Pre-Christmas Winter Storm Potential

[Toronto4]

Just issued by Environment Canada:

City of Toronto

4:12 PM EST Tuesday 17 December 2013

Special weather statement for

City of Toronto issued

Significant winter weather expected late this week and this weekend.

Several disturbances originating in Texas are expected to track towards the Lower Great Lakes on Friday. A sharp front will lie across Southern Ontario, from lower Michigan to Southern Quebec. Precipitation ahead of this disturbance is expected to spread into Southwestern Ontario Thursday evening and through the remainder of Southern Ontario by Friday morning. The exact location of the front will determine whether the precipitation falls as rain, freezing rain, ice pellets, or snow.

Computer models suggest that areas north of a line from Kincardine to Barrie to Ottawa are likely to see mainly snow. South of this line, precipitation could fall as snow, ice pellets, freezing rain or even periods of rain.

The precipitation may become more intermittent on Saturday before another more potent disturbance approaches Southern Ontario on Sunday. This system is expected to tap into gulf moisture and could bring significant snowfall accumulations to Southern Ontario Saturday night through Sunday. A significant area of prolonged freezing rain and ice pellets is also possible across the Lower Great Lakes.

There is still considerable uncertainty surrounding these disturbances and their exact tracks. Any change in the storm tracks will affect precipitation amounts and type. However, it is very likely that travel will be impacted. Environment Canada will continue to monitor this developing situation.

Please monitor the latest forecasts and warnings from Environment Canada at www.weatheroffice.gc.ca.

[Thundersnow12]

Model consensus on surface low(s) between far S. IL and western OH is solid...which would normally be decent for many of us but the ULL picture is ugly.

Even if its ugly and with the marginal cold air as it looks now, hard to find a somewhat strong system in the past that didn't produce good snows here with the low passing through southern IL.

[snowstormcanuck]

Environment Canada already out with a special weather statement. Usually they wait for the last moment for any type of headline so it speaks volumes as to how seriously they're taking this threat when they issue one 5 days in advance.

[TimChgo9]

Weren't you staying away from the models until Friday?

No.

I mean, I want to.

But I can't.

 

Skilling posted on Facebook, he seems pretty sure there is going to be snow this weekend.

[snowstormcanuck]

btw...for several runs most here have resisted the urge to extrapolate the 84 hour NAM. Kudos to you. 

[RJSnowLover]

New LOT:
 

 

OTHERWISE ATTENTION TURNS TO THE SYSTEM EXPECTED TO DIG ACROSS THE
SOUTHWEST..NEAR BAJA CALIFORNIA BY FRIDAY NIGHT. THIS DIGGING SYSTEM
IS EXPECTED TO TRANSITION A QUASI-ZONAL FLOW PATTERN ACROSS THE
CONUS INTO A SOUTHWESTERLY FLOW PATTERN ALOFT...AS DOWNSTREAM HEIGHT
RISES LEAD TO POSITIVE HEIGHT ANOMALIES AND RIDGING ACROSS THE
EASTERN CONUS. THIS PATTERN IS VERY CONDUCIVE TO PRODUCING A
SIGNIFICANT PRECIP EVENT ACROSS PORTIONS OF THE CENTRAL CONUS. A
STRONG AND IMPRESSIVE SOUTHERLY 60+ KT LOW LEVEL JET IS PROGGED TO
DEVELOP BY SATURDAY IN RESPONSE TO THE PATTERN SHIFT...WITH LOW
PRESSURE DEVELOPING ACROSS TEXAS. THIS LOW LEVEL JET WILL TRANSPORT
COPIOUS AMOUNTS OF MOISTURE NORTHWARD ACROSS THE MISSISSIPPI AND OHIO
VALLEYS.

OVERALL...THIS CONTINUES TO BE A VERY COMPLEX FORECAST AS
THE SYSTEM APPEARS THAT IT WILL...AT LEAST TEMPORALLY...SEPARATE
ITSELF FROM THE MAIN SOUTHERN STREAM FLOW. MUCH OF THE GUIDANCE IS
IN FAIR AGREEMENT WITH TAKING THIS SYSTEM EAST-NORTHEASTWARD ACROSS
THE TEXAS PANHANDLE LATE SATURDAY AND THEN MERGING BACK INTO THE
MAIN TROUGH BY SUNDAY AS IT MOVES ACROSS MISSOURI. OVERALL...IN THE
LOWER LEVELS...THIS LOOKS TO SET UP A FRONTAL BOUNDARY RIGHT ACROSS
THE CENTRAL STATES...WITH AN ELONGATED AREA OF SURFACE LOW PRESSURE
LIKELY TO TRANSITION ALONG THE BOUNDARY THROUGH THE WEEKEND. STRONG
MOISTURE CONVERGENCE AND FRONTOGENESIS IS LIKELY IN THE VICINITY OF THE
SOUTHWEST TO NORTHEAST ORIENTED BOUNDARY...ALONG THE NOSE OF THE LOW
LEVEL JET. THIS WILL LIKELY RESULT IN HEAVY PRECIPITATION ACROSS AT
LEAST PORTIONS OF THE AREA LATE SATURDAY INTO SUNDAY. THE MAIN
QUESTIONS AT THIS POINT CONTINUE TO BE...WHAT FORM WILL THE PRECIP
BE? I CONTINUE TO FOLLOWER CLOSER TO THE ECMWF SOLUTION FOR THE
SYSTEM AS IT HAS BEEN VERY GOOD LATELY.

THE MAIN CONCERNS I HAVE IS THE THERMAL PROFILE WITH THIS SYSTEM. IT
IS POSSIBLE THAT THE PRECIP BEGINS AS A WINTER MIX OF RAIN FREEZING
RAIN SLEET AND SNOW...ESPECIALLY ACROSS THE NORTH. MY SOUTHERN
COUNTIES MAY BECOME WARM ENOUGH TO RESULT IN MAINLY RAIN...AT LEAST
THROUGH SATURDAY NIGHT. THERE ARE DEFINITELY SIGNS THAT THIS
SYSTEM COULD TRANSITION OVER TO FREEZING RAIN AND THEN SNOW
SATURDAY NIGHT ACROSS NORTHERN ILLINOIS AS THE SYSTEM TRYS TO PULL
IN COLDER AIR IN THE LOWER LEVELS FOR THE NORTH. SIGNIFICANT
ACCUMULATIONS ARE CERTAINLY POSSIBLE ACROSS PORTIONS OF NORTHERN
ILLINOIS. HOWEVER...THE THERM PROFILE...AND HENCE WHERE SNOW VERSE
RAIN WILL FALL COULD EASILY CHANGE IN FUTURE FORECASTS. SO...IN
SPITE OF THE FACT CONFIDENCE IS INCREASING THAT WE WILL SEE A
DECENT PRECIP EVENT ACROSS THE AREA. CONFIDENCE ON PRECIP
TYPE...AND WHERE THE RAIN/VERSES HEAVY SNOW LINE SETS UP REMAINS
LOW AT THIS TIME. FOR THESE REASONS...IT IS TOO EARLY TO START
MENTIONING AMOUNTS OF SNOW OR ICE FOR ANY GIVEN AREAS.

THE AMOUNT OF PRECIP WITH THIS SYSTEM COULD CAUSE HYDRO
ISSUES...WITH PRECIP AMOUNTS POSSIBLY EXCEEDING AN INCH OR TWO
ACROSS PORTIONS OF THE AREA. THIS WILL HAVE TO BE
WATCHED...ESPECIALLY IF THE PRECIP FALLS AS RAIN ON TOP OF ANY
REMAINING SNOW PACK.

ANOTHER SHOT OF COLDER AIR WILL OVERSPREAD THE AREA EARLY NEXT WEEK
IN THE WAKE OF THIS SYSTEM...WITH HIGH PRESSURE BUILDING IN ACROSS
THE REGION.

[ayuud11]

 

 

 

CONFIDENCE IS BEGINNING TO BUILD REGARDING THE POTENTIAL FOR A
SIGNIFICANT WEATHER EVENT ACROSS WESTERN AND NORTH CENTRAL NEW YORK
THIS WEEKEND. MODELS SHOW FAIRLY GOOD AGREEMENT ON THE BASIC
INGREDIENTS...A POWERFUL 200+KT UPPER LEVEL JET STREAK CENTERED OVER
NORTHERN ONTARIO/QUEBEC...A WELL DEFINED BAROCLINIC ZONE STRETCHING
FROM THE MIDWEST ACROSS THE LOWER GREAT LAKES...A POWERFUL SHORTWAVE
EJECTING OUT OF THE SOUTHERN PLAINS HELPING TO GENERATE A SURFACE
LOW OVER THE MISSISSIPPI VALLEY...AND FINALLY A WELL DEFINED RETURN
FLOW OFF THE GULF OF MEXICO THAT WILL ADVECT EXTREMELY MOIST AIR UP
AND OVER THE AFOREMENTIONED BAROCLINIC ZONE. ALL OF THESE FACTORS
WILL CREATE AN IDEAL SETUP FOR HEAVY RAIN ACROSS THE LOWER GREAT
LAKES THIS WEEKEND.

THE TEMPERATURE GRADIENT IN PLACE ACROSS THE FORECAST AREA WILL
RESULT IN A COMPLICATED SET OF POTENTIAL FORECAST PROBLEMS. ACROSS
THE SOUTHERN TIER WHERE TEMPERATURES ARE EXPECTED TO CLIMB WELL
ABOVE FREEZING...POSSIBLY AS HIGH AS THE MID 50S ON SUNDAY...THE HEAVY
RAIN SATURDAY INTO SUNDAY COULD RESULT IN A FLOODING THREAT. ACROSS
THE NORTH COUNTRY WHERE LIGHT NORTH-NORTHEASTERLY FLOW INTO THE
TROUGH COULD HAVE THE EFFECT OF DROPPING SURFACE TEMPERATURES BACK
BELOW FREEZING ON SATURDAY...THE THREAT FOR A MAJOR FREEZING RAIN
EVENT WILL EXIST SATURDAY INTO SUNDAY. IN FACT...SEVERAL OF THE
CURRENT CIPS ANALOGS TO THIS WEEKEND`S PROGGED PATTERN INVOLVE
SIGNIFICANT FREEZING RAIN ACROSS THE SAINT LAWRENCE
VALLEY...INCLUDING THE INFAMOUS FREEZING RAIN EVENT OF JANUARY 1998
THAT SEVERELY IMPACTED THE SAINT LAWRENCE VALLEY...THE NORTHERN
ADIRONDACKS...AND QUEBEC. IN BETWEEN THESE TWO EXTREMES...THE
TEMPERATURE WILL HOVER WITHIN A FEW DEGREES EITHER SIDE OF
FREEZING...CREATING A VERY COMPLICATED FORECAST WITH A POTENTIAL FOR
FREEZING RAIN AND/OR FLOODING. IN ADDITION...IT IS ALSO WORTH NOTING
THAT MODELS DIFFER SOMEWHAT ON THE EXACT LOCATION OF THE FREEZING
LINE...CREATING ADDITIONAL UNCERTAINTY. ALL OF THAT SAID...ALL IT
WILL TAKE IS FOR THE AXIS OF THE BAROCLINIC ZONE TO MOVE 100 MILES
AND EITHER DIRECTION AND THE LOCATIONS OF THE ABOVE HAZARDS WILL
SHIFT ACCORDINGLY. STAY TUNED AS DETAILS BECOME CLEARER ON THIS
POTENTIALLY SIGNIFICANT WEATHER EVENT THIS WEEKEND.

BY SUNDAY NIGHT/MONDAY SOME MEASURE OF CLARITY RETURNS TO THE
FORECAST PICTURE AS THE SURFACE LOW TRACKS ACROSS THE NORTHEASTERN
U.S. AND A COLD FRONT SWEEPS ACROSS THE FORECAST AREA...USHERING IN THE
RETURN OF SUB-FREEZING TEMPERATURES ALONG WITH LAKE EFFECT SNOW AS
AN UPPER LEVEL TROUGH DIPS ACROSS THE GREAT LAKES.

-- End Changed Discussion --

[Harry]

here's GRR thoughts

 

THERE IS POTENTIAL FOR A MAJOR WINTER STORM TO IMPACT LOWER MICHIGAN

SATURDAY NIGHT AND SUNDAY. LOW PRESSURE DEVELOPING OVER THE ARKLATEX

REGION SATURDAY WILL TRACK NE AND POTENTIALLY BRING HEAVY SNOW

SATURDAY NIGHT AND SUNDAY.

ONCE AGAIN IT IS TOO EARLY TO GET INTO TOO MANY SPECIFICS GIVEN SOME

UNCERTAINTY REGARDING THE EVOLUTION AND EXACT TRACK AND STRENGTH OF

THE SYSTEM. IN THIS REGARD 12Z GFS GUIDANCE SUGGESTS THAT THE

HEAVIEST SWATH OF PCPN WOULD STAY SE OF OUR FCST AREA... BUT THAT A

SIGNIFICANT BAND OF SNOW COULD STILL AFFECT PARTS OF OUR FCST AREA

FAR TO THE NW OF THE SFC LOW TRACK BUT THAT THE DRY SLOT COULD GET

UP INTO SOUTHERN LWR MI REDUCING POTENTIAL SNOW AMOUNTS.

HOWEVER THE ECMWF HAS BEEN QUITE CONSISTENT FOR NUMEROUS CONSECUTIVE

RUNS NOW IN SHOWING THIS SYSTEM WILL HAVE A TREMENDOUS AMOUNT OF

GULF MOISTURE TO WORK WITH AND THAT HEAVY SNOW WILL REACH AT LEAST

THE SOUTHERN HALF OF LOWER MICHIGAN. THE 12Z ECMWF CONTINUES TO

SUPPORT THIS NOTION WITH A SFC LOW TRACK FROM NEAR IND NE TO BETWEEN

TOL AND CLE... WHICH IS QUITE FAVORABLE FOR ROUGHLY THE SE HALF OF

FORECAST AREA TO GET VERY HEAVY SNOW. THIS NOTION IS ALSO SUPPORTED

BY THE 12Z GLOBAL CANADIAN. 12Z UKMET GUIDANCE HAS THE LOW NEAR THE

MI/IN STATE LINE AT 12Z SUNDAY BUT IS AN OUTLIER WITH IT/S FURTHEST

NORTHWEST SFC LOW TRACK.

THE 12Z ECMWF SOLUTION SUGGESTS THE HEAVIEST SNOW WOULD COME

SATURDAY NIGHT THROUGH MID MORNING SUNDAY... BUT THAT SIGNIFICANT

DEFORMATION ZONE SNOW WOULD LINGER ON THE BACK SIDE OF THE SYSTEM

THROUGH SUNDAY ACROSS MOST IF NOT ALL OF OUR FCST AREA.

IN THE NEARER TERM... INCREASING POTENTIAL FOR A WINTRY MIX OF PCPN

TO INCLUDE FZDZ/LIGHT FREEZING RAIN IN THE THURSDAY NIGHT AND FRIDAY

TIME FRAME. BEST CHANCE FOR THIS WOULD MOST LIKELY BE NEAR TO MAINLY

NORTH OF I-96 WITH PCPN TYPE LIKELY IN MAINLY LIQUID FORM OVER OUR

SOUTHERNMOST FCST AREA. MEANWHILE P-TYPE THURSDAY NIGHT AND FRIDAY

OVER OUR FAR NORTHERN COUNTIES WILL LIKELY BE PLAIN LIGHT SNOW.

COULD BE DEALING WITH SOME FOG IN THAT TIME FRAME AS WELL GIVEN HIGH

BOUNDARY LAYER MOISTURE AND AS THE TEMP/DEW PT SPREAD BECOMES SMALL.

ALSO OF NOTE... TEMPS WILL FALL TO BELOW TO POTENTIALLY MUCH BELOW

NORMAL EARLY NEXT WEEK BEHIND THE STRONG LOW PRESSURE SYSTEM WITH

MAX TEMPS ONLY REACHING THE TEENS TO TWENTIES MONDAY AND TUESDAY

WITH ADDITIONAL POTENTIAL FOR SNOW (COMBINATION LAKE EFFECT AND

UPPER SHORTWAVES DROPPING DOWN FROM THE NW).

 

What that says to me is the are also assuming the outcome will be colder. If so my guess is it has to do with models being to slow with northern stuff so far on modeling. Thus one of the seasonal trends.. Other then that it is the classic track for big snows here.. We'll see.

[buckeye]

Dunno, looks a lot like the GGEM output to me in terms of p-types. Obviously the red arrow low 'track' is complete wishwash.

 

Regardless still a typical accu graphic.

 

That track graphic as depicted is ridiculous.  I'm not sure who makes those graphics but even a hobbiest following this event would know better.   A low cutting thru the eastern TennV and up the western slopes of the apps, as shown, would probably completely whiff Chicago and give us here in Columbus a hell of a winterstorm.   If only...

[A-L-E-K]

Even if its ugly and with the marginal cold air as it looks now, hard to find a somewhat strong system in the past that didn't produce good snows here with the low passing through southern IL.

it's just not happening if the 850 nearly crosses Chicago like on the gfs.

[Hoosier]

Even if its ugly and with the marginal cold air as it looks now, hard to find a somewhat strong system in the past that didn't produce good snows here with the low passing through southern IL.

 

 

The thing to me is what's happening aloft.  Models are basically taking the 850 mb low toward Chicago or very close at least.  With these SW systems, normally you can't get away with that unless the antecedent airmass is frigid or the storm is occluding.  We'll see what later runs show.

[Jonger]

Even the warm scenarios here are 33F to at most 34F with heavy rain. We will have frozen ground and probably still a decent snowpack down. This could definitely be interesting.

 

Well... Its going to melt on Thur-Fri and Sat-Sun now.

 

Parking lot piles.

 

Myself, I might end up with a snow storm. Or not.

[Thundersnow12]

Another thing, did we get this in detail this far out with the GHD storm? 

[A-L-E-K]

The thing to me is what's happening aloft. Models are basically taking the 850 mb low toward Chicago or very close at least. With these SW systems, normally you can't get away with that unless the antecedent airmass is frigid or the storm is occluding. We'll see what later runs show.

this. nice disco from lot as well.

[A-L-E-K]

Another thing, did we get this in detail this far out with the GHD storm?

it didn't have these kinds of wishy washy thermals but yeah, we did

[Chicago WX]

it didn't have these kinds of wishy washy thermals but yeah, we did

Speak for yourself.

[Northern_IN_Wx]

_{Trend is my friend...I'll take 34 and rain any day over freezing rain.  Silver lining!}   

[TimChgo9]

LOT's write up was nice, but, understandably, confidence in precip type, and where it will fall, and how much is low at this time.  If the 850 line doesn't move, and stays where it is (and GFS hasn't really moved it much over the last several runs) then, we can count on a wintry mess here in LOT-land.  But, being as it is still 4 days or so, we will have to see what changes come about, if any.

[A-L-E-K]

new gfs coming in slower and warmer at 850 through 99HRS

[cyclone77]

DVN really doesn't add too much of interest.  Just mentions precip type questions, etc. 

 

A WINTER STORM SYSTEM REMAINS POSSIBLE FOR THE AREA FOR SAT AM
THROUGH SUN PM. AT THIS TIME...IT APPEARS THAT A MIX OF RA/FZRA AND
SN WILL BE POSSIBLE SE OF IOWA CITY TO FREEPORT SAT. THE SE AREAS
MAY SEE A FZRA/SN MIX GOING INTO THE EVENING AND OVERNIGHT...WITH NW
PARTS ALL SNOW. DUE TO UNCERTAINTIES IN THE TRACK OF THIS STORM...
AS WELL AS...TEMPS AND PRECIP TYPES... BROAD-BRUSHED THE GRIDS TO
SHOW POTENTIAL OF THE PREDOMINANT WINTRY MIX. DO BELIEVE AN ABUNDANT
AMOUNT OF MOISTURE WILL BE ASSOCIATED WITH THIS...HOWEVER IT IS
UNKNOWN HOW MUCH WILL FALL AS RAIN...WHICH WOULD GREATLY AFFECT ANY
SNOWFALL TOTALS. IN ADDITION...ICING PROBLEMS MAY BE AN ISSUE FOR
PARTS OF THE AREA. ALL OF THIS WILL HOPEFULLY COME INTO BETTER
CLARITY OVER THE COMING DAYS. WINDS ARE EXPECTED TO BE GUSTY FROM
THE NNW THROUGH THE DAY SUN.

[Hoosier]

GFS is deeper on this run.

[Thundersnow12]

Snow band ends up further southeast and looks colder here this run.

[Gilbertfly]

FWIW....

 

12Z GFS #1 analog for H120 is January 1, 1985...#2 was January 1, 1979

[Geos]

12z run suite comparison. Wanted to see how much agreement there was by overlaying each map and outlining the 2"+ areas.

 

[cyclone77]

For the QCA the notable difference with the 18z GFS compared to the Euro is much less freezing rain.  The first slug of moisture stays southeast of here, so we stay dry.  Then when the main deform kicks northeast out of Kansas we're cold enough for all snow by then.  This is a much more desirable setup for this area if we want to keep our trees and power lines from being damaged.

[A-L-E-K]

Snow band ends up further southeast and looks colder here this run.

 

850 passes over Gary, would prefer that 50-75 miles further south.

 

It does look like a double-barrel solution is gaining steam.

[Geos]

6" amounts are over mby now, instead of adjacent.

 

[Whitelakeroy]

Well... Its going to melt on Thur-Fri and Sat-Sun now.

 

Parking lot piles.

 

Myself, I might end up with a snow storm. Or not.

Hopefully we get snow!!  Still hoping that first wave on Friday is stronger.

[Jonger]

As Stebo said once.... I prefer warm ups, better chance we could run into a storm.

Green Christmas it is.

Give me a few clippers and a deep freeze.

Sent from my HTC6435LVW using Tapatalk

[michsnowfreak]

Well... Its going to melt on Thur-Fri and Sat-Sun now.

Parking lot piles.

Myself, I might end up with a snow storm. Or not.

There is no way we lose all this snowpack thu-fri. Temps may not even hit 40 as it stands and we have a solid 8-10" snowpack south of Detroit to the OH border, probably twice what Howell has. And obviously howell will be colder sunday by a degree or two offsetting tge snowcover difference. I think an ice cold rain on snowcovered ground is the worst scenario as it looks now for southern Michigan.