Absolute Vorticity

Members 2, 4, 13, and 20 are pleasing to the eye.

tpweather wrote: ↑Wed Feb 02, 2022 7:43 am

Trevor wrote: ↑Wed Feb 02, 2022 7:38 am 09z RAP (extended range run) snowfall.

Love this map as my back yard gets 8 inches and my front yard gets 1inch

Very good! Lol

42 / 38 at CVG

From the boys:

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Will try to keep this Near Term discussion brief, and get into
the main part of the winter storm in the Short Term section
below.

Temperatures are generally remaining in the 40s across the
forecast area right now, outside of some of the typical cool
spots (particularly in the eastern half of the CWA) where there
are some readings as low as the lower 30s. As the day
progresses, deep-layer southerly flow will continue to advect
moisture into the region, with some potential for wind gusts to
around 20 knots. Rain and clouds will keep temperatures from
getting anywhere near as warm as yesterday. Precipitation is
already on the doorstep of the CWA, and will spread across the
area west-to-east through by 18Z this afternoon.

For the most part, this precipitation is expected to remain rain
through 00Z tonight, with the exception of the far northern ILN
counties (Mercer/Auglaize/Hardin) where some mix with snow may
already begin occurring by then.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
A significant winter weather event is expected over the next few
days. There remains high confidence in hazardous conditions
across the ILN forecast area, but unfortunately, confidence
remains somewhat mixed with regards to specific precipitation
timing and placement.

A frigid (though shallow) near-surface air mass will be moving
south into the area later today, gradually making more southward
progress over the course of Thursday. Atop this boundary,
southwesterly flow (under the right entrance region of a jet
streak) will bring moisture and lift into the area. This will
spark the first main wave of precipitation, which is expected
from Wednesday morning (moving into the area as rain right now)
through early Thursday morning. Overall confidence in the timing
and placement of this precipitation, including precipitation
type, is actually fairly good for this first wave. As time goes
on, particularly tonight, this activity will start to see more
of a mixed precipitation profile -- as the cold surface air
undercuts some warmer air aloft. It still looks like the far
northern ILN CWA will be mainly snow, with a transition zone
(including freezing rain and sleet) across east-central Indiana,
the Miami Valley, and central Ohio.

Although there may be no clean break between the two waves of
precipitation, there will definitely be an uptick in intensity
with the second wave, as it begins early Thursday afternoon.
This is where the forecast gets much more complicated, as
confidence in the location of the transition zone is fairly low.
As an illustration, at 18Z Thursday, it is virtually guaranteed
that there will be snow in Mercer County OH and rain in Lewis
County KY. What happens in between is the crux of the forecast,
particularly as this is the beginning of the time period in
which accumulations will be at their most robust. There has
definitely been an overall trend in the models that suggests the
potential for a few things. First, slightly lower snow
accumulations near the southern edge of the heavy snow, due to
potential sleet contamination. Second, a slight southward shift
with the ice accumulations. It is still possible that there will
be a band of more significant ice numbers, somewhere south of
the Interstate 71 corridor, but unfortunately confidence has not
yet increased in where exactly this may occur. There have also
been a few models suggesting a brief period of heavy snow making
it as far south as the Interstate 71 corridor on Thursday
evening, just behind the mixed precipitation, but for now this
is just a possible solution to note -- and the expectation for
more of a mix will remain in this forecast update.

Overall, this forecast did not make significant changes to the
previous snow and ice numbers. There was a slight reduction in
snow amounts through the middle part of the CWA, particularly
from east-central Indiana through the Columbus OH area. The ice
forecast is very similar to before, perhaps slightly further
southeast, but with similar value. Would prefer not to indicate
anything higher than about 0.2" to 0.4" of ice unless higher
confidence in a particular focused band develops.

This was not an easy forecast for deciding on Watches and
Warnings, with forecast uncertainties and different timing
concerns all factoring into the collaboration with surrounding
NWS offices. To be specific, there are some portions of the ILN
forecast area that might not reach the hard warning criteria
for either ice /or/ snow amounts. With that said, there is
little doubt that the overall combined impacts will be warning
level in practice, if not in the numbers. Thus, the vast
majority of the ILN CWA has been upgraded to a Winter Storm
Warning. It is definitely not an ideal scenario to have to make
a decision to issue a warning for some counties in which
hazardous wintry weather is still 36 hours from beginning,
particularly when precipitation type forecasts for that second
wave remain so uncertain. The absolute greatest uncertainty
remains in the far southeastern CWA, where snow will be limited
to the back side of the system, and ice may not even begin until
late Thursday afternoon. So, although it was just two counties,
it seemed very prudent to leave Scioto OH and Lewis KY in the
watch phase.

Some consideration was also given to the idea of an Ice Storm
Warning, given that there will be some parts of the ILN CWA
where FZRA is the primary hazard. Given the aforementioned
uncertainties regarding where the worst of the FZRA will set up
(and the potential for an oops all sleet scenario) it was
decided that a more general Winter Storm Warning was the smarter
call for now. This can always be adjusted if confidence
increases.

A few other items to note...
* It is possible that a brief period of freezing rain or
freezing drizzle could occur early Thursday morning in the far
northern ILN CWA, when forcing is lighter in between the two
main waves of precipitation.
* Blowing Snow is likely once the transition to snow has
occurred, particularly north of the Interstate 71 corridor on
Thursday afternoon and evening. Winds will gust up to 25-35
MPH.
* There remains a very low potential for some hydrologic issues,
as the air mass in the rainy part of the event will be quite
moist, but as of now the expected precipitation amounts do not
raise too much cause for concern.

tron777 wrote: ↑Wed Feb 02, 2022 8:01 am42 / 38 at CVG

Les I believe the temp is something to look at and a few degrees can have huge impacts. Though we hit 61 at Cvg yesterday we only had 7 hours of 50 and above and with the rain have cooled off quite a bit. So yes we had some warming yesterday but we had been cold before and not sure how far surface temps went up after the brief warm up yesterday.

tpweather wrote: ↑Wed Feb 02, 2022 8:06 am

tron777 wrote: ↑Wed Feb 02, 2022 8:01 am42 / 38 at CVG

Les I believe the temp is something to look at and a few degrees can have huge impacts. Though we hit 61 at Cvg yesterday we only had 7 hours of 50 and above and with the rain have cooled off quite a bit. So yes we had some warming yesterday but we had been cold before and not sure how far surface temps went up after the brief warm up yesterday.

Road temps are up into the low to mid 40s so they will take a while to cool down. I'd be where you want to be after tonight. Road issues for us down here begin Thurs afternoon. Thurs morning looks tough for I-70 Crew.

Yea can't wait to drive to work in the morning. Anyone have chains

If you're down Matt's way,. road issues down there will begin Thurs evening.

0.04" of rain in the books at CVG as of 8am to get the obs kicked off. Seriously, obs will be critical once frozen precip begins in your area tonight and tomorrow. Please report precip type, temps, pics, whatever. But do so safely. Let's all have some fun and a good time with this storm!

Older MD that came out overnight for frz rain: STL now is snowing as we know.

https://www.spc.noaa.gov/products/md/md0105.html

Heavy snow MD - NEW:

https://www.spc.noaa.gov/products/md/md0107.html

Current radar (8:20 am)

Surface temps as of 8am:


Critical thicknesses:

12z HRRR rolling in now

cloudy72 wrote: ↑Wed Feb 02, 2022 8:28 am 12z HRRR rolling in now

Coming in colder than 06z through hour 32.

HRRR says my hood flips to heavy snow around 20z Thursday

10.9" snow report out of ILL per a Tweet from BG.

0.50-0.70" of ZR for Cincy so far at hour 34. VERY HEAVY snow for Butler Co on north.

Switching to sleet at hour 35. Heavy snow continues for Butler Co on north.

Looking very nice for I-70 Crew in terms of snow Thurs afternoon on. Sleety for the Metro and a nasty ice storm SE Counties.

This run is big time ice (ZR) storm for Cincinnati. Less sleet, more freezing rain. Trying to switch to snow at hour 36.

CVG may even changeover to snow around 9-10pm.

Transitioning to a period of heavy snow for Cincinnati at hour 37.

Trevor wrote: ↑Wed Feb 02, 2022 8:35 am 0.50-0.70" of ZR for Cincy so far at hour 34. VERY HEAVY snow for Butler Co on north.

This current run is a big time killer in terms of winter weather . The low is somewhat further south and maybe a tad slower. Not sure if this model is onto something but need to watch the trends.

Snow/sleet continues at hour 39.

Trevor wrote: ↑Wed Feb 02, 2022 8:37 am This run is big time ice (ZR) storm for Cincinnati. Less sleet, more freezing rain. Trying to switch to snow at hour 36.

That is another trend to keep watching. Run may be wrong but the system still not gaining strength but staying a little further south. Please no frz/rain