AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
1012 PM EST TUE DEC 9 2008
.UPDATE...
BIGGEST CONCERN FOR THE UPDATE WAS ONGOING LAKE EFFECT SNOW EVENT
FOR ERN MQT AND ALGER COUNTIES.
MQT RADAR REVEALS FAIRLY IMPRESSIVE WIND-PARALLEL MULTIBAND LES FROM
NEGAUNEE EAST INTO ALGER COUNTY. 30+ MAX DBZ RETURNS NOTED WITHIN
THE MORE INTENSE BANDS PROBABLY YIELDING CLOSE TO INCH/HR
ACCUMULATION RATES. FAIRLY UNIDIRECTIONAL 350-360 WIND FLOW NOTED ON
VWP FROM SFC THROUGH 6KFT. 01Z TAMDAR SNDG AT KSAW SHOWING MOIST
PROFILE UP THROUGH 800 MB ALTHOUGH BASE OF INVERSION IS NOTED BLO
4KFT. LOWER INVERSION HEIGHT DOESN`T APPEAR TO BE NEGATIVELY
IMPACTING BANDS AND PRETTY MUCH ENTIRE MOIST LYR IS LOCATED WITHIN
FAVORABLE DENDRITIC GROWTH ZONE. FAVORABLE DGZ ALSO RESULTING IN
FLUFFY 35-40/1 SNOW/WATER RATIOS.
00Z WRF-ARW CONSISTENT WITH PREV RUNS IN SHOWING LOW-LEVEL
CONVERGENCE INCREASING OVER ERN MQT-WRN ALGER COUNTIES LATER THIS
EVENING WITH DEVELOPING LAND BREEZES AND THEN BACKING FLOW FROM N TO
NW WILL GRADUALLY PUSH LES BANDS OUT OF MQT COUNTY BY 08-09Z. A
DOMINANT BAND WILL THEN FOCUS OVER ALGER COUNTY FROM MUNISING TO
MELSTRAND FROM LATE TONIGHT INTO WED MORNING. GIVEN THE INCREASING
CONVERGENCE AND CONTINUED ADDITIONAL LES ACCUMS DECIDED TO GO WITH A
LAKE EFFECT SNOW ADVISORY FOR MQT COUNTY UNTIL 3 AM AND FOR ALGER
COUNTY 11 AM WED.
NO OTHER CHANGES MADE TO FCST.
&&
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A POSITIVE TILT UNPHASED
TROF EXTENDING FROM HUDSON BAY TO TX. IN THE SRN STREAM...ONE
WEAKENING SHORTWAVE IS LIFTING NE THRU THE CNTRL/LWR LAKES
REGION...ANOTHER SHORTWAVE WAS OVER OK/KS WITH A THIRD IN THE VCNTY
OF SRN NM/W TX. IN THE NRN STREAM...A SHORTWAVE WAS DROPPING SE
THRU MANITOBA. THIS SHORTWAVE WILL PASS ACROSS THE UPPER LAKES
TONIGHT. CLOSER TO HOME...IN THE WAKE OF DEPARTING -SN/DEEPER
MOISTURE ASSOCIATED WITH SRN STREAM SHORTWAVES...LES REGIME HAS
DEVELOPED OFF LAKE SUPERIOR UNDER NRLY FLOW CAA. DRY AIRMASS HEADING
S (PER 12Z CWPL SOUNDING) HAS KEPT LES GENERALLY ON THE LIGHT
SIDE...BUT THE FLUFF FACTOR HAS BEEN STEADILY INCREASING AS AIRMASS
IN THE CONVECTIVE LAYER COOLS TO FAVORABLE TEMPS FOR DENDRITES TO
GROW. AFTN TAMDAR SOUNDING SHOWED INVERSION BASED AT 850MB WITH TEMP
AT INVERSION BASE OF -16C...SUPPORTING THE INCREASE IN SNOW TO WATER
RATIOS THIS AFTN. LONGER FETCH AIDED BY LAKE NIPIGON MAY HAVE LED TO
SOME LOCALLY HEAVIER LES IN FAR WRN UPPER MI IN THE VCNTY OF KIWD
DURING THE DAY AS SUGGESTED BY VIS SATELLITE IMAGERY.
&&
.SHORT TERM (TONIGHT/WED)...
LES AND TEMPS ARE THE MAIN FCST ISSUES TONIGHT.
SHORTWAVE OVER MANITOBA WILL PASS ACROSS THE UPPER LAKES TONIGHT.
WITH TRACK OVER THE AREA...BEST FORCING WILL PASS N OF HERE. IN
ADDITION...SINCE LOW-LEVEL CAA IS DOMINATING...THERE IS LITTLE OR NO
FORCING ACROSS THE FCST AREA. NONETHELESS...WOULD STILL EXPECT TO
SEE AT LEAST A LITTLE ENHANCEMENT AS INVERSIONS SHOULD RISE A BIT
WITH APPROACH OF SHORTWAVE. SNOW TO WATER RATIOS SHOULD BE HIGH WITH
FAVORABLE DENDRITIC SNOW GROWTH TEMPS DOMINATING BLO THE INVERSION.
SO A GOOD FLUFF FACTOR (PROBABLY AT LEAST 25 TO 1) WILL BOOST SNOW
ACCUMULATIONS TONIGHT. BEST LES TONIGHT SHOULD TEND TO BECOME
FOCUSED INTO ALGER COUNTY AND AT LEAST FAR ERN MARQUETTE COUNTY FOR
A TIME. THIS AREA WILL BE FAVORED AS LAND BREEZES WILL RESULT IN
STRONGER LOW-LEVEL CONVERGENCE DEVELOPING THERE. IN ADDITION...THAT
AREA WILL BE INLINE FOR PRECONDITIONING FROM STILL OPEN LAKE
NIPIGON. THE RUC13...WHICH OFTEN DOES A NICE JOB ON LAND/LAKE
INTERACTIONS (BUT SOMETIMES DOES OVERDO IT)...SHOWS A MESOLOW
DEVELOPING NEAR MUNISING LATE TONIGHT/WED MORNING. THE NAM AND LOCAL
HIGH RES WRF-ARW ALSO HINT AT A CIRCULATION IN THAT GENERAL
LOCATION...BUT IT`S MORE SO WED MORNING/EARLY AFTN IN THE COL AREA
WITHIN PASSING SFC RIDGE AXIS. IN ANYCASE...IT WILL BE SOMETHING TO
WATCH FOR SINCE ITS DEVELOPMENT WOULD RESTRUCTURE WIND PARALLEL
BANDS DOMINATING FOR MUCH OF THE NIGHT AND COULD REALLY FOCUS
LOCALLY HEAVIER SNOW. FOR NOW...WILL ASSUME JUST STRENGTHENING
CONVERGENCE BTWN MARQUETTE/MUNISING OVERNIGHT. HAVE PAINTED 2-5 INCH
ACCUMULATIONS IN THAT AREA...BUT IT`S POSSIBLE ACCUMULATIONS COULD
RISE TO ADVY CRITERIA DEPENDING ON HOW DEVELOPING DOMINANT BANDS
ORGANIZE THIS EVENING. ELSEWHERE IN THE LES AREAS...FLUFFY
ACCUMULATIONS TONIGHT SHOULD RANGE FROM 1-3 INCHES.
AWAY FROM LAKE SUPERIOR LES...EXPECT DRY WEATHER WITH TEMPS THE MAIN
ISSUE. SHOULD IT CLEAR OUT...TEMPS WILL CRASH. HOWEVER...IT APPEARS
WINDS IN THE CLOUD BEARING LAYER WILL RETAIN ENOUGH OF A NRLY
COMPONENT THAT LAKE EFFECT CLOUDS SHOULD DOMINATE EVEN WELL INLAND
AWAY FROM LES. UNDER THIS ASSUMPTION...TOOK A CONSERVATIVE APPROACH
TO MINS...NOT GOING ANY LWR THAN AROUND 5F OVER THE INTERIOR SW. BIG
TEMP BUST POTENTIAL IS THERE.
LINGERING LES OFF LAKE SUPERIOR WILL END WED AS HIGH PRES RIDGE
PASSES AND WINDS BECOME SRLY. ANOTHER INCH OR TWO OF ACCUMULATION IS
POSSIBLE ACROSS ALGER COUNTY WED MORNING BEFORE LES SHIFTS OFFSHORE.
IN THE AFTN...WILL NEED TO WATCH FOR THE POTENTIAL OF LES STREAMING
IN OFF LAKE MICHIGAN INTO THE SE FCST AREA AS WINDS BECOME SRLY.
SOME OF THE HIGHER RES MODELS SHOW MIDLAKE CONVERGENCE THAT COULD
SET THE STAGE FOR A PERIOD OF DECENT LES. THIS SHOULD BE MORE AN
ISSUE HEADING INTO WED NIGHT AS SRLY WINDS STRENGTHEN. OTHERWISE...
ATTENTION TURNS TO NEXT SHORTWAVE HEADING SE TOWARD THE UPPER
MISSISSIPPI VALLEY. ASSOCIATED SFC LOW WILL REACH NRN MN LATE
AFTN/EARLY EVENING. DECENT ISENTROPIC ASCENT REGIME AND DEEP LAYER
QVECTOR CONVERGENCE AHEAD OF FEATURE SHOULD RESULT IN -SN SPREADING
INTO WRN UPPER MI DURING THE AFTN.
.LONG TERM (WED NIGHT THROUGH NEXT TUE)...
MAIN FORECAST CONCERNS ARE SNOWFALL AMOUNTS WITH CLIPPER SYSTEM WED
NIGHT AND THEN MIXED PCPN SCENARIO FOR SUN/MON.
WED NIGHT...CLIPPER SYSTEM INDICATED YESTERDAY TO MOVE ACROSS LAKE
SUPERIOR IS STILL SHOWN TODAY...WITH TIMING ABOUT THE SAME.
HOWEVER...THE NAM HAS SLOWED UP A LITTLE BIT. RIGHT NOW...FAVOR THE
FASTER ECMWF/UKMET/GFS/LOCAL WRF-ARW WHICH BRING THE LOW FROM NRN MN
AT 00Z THU TO NE LAKE SUPERIOR BY 12Z THU. THE NAM ONLY BRINGS IT
INTO WESTERN LAKE SUPERIOR. CLIPPER SHOULD BRING SOME WARM ADVECTION
SNOW ACROSS THE AREA...ESPECIALLY OVER THE NORTHERN PORTION OF THE
CWA AND ACROSS LAKE SUPERIOR...CLOSER TO THE BETTER DYNAMICS FROM
THE SHRTWV ASSOCIATED WITH THE CLIPPER. SOUNDINGS ARE ACTUALLY QUITE
IMPRESSIVE WITH THE LIFT FROM ALL MODELS...WHICH COINCIDES WITH THE
DENDRITIC GROWTH ZONE (DGZ). THE AIRMASS BELOW THE DGZ IS NOT ALL
THAT COLD EITHER...WHICH SHOULD HELP REDUCE AGGREGATION. THEREFORE
HAVE GONE WITH SNOW TO WATER RATIOS AROUND 20 TO 1...WHICH RESULTS
IN A COUPLE INCHES OF SNOW BASED ON WELL AGREED UPON QPF FROM THE
GFS/REGIONAL CANADIAN/LOCAL WRF-ARW. ANOTHER AREA OF INTEREST IS SE
SCHOOLCRAFT INTO LUCE COUNTY WITH A STRONG LIKELIHOOD OF A LAKE
MICHIGAN BAND IMPACTING THIS PORTION OF THE CWA. LUCKILY THE LLVL
FLOW DOES NOT FAVOR A BAND STAYING IN ONE SPOT...AS THE BAND SHOULD
MOVE IN AROUND 06Z THEN STARTING MOVING SLOWLY EAST AS THE FLOW GOES
FROM SOUTH TO SW. NONETHELESS...AN ADVISORY LOOKS TO BE NEEDED AT
LEAST FOR LUCE COUNTY. LATE IN THE NIGHT...A COLD FRONT ASSOCIATED
WITH THE CLIPPER WILL BE MOVING INTO THE WESTERN U.P.. WITH 850MB
TEMPS FALLING TO -12 TO -14C ALONG THE FRONT...IT IS LIKELY THERE
WILL BE A BAND OF LAKE EFFECT SNOW ALONG IT. THEREFORE...POP GRIDS
AFTER 06Z DENOTE LIKELY WORDING IN THE WEST AS WELL. LOW
TEMPERATURES GENERALLY A BLEND OF MET/MAV GUIDANCE...GIVEN THAT
PLENTY OF CLOUDS AND WIND WILL BE AROUND.
THU THROUGH FRI...MUCH OF THIS PERIOD IS DOMINATED BY LAKE EFFECT...
AS AN UPPER TROUGH SETTLES IN OVER THE GREAT LAKES. THE MAIN PORTION
OF THIS UPPER TROUGH COMES DOWN OUT OF NORTHWEST TERRITORIES. 850MB
TEMPS DROP DOWN TO -20 TO -22C BY 12Z FRI. THEREFORE HIGHS AND LOWS
WILL BE COLD DURING THIS PERIOD...ESPECIALLY WITH LOWS ON THU NIGHT.
STAYED TOWARDS THE LOW END OF GUIDANCE FOR THU NIGHT...BUT LUCKILY
THERE SHOULD BE SOME CLOUDS AND WIND TO PREVENT TEMPS FROM
PLUMMETING TOO MUCH. REGARDING THE LAKE EFFECT...HAVE INCREASED POPS
TO LIKELY FOR THE WEST AND AREAS EAST OF MARQUETTE WITH A GENERAL NW
FLOW EXPECTED. SNOW TO WATER RATIOS SHOULD BE FAIRLY HIGH ON THU...
20 TO 1 OR SO. AS THE COLD AIR COMES IN...THE RATIOS WILL DROP SOME
OVER THE WEST AS A PORTION OF THE DGZ FALLS BELOW THE CLOUD BASE.
HOWEVER...THE LONGER FETCH OF WARMER AIR OFF EASTERN LAKE SUPERIOR
WILL BE ABLE TO HOLD THE DGZ IN THE CLOUD...SO HAVE INCREASED RATIOS
IN THE EASTERN CWA. RATIOS WILL STABILIZE AGAIN ON FRI AROUND 20 TO
1 AS DAYTIME HEATING HELPS WARM UP THE LOW LEVELS. AMOUNT WISE OVER
THIS TIME PERIOD...IT APPEARS MOST OF IT SHOULD BE LIGHT...WITH
TOTALS PERHAPS UP TO 6 INCHES IN THE EASTERN CWA. OF COURSE THERE IS
ALWAYS POTENTIAL FOR A DOMINANT BAND TO HELP INCREASE AMOUNTS
MORE...WHICH DEFINITELY CANNOT BE RULED OUT FOR ALGER COUNTY AS THE
LAND BREEZE KICKS IN OFF OF MARQUETTE COUNTY.
FRI NIGHT THROUGH TUESDAY...MODELS AGREE AGAIN WELL ON THE UPPER
LEVEL PATTERN...TRANSITIONING TO A WESTERN TROUGH AND EAST COAST
RIDGE BY LATE SUN...THEN REMAINING THAT WAY THROUGH AT LEAST MONDAY
AND LIKELY INTO TUESDAY. HOWEVER...THERE REMAINS A MAJOR QUESTION ON
WHAT HAPPENS DURING THE SAT NIGHT TO MON TIME FRAME. THE 06Z GFS AND
00Z CANADIAN NOW LOOK LIKE THE 08/00Z ECMWF RUN BRINGING A SFC LOW
ACROSS THE CWA ON SUN...WITH COLD AIR FLOWING IN BEHIND IT FOR MON.
ON THE OTHER HAND...THE 00Z ECMWF/UKMET ARE SLOWER AND REMAIN FAIRLY
CONSISTENT WITH THE 08/12Z ECMWF IN SHOWING THE LOW CROSSING MON
MORNING. THE PROBLEM WITH THIS SYSTEM IS THAT NO MATTER WHICH TIME
FRAME IS PREFERRED FOR IT MOVE THROUGH...850MB TEMPS WARM UP ENOUGH
TO TURN PCPN AT A MINIMUM TO SLEET/FREEZING RAIN AND LIKELY RAIN. IT
APPEARS THE DIFFERENCE BTWN THE FASTER AND SLOWER RUNS IS RELATED TO
A NRN STREAM SHRTWV TROUGH CROSSING CENTRAL CANADA LATE SAT...AND
WHERE THE SHRTWV ASSOCIATED WITH THE SFC LOW IS LOCATED. THE 00Z
ECMWF/UKMET HAVE THE SHRTWV IN EASTERN IDAHO AT 00Z SUN COMPARED TO
THE 06Z GFS WHICH IS IN THE WRN DAKOTAS...CLOSER TO BEING PICKED UP
BY THE NRN STREAM SHRTWV. GIVEN THE FLUCTUATION SEEN IN THE GFS
DURING THE PAST FOUR RUNS AND THAT PRACTICALLY ALL OF THE 00Z GFS
ENSEMBLES AGREE WITH THE 00Z ECMWF...HAVE DECIDED TO LEAN TOWARDS
THE ECMWF FOR THE FORECAST WITH THIS SYSTEM. OUTSIDE OF THIS
SYSTEM...MODELS ARE IN GOOD AGREEMENT.
SOME OF THE DETAILS. FOR FRI NIGHT...INCREASING WARM ADVECTION IN
THE WAKE OF THE TROUGH ON FRI AND AHEAD OF A WEAK SHRTWV MOVING
THROUGH THE FLOW SHOULD BRING SOME LIGHT SNOW TO THE AREA. BULK OF
THE SNOW APPEARS RIGHT NOW TO STAY TO THE NORTH...THOUGH...OVER NRN
LAKE SUPERIOR. THERE AGAIN COULD BE A BAND OFF LAKE MICHIGAN...BUT
NOW THE WINDS MIGHT BE TOO SW TO ALLOW FOR THE BAND TO IMPACT THE
CWA. WARM ADVECTION CONTINUES DURING THE DAY SAT WITH YET ANOTHER
SHRTWV INDICATED TO MOVE THROUGH THE FLOW. THIS ADVECTION LOOKS
STRONGER...WITH 850MB WINDS REACHING 45-50 KT. IN ADDITION...MORE
MOISTURE IS TAPPED OUT OF THE GULF OF MEXICO...SO MORE PCPN IS
POSSIBLE. 850MB TEMPS ONLY RISE TO -2 TO -4C...SO RIGHT NOW IT IS
ASSUMED THAT THE MAJORITY OF THE PCPN WILL FALL AS SNOW. WARM
ADVECTION CONTINUES SAT NIGHT INTO SUN AS THE LOW PRESSURE SYSTEM
OUT OF THE WESTERN U.S. LIFTS TOWARDS UPPER MI. PCPN SAT NIGHT MAY
TURN INTO A MIX OF RAIN/SNOW AS 850MB TEMPS CONTINUE TO WARM...THEN
CHANGE MOSTLY TO RAIN OVER THE SOUTH CENTRAL AND EAST ON SUN. 00Z
ECMWF ACTUALLY HAS READINGS OF 4-6C OVER THE SOUTH CENTRAL BY 00Z
MON. GIVEN THESE READINGS...CONCERN ACTUALLY STARTS TO EXIST OF
THUNDER. WILL NOT INCLUDE THUNDER AT THE MOMENT...SINCE SHOWALTER
INDICES ARE 0-2C JUST TO OUR SOUTH. MUCH OF UPPER MI MAY END UP
DEALING WITH ONLY RAIN SUN NIGHT AS THE ENTIRE EASTERN 2/3 OF THE
CWA HAS 850MB TEMPS OF 2-6C BY 12Z MON PER THE 00Z ECMWF RUN. NEW
12Z ECMWF RUN IS A BIT COLDER NOW. THEREFORE...WILL STILL KEEP A
RAIN/SNOW MIX GOING. COLD FRONT COMES THROUGH MON...WHICH ACTUALLY
LOOKS QUITE STRONG AS 850MB TEMPS PLUMMET TO -16C OVER WESTERN
SUPERIOR BY 00Z TUE...SO FALLING TEMPS ON MON ARE PLANNED. FURTHER
COOLING IS EXPECTED MON NIGHT AND TUE AS A PORTION OF THE WESTERN
UPPER TROUGH MOVES THROUGH UPPER MI. WIND FLOW GOES FROM WEST TO
NORTH...BUT NOT MUCH MOISTURE IS PRESENT AS A CANADIAN HIGH BUILDS
IN AT THE SFC...SO ONLY LIGHT LAKE EFFECT SNOW SHOWERS ARE EXPECTED.
FUTURE SHIFTS WILL NEED TO CONTINUE TO MONITOR THE SYSTEM FOR THIS
WEEKEND. HAVE DECLINED TO MENTION FZRA OR SLEET BECAUSE IT IS SO FAR
OUT AND THOSE DETAILS CAN CHANGE GREATLY. NONETHELESS...EACH ONE IS
POSSIBLE. 12Z CYCLE UPDATE...THE 12Z GFS ENSEMBLES SHOW MUCH MORE
SPREAD...WITH HALF OF THEM LOOKING MORE LIKE THE 00Z ECMWF/CANADIAN
AND THE OTHER HALF LIKE THE 06Z/12Z GFS. THE 12Z CANADIAN CONTINUES
TO LOOK LIKE ITS PREDECESSOR...AS DOES THE NEW 12Z ECMWF...SO
UNCERTAINTY STILL REMAINS.
&&
.AVIATION (FOR THE 00Z TAF ISSUANCE)...
AS THE LOW-LEVEL FLOW GRADUALLY BACKS FROM N TO NW LATER THIS
EVENING WITH THE APPROACH OF A HIGH PRES RIDGE FROM THE W...-SHSN
SHOULD DIMINISH TO FLURRIES AT KCMX AND PROBABLY END AT KSAW.
HOWEVER...LOOK FOR MVFR CIGS TO PERSIST AT KSAW UNTIL LATER WED
MORNING WHEN WINDS BACK FURTHER TO THE W OR SW...RESULTING IN BETTER
DOWNSLOPING. AT KCMX...WINDS SHOULD REMAIN FAVORABLE FOR MAINTAIN
MVFR CIGS TONIGHT THROUGH WED. EXPECT WARM ADVECTION SNOW TO SPREAD
INTO AREA LATE WED AHEAD OF NEXT CLIPPER SYSTEM DIVING THROUGH THE
NRN PLAINS. IFR VSBYS IN SNOW WILL REACH KCMX BY 21Z WITH MVFR
CONDITIONS REACHING KSAW BY 23Z.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
HIGH PRES RIDGE DRIFTING E AND REACHING LAKE SUPERIOR WED MORNING
WILL RESULT IN A STEADY DIMINISHING OF WINDS FROM W TO E TONIGHT
THRU WED MORNING. A PERIOD OF VARIABLE WINDS IN THE 5-15KT RANGE
SHOULD OCCUR AS THE RIDGE PASSES. SRLY WINDS WILL THEN STRENGTHEN
FROM W TO E WED AFTN INTO THE EVENING AHEAD OF APPROACHING LOW PRES.
LOW PRESSURE SYSTEM OVER NRN MN WED EVENING WILL SHIFT EAST ACROSS
NRN LAKE SUPERIOR WED NIGHT INTO THU MORNING. SOUTH TO SW WINDS
SHOULD APPROACH 30 KT AHEAD OF THE LOW...THEN SHIFT WEST TO NW AT
ABOUT THE SAME SPEED BEHIND IT FOR THU. LOOK FOR WINDS TO GRADUALLY
DIMINISH TO EVENTUALLY BELOW 20 KT BY EARLY FRI AFTN AS A RIDGE OF
HIGH PRESSURE CROSSES LAKE SUPERIOR. AS THE HIGH SHIFTS EAST FRI
NIGHT...SOUTHERLY WINDS WILL INCREASE AGAIN...REACHING UP TO 30 KT
BY SAT MORNING. FURTHER INCREASING IS EXPECTED ON SAT AS A LOW
PRESSURE TROUGH SETS UP OVER FAR WESTERN LAKE SUPERIOR...WITH GALES
UP TO 35 KT ON EASTERN SUPERIOR POSSIBLE LATE SAT. THIS TROUGH WILL
MOVE EAST INTO CENTRAL LAKE SUPERIOR ON SUN AND BECOME STATIONARY.
WINDS ARE EXPECTED TO TURN NE BEHIND THE TROUGH WITH SPEEDS TO 30 KT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...LAKE EFFECT SNOW ADVISORY IN EFFECT UNTIL 3 AM EST
WEDNESDAY FOR MIZ005.
LAKE EFFECT SNOW ADVISORY IN EFFECT UNTIL 11 AM EST
WEDNESDAY FOR MIZ006.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.
&&
$$
UPDATE...VOSS
SYNOPSIS/SHORT TERM...ROLFSON
LONG TERM...AJ
AVIATION...JV
MARINE...ROLFSON/AJ
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
745 PM EST TUE DEC 9 2008
LATEST UPDATE...SYNOPSIS AND SHORT TERM...
.SYNOPSIS...(745 PM EST TUE DEC 9 2008)
A FRONTAL BOUNDARY WILL SLIDE SOUTHEAST THROUGH THE AREA THIS
EVENING...CHANGING ANY MIXED PRECIPITATION OVER TO SNOW. ANOTHER
ONE TO THREE INCHES OF SNOW IS POSSIBLE THIS EVENING NEAR AND
SOUTHEAST OF A LINE FROM MUSKEGON TO BIG RAPIDS AND MT. PLEASANT.
AS COLDER AIR FILTERS INTO THE REGION INTO WEDNESDAY SOME LIGHT LAKE
EFFECT SNOW SHOWERS ARE POSSIBLE TOWARD THE COAST...BUT ANY
ACCUMULATIONS WILL BE LIGHT. ANOTHER SYSTEM WILL TRAVERSE THE AREA
WEDNESDAY NIGHT INTO THURSDAY BRINGING SOUTHWEST LOWER MICHIGAN
ANOTHER CHANCE FOR SNOW. ANY ACCUMULATIONS OF SNOW WOULD BE LIGHT. A
WARM UP IS EXPECTED INTO THE WEEKEND...WITH HIGHS PUSHING TOWARD 40
DEGREES.
&&
.SHORT TERM...(745 PM EST TUE DEC 9 2008)
(TONIGHT)
BASED ON RGNL RADAR TRENDS/SFC OBS WE HAVE DECIDED TO ISSUE A WINTER
WX ADVISORY FOR OUR SOUTHERN CWFA UNTIL 08Z. RADAR TRENDS SHOW
CONVECTIVE ELEMENTS IN PCPN IMPACING OUR SOUTHERN CWFA CONCURRENT
WITH FALLING TEMPS. IN FACT A LAPS SOUNDING TAKEN AT JXN SHOWS PCPN
SHOULD SOON TRANSITION TO SNOW. WE ANTICIPATE HAZARDOUS TRAVEL
CONDITIONS WILL CONTINUE TO DEVELOP THROUGH THE EARLY MORNING HRS
ACROSS THIS AREA. WE WILL ALSO BE EXTENDING THE REMAINDER OF OUR
HEADLINES THROUGH 06Z.
&&
.LONG TERM...(440 AM EST TUE DEC 9 2008)
(WEDNESDAY THROUGH TUESDAY)
THE LOW PRESSURE SYSTEM THAT/S CAUSED THE RAIN/SNOW TODAY AND LAST
NIGHT WILL BE MOVING AWAY FROM THE CWA WEDNESDAY. THERE ISN/T A BIG
BLAST OF COLD AIR BEHIND THIS SYSTEM SO WE THINK THAT LAKE EFFECT
POTENTIAL IS MINIMAL. THAT SAID...H8 TEMPS WILL BRIEFLY FALL TO
AROUND -11C EARLY WEDNESDAY. WE/LL KEEP POP IN OVER THE LAKE SHORE
BUT DIMINISH THROUGH THE DAY.
ANOTHER CLIPPER WILL MOVE ACROSS LAKE SUPERIOR WED NIGHT/THURSDAY.
SOME LIGHT SNOW IS POSSIBLE WITH THIS SYSTEM ESPECIALLY ACROSS THE
NRN CWA BUT THE MAIN FORCING WITH THE LOW IS NORTH OF THE CWA. A
COLD FRONT WILL MOVE THROUGH BEHIND THE SYSTEM MID DAY THURSDAY. A
LITTLE BETTER SHOT OF COLD AIR IS ASSOCIATED WITH THIS SYSTEM. POPS
WILL BE A BIT HIGHER...BUT DON/T WANT TO GO ABOVE CHC DUE TO LIMITED
MOISTURE. BUFKIT RH PROFILES SHOWS MOISTURE ONLY CLIMBING TO AROUND
4-5K FEET. THAT WON/T SUPPORT MUCH LAKE SHSN. PCPN WITH THAT SYSTEM
WILL END LATE FRIDAY. A WARM FRONT WILL MOVE BACK THROUGH FRIDAY
NIGHT AND WARMER AIR WILL BE MOVING IN FOR THE WEEKEND. A CLIPPER
MOVING SOUTHEAST WILL DEVELOP A STRONG SOUTHWEST FLOW AHEAD OF IT.
SATURDAY COULD BE BREEZY. TEMPS WILL LIKELY CLIMB INTO THE UPPER 30S
TO LOWER 40S SATURDAY AND SUNDAY. A SECONDARY LOW DEVELOPING ON THE
SOUTHERN END OF THE FRONT WILL PRODUCE SOME PCPN SATURDAY NIGHT INTO
SUNDAY. AT THIS POINT...THERMAL PROFILES SUPPORT MIXED RAIN AND SNOW
SATURDAY NIGHT AND RAIN SUNDAY AND SUNDAY NIGHT. ECMWF AND GFS
DIFFER A BIT ON TIMING THE COLD FRONT THROUGH THE REGION. THE GFS
BRINGS THE FRONT THROUGH MONDAY AROUND 12Z AND THE ECMWF 12 HRS
LATER. WE/LL SPLIT THE MIDDLE AT THIS POINT AND RUN WITH MOSTLY A
RAIN/SNOW MIX. MODELS KEEP THE FRONTAL BOUNDARY OVER THE CWA THROUGH
TUESDAY WHICH WILL LIKELY MEAN A HIGHER CHC OF RAIN ACROSS THE SOUTH
AND SNOW ACROSS THE NORTHERN CWA.
&&
.MARINE...(400 PM EST TUE DEC 9 2008)
WINDS ARE INCREASING OUT OF THE NORTH ON LAKE MICHIGAN AS THE FRONT
SLIDES SOUTH. WINDS CURRENTLY ARE GUSTING 22 KNOTS AT BIG SABLE
POINT. EXPECTING WINDS TO PEAK THIS EVENING AROUND 30 KNOTS...WHICH
WILL PUSH WAVES TO 7 TO 10 FEET. WAVES WILL GRADUALLY SUBSIDE INTO
WEDNESDAY AFTERNOON AND EVENING AS RIDGING BUILDS INTO THE AREA.
&&
.AVIATION...(700 PM EST TUE DEC 9 2008)
AS COLDER AIR MOVES IN FROM THE NORTH...THE SOUTHERN TAF SITES KJXN
KBTL KAZO AND KLAN WILL TRANSITION TO SNOW. THE SNOW WILL LAST FOR
SEVERAL HOURS AT ALL TAF SITES BEFORE TAPERING OFF AROUND MIDNIGHT.
CONDITIONS SHOULD REMAIN MAINLY IFR FOR ALL TAF SITES WITH SOME
TEMPO LIFR WITH AN IMPROVING TREND FROM NORTH TO SOUTH THROUGH 06Z
TO MVFR. KJXN SHOULD BE THE LAST TO IMPROVE. WHILE SOME FZRA WAS
SEEN AT KLAN...TAMDAR DATA AND LAPS SOUNDINGS SUGGESTS IT WILL BE
VERY BRIEF WITH THE TRANSITION TO SNOW TO OCCUR RATHER RAPIDLY. AS
DRIER AIR WORKS ITS WAY DOWN FROM THE NORTH WEDNESDAY MORNING
CONDITIONS ARE EXPECTED TO GO TO VFR. THERE IS A POTENTIAL FOR THE
MVFR CONDITIONS TO LINGER THROUGH WEDNESDAY...WHICH WE WILL NEED TO
MONITOR.
&&
.HYDROLOGY...(400 PM EST TUE DEC 9 2008)
PRECIPITATION TOTALS HAVE NOT BEEN HEAVY ENOUGH TO AFFECT RIVER
LEVELS...SO NO HYDRO ISSUES ARE ANTICIPATED IN THE NEXT COUPLE DAYS.
JACKSON HAS SEEN A RISE IN RIVER LEVELS...BUT IS STILL WELL WITHIN
BANK. SCOTTVILLE IS SHOWING A RISE AS WELL...WHICH IS THE RESULT OF
SOME ICE IN THE RIVER.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING IN EFFECT FROM MUSKEGON...
MONTCALM AND GRATIOT COUNTIES NORTHWARD THROUGH 06Z WED.
WINTER WEATHER ADVISORY CONTINUES IN EFFECT FOR OTTAWA... KENT...
IONIA AND CLINTON COUNTIES THROUGH 06Z WED.
WINTER WEATHER ADVISORY GOING INTO EFFECT THROUGH 08Z WED FOR OUR
SOUTHERN TWO TIERS OF COUNTIES.
LM...SMALL CRAFT ADVISORY ST. JOSEPH TO MANISTEE THROUGH WEDNESDAY
AFTERNOON.
&&
$$
SYNOPSIS: DUKE/LAURENS
SHORT TERM: LAURENS
LONG TERM: 93
MARINE: DUKE
AVIATION: MJS
HYDROLOGY: DUKE
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
728 PM EST TUE DEC 9 2008
UPDATED FOR 00Z AVIATION DISCUSSION
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A POSITIVE TILT UNPHASED
TROF EXTENDING FROM HUDSON BAY TO TX. IN THE SRN STREAM...ONE
WEAKENING SHORTWAVE IS LIFTING NE THRU THE CNTRL/LWR LAKES
REGION...ANOTHER SHORTWAVE WAS OVER OK/KS WITH A THIRD IN THE VCNTY
OF SRN NM/W TX. IN THE NRN STREAM...A SHORTWAVE WAS DROPPING SE
THRU MANITOBA. THIS SHORTWAVE WILL PASS ACROSS THE UPPER LAKES
TONIGHT. CLOSER TO HOME...IN THE WAKE OF DEPARTING -SN/DEEPER
MOISTURE ASSOCIATED WITH SRN STREAM SHORTWAVES...LES REGIME HAS
DEVELOPED OFF LAKE SUPERIOR UNDER NRLY FLOW CAA. DRY AIRMASS HEADING
S (PER 12Z CWPL SOUNDING) HAS KEPT LES GENERALLY ON THE LIGHT
SIDE...BUT THE FLUFF FACTOR HAS BEEN STEADILY INCREASING AS AIRMASS
IN THE CONVECTIVE LAYER COOLS TO FAVORABLE TEMPS FOR DENDRITES TO
GROW. AFTN TAMDAR SOUNDING SHOWED INVERSION BASED AT 850MB WITH TEMP
AT INVERSION BASE OF -16C...SUPPORTING THE INCREASE IN SNOW TO WATER
RATIOS THIS AFTN. LONGER FETCH AIDED BY LAKE NIPIGON MAY HAVE LED TO
SOME LOCALLY HEAVIER LES IN FAR WRN UPPER MI IN THE VCNTY OF KIWD
DURING THE DAY AS SUGGESTED BY VIS SATELLITE IMAGERY.
&&
.SHORT TERM (TONIGHT/WED)...
LES AND TEMPS ARE THE MAIN FCST ISSUES TONIGHT.
SHORTWAVE OVER MANITOBA WILL PASS ACROSS THE UPPER LAKES TONIGHT.
WITH TRACK OVER THE AREA...BEST FORCING WILL PASS N OF HERE. IN
ADDITION...SINCE LOW-LEVEL CAA IS DOMINATING...THERE IS LITTLE OR NO
FORCING ACROSS THE FCST AREA. NONETHELESS...WOULD STILL EXPECT TO
SEE AT LEAST A LITTLE ENHANCEMENT AS INVERSIONS SHOULD RISE A BIT
WITH APPROACH OF SHORTWAVE. SNOW TO WATER RATIOS SHOULD BE HIGH WITH
FAVORABLE DENDRITIC SNOW GROWTH TEMPS DOMINATING BLO THE INVERSION.
SO A GOOD FLUFF FACTOR (PROBABLY AT LEAST 25 TO 1) WILL BOOST SNOW
ACCUMULATIONS TONIGHT. BEST LES TONIGHT SHOULD TEND TO BECOME
FOCUSED INTO ALGER COUNTY AND AT LEAST FAR ERN MARQUETTE COUNTY FOR
A TIME. THIS AREA WILL BE FAVORED AS LAND BREEZES WILL RESULT IN
STRONGER LOW-LEVEL CONVERGENCE DEVELOPING THERE. IN ADDITION...THAT
AREA WILL BE INLINE FOR PRECONDITIONING FROM STILL OPEN LAKE
NIPIGON. THE RUC13...WHICH OFTEN DOES A NICE JOB ON LAND/LAKE
INTERACTIONS (BUT SOMETIMES DOES OVERDO IT)...SHOWS A MESOLOW
DEVELOPING NEAR MUNISING LATE TONIGHT/WED MORNING. THE NAM AND LOCAL
HIGH RES WRF-ARW ALSO HINT AT A CIRCULATION IN THAT GENERAL
LOCATION...BUT IT`S MORE SO WED MORNING/EARLY AFTN IN THE COL AREA
WITHIN PASSING SFC RIDGE AXIS. IN ANYCASE...IT WILL BE SOMETHING TO
WATCH FOR SINCE ITS DEVELOPMENT WOULD RESTRUCTURE WIND PARALLEL
BANDS DOMINATING FOR MUCH OF THE NIGHT AND COULD REALLY FOCUS
LOCALLY HEAVIER SNOW. FOR NOW...WILL ASSUME JUST STRENGTHENING
CONVERGENCE BTWN MARQUETTE/MUNISING OVERNIGHT. HAVE PAINTED 2-5 INCH
ACCUMULATIONS IN THAT AREA...BUT IT`S POSSIBLE ACCUMULATIONS COULD
RISE TO ADVY CRITERIA DEPENDING ON HOW DEVELOPING DOMINANT BANDS
ORGANIZE THIS EVENING. ELSEWHERE IN THE LES AREAS...FLUFFY
ACCUMULATIONS TONIGHT SHOULD RANGE FROM 1-3 INCHES.
AWAY FROM LAKE SUPERIOR LES...EXPECT DRY WEATHER WITH TEMPS THE MAIN
ISSUE. SHOULD IT CLEAR OUT...TEMPS WILL CRASH. HOWEVER...IT APPEARS
WINDS IN THE CLOUD BEARING LAYER WILL RETAIN ENOUGH OF A NRLY
COMPONENT THAT LAKE EFFECT CLOUDS SHOULD DOMINATE EVEN WELL INLAND
AWAY FROM LES. UNDER THIS ASSUMPTION...TOOK A CONSERVATIVE APPROACH
TO MINS...NOT GOING ANY LWR THAN AROUND 5F OVER THE INTERIOR SW. BIG
TEMP BUST POTENTIAL IS THERE.
LINGERING LES OFF LAKE SUPERIOR WILL END WED AS HIGH PRES RIDGE
PASSES AND WINDS BECOME SRLY. ANOTHER INCH OR TWO OF ACCUMULATION IS
POSSIBLE ACROSS ALGER COUNTY WED MORNING BEFORE LES SHIFTS OFFSHORE.
IN THE AFTN...WILL NEED TO WATCH FOR THE POTENTIAL OF LES STREAMING
IN OFF LAKE MICHIGAN INTO THE SE FCST AREA AS WINDS BECOME SRLY.
SOME OF THE HIGHER RES MODELS SHOW MIDLAKE CONVERGENCE THAT COULD
SET THE STAGE FOR A PERIOD OF DECENT LES. THIS SHOULD BE MORE AN
ISSUE HEADING INTO WED NIGHT AS SRLY WINDS STRENGTHEN. OTHERWISE...
ATTENTION TURNS TO NEXT SHORTWAVE HEADING SE TOWARD THE UPPER
MISSISSIPPI VALLEY. ASSOCIATED SFC LOW WILL REACH NRN MN LATE
AFTN/EARLY EVENING. DECENT ISENTROPIC ASCENT REGIME AND DEEP LAYER
QVECTOR CONVERGENCE AHEAD OF FEATURE SHOULD RESULT IN -SN SPREADING
INTO WRN UPPER MI DURING THE AFTN.
.LONG TERM (WED NIGHT THROUGH NEXT TUE)...
MAIN FORECAST CONCERNS ARE SNOWFALL AMOUNTS WITH CLIPPER SYSTEM WED
NIGHT AND THEN MIXED PCPN SCENARIO FOR SUN/MON.
WED NIGHT...CLIPPER SYSTEM INDICATED YESTERDAY TO MOVE ACROSS LAKE
SUPERIOR IS STILL SHOWN TODAY...WITH TIMING ABOUT THE SAME.
HOWEVER...THE NAM HAS SLOWED UP A LITTLE BIT. RIGHT NOW...FAVOR THE
FASTER ECMWF/UKMET/GFS/LOCAL WRF-ARW WHICH BRING THE LOW FROM NRN MN
AT 00Z THU TO NE LAKE SUPERIOR BY 12Z THU. THE NAM ONLY BRINGS IT
INTO WESTERN LAKE SUPERIOR. CLIPPER SHOULD BRING SOME WARM ADVECTION
SNOW ACROSS THE AREA...ESPECIALLY OVER THE NORTHERN PORTION OF THE
CWA AND ACROSS LAKE SUPERIOR...CLOSER TO THE BETTER DYNAMICS FROM
THE SHRTWV ASSOCIATED WITH THE CLIPPER. SOUNDINGS ARE ACTUALLY QUITE
IMPRESSIVE WITH THE LIFT FROM ALL MODELS...WHICH COINCIDES WITH THE
DENDRITIC GROWTH ZONE (DGZ). THE AIRMASS BELOW THE DGZ IS NOT ALL
THAT COLD EITHER...WHICH SHOULD HELP REDUCE AGGREGATION. THEREFORE
HAVE GONE WITH SNOW TO WATER RATIOS AROUND 20 TO 1...WHICH RESULTS
IN A COUPLE INCHES OF SNOW BASED ON WELL AGREED UPON QPF FROM THE
GFS/REGIONAL CANADIAN/LOCAL WRF-ARW. ANOTHER AREA OF INTEREST IS SE
SCHOOLCRAFT INTO LUCE COUNTY WITH A STRONG LIKELIHOOD OF A LAKE
MICHIGAN BAND IMPACTING THIS PORTION OF THE CWA. LUCKILY THE LLVL
FLOW DOES NOT FAVOR A BAND STAYING IN ONE SPOT...AS THE BAND SHOULD
MOVE IN AROUND 06Z THEN STARTING MOVING SLOWLY EAST AS THE FLOW GOES
FROM SOUTH TO SW. NONETHELESS...AN ADVISORY LOOKS TO BE NEEDED AT
LEAST FOR LUCE COUNTY. LATE IN THE NIGHT...A COLD FRONT ASSOCIATED
WITH THE CLIPPER WILL BE MOVING INTO THE WESTERN U.P.. WITH 850MB
TEMPS FALLING TO -12 TO -14C ALONG THE FRONT...IT IS LIKELY THERE
WILL BE A BAND OF LAKE EFFECT SNOW ALONG IT. THEREFORE...POP GRIDS
AFTER 06Z DENOTE LIKELY WORDING IN THE WEST AS WELL. LOW
TEMPERATURES GENERALLY A BLEND OF MET/MAV GUIDANCE...GIVEN THAT
PLENTY OF CLOUDS AND WIND WILL BE AROUND.
THU THROUGH FRI...MUCH OF THIS PERIOD IS DOMINATED BY LAKE EFFECT...
AS AN UPPER TROUGH SETTLES IN OVER THE GREAT LAKES. THE MAIN PORTION
OF THIS UPPER TROUGH COMES DOWN OUT OF NORTHWEST TERRITORIES. 850MB
TEMPS DROP DOWN TO -20 TO -22C BY 12Z FRI. THEREFORE HIGHS AND LOWS
WILL BE COLD DURING THIS PERIOD...ESPECIALLY WITH LOWS ON THU NIGHT.
STAYED TOWARDS THE LOW END OF GUIDANCE FOR THU NIGHT...BUT LUCKILY
THERE SHOULD BE SOME CLOUDS AND WIND TO PREVENT TEMPS FROM
PLUMMETING TOO MUCH. REGARDING THE LAKE EFFECT...HAVE INCREASED POPS
TO LIKELY FOR THE WEST AND AREAS EAST OF MARQUETTE WITH A GENERAL NW
FLOW EXPECTED. SNOW TO WATER RATIOS SHOULD BE FAIRLY HIGH ON THU...
20 TO 1 OR SO. AS THE COLD AIR COMES IN...THE RATIOS WILL DROP SOME
OVER THE WEST AS A PORTION OF THE DGZ FALLS BELOW THE CLOUD BASE.
HOWEVER...THE LONGER FETCH OF WARMER AIR OFF EASTERN LAKE SUPERIOR
WILL BE ABLE TO HOLD THE DGZ IN THE CLOUD...SO HAVE INCREASED RATIOS
IN THE EASTERN CWA. RATIOS WILL STABILIZE AGAIN ON FRI AROUND 20 TO
1 AS DAYTIME HEATING HELPS WARM UP THE LOW LEVELS. AMOUNT WISE OVER
THIS TIME PERIOD...IT APPEARS MOST OF IT SHOULD BE LIGHT...WITH
TOTALS PERHAPS UP TO 6 INCHES IN THE EASTERN CWA. OF COURSE THERE IS
ALWAYS POTENTIAL FOR A DOMINANT BAND TO HELP INCREASE AMOUNTS
MORE...WHICH DEFINITELY CANNOT BE RULED OUT FOR ALGER COUNTY AS THE
LAND BREEZE KICKS IN OFF OF MARQUETTE COUNTY.
FRI NIGHT THROUGH TUESDAY...MODELS AGREE AGAIN WELL ON THE UPPER
LEVEL PATTERN...TRANSITIONING TO A WESTERN TROUGH AND EAST COAST
RIDGE BY LATE SUN...THEN REMAINING THAT WAY THROUGH AT LEAST MONDAY
AND LIKELY INTO TUESDAY. HOWEVER...THERE REMAINS A MAJOR QUESTION ON
WHAT HAPPENS DURING THE SAT NIGHT TO MON TIME FRAME. THE 06Z GFS AND
00Z CANADIAN NOW LOOK LIKE THE 08/00Z ECMWF RUN BRINGING A SFC LOW
ACROSS THE CWA ON SUN...WITH COLD AIR FLOWING IN BEHIND IT FOR MON.
ON THE OTHER HAND...THE 00Z ECMWF/UKMET ARE SLOWER AND REMAIN FAIRLY
CONSISTENT WITH THE 08/12Z ECMWF IN SHOWING THE LOW CROSSING MON
MORNING. THE PROBLEM WITH THIS SYSTEM IS THAT NO MATTER WHICH TIME
FRAME IS PREFERRED FOR IT MOVE THROUGH...850MB TEMPS WARM UP ENOUGH
TO TURN PCPN AT A MINIMUM TO SLEET/FREEZING RAIN AND LIKELY RAIN. IT
APPEARS THE DIFFERENCE BTWN THE FASTER AND SLOWER RUNS IS RELATED TO
A NRN STREAM SHRTWV TROUGH CROSSING CENTRAL CANADA LATE SAT...AND
WHERE THE SHRTWV ASSOCIATED WITH THE SFC LOW IS LOCATED. THE 00Z
ECMWF/UKMET HAVE THE SHRTWV IN EASTERN IDAHO AT 00Z SUN COMPARED TO
THE 06Z GFS WHICH IS IN THE WRN DAKOTAS...CLOSER TO BEING PICKED UP
BY THE NRN STREAM SHRTWV. GIVEN THE FLUCTUATION SEEN IN THE GFS
DURING THE PAST FOUR RUNS AND THAT PRACTICALLY ALL OF THE 00Z GFS
ENSEMBLES AGREE WITH THE 00Z ECMWF...HAVE DECIDED TO LEAN TOWARDS
THE ECMWF FOR THE FORECAST WITH THIS SYSTEM. OUTSIDE OF THIS
SYSTEM...MODELS ARE IN GOOD AGREEMENT.
SOME OF THE DETAILS. FOR FRI NIGHT...INCREASING WARM ADVECTION IN
THE WAKE OF THE TROUGH ON FRI AND AHEAD OF A WEAK SHRTWV MOVING
THROUGH THE FLOW SHOULD BRING SOME LIGHT SNOW TO THE AREA. BULK OF
THE SNOW APPEARS RIGHT NOW TO STAY TO THE NORTH...THOUGH...OVER NRN
LAKE SUPERIOR. THERE AGAIN COULD BE A BAND OFF LAKE MICHIGAN...BUT
NOW THE WINDS MIGHT BE TOO SW TO ALLOW FOR THE BAND TO IMPACT THE
CWA. WARM ADVECTION CONTINUES DURING THE DAY SAT WITH YET ANOTHER
SHRTWV INDICATED TO MOVE THROUGH THE FLOW. THIS ADVECTION LOOKS
STRONGER...WITH 850MB WINDS REACHING 45-50 KT. IN ADDITION...MORE
MOISTURE IS TAPPED OUT OF THE GULF OF MEXICO...SO MORE PCPN IS
POSSIBLE. 850MB TEMPS ONLY RISE TO -2 TO -4C...SO RIGHT NOW IT IS
ASSUMED THAT THE MAJORITY OF THE PCPN WILL FALL AS SNOW. WARM
ADVECTION CONTINUES SAT NIGHT INTO SUN AS THE LOW PRESSURE SYSTEM
OUT OF THE WESTERN U.S. LIFTS TOWARDS UPPER MI. PCPN SAT NIGHT MAY
TURN INTO A MIX OF RAIN/SNOW AS 850MB TEMPS CONTINUE TO WARM...THEN
CHANGE MOSTLY TO RAIN OVER THE SOUTH CENTRAL AND EAST ON SUN. 00Z
ECMWF ACTUALLY HAS READINGS OF 4-6C OVER THE SOUTH CENTRAL BY 00Z
MON. GIVEN THESE READINGS...CONCERN ACTUALLY STARTS TO EXIST OF
THUNDER. WILL NOT INCLUDE THUNDER AT THE MOMENT...SINCE SHOWALTER
INDICES ARE 0-2C JUST TO OUR SOUTH. MUCH OF UPPER MI MAY END UP
DEALING WITH ONLY RAIN SUN NIGHT AS THE ENTIRE EASTERN 2/3 OF THE
CWA HAS 850MB TEMPS OF 2-6C BY 12Z MON PER THE 00Z ECMWF RUN. NEW
12Z ECMWF RUN IS A BIT COLDER NOW. THEREFORE...WILL STILL KEEP A
RAIN/SNOW MIX GOING. COLD FRONT COMES THROUGH MON...WHICH ACTUALLY
LOOKS QUITE STRONG AS 850MB TEMPS PLUMMET TO -16C OVER WESTERN
SUPERIOR BY 00Z TUE...SO FALLING TEMPS ON MON ARE PLANNED. FURTHER
COOLING IS EXPECTED MON NIGHT AND TUE AS A PORTION OF THE WESTERN
UPPER TROUGH MOVES THROUGH UPPER MI. WIND FLOW GOES FROM WEST TO
NORTH...BUT NOT MUCH MOISTURE IS PRESENT AS A CANADIAN HIGH BUILDS
IN AT THE SFC...SO ONLY LIGHT LAKE EFFECT SNOW SHOWERS ARE EXPECTED.
FUTURE SHIFTS WILL NEED TO CONTINUE TO MONITOR THE SYSTEM FOR THIS
WEEKEND. HAVE DECLINED TO MENTION FZRA OR SLEET BECAUSE IT IS SO FAR
OUT AND THOSE DETAILS CAN CHANGE GREATLY. NONETHELESS...EACH ONE IS
POSSIBLE. 12Z CYCLE UPDATE...THE 12Z GFS ENSEMBLES SHOW MUCH MORE
SPREAD...WITH HALF OF THEM LOOKING MORE LIKE THE 00Z ECMWF/CANADIAN
AND THE OTHER HALF LIKE THE 06Z/12Z GFS. THE 12Z CANADIAN CONTINUES
TO LOOK LIKE ITS PREDECESSOR...AS DOES THE NEW 12Z ECMWF...SO
UNCERTAINTY STILL REMAINS.
&&
.AVIATION (FOR THE 00Z TAF ISSUANCE)...
AS THE LOW-LEVEL FLOW GRADUALLY BACKS FROM N TO NW LATER THIS
EVENING WITH THE APPROACH OF A HIGH PRES RIDGE FROM THE W...-SHSN
SHOULD DIMINISH TO FLURRIES AT KCMX AND PROBABLY END AT KSAW.
HOWEVER...LOOK FOR MVFR CIGS TO PERSIST AT KSAW UNTIL LATER WED
MORNING WHEN WINDS BACK FURTHER TO THE W OR SW...RESULTING IN BETTER
DOWNSLOPING. AT KCMX...WINDS SHOULD REMAIN FAVORABLE FOR MAINTAIN
MVFR CIGS TONIGHT THROUGH WED. EXPECT WARM ADVECTION SNOW TO SPREAD
INTO AREA LATE WED AHEAD OF NEXT CLIPPER SYSTEM DIVING THROUGH THE
NRN PLAINS. IFR VSBYS IN SNOW WILL REACH KCMX BY 21Z WITH MVFR
CONDITIONS REACHING KSAW BY 23Z.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
HIGH PRES RIDGE DRIFTING E AND REACHING LAKE SUPERIOR WED MORNING
WILL RESULT IN A STEADY DIMINISHING OF WINDS FROM W TO E TONIGHT
THRU WED MORNING. A PERIOD OF VARIABLE WINDS IN THE 5-15KT RANGE
SHOULD OCCUR AS THE RIDGE PASSES. SRLY WINDS WILL THEN STRENGTHEN
FROM W TO E WED AFTN INTO THE EVENING AHEAD OF APPROACHING LOW PRES.
LOW PRESSURE SYSTEM OVER NRN MN WED EVENING WILL SHIFT EAST ACROSS
NRN LAKE SUPERIOR WED NIGHT INTO THU MORNING. SOUTH TO SW WINDS
SHOULD APPROACH 30 KT AHEAD OF THE LOW...THEN SHIFT WEST TO NW AT
ABOUT THE SAME SPEED BEHIND IT FOR THU. LOOK FOR WINDS TO GRADUALLY
DIMINISH TO EVENTUALLY BELOW 20 KT BY EARLY FRI AFTN AS A RIDGE OF
HIGH PRESSURE CROSSES LAKE SUPERIOR. AS THE HIGH SHIFTS EAST FRI
NIGHT...SOUTHERLY WINDS WILL INCREASE AGAIN...REACHING UP TO 30 KT
BY SAT MORNING. FURTHER INCREASING IS EXPECTED ON SAT AS A LOW
PRESSURE TROUGH SETS UP OVER FAR WESTERN LAKE SUPERIOR...WITH GALES
UP TO 35 KT ON EASTERN SUPERIOR POSSIBLE LATE SAT. THIS TROUGH WILL
MOVE EAST INTO CENTRAL LAKE SUPERIOR ON SUN AND BECOME STATIONARY.
WINDS ARE EXPECTED TO TURN NE BEHIND THE TROUGH WITH SPEEDS TO 30 KT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.
&&
$$
SYNOPSIS/SHORT TERM...ROLFSON
LONG TERM...AJ
AVIATION...JV
MARINE...ROLFSON/AJ
AREA FORECAST DISCUSSION
NWS GRAND RAPIDS MI
700 PM EST TUE DEC 9 2008
LATEST UPDATE...AVIATION...
.SYNOPSIS...(400 PM EST TUE DEC 9 2008)
A FRONTAL BOUNDARY WILL SLIDE SOUTHEAST THROUGH THE AREA THIS
EVENING...CHANGING ANY MIXED PRECIPITATION OVER TO SNOW. ANOTHER
INCH OR TWO OF SNOW IS POSSIBLE ACROSS CENTRAL LOWER MICHIGAN WITH
LESSER AMOUNTS TO THE SOUTH TOWARD THE INDIANA BORDER. THE RAIN AND
SNOW WILL COME TO AN END TONIGHT FROM NORTHWEST TO SOUTHEAST. AS
COLDER AIR FILTERS INTO THE REGION INTO WEDNESDAY SOME LIGHT LAKE
EFFECT SNOW SHOWERS ARE POSSIBLE TOWARD THE COAST...BUT ANY
ACCUMULATIONS WILL BE LIGHT. ANOTHER SYSTEM WILL TRAVERSE THE AREA
WEDNESDAY NIGHT INTO THURSDAY BRINGING SOUTHWEST LOWER MICHIGAN
ANOTHER CHANCE FOR SNOW. ANY ACCUMULATIONS OF SNOW WOULD BE LIGHT. A
WARM UP IS EXPECTED INTO THE WEEKEND...WITH HIGHS PUSHING TOWARD 40
DEGREES.
&&
.SHORT TERM...(400 PM EST TUE DEC 9 2008)
(TONIGHT)
HAVE OPTED TO LEAVE THE HEADLINES IN PLACE THIS EVENING...AS AN AREA
OF SNOW EXPANDS OUT OF SOUTHERN WISCONSIN AND NORTHERN ILLINOIS.
THIS PRECIPITATION IS POST FRONTAL AND LIKELY ASSOCIATED WITH FGEN.
850MB-700MB LAYER 2D FRONTOGENESIS PICKS UP THE AREA QUITE WELL. IT
SHIFTS THE ZONE OF FRONTOGENESIS RATHER QUICKLY TO THE SOUTH THIS
EVENING. WILL MENTION ANOTHER INCH OR TWO POSSIBLE IN THE WARNING
AREA AS RETURNS HAVE SPIKED UP MARKEDLY IN THE LAST HOUR. WILL
MENTION AROUND AN INCH POSSIBLE IN THE ADVISORY COUNTIES AND AN INCH
OR LESS IN THE SOUTH.
EXPECT THAT AS THE FRONT PULLS AWAY TO THE EAST THROUGH THE COURSE
OF THE EVENING...THE MOISTURE WILL BEGIN TO BECOME SHALLOW AND THE
PRECIPITATION SHOULD DIMINISH. REELED IN THE TIME OF THE
HEADLINES TO 1000PM. WE WILL BE MONITORING RADAR TRENDS CLOSELY THIS
EVENING.
&&
.LONG TERM...(440 AM EST TUE DEC 9 2008)
(WEDNESDAY THROUGH TUESDAY)
THE LOW PRESSURE SYSTEM THAT/S CAUSED THE RAIN/SNOW TODAY AND LAST
NIGHT WILL BE MOVING AWAY FROM THE CWA WEDNESDAY. THERE ISN/T A BIG
BLAST OF COLD AIR BEHIND THIS SYSTEM SO WE THINK THAT LAKE EFFECT
POTENTIAL IS MINIMAL. THAT SAID...H8 TEMPS WILL BRIEFLY FALL TO
AROUND -11C EARLY WEDNESDAY. WE/LL KEEP POP IN OVER THE LAKE SHORE
BUT DIMINISH THROUGH THE DAY.
ANOTHER CLIPPER WILL MOVE ACROSS LAKE SUPERIOR WED NIGHT/THURSDAY.
SOME LIGHT SNOW IS POSSIBLE WITH THIS SYSTEM ESPECIALLY ACROSS THE
NRN CWA BUT THE MAIN FORCING WITH THE LOW IS NORTH OF THE CWA. A
COLD FRONT WILL MOVE THROUGH BEHIND THE SYSTEM MID DAY THURSDAY. A
LITTLE BETTER SHOT OF COLD AIR IS ASSOCIATED WITH THIS SYSTEM. POPS
WILL BE A BIT HIGHER...BUT DON/T WANT TO GO ABOVE CHC DUE TO LIMITED
MOISTURE. BUFKIT RH PROFILES SHOWS MOISTURE ONLY CLIMBING TO AROUND
4-5K FEET. THAT WON/T SUPPORT MUCH LAKE SHSN. PCPN WITH THAT SYSTEM
WILL END LATE FRIDAY. A WARM FRONT WILL MOVE BACK THROUGH FRIDAY
NIGHT AND WARMER AIR WILL BE MOVING IN FOR THE WEEKEND. A CLIPPER
MOVING SOUTHEAST WILL DEVELOP A STRONG SOUTHWEST FLOW AHEAD OF IT.
SATURDAY COULD BE BREEZY. TEMPS WILL LIKELY CLIMB INTO THE UPPER 30S
TO LOWER 40S SATURDAY AND SUNDAY. A SECONDARY LOW DEVELOPING ON THE
SOUTHERN END OF THE FRONT WILL PRODUCE SOME PCPN SATURDAY NIGHT INTO
SUNDAY. AT THIS POINT...THERMAL PROFILES SUPPORT MIXED RAIN AND SNOW
SATURDAY NIGHT AND RAIN SUNDAY AND SUNDAY NIGHT. ECMWF AND GFS
DIFFER A BIT ON TIMING THE COLD FRONT THROUGH THE REGION. THE GFS
BRINGS THE FRONT THROUGH MONDAY AROUND 12Z AND THE ECMWF 12 HRS
LATER. WE/LL SPLIT THE MIDDLE AT THIS POINT AND RUN WITH MOSTLY A
RAIN/SNOW MIX. MODELS KEEP THE FRONTAL BOUNDARY OVER THE CWA THROUGH
TUESDAY WHICH WILL LIKELY MEAN A HIGHER CHC OF RAIN ACROSS THE SOUTH
AND SNOW ACROSS THE NORTHERN CWA.
&&
.MARINE...(400 PM EST TUE DEC 9 2008)
WINDS ARE INCREASING OUT OF THE NORTH ON LAKE MICHIGAN AS THE FRONT
SLIDES SOUTH. WINDS CURRENTLY ARE GUSTING 22 KNOTS AT BIG SABLE
POINT. EXPECTING WINDS TO PEAK THIS EVENING AROUND 30 KNOTS...WHICH
WILL PUSH WAVES TO 7 TO 10 FEET. WAVES WILL GRADUALLY SUBSIDE INTO
WEDNESDAY AFTERNOON AND EVENING AS RIDGING BUILDS INTO THE AREA.
&&
.AVIATION...(700 PM EST TUE DEC 9 2008)
AS COLDER AIR MOVES IN FROM THE NORTH...THE SOUTHERN TAF SITES KJXN
KBTL KAZO AND KLAN WILL TRANSITION TO SNOW. THE SNOW WILL LAST FOR
SEVERAL HOURS AT ALL TAF SITES BEFORE TAPERING OFF AROUND MIDNIGHT.
CONDITIONS SHOULD REMAIN MAINLY IFR FOR ALL TAF SITES WITH SOME
TEMPO LIFR WITH AN IMPROVING TREND FROM NORTH TO SOUTH THROUGH 06Z
TO MVFR. KJXN SHOULD BE THE LAST TO IMPROVE. WHILE SOME FZRA WAS
SEEN AT KLAN...TAMDAR DATA AND LAPS SOUNDINGS SUGGESTS IT WILL BE
VERY BRIEF WITH THE TRANSITION TO SNOW TO OCCUR RATHER RAPIDLY. AS
DRIER AIR WORKS ITS WAY DOWN FROM THE NORTH WEDNESDAY MORNING
CONDITIONS ARE EXPECTED TO GO TO VFR. THERE IS A POTENTIAL FOR THE
MVFR CONDITIONS TO LINGER THROUGH WEDNESDAY...WHICH WE WILL NEED TO
MONITOR.
&&
.HYDROLOGY...(400 PM EST TUE DEC 9 2008)
PRECIPITATION TOTALS HAVE NOT BEEN HEAVY ENOUGH TO AFFECT RIVER
LEVELS...SO NO HYDRO ISSUES ARE ANTICIPATED IN THE NEXT COUPLE DAYS.
JACKSON HAS SEEN A RISE IN RIVER LEVELS...BUT IS STILL WELL WITHIN
BANK. SCOTTVILLE IS SHOWING A RISE AS WELL...WHICH IS THE RESULT OF
SOME ICE IN THE RIVER.
&&
.GRR WATCHES/WARNINGS/ADVISORIES...
MI...WINTER STORM WARNING IN EFFECT FROM MUSKEGON...
MONTCALM AND GRATIOT COUNTIES NORTHWARD THROUGH 03Z WED.
WINTER WEATHER ADVISORY CONTINUES IN EFFECT FOR OTTAWA... KENT...
IONIA AND CLINTON COUNTIES THROUGH 03Z WED.
LM...SMALL CRAFT ADVISORY ST. JOSEPH TO MANISTEE THROUGH WEDNESDAY
AFTERNOON.
&&
$$
SYNOPSIS: DUKE
SHORT TERM: DUKE
LONG TERM: 93
MARINE: DUKE
AVIATION: MJS
HYDROLOGY: DUKE
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
450 PM EST TUE DEC 9 2008
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A POSITIVE TILT UNPHASED
TROF EXTENDING FROM HUDSON BAY TO TX. IN THE SRN STREAM...ONE
WEAKENING SHORTWAVE IS LIFTING NE THRU THE CNTRL/LWR LAKES
REGION...ANOTHER SHORTWAVE WAS OVER OK/KS WITH A THIRD IN THE VCNTY
OF SRN NM/W TX. IN THE NRN STREAM...A SHORTWAVE WAS DROPPING SE
THRU MANITOBA. THIS SHORTWAVE WILL PASS ACROSS THE UPPER LAKES
TONIGHT. CLOSER TO HOME...IN THE WAKE OF DEPARTING -SN/DEEPER
MOISTURE ASSOCIATED WITH SRN STREAM SHORTWAVES...LES REGIME HAS
DEVELOPED OFF LAKE SUPERIOR UNDER NRLY FLOW CAA. DRY AIRMASS HEADING
S (PER 12Z CWPL SOUNDING) HAS KEPT LES GENERALLY ON THE LIGHT
SIDE...BUT THE FLUFF FACTOR HAS BEEN STEADILY INCREASING AS AIRMASS
IN THE CONVECTIVE LAYER COOLS TO FAVORABLE TEMPS FOR DENDRITES TO
GROW. AFTN TAMDAR SOUNDING SHOWED INVERSION BASED AT 850MB WITH TEMP
AT INVERSION BASE OF -16C...SUPPORTING THE INCREASE IN SNOW TO WATER
RATIOS THIS AFTN. LONGER FETCH AIDED BY LAKE NIPIGON MAY HAVE LED TO
SOME LOCALLY HEAVIER LES IN FAR WRN UPPER MI IN THE VCNTY OF KIWD
DURING THE DAY AS SUGGESTED BY VIS SATELLITE IMAGERY.
&&
.SHORT TERM (TONIGHT/WED)...
LES AND TEMPS ARE THE MAIN FCST ISSUES TONIGHT.
SHORTWAVE OVER MANITOBA WILL PASS ACROSS THE UPPER LAKES TONIGHT.
WITH TRACK OVER THE AREA...BEST FORCING WILL PASS N OF HERE. IN
ADDITION...SINCE LOW-LEVEL CAA IS DOMINATING...THERE IS LITTLE OR NO
FORCING ACROSS THE FCST AREA. NONETHELESS...WOULD STILL EXPECT TO
SEE AT LEAST A LITTLE ENHANCEMENT AS INVERSIONS SHOULD RISE A BIT
WITH APPROACH OF SHORTWAVE. SNOW TO WATER RATIOS SHOULD BE HIGH WITH
FAVORABLE DENDRITIC SNOW GROWTH TEMPS DOMINATING BLO THE INVERSION.
SO A GOOD FLUFF FACTOR (PROBABLY AT LEAST 25 TO 1) WILL BOOST SNOW
ACCUMULATIONS TONIGHT. BEST LES TONIGHT SHOULD TEND TO BECOME
FOCUSED INTO ALGER COUNTY AND AT LEAST FAR ERN MARQUETTE COUNTY FOR
A TIME. THIS AREA WILL BE FAVORED AS LAND BREEZES WILL RESULT IN
STRONGER LOW-LEVEL CONVERGENCE DEVELOPING THERE. IN ADDITION...THAT
AREA WILL BE INLINE FOR PRECONDITIONING FROM STILL OPEN LAKE
NIPIGON. THE RUC13...WHICH OFTEN DOES A NICE JOB ON LAND/LAKE
INTERACTIONS (BUT SOMETIMES DOES OVERDO IT)...SHOWS A MESOLOW
DEVELOPING NEAR MUNISING LATE TONIGHT/WED MORNING. THE NAM AND LOCAL
HIGH RES WRF-ARW ALSO HINT AT A CIRCULATION IN THAT GENERAL
LOCATION...BUT IT`S MORE SO WED MORNING/EARLY AFTN IN THE COL AREA
WITHIN PASSING SFC RIDGE AXIS. IN ANYCASE...IT WILL BE SOMETHING TO
WATCH FOR SINCE ITS DEVELOPMENT WOULD RESTRUCTURE WIND PARALLEL
BANDS DOMINATING FOR MUCH OF THE NIGHT AND COULD REALLY FOCUS
LOCALLY HEAVIER SNOW. FOR NOW...WILL ASSUME JUST STRENGTHENING
CONVERGENCE BTWN MARQUETTE/MUNISING OVERNIGHT. HAVE PAINTED 2-5 INCH
ACCUMULATIONS IN THAT AREA...BUT IT`S POSSIBLE ACCUMULATIONS COULD
RISE TO ADVY CRITERIA DEPENDING ON HOW DEVELOPING DOMINANT BANDS
ORGANIZE THIS EVENING. ELSEWHERE IN THE LES AREAS...FLUFFY
ACCUMULATIONS TONIGHT SHOULD RANGE FROM 1-3 INCHES.
AWAY FROM LAKE SUPERIOR LES...EXPECT DRY WEATHER WITH TEMPS THE MAIN
ISSUE. SHOULD IT CLEAR OUT...TEMPS WILL CRASH. HOWEVER...IT APPEARS
WINDS IN THE CLOUD BEARING LAYER WILL RETAIN ENOUGH OF A NRLY
COMPONENT THAT LAKE EFFECT CLOUDS SHOULD DOMINATE EVEN WELL INLAND
AWAY FROM LES. UNDER THIS ASSUMPTION...TOOK A CONSERVATIVE APPROACH
TO MINS...NOT GOING ANY LWR THAN AROUND 5F OVER THE INTERIOR SW. BIG
TEMP BUST POTENTIAL IS THERE.
LINGERING LES OFF LAKE SUPERIOR WILL END WED AS HIGH PRES RIDGE
PASSES AND WINDS BECOME SRLY. ANOTHER INCH OR TWO OF ACCUMULATION IS
POSSIBLE ACROSS ALGER COUNTY WED MORNING BEFORE LES SHIFTS OFFSHORE.
IN THE AFTN...WILL NEED TO WATCH FOR THE POTENTIAL OF LES STREAMING
IN OFF LAKE MICHIGAN INTO THE SE FCST AREA AS WINDS BECOME SRLY.
SOME OF THE HIGHER RES MODELS SHOW MIDLAKE CONVERGENCE THAT COULD
SET THE STAGE FOR A PERIOD OF DECENT LES. THIS SHOULD BE MORE AN
ISSUE HEADING INTO WED NIGHT AS SRLY WINDS STRENGTHEN. OTHERWISE...
ATTENTION TURNS TO NEXT SHORTWAVE HEADING SE TOWARD THE UPPER
MISSISSIPPI VALLEY. ASSOCIATED SFC LOW WILL REACH NRN MN LATE
AFTN/EARLY EVENING. DECENT ISENTROPIC ASCENT REGIME AND DEEP LAYER
QVECTOR CONVERGENCE AHEAD OF FEATURE SHOULD RESULT IN -SN SPREADING
INTO WRN UPPER MI DURING THE AFTN.
.LONG TERM (WED NIGHT THROUGH NEXT TUE)...
MAIN FORECAST CONCERNS ARE SNOWFALL AMOUNTS WITH CLIPPER SYSTEM WED
NIGHT AND THEN MIXED PCPN SCENARIO FOR SUN/MON.
WED NIGHT...CLIPPER SYSTEM INDICATED YESTERDAY TO MOVE ACROSS LAKE
SUPERIOR IS STILL SHOWN TODAY...WITH TIMING ABOUT THE SAME.
HOWEVER...THE NAM HAS SLOWED UP A LITTLE BIT. RIGHT NOW...FAVOR THE
FASTER ECMWF/UKMET/GFS/LOCAL WRF-ARW WHICH BRING THE LOW FROM NRN MN
AT 00Z THU TO NE LAKE SUPERIOR BY 12Z THU. THE NAM ONLY BRINGS IT
INTO WESTERN LAKE SUPERIOR. CLIPPER SHOULD BRING SOME WARM ADVECTION
SNOW ACROSS THE AREA...ESPECIALLY OVER THE NORTHERN PORTION OF THE
CWA AND ACROSS LAKE SUPERIOR...CLOSER TO THE BETTER DYNAMICS FROM
THE SHRTWV ASSOCIATED WITH THE CLIPPER. SOUNDINGS ARE ACTUALLY QUITE
IMPRESSIVE WITH THE LIFT FROM ALL MODELS...WHICH COINCIDES WITH THE
DENDRITIC GROWTH ZONE (DGZ). THE AIRMASS BELOW THE DGZ IS NOT ALL
THAT COLD EITHER...WHICH SHOULD HELP REDUCE AGGREGATION. THEREFORE
HAVE GONE WITH SNOW TO WATER RATIOS AROUND 20 TO 1...WHICH RESULTS
IN A COUPLE INCHES OF SNOW BASED ON WELL AGREED UPON QPF FROM THE
GFS/REGIONAL CANADIAN/LOCAL WRF-ARW. ANOTHER AREA OF INTEREST IS SE
SCHOOLCRAFT INTO LUCE COUNTY WITH A STRONG LIKELIHOOD OF A LAKE
MICHIGAN BAND IMPACTING THIS PORTION OF THE CWA. LUCKILY THE LLVL
FLOW DOES NOT FAVOR A BAND STAYING IN ONE SPOT...AS THE BAND SHOULD
MOVE IN AROUND 06Z THEN STARTING MOVING SLOWLY EAST AS THE FLOW GOES
FROM SOUTH TO SW. NONETHELESS...AN ADVISORY LOOKS TO BE NEEDED AT
LEAST FOR LUCE COUNTY. LATE IN THE NIGHT...A COLD FRONT ASSOCIATED
WITH THE CLIPPER WILL BE MOVING INTO THE WESTERN U.P.. WITH 850MB
TEMPS FALLING TO -12 TO -14C ALONG THE FRONT...IT IS LIKELY THERE
WILL BE A BAND OF LAKE EFFECT SNOW ALONG IT. THEREFORE...POP GRIDS
AFTER 06Z DENOTE LIKELY WORDING IN THE WEST AS WELL. LOW
TEMPERATURES GENERALLY A BLEND OF MET/MAV GUIDANCE...GIVEN THAT
PLENTY OF CLOUDS AND WIND WILL BE AROUND.
THU THROUGH FRI...MUCH OF THIS PERIOD IS DOMINATED BY LAKE EFFECT...
AS AN UPPER TROUGH SETTLES IN OVER THE GREAT LAKES. THE MAIN PORTION
OF THIS UPPER TROUGH COMES DOWN OUT OF NORTHWEST TERRITORIES. 850MB
TEMPS DROP DOWN TO -20 TO -22C BY 12Z FRI. THEREFORE HIGHS AND LOWS
WILL BE COLD DURING THIS PERIOD...ESPECIALLY WITH LOWS ON THU NIGHT.
STAYED TOWARDS THE LOW END OF GUIDANCE FOR THU NIGHT...BUT LUCKILY
THERE SHOULD BE SOME CLOUDS AND WIND TO PREVENT TEMPS FROM
PLUMMETING TOO MUCH. REGARDING THE LAKE EFFECT...HAVE INCREASED POPS
TO LIKELY FOR THE WEST AND AREAS EAST OF MARQUETTE WITH A GENERAL NW
FLOW EXPECTED. SNOW TO WATER RATIOS SHOULD BE FAIRLY HIGH ON THU...
20 TO 1 OR SO. AS THE COLD AIR COMES IN...THE RATIOS WILL DROP SOME
OVER THE WEST AS A PORTION OF THE DGZ FALLS BELOW THE CLOUD BASE.
HOWEVER...THE LONGER FETCH OF WARMER AIR OFF EASTERN LAKE SUPERIOR
WILL BE ABLE TO HOLD THE DGZ IN THE CLOUD...SO HAVE INCREASED RATIOS
IN THE EASTERN CWA. RATIOS WILL STABILIZE AGAIN ON FRI AROUND 20 TO
1 AS DAYTIME HEATING HELPS WARM UP THE LOW LEVELS. AMOUNT WISE OVER
THIS TIME PERIOD...IT APPEARS MOST OF IT SHOULD BE LIGHT...WITH
TOTALS PERHAPS UP TO 6 INCHES IN THE EASTERN CWA. OF COURSE THERE IS
ALWAYS POTENTIAL FOR A DOMINANT BAND TO HELP INCREASE AMOUNTS
MORE...WHICH DEFINITELY CANNOT BE RULED OUT FOR ALGER COUNTY AS THE
LAND BREEZE KICKS IN OFF OF MARQUETTE COUNTY.
FRI NIGHT THROUGH TUESDAY...MODELS AGREE AGAIN WELL ON THE UPPER
LEVEL PATTERN...TRANSITIONING TO A WESTERN TROUGH AND EAST COAST
RIDGE BY LATE SUN...THEN REMAINING THAT WAY THROUGH AT LEAST MONDAY
AND LIKELY INTO TUESDAY. HOWEVER...THERE REMAINS A MAJOR QUESTION ON
WHAT HAPPENS DURING THE SAT NIGHT TO MON TIME FRAME. THE 06Z GFS AND
00Z CANADIAN NOW LOOK LIKE THE 08/00Z ECMWF RUN BRINGING A SFC LOW
ACROSS THE CWA ON SUN...WITH COLD AIR FLOWING IN BEHIND IT FOR MON.
ON THE OTHER HAND...THE 00Z ECMWF/UKMET ARE SLOWER AND REMAIN FAIRLY
CONSISTENT WITH THE 08/12Z ECMWF IN SHOWING THE LOW CROSSING MON
MORNING. THE PROBLEM WITH THIS SYSTEM IS THAT NO MATTER WHICH TIME
FRAME IS PREFERRED FOR IT MOVE THROUGH...850MB TEMPS WARM UP ENOUGH
TO TURN PCPN AT A MINIMUM TO SLEET/FREEZING RAIN AND LIKELY RAIN. IT
APPEARS THE DIFFERENCE BTWN THE FASTER AND SLOWER RUNS IS RELATED TO
A NRN STREAM SHRTWV TROUGH CROSSING CENTRAL CANADA LATE SAT...AND
WHERE THE SHRTWV ASSOCIATED WITH THE SFC LOW IS LOCATED. THE 00Z
ECMWF/UKMET HAVE THE SHRTWV IN EASTERN IDAHO AT 00Z SUN COMPARED TO
THE 06Z GFS WHICH IS IN THE WRN DAKOTAS...CLOSER TO BEING PICKED UP
BY THE NRN STREAM SHRTWV. GIVEN THE FLUCTUATION SEEN IN THE GFS
DURING THE PAST FOUR RUNS AND THAT PRACTICALLY ALL OF THE 00Z GFS
ENSEMBLES AGREE WITH THE 00Z ECMWF...HAVE DECIDED TO LEAN TOWARDS
THE ECMWF FOR THE FORECAST WITH THIS SYSTEM. OUTSIDE OF THIS
SYSTEM...MODELS ARE IN GOOD AGREEMENT.
SOME OF THE DETAILS. FOR FRI NIGHT...INCREASING WARM ADVECTION IN
THE WAKE OF THE TROUGH ON FRI AND AHEAD OF A WEAK SHRTWV MOVING
THROUGH THE FLOW SHOULD BRING SOME LIGHT SNOW TO THE AREA. BULK OF
THE SNOW APPEARS RIGHT NOW TO STAY TO THE NORTH...THOUGH...OVER NRN
LAKE SUPERIOR. THERE AGAIN COULD BE A BAND OFF LAKE MICHIGAN...BUT
NOW THE WINDS MIGHT BE TOO SW TO ALLOW FOR THE BAND TO IMPACT THE
CWA. WARM ADVECTION CONTINUES DURING THE DAY SAT WITH YET ANOTHER
SHRTWV INDICATED TO MOVE THROUGH THE FLOW. THIS ADVECTION LOOKS
STRONGER...WITH 850MB WINDS REACHING 45-50 KT. IN ADDITION...MORE
MOISTURE IS TAPPED OUT OF THE GULF OF MEXICO...SO MORE PCPN IS
POSSIBLE. 850MB TEMPS ONLY RISE TO -2 TO -4C...SO RIGHT NOW IT IS
ASSUMED THAT THE MAJORITY OF THE PCPN WILL FALL AS SNOW. WARM
ADVECTION CONTINUES SAT NIGHT INTO SUN AS THE LOW PRESSURE SYSTEM
OUT OF THE WESTERN U.S. LIFTS TOWARDS UPPER MI. PCPN SAT NIGHT MAY
TURN INTO A MIX OF RAIN/SNOW AS 850MB TEMPS CONTINUE TO WARM...THEN
CHANGE MOSTLY TO RAIN OVER THE SOUTH CENTRAL AND EAST ON SUN. 00Z
ECMWF ACTUALLY HAS READINGS OF 4-6C OVER THE SOUTH CENTRAL BY 00Z
MON. GIVEN THESE READINGS...CONCERN ACTUALLY STARTS TO EXIST OF
THUNDER. WILL NOT INCLUDE THUNDER AT THE MOMENT...SINCE SHOWALTER
INDICES ARE 0-2C JUST TO OUR SOUTH. MUCH OF UPPER MI MAY END UP
DEALING WITH ONLY RAIN SUN NIGHT AS THE ENTIRE EASTERN 2/3 OF THE
CWA HAS 850MB TEMPS OF 2-6C BY 12Z MON PER THE 00Z ECMWF RUN. NEW
12Z ECMWF RUN IS A BIT COLDER NOW. THEREFORE...WILL STILL KEEP A
RAIN/SNOW MIX GOING. COLD FRONT COMES THROUGH MON...WHICH ACTUALLY
LOOKS QUITE STRONG AS 850MB TEMPS PLUMMET TO -16C OVER WESTERN
SUPERIOR BY 00Z TUE...SO FALLING TEMPS ON MON ARE PLANNED. FURTHER
COOLING IS EXPECTED MON NIGHT AND TUE AS A PORTION OF THE WESTERN
UPPER TROUGH MOVES THROUGH UPPER MI. WIND FLOW GOES FROM WEST TO
NORTH...BUT NOT MUCH MOISTURE IS PRESENT AS A CANADIAN HIGH BUILDS
IN AT THE SFC...SO ONLY LIGHT LAKE EFFECT SNOW SHOWERS ARE EXPECTED.
FUTURE SHIFTS WILL NEED TO CONTINUE TO MONITOR THE SYSTEM FOR THIS
WEEKEND. HAVE DECLINED TO MENTION FZRA OR SLEET BECAUSE IT IS SO FAR
OUT AND THOSE DETAILS CAN CHANGE GREATLY. NONETHELESS...EACH ONE IS
POSSIBLE. 12Z CYCLE UPDATE...THE 12Z GFS ENSEMBLES SHOW MUCH MORE
SPREAD...WITH HALF OF THEM LOOKING MORE LIKE THE 00Z ECMWF/CANADIAN
AND THE OTHER HALF LIKE THE 06Z/12Z GFS. THE 12Z CANADIAN CONTINUES
TO LOOK LIKE ITS PREDECESSOR...AS DOES THE NEW 12Z ECMWF...SO
UNCERTAINTY STILL REMAINS.
&&
.AVIATION (FOR THE 18Z TAF ISSUANCE)...
WITH INCREASINGLY COLDER AIR FLOWING ACROSS LAKE SUPERIOR...LAKE
EFFECT -SHSN WILL CONTINUE. IN GENERAL...MVFR CONDITIONS SHOULD
PREVAIL AT KCMX/KSAW THRU THE AFTN WITH PERIODS OF IFR...ESPECIALLY
AT KSAW AS NRLY WINDS ARE MORE FAVORABLE FOR LAKE EFFECT -SHSN AND
STRONGER WINDS. AS LOW-LEVEL FLOW GRADUALLY BACKS MORE TO THE NW
TONIGHT WITH APPROACH OF HIGH PRES RIDGE...-SHSN WILL DIMINISH TO
FLURRIES OR END AT KSAW. HOWEVER...MVFR CIGS MAY PERSIST UNTIL LATER
WED MORNING WHEN WINDS BACK FURTHER...RESULTING IN BETTER
DOWNSLOPING. AT KCMX...WINDS WILL REMAIN FAVORABLE FOR -SHSN AND
MVFR CONDITIONS THRU THE END OF THIS FCST PERIOD.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
HIGH PRES RIDGE DRIFTING E AND REACHING LAKE SUPERIOR WED MORNING
WILL RESULT IN A STEADY DIMINISHING OF WINDS FROM W TO E TONIGHT
THRU WED MORNING. A PERIOD OF VARIABLE WINDS IN THE 5-15KT RANGE
SHOULD OCCUR AS THE RIDGE PASSES. SRLY WINDS WILL THEN STRENGTHEN
FROM W TO E WED AFTN INTO THE EVENING AHEAD OF APPROACHING LOW PRES.
LOW PRESSURE SYSTEM OVER NRN MN WED EVENING WILL SHIFT EAST ACROSS
NRN LAKE SUPERIOR WED NIGHT INTO THU MORNING. SOUTH TO SW WINDS
SHOULD APPROACH 30 KT AHEAD OF THE LOW...THEN SHIFT WEST TO NW AT
ABOUT THE SAME SPEED BEHIND IT FOR THU. LOOK FOR WINDS TO GRADUALLY
DIMINISH TO EVENTUALLY BELOW 20 KT BY EARLY FRI AFTN AS A RIDGE OF
HIGH PRESSURE CROSSES LAKE SUPERIOR. AS THE HIGH SHIFTS EAST FRI
NIGHT...SOUTHERLY WINDS WILL INCREASE AGAIN...REACHING UP TO 30 KT
BY SAT MORNING. FURTHER INCREASING IS EXPECTED ON SAT AS A LOW
PRESSURE TROUGH SETS UP OVER FAR WESTERN LAKE SUPERIOR...WITH GALES
UP TO 35 KT ON EASTERN SUPERIOR POSSIBLE LATE SAT. THIS TROUGH WILL
MOVE EAST INTO CENTRAL LAKE SUPERIOR ON SUN AND BECOME STATIONARY.
WINDS ARE EXPECTED TO TURN NE BEHIND THE TROUGH WITH SPEEDS TO 30 KT.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...NONE.
LAKE MICHIGAN...NONE.
&&
$$
SYNOPSIS/SHORT TERM...ROLFSON
LONG TERM...AJ
AVIATION...ROLFSON
MARINE...ROLFSON/AJ
AREA FORECAST DISCUSSION
NWS ST LOUIS MO
404 PM CST TUE DEC 9 2008
.DISCUSSION...
/341 PM CST TUE DEC 9 2008/
THE STRONG COLD FRONT CONTINUES TO PUSH THROUGH THE SERN PORTION
OF THE CWA AT MID-AFTERNOON. SO FAR IT HAS BEEN WELL-BEHAVED WITH
SOME SPOTTY 1-2 IN SNOW ACCUMULATIONS IN KNOX COUNTY. ELSEWHERE
WINTRY PCPN HAS BEEN RATHER LIGHT AND NOT MUCH OF AN ISSUE. THE
PCPN ATTM IS OCCURING IN TWO AREAS. THE SNOW IN NE MO IS OCCURING
IN ASSOCN WITH A LONG FRONTOGENETIC BAND WHICH STRETCHES FROM NRN
OK ACROSS NRN MO...WHILE ANOTHER AREA OF RAIN IS OVER SW IL IN
ASSOCIATION WITH WK LIFT AHEAD OF THE TROF AND WAA ALOFT. PRIND
ARE THAT THE FRONTOGENETIC BAND IMPACTING NE MO WILL GRADUALLY
DSIPT DURING THE EARLY EVENING WITH SOME ADDITIONAL LIGHT ACCUMS.
WHILE THE RAIN AREA SHOULD MOVE EASTWARD...GENERALLY IN ADVANCE OF
THE SUB-FREEZING AREA. IN BETWEEN THESE ZONES THE PCPN CHANCES
APPEAR TO BE MUCH LESS GIVEN WEAK FORCING AND ANY AMOUNTS WOULD BE
LIGHT. P-TYPES CUD RUN THE GAMIT WITH DEEP COLD AIR STILL LAGGING
THE LEADING EDGE OF THE SURFACE FREEZING LINE. I HAVE CARRIED JUST
CHANCE POPS GIVEN THE UNCERTAINTY AND AGAIN EXPECTING ANY PCPN TO
BE LIGHT...HOWEVER THIS COULD STILL CAUSE ISSUES.
FOR THE OVERNIGHT HOURS INTO WEDNESDAY THE LAST 2 RUNS OF THE NAM
HAVE THROWN A WRENCH INTO AN OTHERWISE STRAIGHTFORWARD FCST. THE
12Z AND 18Z NAM RUNS WANT TO DEVELOP A NEW DEFORMATION
ZONE/FRONTOGENETIC PCPN BAND ACROSS SRN MO LATER TONIGHT DUE TO A
MID LEVEL LOW MOVING INVOF OF THE OK AND MO/AR BORDER OVER THE
NEXT 18H...IMPACTING THE OZARKS LATER TONIGHT AND THE ERN OZARKS
AND SOUTHERN IL ON WEDNESDAY. THIS IS QUITE AN OUTLIER FROM THE
OTHER AVAILABLE GUIDANCE BUT CAN`T BE DISCOUNTED AS THE PROFILER
AND SATELLITE DATA IS SHOWING A POSSIBLE CIRCLN IN NW OK ATTM.
WHILE MY CONFIDENCE IS LOW...I HAVE HIGHEST POPS OVERNIGHT ACROSS
THE SOUTH AND HAVE NOW INTRODUCED A CHANCE OF SNOW ACROSS THE ERN
OZARKS AND EXTREME SW IL ON WED. LATER SHIFTS WILL HAVE TO
CAREFULLY EXAMINE OBSERVATIONS AND NEWER MODEL DATA TO SEE IF THIS
CHANCE MERITS EVEN GREATER EMPHASIS.
EXPECTING A DAY OR SO OF COLD WEATHER AND THEN A NICE MODERATION
INTO THE WEEKEND AS THE PATTERN CHANGES AND HEIGHTS RISE ALOFT
WITH SLY LOW LEVEL FLOW BECOMING ESTABLISHED. PRIND ARE TEMPS WILL
BE ABOVE NORMAL THIS WEEKEND. THE BOTTOM WILL DROP OUT HOWEVER
DURING THE FIRST PART OF NEXT WEEK. THE FAVORED ECMWF AND CMC GEM
ARE SHOWING A STRONG ARCTIC FRONT WILL PUSH THRU THE AREA SOMETIME
ON MONDAY WITH A POTENTIAL ICE STORM ENSUING AS SHALLOW COLD AIR
INVADES THE MID MS VLY. STAY TUNED.
GLASS
&&
.AVIATION...
/506 AM CST TUE DEC 9 2008/
FOR THE 12Z TAFS...
LOW PRES CURRENTLY ELONGATED ALONG AN AXIS FROM SE IOWA SWWD INTO
ERN OKLAHOMA AHEAD OF WHICH STG SLY FLOW DOMINATES IN CONCERT WITH
AN UPR LVL TROF OVR THE INTER-MTN WEST. THIS HAS ALLOWED FOR THE
DEVELOPMENT OF RA AND TSRA OVR MISSOURI AND ILLINOIS THIS MORNING
WITH MVFR CONDITIONS OVR MOST TAF LOCALES. SCT WET WEATHER
CONTINUE THRU MRNG AS STRONG MOIST SLY FLOW IN TANDEM WITH UPR LVL
INSTABILITY AND FORCING...THIS WL KEEP ALL TAF LOCALES WITHIN MVFR
CONDITIONS. IN ADDITION LOCAL AIRCRAFT SOUNDINGS AND WSR-88D
VERTICAL WIND PROFILES HV SHOWN STRONGER WINDS SLIGHTLY ALOFT AND
THUS HAVE PUT IN LLWS FOR KSTL AND KSUS. COLD FRNT WL PROGRESS
THRU KUIN AND KCOU AROUND 15Z AFTER WHICH CONDITIONS WL
DETERIORATE TO IFR AND PSBL LIFR CONDITIONS AS CIGS WL LOWER AOA
500 FEET...SUCH CONDITIONS SHLD PREVAIL AROUND 18Z FOR KSTL AND
KSUS. STRONG NWLY WINDS SUSTAINED AOA 15KTS GUSTS UP TO 25KTS ARE
TO BE ANTICIPATED BEHIND THE FRONT AS STRONG HIGH PRES FROM THE
NRN PLNS BUILDS SWD. WITH COLD AIR ENTRENCHING OVR THE RGN RAIN
SHLD GRADUALLY TRANSITION TO SNOW. WITH REGARDS TO SNOW HV KEPT
BETTER CHCS NWD OVR KCOU AND KUIN WITH THE PROGRESSION OF THE LOW
CENTER JUST NORTH...LESSER CHCS FOR KSTL AND KSUS...WL RE-EVALUATE
WITH LATER FCSTS. UNTIL THEN HV TEMPO -SN FOR KSTL AND KSUS WITH
IFR VSBYS OF 2SM...WHILE PREDOMINANT OVR KCOU AND KUIN INTO THE LATE
AFTN HRS AND INTO THE EVNG WITH THE POTENTIAL OF SN AND VSBYS TO
LIFR OF 1/2SM.
SIPPRELL
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
IL...NONE.
&&
$$
WFO LSX
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
315 AM CST MON DEC 8 2008
.DISCUSSION...
THE STORM SYSTEM THAT WILL AFFECT THE REGION TONIGHT INTO TUESDAY IS
THE MAIN FORECAST CONCERN. WILL CONTINUE WINTER STORM WATCH THAT WAS
ISSUED YESTERDAY AND LET DAY SHIFT TRANSITION THINGS OVER. WHAT IS
MOST LIKELY TO HAPPEN IS THAT AN ADVISORY WILL BE ISSUED...BUT LETS
SEE WHAT THE 12Z MODELS INDICATE.
WATER VAPOR SATELLITE IMAGERY LOOP EARLY THIS MORNING SHOWED DECENT
WAVE PUSHING SEWD FROM THE PACIFIC NW AND A SLIGHTLY MORE IMPRESSIVE
CIRCULATION OVER SWRN AZ. THERE WAS SOME LIGHTNING ASSOCIATED WITH
THE SECOND FEATURE. PLOTS FROM 00Z SHOWED THE FOLLOWING. THERE WAS
NOT MUCH MOISTURE NOTED IN THE SOUTHERN PLAINS. ALL 850 MB DEWPOINTS
WERE LESS THAN ZERO. AT 500 MB...12 HOUR HEIGHT FALLS OF 50 METERS
OR MORE WERE NOTED OVER MOST OF THE WRN U.S. WITH TWO AREAS OF MORE
SIGNIFICANT FALLS. FIRST WAS OVER WA/OR/ID/WRN MT (UP TO 130 METER
FALLS) AND THE OTHER WAS OVER SRN CA (120 METER FALL AT SAN DIEGO).
AT 300 MB...A JETSTREAK OF AT LEAST 130 KTS WAS PUNCHING INTO THE
WA/OR COAST. THERE WAS A 145 KT MAX NOTED OVER NRN MN (AN AIRCRAFT
REPORT). SURFACE ANALYSIS AT 09Z SHOWED LOW PRESSURE EXTENDING SWD
OVER THE WRN HIGH PLAINS...WITH MAIN LOW APPARENTLY NEAR THE BORDER
OF CO/KS/OK. A WARM FRONT WAS LOCATED TO OUR SOUTH ACROSS PARTS OF
KS AND MO. SOME OF THE WARMER AIR SOUTH OF THE FRONT SHOULD PUSH
INTO PARTS OF SERN NE TODAY. WENT WITH HIGHS FROM AROUND 50 FAR SRN
ZONES TO MID 30S ALONG THE SD BORDER. PCPN CHANCES WILL BE ON THE
INCREASE DURING THE DAY. NERN NE IS THE MOST LIKELY AREA TO HAVE
MEASURABLE PCPN BEFORE 00Z TUESDAY.
GENERAL MODEL CONSENSUS IS THAT THE MAIN LOW WILL DEVELOP/MOVE SEWD
INTO THE TX PNHDL BY THIS EVENING...THEN EJECT NEWD INTO MO BY 12Z
TUESDAY. IT APPEARS PCPN WILL BE HEAVIEST IN TWO BANDS. FIRST FROM
ERN OK TOWARD IL AND THE OTHER FROM SRN MN INTO WI. NERN NE SHOULD
BE ON THE SWRN EDGE OF THE SECOND AREA. 00Z NAM OUTPUT INDICATED A
DECENT POTENTIAL FOR A BAND OF PCPN TO SETUP UNDER DEFORMATION ZN.
06Z NAM NOT QUITE AS AGGRESSIVE. IN GENERAL...MODELS ARE NOT QUITE
AS HEAVY WITH QPF. DID NOT WANT TO BACK OFF TOO MUCH...SO KEPT THE
POSSIBLE STORM TOTAL AMOUNTS FROM 2 TO 4 INCHES. SOME SPOTS COULD
HAVE A LITTLE MORE AND SOME WILL HAVE A LITTLE LESS. MODELS STILL
SHOW FAIRLY DECENT MID LEVEL MOISTURE...WITH 750-700 MB MIXING
RATIOS 3 TO 4 G/KG TONIGHT. IT DOES DROP OFF TO ABOUT 2 G/KG OVER
NERN NE LATE. EXPECT PCPN TO CHANGE OVER FROM RAIN TO SNOW FAIRLY
QUICKLY. CAN NOT COMPLETELY RULE OUT SOME MIXED PCPN FOR A FEW
HOURS THIS EVENING.
SNOW SHOULD BE MOSTLY MOVING OUT BY 18Z TUESDAY...BUT KEPT SOME
LOW POPS GOING INTO THE AFTERNOON BASED ON 03Z SREF OUTPUT WHICH
STILL SHOWED SOME SNOW FOR SERN HALF OF THE FORECAST AREA IN THE
AFTERNOON. NORTH WINDS WILL INCREASE FOR TONIGHT AND STAY STRONG
THROUGH THE DAY TUESDAY...THEN COLD HIGH PRESSURE WILL BUILD IN
FOR TUESDAY NIGHT. TEMPERATURES SHOULD BE STEADY OR EVEN SLOWLY
FALL TUESDAY. HIGHS SHOULD REBOUND A BIT WEDNESDAY...WITH MOSTLY
UPPER 20S IN WRN IA AND LOWER 30S IN ERN NE.
MADE A FEW TWEAKS THROUGH MID WEEK...BUT NOTHING MAJOR.
&&
.AVIATION...
FOR TAF SITES KOFK/KOMA/KLNK THROUGH 09/06Z.
VFR CONDITIONS EXPECTED AT ALL TAF SITES THROUGH 0800Z. MVFR
CONDITIONS DEVELOPING 0900Z-06Z WITH R- CHANGING TO S-. LATEST
FORECAST SOUNDINGS SUGGEST QUICK TURNOVER TO SNOW.
&&
.OAX WATCHES/WARNINGS/ADVISORIES...
NE...WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON
FOR NEZ015-031>034-042>045-050>053-065>068.
IA...WINTER STORM WATCH FROM THIS EVENING THROUGH TUESDAY AFTERNOON
FOR IAZ043-055-056-069-079-080-090-091.
&&
$$
DISCUSSION...MILLER
AVIATION...FOBERT
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
501 AM CST MON DEC 8 2008
.AVIATION...
MVFR CIGS WHICH HAVE DEVELOPED THIS MORNING WILL STICK AROUND FOR
MUCH OF THE FORECAST PERIOD. CIGS MAY BRIEFLY BECOME VFR THIS
AFTERNOON AND EVENING...BUT WILL PREVAIL MVFR. A TIGHTENING
PRESSURE GRADIENT ALONG WITH AMPLE MIXING WILL ALLOW WINDS TO
INCREASE TO 20G30 OR SO BY 081400 AND REMAIN THERE THROUGH SUNSET.
GFS SEEMS BULLISH ON PRECIP AND WILL CONTINUE WITH VCTS/VCSH FOR
NOW. MOST LIKELY TIME FOR TSRA STILL APPEARS TO BE AFTER 09000.
FROPA IS EXPECTED AT THE METROPLEX AROUND 091500 AND AT WACO A FEW
HOURS AFTER THIS TAF CYCLE ENDS. SH/13
&&
.PREV DISCUSSION... /ISSUED 405 AM CST MON DEC 8 2008/
THE PRESSURE GRADIENT RESULTING FROM A STRONG SURFACE LOW OVER
SOUTHEASTERN COLORADO AND A RIDGE OVER THE SOUTHEASTERN U.S. IS
RESULTING IN GUSTY SOUTHERLY WINDS. ACARS AND KFWS AND KGRK VWP
DATA INDICATE THAT THERE IS A 50-55 KNOT LOW LEVEL JET...WHICH IS
FUNNELING LOW LEVEL MOISTURE INTO THE REGION. WE HAVE ISSUED A
WIND ADVISORY FOR ALL BUT THE EXTREME EASTERN ZONES FROM 8 AM
TODAY THROUGH 8 PM TONIGHT. THE UPPER LOW THAT CURRENTLY ENTERING
SOUTHWESTERN ARIZONA AS OF 0930Z...WILL CONTINUE TO MOVE EAST...
SLIDING ACROSS TEXAS TUESDAY NIGHT. THERE MAY BE A FEW SPRINKLES
THIS MORNING AND WE WILL SEE A CHANCE OF SHOWERS AND THUNDERSTORMS
THIS AFTERNOON AND TONIGHT AREAWIDE...AND SOME OF THESE STORMS MAY
BE SEVERE...SEE THE HAZARDOUS WEATHER OUTLOOK /FLUS44 KFWD...OR
FTWHWOFWD/ FOR DETAILS. THE COLD FRONT WILL MOVE INTO THE
NORTHWESTERN ZONES TOWARD DAYBREAK TUESDAY AND THROUGH THE
SOUTHEAST DURING THE EARLY AFTERNOON. AS THE UPPER TROUGH MOVES
ACROSS THE REGION TUESDAY NIGHT.. MOST OF THE PRECIPITATION SHOULD
HAVE ENDED. THERE IS THE POSSIBILITY OF SOME FLURRIES...BUT GIVEN
THE MODEL DISAGREEMENTS AS TO HOW MUCH LOW LEVEL MOISTURE WILL
REMAIN AT THAT POINT...HAVE NOT MENTIONED THIS IN THE FORECAST. MUCH
COLDER WEATHER IS EXPECTED FOR WEDNESDAY AND WEDNESDAY NIGHT
FOLLOWED BY MODERATING TEMPERATURES FOR THURSDAY INTO THE WEEKEND.
A WEAK SHORTWAVE WILL MOVE ACROSS THE REGION FRIDAY...BUT MOISTURE
IS EXPECTED TO BE LIMITED. WE MAY SEE SOME LOW CHANCES OF RAIN
RETURN BY SUNDAY.
58
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 71 57 59 31 50 / 20 60 30 20 0
WACO, TX 71 60 66 31 52 / 20 50 30 20 0
PARIS, TX 63 56 60 28 49 / 30 70 40 20 0
DENTON, TX 69 53 54 28 50 / 20 60 20 20 0
MCKINNEY, TX 66 57 57 28 49 / 30 70 30 20 0
DALLAS, TX 69 57 59 32 50 / 20 60 30 20 0
TERRELL, TX 67 58 60 33 49 / 30 70 30 20 0
CORSICANA, TX 67 58 64 32 50 / 20 60 40 20 0
TEMPLE, TX 71 62 70 34 52 / 20 40 30 20 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 8 AM THIS MORNING TO 8 PM CST THIS EVENING
FOR TXZ091>094-100>105-115>121-129>134-141>146-156>161-174.
&&
$$
13/58
AREA FORECAST DISCUSSION
NWS FORT WORTH TX
405 AM CST MON DEC 8 2008
.DISCUSSION...
THE PRESSURE GRADIENT RESULTING FROM A STRONG SURFACE LOW OVER
SOUTHEASTERN COLORADO AND A RIDGE OF THE SOUTHEASTERN U.S. IS
RESULTING IN GUSTY SOUTHERLY WINDS. ACARS AND KFWS AND KGRK VWP
DATA INDICATE THAT THERE IS A 50-55 KNOT LOW LEVEL JET...WHICH IS
FUNNELING LOW LEVEL MOISTURE INTO THE REGION. WE HAVE ISSUED A
WIND ADVISORY FOR ALL BUT THE EXTREME EASTERN ZONES FROM 8 AM
TODAY THROUGH 8 PM TONIGHT. THE UPPER LOW THAT CURRENTLY ENTERING
SOUTHWESTERN ARIZONA AS OF 0930Z...WILL CONTINUE TO MOVE EAST...
SLIDING ACROSS TEXAS TUESDAY NIGHT. THERE MAY BE A FEW SPRINKLES
THIS MORNING AND WE WILL SEE A CHANCE OF SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND TONIGHT AREAWIDE...AND SOME OF
THESE STORMS MAY BE SEVERE...SEE THE HAZARDOUS WEATHER OUTLOOK
/FLUS44 KFWD...OR FTWHWOFWD/FOR DETAILS. THE COLD FRONT WILL MOVE
INTO THE NORTHWESTERN ZONES TOWARD DAYBREAK TUESDAY AND THROUGH
THE SOUTHEAST DURING THE EARLY AFTERNOON. AS THE UPPER TROUGH
MOVES ACROSS THE REGION TUESDAY NIGHT.. MOST OF THE PRECIPITATION
SHOULD HAVE ENDED. THERE IS THE POSSIBILITY OF SOME
FLURRIES...BUT GIVEN THE MODEL DISAGREEMENTS AS TO HOW MUCH LOW
LEVEL MOISTURE WILL REMAIN AT THAT POINT...HAVE NOT MENTION THIS
IN THE FORECAST. MUCH COLDER WEATHER IS EXPECTED FOR WEDNESDAY
AND WEDNESDAY NIGHT FOLLOWED BY MODERATING TEMPERATURES FOR
THURSDAY INTO THE WEEKEND. A WEAK SHORTWAVE WILL MOVE ACROSS THE
REGION FRIDAY...BUT MOISTURE IS EXPECTED TO BE LIMITED. WE MAY
SEE SOME LOW CHANCES OF RAIN RETURN BY SUNDAY.
58
&&
.PRELIMINARY POINT TEMPS/POPS...
DALLAS-FT. WORTH, TX 71 57 59 31 50 / 20 60 30 20 0
WACO, TX 71 60 66 31 52 / 20 50 30 20 0
PARIS, TX 63 56 60 28 49 / 30 70 40 20 0
DENTON, TX 69 53 54 28 50 / 20 60 20 20 0
MCKINNEY, TX 66 57 57 28 49 / 30 70 30 20 0
DALLAS, TX 69 57 59 32 50 / 20 60 30 20 0
TERRELL, TX 67 58 60 33 49 / 30 70 30 20 0
CORSICANA, TX 67 58 64 32 50 / 20 60 40 20 0
TEMPLE, TX 71 62 70 34 52 / 20 40 30 20 0
&&
.FWD WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FROM 8 AM THIS MORNING TO 8 PM CST THIS EVENING
FOR TXZ091>094-100>105-115>121-129>134-141>146-156>161-174.
&&
$$
21/58
AREA FORECAST DISCUSSION
NWS SEATTLE WA
930 PM PST SUN DEC 7 2008
.SYNOPSIS...SCATTERED SHOWERS WILL DECREASE OVERNIGHT. HIGH PRESSURE
WILL BUILD MONDAY. A WARM FRONT WILL REACH THE AREA TUESDAY AND
WEDNESDAY. THE WEATHER PATTERN WILL CHANGE DRAMATICALLY TOWARD THE
END OF NEXT WEEK AS A COLD UPPER TROUGH DEVELOPS OVER THE WESTERN
UNITED STATES.
&&
.SHORT TERM...AIR MASS WILL DRY AND COOL A BIT FURTHER
OVERNIGHT...THE LAST OF THE SHOWERS WILL MOVE OFF INTO THE CASCADES
AND THEN MOSTLY END OVERNIGHT. FCSTS W/ SCT SHOWERS AND THE WINTER
ADVISORY FOR THE MTNS ENDING AT 10PM LOOK JUST FINE. A 1026MB SFC
HIGH PRES AREA WILL SHIFT OVER WA ON MONDAY. ALTHOUGH THE AIR MASS
HAS FINALLY COOLED OFF OVER WRN WA W/ 850MB TEMP ARND -3C THRU
MONDAY THE NEXT FNTL SYS OFFSHORE BRINGS WARM ADVECTION INTO THE
AREA TUE. LOOKS LIKE LATESTS GFS STARTS UP THE PRECIP MIDDAY TUE AND
850 TEMP WARMS TO ARND +3C TUE NITE AND WED. RAIN SAGS SOUTH WED
NITE AND TEMP COOLS OFF BACK TO 0C AS PRECIP ENDS. YOU WOULD THINK
THAT THE SYSTEM OFFSHORE MIGHT OCCLUDE AND END UP GIVING A NICE
SNOWFALL FOR THE MTNS MIDWEEK BUT IT SEEMS THAT THIS WARM WESTERN
U.S. RIDGE THAT HAS PLAGUED THE REGION FOR THE PAST FEW WEEKS TAKES
ONE LAST PARTING SHOT BEFORE RETROGRADING FAR OFFSHORE FOR NEXT
WEEKEND. 19
.LONG TERM...AS MENTIONED ABOVE THE RIDGE SHIFTS WWD AND THE UPPER
HIGH IS CENTERED ARND 40N/140W 12Z FRIDAY AS THE PATTERN CHANGE
BEGINS. ON SAT THE RIDGE BUILDS NORTH ALG 150W AS A CHILLY UPPER
TROF DROPS OVER THE WRN U.S. THE COLD WRN TROF LOOKS LIKE IT WILL
PERSIST FOR AT LEAST SEVERAL DAYS. COLD SURFACE HIGH PRES BUILDS
OVER WRN CANADA AND COLD FRASER OUTFLOW WILL SHOOT ACROSS WRN
WHATCOM AND THE SAN JUANS AND OUT THRU THE STRAIT. UW EXTENSION HAD
A NE GALE IN THOSE AREAS SAT. AS THAT COLD AIR MASS FROM B.C. SLIDES
SOUTH THRU WRN WA SAT THERE COULD BE A LITTLE SNOW. ALTHOUGH
MODIFIED ARCTIC FRONTS MOVG THRU WRN WA TEND TO BE ON THE DRY SIDE
AT THE LEAST IT WILL USHER IN A HARD FREEZE STARTING SAT NITE AS THE
1045MB HIGH BUILDS OVER B.C. THRU SUN. 19
&&
.AVIATION...PUGET SOUND CONVERGENCE ZONE OVER PIERCE COUNTY AT 05Z
WILL CONTINUE TO MOVE SOUTHEAST. ONLY ISOLATED SHOWERS LEFT THIS
EVENING. WIDE RANGE OF CONDITIONS BEING REPORTED AT 05Z WITH SOME
PLACES NEARLY CLEAR WHILE IN THE CENTRAL SOUND A STRATUS LAYER
AROUND 2500 FEET IS IN PLACE. VARIABLE CONDITIONS CONTINUING INTO
THE MORNING HOURS. SURFACE GRADIENTS ARE LIGHT. ACARS SOUNDINGS HAVE
NORTHWESTERLY WINDS FROM 850 MB DOWN TO THE SURFACE BUT THE WINDS
SPREED ARE LESS THAN 10 KNOTS FOR THE MOST PART. WITH THE AMS
STABILIZING OVERNIGHT AND PLENTY OF LOW LEVEL MOISTURE WILL GO FOR
LOW CEILINGS AFT 12Z...BELOW 1000 FEET...FOR THE PUGET SOUND AREA
TERMINALS...WITH HIGHER CEILINGS AT THE OTHER TAF SITES. WITH SOME
CLEARING COULD SEE SOME FOG AT KOLM 10Z-18Z. CEILINGS IMPROVING
LATER MONDAY MORNING WITH THE IMPROVING TREND CONTINUING INTO MONDAY
AFTERNOON. WILL FORECAST CEILINGS ABOVE 3000 FEET BY 00Z TUE.
KSEA...TOUGH CALL AT KSEA FOR THE NEXT FEW HOURS. CEILINGS TO THE
NORTH NEAR 4000 FEET WHILE CEILINGS TO THE SOUTH NEAR 2000 FEET.
KTIW THE LOWEST ONE OF THE BUNCH WITH 800 FOOT CEILINGS. VARIABLE
CONDITIONS CONTINUING THROUGH 12Z WITH CEILINGS BOUNCING AROUND
BETWEEN 1000 AND 4000 FEET. EXPECT CEILINGS TO CONSOLIDATE IN THE
500-1000 FOOT RANGE 12Z-15Z MON. CEILINGS SLOWLY LIFTING LATE
MORNING INTO EARLY AFTERNOON AND BY 00Z TUE CEILINGS ABOVE 3000
FEET. LIGHT AND VARIABLE WINDS THROUGH MONDAY MORNING. FELTON
&&
.MARINE...HIGH PRES WILL BUILD INTO WESTERN WASHINGTON FROM THE WEST
TONIGHT AND MON...THEN SHIFT EAST TUE AS THE WARM FRONT OF AN
APPROACHING SYSTEM BRUSHES THE FORECAST AREA. THE COLD FRONT WILL
SLOWLY CROSS THE WATERS TUE NIGHT AND WED. HIGH PRES WILL REBUILD
THU...AND A COLD FRONT WILL APPROACH FROM THE NORTH ON FRI. SMALL
CRAFT ADVISORIES WINDS CONTINUING CENTRAL AND EASTERN STRAIT PLUS
ADMIRALTY INLET UNTIL 09Z MONDAY. SYSTEM TUESDAY NIGHT AND WEDNESDAY
CONTINUES TO LOOK WEAK WITH THE BEST CHANCE FOR SMALL CRAFT ADVISORY
WINDS WILL BE OVER THE COASTAL WATERS. WESTERLY SWELLS WILL BUILD TO
11 FT OVER THE COASTAL WATERS WEDNESDAY AND PEAK AROUND 13 FT ON
THURSDAY. A COLD FRONT WILL APPROACH THE AREA FROM THE NORTH ON
FRIDAY. FELTON
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
WA...WINTER WEATHER ADVISORY ENDS AT 10PM
PZ...SMALL CRAFT ADVISORY COAST...CENTRAL STRAIT...EAST ENTRANCE...
ADMIRALTY INLET...NORTHERN INLAND WATERS.
$$
WEATHER.GOV/SEATTLE
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