Feb 3rd - 5th Potential strong stm threat

[Hoosier]

1 minute ago, McHenrySnow said:

At the end of the day, I agree more with an impact-based system, just not sure those counties will experience anything drastically different from the rest of N IL. The general public doesn't know and doesn't care about "criteria" anyhow. 

That's a fair point.  Conditions look like they will be pretty similar in the advisory and warning areas.

[IWXwx]

1 minute ago, Hoosier said:

RC said they are shifting more impact based, so with the wind/blowing snow/rapid temp drop factors, that may be why they went with a warning despite amounts generally staying under criteria.

Agree. The winds will be howling and even though it's cement, there will be some reduced visibilities, some drifting, and a possible flash freeze. I would like to see NWS offices do more of this, rather than worry so much about their verification scores.

[sbnwx85]

Advisory coming for my neck of the woods. 

[Thundersnow12]

3.7” in hourly. I’ll go under 

[Geoboy645]

GRB just released WSW's for their entire CWA. Around here by Green Bay they are calling for 5-9" which seems pretty reasonable IMO. The wind probably won't be AS big of an issue here as further south but it will still be pretty bad. Fortuantley where I am at least is relatively protected being at the bottom of the Fox valley and all that. Still going to suck walking to classes though.

[Hoosier]

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
308 PM CST Wed Feb 3 2021

.SHORT TERM...
307 PM CST

Through Thursday night...

A quick Bottom Lines Up Front AFD here, with a full technical
discussion by 430 PM.

The Winter Storm Watch has been converted to a Winter Storm
Warning for Lee, Ogle, Winnebago, and Boone Counties, with a start
time that`s been moved up slightly to 10 AM Thursday. While
snowfall amounts have not materially increased in the warning
(3-5" with isolated amounts to 6" possible), the combination of a
period of rather heavy, convectively-driven rates coinciding with
the afternoon/evening commute, rapidly increasing snow:liquid
ratios and a likely period of fairly strong westerly winds gusting
to 40 if not 45 mph by later Thursday afternoon and evening were
concerning enough to warrant an impacts-based warning there.

To the east of the warning, we`ve layered on a Winter Weather
Advisory where slightly lower snowfall amounts (generally in the
2-5" range, although we`ll note a potential for overperformance
given the impressive lapse rate plume with this system) and a
slightly shorter window of stronger winds are expected to help
mute impacts a bit more. Still, as it stands right now, guidance
suggests that the Thursday afternoon/evening commute won`t be
terribly pleasant, with a period of potentially heavy snowfall
coinciding with the rush. Marginal surface temperatures near or
even just above freezing may help blunt the threat for
accumulation on the main thoroughfares (outside of heavier rates),
but reduced visibilities, and the potential for sharply falling
temperatures into the evening spells at least a non-zero potential
for a flash freeze scenario where wet roadways remain.

Think the threat for accumulating snowfall is more or less over by
midnight Thursday night, but the threat for blowing snow will
continue overnight and into Friday.

Full technical discussion will be issued by 430 PM.

Carlaw

[A-L-E-K]

Nice gfs run

And carlaw is good obv 

[Thundersnow12]

18z para GFS solid too with 3-5” for metro locally higher west 

[Hoosier]

3 minutes ago, A-L-E-K said:

Nice gfs run

And carlaw is good obv 

Can see the difference in the 10:1 and Kuchera.  The 10:1 looks good in the city and south, the Kuchera not as much.

 

[A-L-E-K]

Widespread 4-5 on kuchera

Matt's under 

[Powerball]

I'd keep an eye out for TSSN on Thursday afternoon/evening too, as it looks like some pretty decent mid-level instability is showing up. 

[purduewx80]

Feeling pretty good about seeing some TSSN in the region tomorrow. Will want to see lapse rates verify on the 12Z TOP and SGF soundings. At the very least some swaths of 1-2”/hr rates are probable. 

[purduewx80]

2 minutes ago, Powerball said:

I'd keep an eye out for TSSN on Thursday afternoon/evening too, as looks like some pretty decent mid-level instability is showing up. 

Hahaha beat me to it. 

[Thundersnow12]

4 minutes ago, A-L-E-K said:

Widespread 4-5 on kuchera

Matt's under 

Worried about stacking early on in after with temps near/above freezing and wasting some QPF till CAA kicks in but we’ll see.

[Hoosier]

This should really plaster the trees and other objects nicely around here.  Curious to see what happens when the temps drop and the winds increase... does the snow freeze on the trees or does it start falling off.

[Chicago Storm]

Worried about stacking early on in after with temps near/above freezing and wasting some QPF till CAA kicks in but we’ll see.

It’ll be snowing hard enough, that won’t be an issue.


.

[Baum]

From Carlaw discussion at LOT:

"DON'T THINK IT'S OVERLY OUTLANDISH TO EXPECT A BRIEF WINDOW WHERE   
THUNDERSNOW IS A POSSIBILITY."

good long read on this event just updated btw for those so inclined.

 

[Hoosier]

A little more optimistic than yesterday since we're dealing with more of an elongated pressure trough into the afternoon and not the earlier rapid deepening sfc low (a good thing while you're still in the "warm" sector) but still enough concerns over temps that I'm hesitant to go beyond 2-3" here.  If temps can end up just a tick colder, then could probably add an inch or maybe two to that. 

[Stebo]

I think 3-4" is a good call here

[Radtechwxman]

Is ILX having issues today? Said AFD was out at 223pm but still showing last nights. I personally think IL River and points west should have WWA. Most models showing 1-2in and equally strong winds. Some models have a quicker changeover here. More excited for the next few waves after this one because they actually have potential south of I80! 

[michsnowfreak]

1 hour ago, Stebo said:

I think 3-4" is a good call here

What about thundersnow? 

[Stebo]

25 minutes ago, michsnowfreak said:

What about thundersnow? 

Absolutely think there is a legit potential, and if that happens lean higher.

[AWMT30]

Yeah thundersnow looks real good on the HRRR that is some real intense snow. 4-5" in about 4-5 hours going to be an awesome night 

[OrdIowPitMsp]

Getting some light freezing rain and ice pellets at the moment. Wasn’t expecting any precip this early. 

[hawkeye_wx]

The 00z NAMs have suddenly thrown a 5-8" band over eastern Iowa, but the 00z HRRR has nothing like that.  The HRRR is more in line with other models showing a few inches around here.

[cyclone77]

Looks like a solid 2-4" refresher for the QCA after a short period of rain.  The rain will make layer number 3 of ice within the snowpack lol.  

[purduewx80]

Nice altocu field at sunset this evening, indicative of the already steep lapse rates below 500mb. 

[ILSNOW]

0z GFS wave #1

[hawkeye_wx]

Both NAMs and both GFSs are going nuts around here with a very intense snow band dropping several inches.  Other models are in the 3-4" range.  Meanwhile, the NWS forecast has 1-3".

[OrdIowPitMsp]

What’s falling imby and radar trends definitely more impressive then what the HRRR and NAM have been showing. Still thinking 2” here but we’ll see if it’s rip city when I wake up.