Clippers/LES January 20th-January 23rd

[Scott26]

The next couple of days look interesting with a weak clipper moving across the area and some Lake Enhancement to go along with it. After the synoptic snows pass to the east a rather favorable LES snow event will set up for NE IL and NW Indiana. The 12Z NAM shows the band develop in Lake County, IL and slowly move SE and into NW Indiana. Eastern Cook/Will may be in line for a Lake Effect Snow Warning for 6 plus inches of pure Lake Effect. Even Lake County, IL may get in the band for a while and may need at least an Advisory.

[Geos]

Hi-res NAM favoring IL more.

 

[DominicR]

Hi-res NAM favoring IL more.

 

http://models.weatherbell.com/hires/2014012012/chicago/hires_t_precip_chicago_12.png

 

Interesting. I am very close to .25+ in east-central Cook. Could I possibly be looking at 6+ with this set up? Looks NAM is pretty favorable up this way. Exciting evening it looking like here. Hope that bands crushes me.

[Scott26]

Interesting. I am very close to .25+ in east-central Cook. Could I possibly be looking at 6+ with this set up? Looks NAM is pretty favorable up this way. Exciting evening it looking like here. Hope that bands crushes me.

I think you have a  good chance of getting slammed. City on south looks good for a possible 6 plus. Models have been shifting the heaviest LES west since yesterday. Now it looks like NE IL and far NW Indiana will be in the jackpot while further east in Indiana looks more uncertain.

[Geos]

LOT will probably put Cook under a watch on the next update.

[Sciascia]

Always nice to wake up to surprise snow potential. Is this supposed to be an afternoon-night event or a night-overnight event?

[Geos]

14z RAP at midnight.

 

 

STL WRF

 

[Geos]

Cook County put under a watch now.

 

 

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE CHICAGO IL
943 AM CST MON JAN 20 2014

...HEAVY LAKE EFFECT SNOW POSSIBLE TONIGHT THROUGH EARLY TUESDAY
AFTERNOON...

.A BAND OF INTENSE LAKE EFFECT SNOW IS FORECAST TO DEVELOP OVER
SOUTHERN LAKE MICHIGAN THIS EVENING...MOVING SLOWLY WEST TOWARD
THE FAR SOUTHWEST SHORE AFTER MIDNIGHT. THE BAND OF HEAVY SNOW
COULD AFFECT AREAS NEAR THE LAKE IN COOK COUNTY FOR A TIME LATE
TONIGHT BEFORE PIVOTING STEADILY EASTWARD INTO INDIANA BY EARLY
TUESDAY MORNING. THE BAND WILL THEN CONTINUE EAST ACROSS LAKE AND
PORTER COUNTIES TUESDAY MORNING INTO THE EARLY AFTERNOON. THE BAND
OF HEAVY SNOW IS FORECAST TO ONLY BE LESS THAN 10 MILES WIDE...SO
CONDITIONS WILL LIKELY VARY GREATLY OVER A VERY SHORT DISTANCE.

ILZ014-202345-
/O.EXB.KLOT.LE.A.0001.140121T0500Z-140121T1500Z/
COOK-
INCLUDING THE CITY OF...CHICAGO
943 AM CST MON JAN 20 2014

...LAKE EFFECT SNOW WATCH IN EFFECT FROM THIS EVENING THROUGH
TUESDAY MORNING...

THE NATIONAL WEATHER SERVICE IN CHICAGO HAS ISSUED A LAKE EFFECT
SNOW WATCH...WHICH IS IN EFFECT FROM THIS EVENING THROUGH TUESDAY
MORNING.

* TIMING...HEAVY LAKE EFFECT SNOW COULD MOVE ONSHORE AND AFFECT
AREAS NEAR THE LAKE AND INTO SOUTHEAST COOK COUNTY LATE TONIGHT.

* SNOW ACCUMULATIONS...MOST AREAS WILL SEE LITTLE OR NO LAKE EFFECT
SNOW ACCUMULATIONS LATE TONIGHT...HOWEVER ISOLATED TOTALS IN
EXCESS OF 6 INCHES ARE POSSIBLE NEAR THE LAKE AND OVER SOUTHEAST
COOK COUNTY.

* OTHER IMPACTS...IF THE HEAVY LAKE EFFECT SNOW BAND MOVES INLAND
INTO COOK COUNTY...THEN VISIBILITY WILL BE REDUCED TO NEAR ZERO
AT TIMES WITH SNOWFALL RATES IN EXCESS OF 2 INCHES PER HOUR
LIKELY NEAR THE LAKE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A LAKE EFFECT SNOW WATCH MEANS THERE IS A POTENTIAL FOR A LARGE
AMOUNT OF SNOW IN ONLY A FEW HOURS. VISIBILITIES AND DEPTH OF
SNOW CAN VARY GREATLY...IMPACTING TRAVEL SIGNIFICANTLY. CONTINUE
TO MONITOR THE LATEST FORECASTS.

&&

$

 

[Scott26]

It looks like the synoptic snows tonight could give NE IL 2-3 inches with some lake enhancement for Lake and Cook county. The LES band originates near the IL/WI border and seems to remain fairly transient until it stalls in Southern Cook County. I wouldn't be surprised if we have a mesolow like the last LES event which shifts some heavier snow inland.

[Tom]

Nice Call Scott!  Yesterday this LES set up was looking very promising as the RGEM and other high rez models were picking up on it.  Been watching this set up for a few days and new it would come into fruition as we got closer.  That wave passing to the south sets up favorable winds out of the NNE.  I would not be surprised if the LES pushes farther inland.  Just look what happened with the NYE storm when counties as far as DuPage and even down to Kankakee got in on the LES.  This set up looks very good and I believe there will be some lollipop totals in S Cook.  ORD may even get 2-3" of pure lake effect after the arctic front snows.  As is always the case, LES events are nowcast events so I'm sure we will be watching the radars tonight!

 

Interesting, RGEM pulling the LES plume farther west in recent runs and now hits areas near the IL/WI border!  Good signs...

 

 

 

[Geos]

Update from Izzi.

 

 

LAKE EFFECT SNOW PARAMETERS ALL POINT TOWARD THE POTENTIAL FOR AN
INTENSE SINGLE BAND OF HEAVY LAKE EFFECT SNOW DEVELOPING LATE THIS
EVENING OVER SOUTHERN LAKE MICHIGAN AND PROPAGATING WEST TOWARD COOK
COUNTY BEFORE ROTATING EAST AROUND THE SOUTH RIM OF THE LAKE ACROSS
LAKE AND THEN PORTER COUNTIES. IN ADDITION TO THE WESTWARD TREND IN
THE MODELS THE OTHER DIFFERENCE COMPARED TO YESTERDAY IS THE BAND IS
EXPECTED TO BE MORE PROGRESSIVE...LIMITING RESIDENCE TIME IN ANY ONE
AREA WHICH FAVORS MAX ACCUMS MORE IN THE 6-12 INCH RANGE VERSUS THE
1 TO 2 FT RANGE THAT LOOKED MORE POSSIBLE YESTERDAY. MAX SNOWFALL
RATES WITHIN THE BAND COULD REACH 2-3 INCHES PER HOUR...SO IT WOULD
ONLY TAKE 2 OR 3 HOURS OF INTENSE SNOW TO REACH WARNING CRITERIA.

WILL VERY LIKELY BE GOING WITH A WARNING FOR LAKE COUNTY INDIANA AND
PROBABLY COOK COUNTY ILLINOIS WITH THE AFTERNOON UPDATE...THOUGH
WOULD LIKE TO GET A LOOK A SOME MORE GUIDANCE BEFORE DECIDING
BETWEEN WARNING AND ADVISORY FOR COOK. PORTER COUNTY MAY NOT SEE THE
HEAVY SNOW UNTIL MID TO LATE TUES MORNING SO COULD POTENTIALLY LEAVE
WATCH THERE FOR ONE MORE CYCLE OR POSSIBLY UPGRADE TO WARNING THERE
THIS AFTERNOON...WILL COORDINATE WITH IWX ON PORTER COUNTY HEADLINE
BEFORE MAKING ANY CHANGES.

IZZI

 

[Tom]

Latest RPM shows the lake effect plume hitting eastern Lake/Cook county around 11:00pm for a few hours then moving eastward.  ORD around 2.8" and Waukegan 2.5".  Models tend to underdo Lake Effect snow events so I would not be surprised to even see ORD get 5-6" if it sets up just right.

[Tom]

12z Euro favoring Lake/Cook/DuPage counties early on from Midnight thru 6:00am tonight.  Check out all that air piling up along the lakeshore.  If this is a trend, they may put Lake County into some sort of an advisory or watch as well.

 

 

[Tony]

LES did get into Dupage county last go around so we can always hope it does so again!

[Scott26]

The RAP seems to be wanting to shift the LES band further SE the last 3 runs or so. Still a pretty good hit for the south side of the city, but would be nothing further north.

[Tom]

RAP doesn't do a good job with meso scale events...

[Scott26]

RAP doesn't do a good job with meso scale events...

True... It's actually not even that good of a short range model. We'll see about this one. LES events always have huge bust potential especially on this side of the lake. Hopefully someone on this side of the Lake will get slammed tomorrow.

[Sciascia]

LES Warning now.

[Tom]

Actually Scott, 16z RAP has the lake effect plume targeting NE IL around 1:00am through 4:00am (that was the last image available this run and still showing snow).

 

[Scott26]

LES Warning now.

Two times in one winter. Very impressive! They went with an advisory for Will also...

[Tom]

Wow, LOT going with 6-12" for eastern Cook and localized 12" totals!

[DominicR]

Will see. ORD prob miss out on most and Midway prob get at least several inches. RAP last few runs seem to be inching east so it could be a trend again to go back east.

[Tom]

18z 4km NAM targeting SE Cook/Lake County Indiana as epicenter.  Still showing some decent snows in northern Cook.  Snow ratios are really high with Lake Effect, probable close to 25:1 in this type of environment.

 

 

 

 

 

[Tony]

Radar starting to get active upstream. Hope to get some nice fluff out of this and maybe over-achieve.

[Tom]

Temps are starting to tumble, down to 29F with winds out of the NNE at 8mph.  I hope that lake effect snow band can wobble a little farther west to hit some parts of N Cook. 

[Tom]

You can see the beginning of the Lake Effect Plume already showing up in the northern parts of Lake Michigan...

 

 

[Tony]

Tom, nice looking plume forming. Hope it really ramp up overnight to a major dump for someone in our area.

[Tony]

Looking at radar so far it seems qpf is farther north.....any thoughts on this?

[Tony]

Updated 20z RAP seems to be farther west with the LES. Seems to keep it on this side of the lake till 14z

[Tom]

What I'm noticing is if that wave is farther north, then the winds will veer more easterly, therefore more LES can be delivered into NE IL.  On the other hand, if it were to go farther south, than the winds would be more northerly. 

 

Tony, you brought up a good point and the precip seems farther north and that would lead us to believe the wave is traveling farther north and winds may end up veering more easterly in result.

 

Should start snowing pretty good in Cook country around 9:00pm.

 

 

[Madtown]

pretty good fluff flying around at the moment here

[tbone8]

I bet cha a shiny new dime, LaPorte County gets the brunt of this...

[Tom]

Just started snowing lightly over here...

[Niko]

I am currently seeing light snow and starting to whiten up everything.

[Tom]

Interesting, 18z GFS has a .20qpf blob in NE IL over N Cook/S Lake...

[Sciascia]

http://www.crh.noaa.gov/images/lot/ifps/TotalSnow/TotalSnow_Fcst.png

 

This came out between 2-3pm.

[Scott26]

Interesting, 18z GFS has a .20qpf blob in NE IL over N Cook/S Lake...

I was just about to post this. The global models at this point are likely not the preferred models, but it's interesting nevertheless. The GFS really Lake enhances the moisture and even has the LES band hanging around for a while.

[Tony]

Returns are looking good for parts of MI as well.

[Geos]

There's been sporadic -SN here in Racine, but probably only 0.2-0.3" so far.

[Sciascia]

LOT...
 

 

AS THE TROUGH AMPLIFIES...THE RESULTANT HEIGHT FALLS/RISING INVERSION
HEIGHTS AND IMPRESSIVE COLD AIR ADVECTION SHOULD RESULT IN AN
IMPRESSIVE LAKE EFFECT EVENT LATE TONIGHT INTO TUESDAY NEAR THE
SOUTHERN TIP OF THE LAKE. ALL LAKE EFFECT PARAMETERS ARE FORECAST TO
BE NEAR THE UPPER ECHELONS OF FAVORABILITY WITH IMPRESSIVE LAKE
INDUCED LOW LEVEL INSTABILITY AND HIGH INVERSION HEIGHTS. BEST
DENDRITIC GROWTH ZONE MAY BE A BIT LOWER THAN I`D LIKE TO SEE AND
PERHAPS A BIT BELOW CLOUD DECK...BUT THAT`S ALSO ASSUMING FORECAST
SOUNDINGS ARE REPRESENTATIVES OF LOW LEVEL THERMODYNAMICS WITHIN THE
LES SNOW BAND...WHICH SOME STUDIES HAVE SHOWN IS NOT THE CASE. GIVEN
ALL OF THE ABOVE SUSPECT AN INTENSE SINGLE BAND WILL DEVELOP
SOMETIME LATER THIS EVENING OVER THE LAKE AND COME ONSHORE INTO COOK
CO AROUND OR JUST BEYOND 06Z AND MEANDER AROUND NE IL OVERNIGHT
BEFORE SHIFTING EAST INTO NW INDY TUES MORNING...THEN PROGRESSING
EAST FROM THERE. SNOWFALL RATES OF AT LEAST 2 INCHES PER HOUR ARE
EXPECTED WITHIN THE MOST INTENSE BAND...WHICH WILL PROBABLY ONLY BE
5-10MI WIDE...WHICH OF COURSE WILL LEAD TO THE TYPICAL WIDELY
VARYING SNOWFALL TOTALS. BEST GUESS WOULD BE FOR TOTALS IN THE 6-12
INCH RANGE OVER EASTERN COOK AND NORTHERN HALF OF LAKE AND PROBABLY
PORTER COUNTY...WITH ISOLATED MAX TOTALS OF UP TO A FOOT AND A HALF
POSSIBLE IF THE RESIDENCE TIME OF THE BAND IS HIGH IN ANY ONE GIVEN
POINT. HAVE OPTED TO HANG ONTO THE WATCH FOR PORTER DUE TO THE LATER
ONSET AND GREATER UNCERTAINTY. ALSO NOT TERRIBLY CONFIDENT IN HOW
FAR INLAND THE HEAVY SNOW WILL PENETRATE...PAST CASES HAVE SEEN
WARNING LEVEL SNOWS REACH EASTERN WILL COUNTY BEFORE AND THAT IS A
DISTINCT POSSIBILITY BUT FELT MORE COMFORTABLE STARTING WITH AN
ADVISORY THERE. NORTHERN JASPER AND POSSIBLY NEWTON MAY NEED AN
ADVISORY EVENTUALLY TOO...BUT THIS ALSO CAN BE ASSESSED BY THE
EVENING OR NIGHT SHIFT.