR IT LOOKS LIKE 2.5 TO 3 INCHES ON THE COAST AND OLYMPIC
PENINSULA...2 TO 2.5 INCHES IN THE NORTH CASCADES...1 TO 2 INCHES IN
THE CENTRAL CASCADES...GENERALLY UP TO AN INCH IN THE INTERIOR
LOWLANDS WITH A NOTICEABLE HOLE NORTH SEATTLE NORTHWARD. FORECASTS
FOR RAINFALL AMOUNTS AND FLOODING ARE MORE OR LESS ON TRACK 12 HOURS
INTO THE STORM WITH 18 HOURS OR SO OF RAIN STILL TO COME. HOWEVER
THERE APPEARS TO BE A LULL OF SORTS IN THE HEAVIEST RAIN...EVEN IN
THE MOUNTAINS...AND NO FLOOD WARNINGS OTHER THAN SKOKOMISH WILL BE
COMING OUT ANYTIME SOON. WATCH REMAINS IN EFFECT.
MODELS STILL HAVE FRONTAL PASSAGE TONIGHT FOR A CHANGE TO SHOWERS.
MONDAY LOOKS DRY...AT LEAST IN THE SEATTLE METRO AREA. GFS HAS NO
PCPN AND STRONG WESTERLY FLOW ALOFT FAVORS A RAIN SHADOW ANYWAY.
THOUGH MOS POPS ARE IN THE LOW CHANCE CATEGORY...MAY GO OUT ON A
LIMB AND REMOVE MENTION OF SHOWERS FOR A FEW ZONES ON MONDAY. WEAKER
SYSTEM TUESDAY SEEMS MAINLY TO AFFECT NORTHERN ZONES BUT WILL
PROBABLY KEEP CHANCE POPS EVERYWHERE...LIKELY NORTH. BURKE
.LONG TERM...PREVIOUS DISCUSSION...ZONAL FLOW WITH AVERAGE HEIGHTS
AND AIR MASS MIDWEEK GRADUALLY GIVES WAY TO SOME MODEST
RIDGING...WITH H5 HEIGHTS CLIMBING TO THE LOWER 570`S BY THU NIGHT
AND FRI. THAT LOOKS GOOD ENOUGH FOR A PARTLY SUNNY AND THU AND FRI
ARE DRY IN THE GFS. A LITTLE LIGHT PRECIP THREATENS WED AND
SAT...FOR NOW WE JUST SHOW A CHANCE OF SHOWERS THRU THE PERIOD. MM
&&
.AVIATION...THE STRONG FRONT HAS LIFTED NORTH INTO VANCOUVER ISLAND
WHILE STRONG FLOW ALOFT CONTINUES TO INTERACT WITH THE TERRAIN.
ACARS SOUNDINGS SHOW 40-45KT SSW WIND AT 1500 FT AT KSEA WHICH IS
PRODUCING AREAS OF LLWS. EXPECT SOME MOMENTUM TRANSFER TO THE
SURFACE JUST N OF KSEA IN THE VICINITY OF A MESO LOW THAT PERSISTS E
OF THE OLYMPICS. ALSO EXPECT THE STRONG WINDS ON THE ORDER OF 50 KT
ABOVE 015 TO IMPACT THE AIRSPACE AROUND SEATTLE.
CONDITIONS ARE QUITE VARIABLE ACROSS THE AREA WITH SCT-BKN LAYERS
AT 010...020...AND 035. VIS GENERALLY 5SM -RA BUT IS OCCASIONALLY
POPPING DOWN TO 1-3 SM IN AREAS OF HEAVIER PRECIPITATION. EXPECT
CONDITIONS TO REMAIN ABOUT WHERE THEY ARE THRU ABOUT 20Z...THEN TO
DETERIORATE SOMEWHAT FROM THE NORTH AS THE FRONT MOVES SWD
INCREASING RAINFALL RATES. THE FRONT WILL PASS THROUGH KSEA
04Z-08Z TIME FRAME. WIND AT KSEA WILL VARY BETWEEN 18015KT WITH
LLWS...TO 18020G30KT DURING PERIODS WHEN MESO LOW DROPS A LITTLE S
INTO PUGET SOUND. HIGH CONFIDENCE IN THE GENERAL TRENDS BUT LOWER
CONFIDENCE IN THE FORECAST OF SPECIFIC DETAILS AT THE KSEA TERMINAL
TODAY.
OVERNIGHT EXPECT WIND TO SHIFT TO 22015G25KT AND CONDITIONS TO
GRADUALLY IMPROVE AT KSEA AS THE FRONT DRIVES SE...FLOW BECOMES MORE
WESTERLY...AND THE OLYMPIC RAIN SHADOW DROPS SWD. ALBRECHT
&&
.MARINE...WINDS HAVE BEEN IN A BIT OF A LULL OVER THE PAST SEVERAL
HOURS. BUT SLY PRESSURE GRADIENTS ARE INCREASING AS A DEEP LOW IN
THE NORTHERN OFFSHORE WATERS DRIVES ENE TOWARD VANCOUVER ISLAND.
EXPECT FULL GALES TO REDEVELOP ALONG THE COAST...ADMIRALTY
INLET...ENTRANCES TO THE STRAIT AND NORTHERN INLAND WATERS. WILL
MAINTAIN A HIGH END SMALL CRAFT ADVISORY FOR PUGET SOUND AND HOOD
CANAL...BUT MAY NEED TO ISSUE A SHORT FUSE GALE IF GRADIENTS
CONTINUE TO INCREASE. THE COLD FRONT WILL SWEEP THRU THE WATERS BY
06Z WITH WINDS GENERALLY TURNING WLY THROUGH THE STRAIT AND
DECREASING ELSEWHERE. ALBRECHT
&&
.AVALANCHE...RAIN, RAIN AND MORE RAIN HAVE COMBINED WITH MELT AND
HIGH FREEZING LEVELS TO SATURATE AND WEAKEN UPPER PART OF THE
SNOWPACK AND SIGNIFICANTLY INCREASE THE AVALANCHE DANGER. CURRENT
WARNINGS WILL BE EXPANDED TO INCLUDE MT HOOD AREA FOR LATE TODAY AS
THE NEXT FRONTAL WAVE SAGS SOUTHWARD. WHILE MARGINAL WEATHER HAS
LIMITED FIELD OBSERVATIONS, EXPECT THAT NATURAL AVALANCHE ACTIVITY
HAS INCREASED IN MOST STEEPER TERRAIN. WITH ANOTHER 1 TO 3 INCHES OR
MORE OF RAIN EXPECTED NEXT 18-24 HOURS, WATER SHOULD PENETRATE
DEEPER INTO THE PACK AND ALLOW FOR SOME LARGER WET SLIDES TO BRING
DOWN ALL THE SNOW ACCUMULATED SINCE MID-FEBRUARY. WITH SOME SKI
AREAS CLOSED DUE TO ANTICIPATED WEATHER, HOPE THIS MESSAGE OF BAD
AND/OR DANGEROUS BACK COUNTRY CONDITIONS WILL BE HEEDED. SEE
WWW.NWAC.US FOR DETAILS. MOORE
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
.FLOOD WATCH ALL OF WESTERN WASHINGTON EXCEPT LEWIS...SAN
JUAN...ISLAND...AND KITSAP COUNTIES.
.GALE WARNING COAST...ENTRANCES...ADMIRALTY INLET AND NORTHERN
INLAND WATERS.
.SMALL CRAFT ADVISORY PUGET SOUND HOOD CANAL AND CENTRAL STRAIT OF
JUAN DE FUCA.
.SMALL CRAFT ADVISORY GRAYS HARBOR FOR ROUGH BAR CONDITIONS.
$$
WEATHER.GOV/SEATTLE
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