ILSNOW

12z HRW WRF-ARW Destroys northern cook county that small orange dot representing 30 inches of snow

NAM 54 hrs

yep its over

Enjoy ALEK

KLOT aviation update A lull in the IFR visibility reducing snow for many areas, except in NW IN and near the lake, has occurred this morning in wake of a leading band overnight into the morning hours. There is a more organized band of snow associated with a secondary upper level jet stream will lead to an uptick in snow at least for a couple of hours this afternoon across the northern IL terminals. Expect ceilings, which have increased to MVFR or even low end VFR to dip back into MVFR or a lower MVFR then currently. Vis may drop back to 3/4SM in this snow with medium-high confidence. Snow rates of 3/4" to 1" per hour may be possible in this band of dry snow.

ukie is liking the same areas

0z GFSV16 24 hr snowfall. I call challenge on the 11 inches over cook county and totals thru 2/16

KLOT The main axis of snowfall amounts in the 2-4" range has shifted a bit north, focused more around the I-80/88 corridors with this update, with amounts lowered to for our southernmost counties to an inch or less. PoP trends for Saturday morning are a bit unclear, as we`ll begin losing the better jet support, resulting in an overall weakening to the already modest mid-level f-gen. This may allow lingering light snow near/south of I-80 to dwindle, before additional ascent from an incoming shortwave pushes across our northwestern locales. Have trimmed PoPs south and east of I-57 as a result, and left the categorical/definites going elsewhere.

silly 18z NAM still thinks that the snow will reach into IL on Monday I guess the GFS hasnt informed it yet!!!

klot aviation Snow is ongoing in a band across Iowa. This band will shift to the east and over the area this evening. Substantial dry air is in place ahead of this band, especially across northern Iowa and northern Illinois. It is plausible that snow/flurries begin as early as 00z, but more likely the accumulating snow will start a few hours later from south to north (1-2z MDW, 3z at ORD). Morning AMDAR soundings show that the dry air is not very strong initially, and should be overcome quickly if no additional dry air moves in, but our latest AMDAR soundings at MDW do show dry air is advecting in. Confidence on snow onset is therefore only medium but current thought is that we may need to push things back a bit if the dry air trends continue. Once snow begins, a prolonged light to moderate snow event will unfold tonight into Saturday over the area TAF sites. Confidence is fairly high in this event beginning over the southern part of the Chicago metro (favoring MDW) before ORD and possibly by several hours. This has the look of 1-2 SM snow for much of this event. Late tonight into Saturday morning, approximately 08Z-15Z, there are some signals for temporary sub 1SM visibility. Ceilings should lower through the MVFR category tonight and temporary IFR is probable Saturday, although when on Saturday morning is still too low of confidence to include at this distance in the TAF. Total accumulation of this dry and powdery snow is forecast at 2 to 3 inches at ORD and MDW by Saturday afternoon. If moderate rates are more frequent, namely at MDW, that could be exceeded.

9z Plumes mean for ORD thru 2-16 is 8.39

both 12z NAM and RGEM bringing decent snows again in the late sun/monday period lets see what the king (GFS) has to say.

12z NAM 2 to 3 inch event tomorrow 12z 3K NAM 2 to 3 with almost a 4 lollipop around cook county

plumes thru monday @ ORD 8.92

GFS is the new King (haha) looking forward 2 another 2 inch refresher

a little late but the 21z Plumes at ORD had jumped up to 7.8 thru monday

KLOT Convergence is maximized on the western shores of southern Lake Michigan. The flow will turn solidly onshore into northeast IL which should allow the dominant band to shift northward. We should also maintain broader lake effect clouds/snow through the afternoon as the convergence will likely become a bit weaker. Rates will be high enough to coat roadways. Flurries should extend well inland across DuPage, Cook, and Lake IL counties. Snow across Iowa is still progged to move through the area this evening. Mid level frontal strengthening (700 mb) combined with modest lapse rates above it in the DGZ should support another period of moderate snow.

12z NAM @ 51 hrs vs GFS same time. How is it possible for them 2 be 100% different? 12z GFS @ 51 hrs

12z RGEM touch wetter general 7-9 area wide includes 2-3 from tonites event

12 z NAM a touch drier and south solid 5-6 inches area wide

KLOT update for tomorrow Our next wave is starting to spread light radar returns across South Dakota at this time, and will be approaching our longitude later Thursday afternoon and (moreso) evening. Latest guidance continues to indicate that snow is a good bet for locales north of I-88, and potentially even towards I-80 as well. The attendant jet streak is fairly robust, and seeing some signs in regional cross sections/BUFKIT soundings that more in the way of convective instability may be present with this system. Latest model consensus continues to support the main corridor of ascent focusing near and north of the state line, but see a potential for a swath of 1-2" of snow north of I-88. Finally, there are some signals pointing towards somewhat more robust LES developing into the northeast Illinois shore tomorrow evening.

0z NAM 0z GFS still significantly different

GFS is a 1-3 with a 4.4 lollipop over cook county GFS para 3-4 with a 5 lollipop over cook county

KLOT (not ricky) Attention will then turn to the Monday/Tuesday timeframe for another round of snow. Ensemble model guidance is in relatively good agreement that a storm system will lift form the Plains to the Great Lakes dropping a swath of snow along the backside. Statistical Cluster Analysis from the Weather Prediction Center (WPC) shows that ~70% of the CMC, GFS, and ECMWF ensemble members drop at least 0.1" of precipitation across northern Illinois and northwest Indiana, with ~50% dropping at least 0.25". The CMC model system is the driest, while the ECMWF is the wettest. With forecast low-level thermal profiles expected to remain cold and squarely in the snowflake growth zone, fluffy snow ratios will again be able to convert even just 0.10" of liquid to several inches of snow. So, we`ll need to keep a keen eye on the Monday/Tuesday timeframe for an impactful snow event somewhere in the Great Lakes.

KLOT (not ricky) First, confidence is increasing that a period of steady snow will occur Saturday as the diffluent right-entrance region of the upper- level jet stream passes overhead. Ensemble QPF from the ECMWF ranges from 0.10" along/south of I-80 to 0.25" along the IL/WI state line. A quick gander at forecast low-level thermodynamic profiles gives credence to very fluffy, perhaps "overperforming" snow ratios with the snowflake growth layer extending well beyond 10,000 feet at times. Plus, a trajectory off Lake Michigan may provide a boost of low-level moisture. Taken altogether, Saturday may end up yet another day to take it slow on the roads due to reduced visibility and accumulations of snow. The current forecast brings 1-2" snow totals from the Kankakee River Valley to I-88, and 2-3" totals from I-88 to the Wisconsin state line. Adjustments upward may be needed in later forecast packages.