Rocktober 2021 Weather Discussion

[tron777]

No changes to my thoughts for today. Rain to our NW currently. Most of that will stay away at this time for this morning. It's the midday to early afternoon period where do we see showers / clouds or a bit of clearing to aid in this evening's development? We'll see, but I'm going with mainly a rain event and isolated strong winds. In other words severe wx threat isn't zero, but it is on the low side in my opinion.

[tron777]

New DT This Week in Weather Video:

[tron777]

Wonderful AFD from the boys and their expectations have been lowered as well for this event:

Widespread SHRA with embedded TSRA continues to move through the
region, just clipping the far NW portion of the ILN CWA through
daybreak. West-central OH and points further to the NW will see
the most widespread and steadiest pcpn through the morning hours
before activity begins to shift a bit further to the north later
in the morning. This will occur as the much-anticipated sfc low
quickly tracks NE through IN into NW OH from late morning
through mid-afternoon. This track will place pretty much the
entire ILN FA in the open warm sector before the low begins to
pull NE away from the local area by late afternoon into early
evening, with the cold front trailing back to the SW.

There is quite a bit to unpack as it relates to today`s severe
threat, but the overall setup appears to be slightly less
favorable than was the case in previous fcst runs. For one, as
already mentioned, the sfc low will already be tracking away
from the local area as early as 21z, with the better LL shear
and SRH going with it. This is most likely the reason for the
removal of the SPC 5% tor risk locally (with a placement of 2%
across the local area). The greatest severe risk will likely
evolve in two general areas -- near and just east of the sfc low
track mid afternoon and then along the trailing cold front
where LL convergence will be maximized late afternoon into early
evening. The former of these areas may manifest itself in the
greatest coverage (SCT) of storms across portions of EC IN/WC
OH into NW/N/NE OH by mid afternoon. This is where the coverage
of rotating storms could be maximized, with the window for
severe potential locally near/immediately E of the sfc low
rather small for the ILN FA... generally be from approximately
2 PM to 5 PM.

The greatest coverage of storms locally is likely to be along
the actual front itself, which will trail back to the SW across
parts of EC IN, WC OH, the Miami Valley, and Tri-State areas by
late afternoon into early evening. But the loss of diurnally-
driven destabilization, as well as the departure of the sfc low
by mid evening, should result in a fairly rapid decrease in
severe potential toward sunset. What this essentially all leads
to is a rather /conditional/ severe threat with several small
overlapping windows for strong to severe storms. The pre-frontal
trof is essentially through the local area by 9-10 PM, with the
baroclinic structure becoming increasingly anafrontal as we
progress later into the evening hours, with all severe threat
over by this time.

From an ingredients perspective, there are several factors that
will support a strong to severe storm risk today. For one, there
will be about 30kts of LL bulk shear with 50-55kts of deeper-
layer bulk shear to work with, supporting /some/ storm
organization, structure, and longevity. LL wind fields, with
H8-H9 layer winds of 25-30kts, are adequate, especially if the
~1000J/kg SBCAPE is realized -- as is being depicted on some hi-
res CAM guidance. The evolution of such a favorable
thermodynamic environment, however, remains a bit more
uncertain. So there are questions as to just how much instby is
able to develop with widespread cloud cover in these areas
through mid afternoon. The LL shear and SRH is likely to be
maximized close to the sfc low track and just to the east of it,
meaning it is likely to set up from WC OH (for a very brief
window around midday) to north of the immediate local area later
in the afternoon. Locally, this would likely be in a line from
Darke to Delaware Counties in OH and points to the north.
However, aside from the backing LL winds in these areas, fcst
soundings elsewhere show a largely unidirectional wind profile,
with sfc winds already more out of the SW during the mid/late
afternoon when SBCAPE is likely to be maximized locally as the
front begins to drift east into the immediate area. And on top
of that, midlevel lapse rates are not going to be all that
impressive. But with all of this being said, there will likely
be a small time window along the actual front itself where one
or more broken cluster of storms, owing to the seasonably strong
deeper- layer shear, could produce instances of strong to
damaging wind, especially if LL lapse rates are able to steepen
sufficiently with daytime heating. The tornado and hail threat
are secondary threats, if there is one to be had at all. And the
progressive nature of the activity should limit anything more
than a very isolated instance of flooding -- a threat that
appears to be low enough as to not include in the HWO. And
although the severe threat looks to be slightly lower in SC OH
and NE KY than for locations closer to the I-71 corridor and
further to the N/W, decided to keep things simple with just one
HWO segment.

[cloudy72]

Yeah I am just not feeling it - still in a SLGT risk but everything I see thus far is in agreement with the lowering of expectations.

[tron777]

Seeing a bit of sun right now but when looking at the visible, it is doubtful that it's going to last too long.

[tron777]

Clouds have rolled back in as expected. Light rain in fact is lurking just to our SW so IMO, our call on this forum of keeping the severe threat low is spot on attm.

[tron777]

Light rain here now...

[tron777]

Surprisingly, there are CAPE values of 500-1000 J/kg despite the cloud cover to our West. Little here due to clouds and light rain. We should see a break in the rain so we'll have to wait and see if we can get any of that CAPE in here. Lapse rates are still terrible even though the wind shear and helicity are good. No changes to my thinking at all. I still believe that the severe threat is low with this system. We shall find out soon enough.

[MVWxObserver]

My gauge picked up a tenth from late last night / predawn this AM.

Currently 72 here in G'ville.

[tron777]

Upper 60s to near 70 around here thanks to the cloud cover and earlier light rain. 1st t-storm watch of the day issued for West KY / TN and NE AR;

https://www.spc.noaa.gov/products/watch/ww0527.html

Clearing has taken place in the watch area and closer to home... seeing a little area of clearing with CU development also in Central IN. We'll have to see if any of that can work in here within the next couple of hours. Otherwise, it's too little, too late and I think the call here of isolated severe only, is looking excellent.

SBCAPE values are 500 J/kg here, 1000 to our west and a tiny area of 1500 is trying where some sun has occurred in Central IN. Lapse rates are still terrible. Surface low is already north of us and will be NE of us later on so the spin or helicity isn't really a problem anymore for tornadoes. Wind shear is still good. So all in all, nothing has really changed. A low strong wind threat, some heavy rain, thunder, lightning, and a sharp drop in temps behind the front. That should about do it.

[tron777]

For rainfall amounts, I've been seeing a lot of news outlets going with at least an inch of rain for us, some in that 1-2" range. I don't see it unless you're lucky enough to get a few rounds of storms. I think most should get a 1/2" or less out of the deal personally.

[tron777]

MD has just been issued for a possible watch over NE Ohio. I can see that since they are still ahead of the surface low. It is bad timing for our local area IMO.

https://www.spc.noaa.gov/products/md/md1865.html

[tpweather]

For rainfall amounts, I've been seeing a lot of news outlets going with at least an inch of rain for us, some in that 1-2" range. I don't see it unless you're lucky enough to get a few rounds of storms. I think most should get a 1/2" or less out of the deal personally.

Hey Les and we are on the same page here. I am going with .25 to .50 for most unless like you mention you get a thundershower. The severe thunderstorm watch is well southwest of us and the more things change the more they stay the same as that area is no doubt the biggest area for severe weather during the fall severe season.

[tron777]

For rainfall amounts, I've been seeing a lot of news outlets going with at least an inch of rain for us, some in that 1-2" range. I don't see it unless you're lucky enough to get a few rounds of storms. I think most should get a 1/2" or less out of the deal personally.

Hey Les and we are on the same page here. I am going with .25 to .50 for most unless like you mention you get a thundershower. The severe thunderstorm watch is well southwest of us and the more things change the more they stay the same as that area is no doubt the biggest area for severe weather during the fall severe season.

Unless something odd happens that we weren't expecting, the forecast is in great shape. Only 71 here and at CVG as of 3pm. No way we'll make the mid or upper 70s today. Clouds kept temps down and will also keep the instability down as we thought it would. The models showed it for the last couple of days as well.

[tron777]

Light rain again here... can't get any heating this way.

[cloudy72]

Looks like some lightning showing up with that cell just south of Greensburg IN

[cloudy72]

Sunshine breaking out here now and quite a bit of clear sky to my west visible out the window.

EDIT: 3:30 SPC day 1 update shaves the SLGT risk from Cincy down to about Bowling Green KY. Still SLGT risk across much of Ohio into western PA along with far western KY into Arkansas.

[tron777]

No sun here since this morning. Been nothing but clouds and a couple periods of light rain. 0.01 to 0.02" range so nothing major but enough to kill the severe wx threat for this area. I can see why the slight risk is dropped down to a marg risk for my hood. It should have stayed as a marg risk the entire time to begin with. This is mid Rocktober, not August so the sun coming out is going to be too little, too late for those of us not in Central / SE Indiana. Just my 2 cents.

[MVWxObserver]

----

[MVWxObserver]

has been playing peek a boo since this morning. Currently is shining again.

Currently 75 and a DP of 63 here in G'ville.

[tron777]

has been playing peek a boo since this morning. Currently is shining again.

Currently 75 and a DP of 63 here in G'ville.

You've got a higher chance then those of us who have seen no sun since this morning. I am actually down to 70 now. Not expecting any severe wx here whatsoever.

[tpweather]

has been playing peek a boo since this morning. Currently is shining again.

Currently 75 and a DP of 63 here in G'ville.

You've got a higher chance then those of us who have seen no sun since this morning. I am actually down to 70 now. Not expecting any severe wx here whatsoever.

Les not expecting much here though I could see some thunder and lighting early this evening as the jet is strong and headed right up this way but severe not expecting that and could see some gusty winds with the front. Saturday not expecting much in the rise of temps and going 55-58 during the afternoon. Next week is interesting though it starts out calm but many details to be worked out for later in the week

[MVWxObserver]

Frost advisories / Freeze warnings from the Upper Midwest to eastern NM and the TX Panhandle.

[tron777]

has been playing peek a boo since this morning. Currently is shining again.

Currently 75 and a DP of 63 here in G'ville.

You've got a higher chance then those of us who have seen no sun since this morning. I am actually down to 70 now. Not expecting any severe wx here whatsoever.

Les not expecting much here though I could see some thunder and lighting early this evening as the jet is strong and headed right up this way but severe not expecting that and could see some gusty winds with the front. Saturday not expecting much in the rise of temps and going 55-58 during the afternoon. Next week is interesting though it starts out calm but many details to be worked out for later in the week

Totally agree. As you mentioned before, you are I are back to being on the same page once again. Speaking of next week and beyond, I continue to see a lot of run to run variability as to the position of that next trough, where does the coldest of air go, any rainfall associated with it? Etc Etc. Just a lot of unknowns as to exactly how it'll play out. What I do think is that we'll see some gorgeous fall weather next week, esp early on with 60s and low 70s for highs and 40s to around 50 for lows. Typical for mid Rocktober. Then, by the end of next week, we should see colder air move in with that next trough. Will we see 60s and sun or 50s and light rain with 30s or 40s at night? That's the unknown part to me at this time. Then, looking way out there for the days approaching Halloween, IMO we'll see another trough and shot of cold air. I believe each shot of air will get cooler and cooler as we progress thru time. Hopefully, the pattern will set us up for some early season fun at some point in November.

[MVWxObserver]

Pouring and thunder here in G'ville.