ILSNOW

You think they drift west enough to make it on shore?

Izzi Forecast on track with no meaningful changes to previous forecast for the approaching winter storm. I am concerned that lake effect snow could overperform a bit very late tonight into Sunday morning over northeast IL and into northern Lake Co Indiana Sunday afternoon, but confidence is a bit too low to justify an upgrade to a winter storm warning at this time. Large winter storm is slowly approaching the area this afternoon though very dry antecedent air mass is taking some time to saturate from top down. WSR-88D imagery does suggests that the low level dry air is being eroded and expect areas of light snow and flurries to begin making it to the surface soon. Light snow will likely continue tonight, especially south of I-80. Most of the ascent tonight appears to be the result of upper level divergence in the right entrance region of developing upper level jet streak over the western Great Lakes. As such, strongest upward vertical velocities (UVVs) are progged to be above 600 mb, well above the very deep DGZ where weak UVVs are progged to be neutral or even weak subsidence. This suggests that predominant snow type for most of tonight will be smaller flake size and resultant lower snow:liquid ratio (SLR). Nudged the forecast SLR down some, but possibly still too high if the snow tonight is mostly pixie dust and low SLR. Confidence wasn`t high enough to make any big adjustments to snowfall totals, but that is something the evening shift will need to look at for the first half of the event tonight. By early Sunday morning, we start to get into an area of coupled jets with some strengthening mid-level frontogenesis. This could result in a period of stronger UVVs below 600mb and closer to the DGZ. This may produce heavier snowfall rates Sunday morning where larger dendrites result in higher SLRs, at least in mesoscale band(s). The system snow should end from west to east from mid afternoon Sunday through early evening. One wildcard will be the lake enhanced snow late tonight into Sunday. While there will be a strong frontal inversion between 800-850mb through the duration of the event, limiting the depth of the lake induced convective instability. While the depth of the instability looks to be rather shallow, the instability below the inversion will be quite strong with lake-850mb delta T values around 20C. This should result in very strong ascent below the inversion, the majority of which will be smack dab in the middle of the DGZ. I am concerned that seeder-feeder process from strong synoptic ascent above 600mb could result in a band of intense lake effect snow embedded within an area of lighter snow and flurries. Wouldn`t be surprised to see snowfall rates >=1" per hour with the lake enhanced snow Sunday morning into NE IL, gradually shifting into NW IN Sunday afternoon. Certainly a play for totals solidly over 6" into northeast IL if the lake enhancement really gets going, but confidence isn`t high enough to justify an upgrade to a warning at this time. Will be something that later shifts will need to closely watch. Intensity of the lake effect should begin to decrease Sunday evening as it loses seeder-feeder with synoptic snows shifting east of the area. Inversion heights are progged to come up a bit Sunday evening, so did maintain likely pops for LES across northeast IN Sunday evening. By late Sunday evening the LES threat should push east of Porter County, so the midnight expiration time for the winter weather advisory looks good for Lake/Porter Counties.

current virga radar

12z Euro

for chicago peeps from Milwaukee NWS Confidence is increasing that a lake effect snow band will come onshore early Sunday morning into Sunday afternoon. If the snow band comes ashore, moderate to heavy rates are possible from Milwaukee southward. Models are indicating more confidence in impacts to Lake Michigan counties (specifically Milwaukee metro southward) during the early morning to midday hours Sunday. With lake temperatures near 3 degrees C and 850 mb temperatures between negative 15 and negative 20 degrees C, more than enough convective potential exists for moderate to heavy snowfall rates (up to 1 inch per hour) if the central portions of the band make it onshore. There is still the chance that high pressure will win out over the developing northeast flow, and therefore still possible that only trace snow showers will make it onshore. However, the forecasted strength of the developing low to the south would make that solution less likely based on the preliminary model data this morning. Alek is going to clean up

latest from Chicago Main focus is on a synoptic accumulating snow system Saturday afternoon through Sunday. Some questions remain with exact snow amounts especially into the Chicago metro area where some lake- enhancement is likely. Expectation is that we`ll end up with a general 3-6" accumulation across the southeast third to half of the cwa, and potentially parts of the Chicago metro where lake- enhancement occurs, with a sharp gradient to lower amounts farther to the northwest. Details of where exactly this gradient lays out will need further refinement, and thus in collaboration with neighbors to the east and west have held off on headline issuance just yet. However, we do anticipate the need for a winter weather advisory for southeast parts of the forecast area and near the lake as the footprint is further narrowed down. Furthermore, a deepening layer of northeasterly low-level flow is likely to producing some degree of lake- enhancement into parts of the Chicago metro area, possibly with an additional small footprint of 3-5" amounts there (perhaps locally 5-6").

odds of happening prolly like 13%

This is supposed to replace the NAM (what is it smoking)

Milwaukee on possible lake effect If the meso vort over the southern basin advects a few lake effect snow bands toward the western coast, there will be a chance for a couple inches of snow when everything is all said and done. This would then be multiple hours of LES and lake enhancement. Southeastern Wisconsin including, Racine, Kenosha, Milwaukee and maybe eastern Waukesha are the mostly likely areas to be impacted by any LES or lake enhanced snow. This area is fairly broad, but there is uncertainty on how far inland this would move. Now the caveat that comes with any LES system, will it or will it not move inland. In the event that this all stays off shore this AFD will be for naught as we may get a dusting from the shortwave trough. On the other hand if the worse happens and we get multiple LES bands moving inland, then there could be some decent snow totals. A real hit or bust forecast.

Desperate holding out for 3-4 lake induced flakes on Sunday.

From our friends at BAM Weather (I know many dont care for them) Upon deep dives hi-res US models are overdoing the strength of the high pressure in the northern plains. It stems from the GFS as these hi-res models are all inner nested versions of the GFS. This can make all the difference in the world for these fringe locations of snow/sleet/ice/rain! Summed up? ECMWF/GDPS/UKMET is the answer. Thoughts??

i believe he is referring to this after next weekends coastal

down to -11

UKMET brings snow north compared to 12z X

going with 3.5 here

so you looked at the 18z Euro and then made a call

watch out for drifting tonight.

be very careful when you disagree with him he will curse you out and start screaming at you. Wright Weather Board!!!~!

RGEM is like the NAM.

snippets from Chicago NWS Forecast attention this weekend focuses on the major winter storm expected to have significant impacts across a good chunk of the southern and eastern CONUS. Locally, our area is expected to remain along the northern periphery of this large and expansive storm system, which naturally adds question marks with regards to how far northwest impactful wintery precipitation will fall. This is especially the case considering that a sharp north- northwestern cutoff in precipitation could occur over, or near parts of northwestern IL. Nevertheless, forecast confidence continues to increase in accumulating snowfall falling across much of central into northeastern IL and northwestern IN, most notably during the Saturday night and on Sunday timeframe. While a majority of the heavy precipitation with this system is expected to fall south of our area, as mentioned, chances continue to increase that much of our local area will experience some accumulating snowfall late Saturday through Sunday. The snow may come in two separate waves, with the first potentially coming Saturday afternoon into the evening, and a second coming Saturday night and on Sunday. Interestingly, with the Arctic airmass remaining in place across our area, the thermodyamics profile in which this snow will be generated within will feature a very deep Dendritic Growth Zone (DGZ), likely in excess of 10,000 ft. This will in turn foster a higher than average liquid-to- snow ratio than is typical for our area, with 20-25+ to 1 ratios certainly in play. Accordingly, even a tenth to two tenths of an inch of QPF that falls could result in a few inches of dry fluffy accumulation. While confidence does continue to increase in at least parts of our local area experiencing some accumulating snowfall Saturday afternoon into Sunday, uncertainty remains with the specifics. For example, as noted above, one of the main question marks that remains is how far northwest into our area accumulating snow will extend. This as the precipitation looks to fight with drier air trying to advect into the region from the Arctic high to our northwest. The other question resides around the extent of lake enhanced snowfall along the south-southwesterly periphery of Lake Michigan Saturday night into Sunday. Low-level thermodynamic conditions do look favorable for this, and there is concern that this could result in higher snow amounts along and near the lakeshore into Sunday. Stay tuned for forecast updates!

going down swinging Alek with almost 9 inches enjoy!!!

It is the NAM (useless) I wonder if DocATL will check back in!!!!

Lock it in X

12z X