Absolute Vorticity

fyrfyter wrote: ↑Wed Jan 10, 2024 10:11 am

tron777 wrote: ↑Wed Jan 10, 2024 9:44 am Anybody got a QPF map from the 12Z NAM? The track looks similar to La Bomba and the model deepens the low to 968 MB over Lake Huron.

EDIT: Never mind. I was able to locate something. Looks like the 1" plus totals are along the track of the low. We get 0.75" over Cincy and our Western counties. Looks like 0.50" for our Eastern counties.

Here:
IMG_0788.jpeg

Thank you Aaron!

Trevor wrote: ↑Wed Jan 10, 2024 10:13 am Not only that, Tim, but a further west track increases our chance to mix down some wicked winds. The NAM went crazy with gusts...

In my forecast update today on my page (I will post here soon) I mentioned gusts exceeding 50mph possible. HWW may be needed.

I also mentioned that possibility Trev early on in this thread due to the low being stronger then our previous system. The potential is certainly there. Ugh... the drive home Friday is going to be awful.

tpweather wrote: ↑Wed Jan 10, 2024 10:18 am Great forecast Trev. I do believe the winds could be worse than yesterday. My guess is you may lower the overnight lows next week if and of course if we get a decent snow Sunday/Monday. Busy is the key word over the next 1-2 weeks and hopefully in February as well.

The only comment I have is that if we see the rest of the 12Z data come in similarly with regards to rainfall amounts, then perhaps say 0.50-0.75" of rain. Otherwise, it looks great! We may also need to hit the wind wording in our posts a little harder too.

tron777 wrote: ↑Wed Jan 10, 2024 10:23 am

tpweather wrote: ↑Wed Jan 10, 2024 10:18 am Great forecast Trev. I do believe the winds could be worse than yesterday. My guess is you may lower the overnight lows next week if and of course if we get a decent snow Sunday/Monday. Busy is the key word over the next 1-2 weeks and hopefully in February as well.

The only comment I have is that if we see the rest of the 12Z data come in similarly with regards to rainfall amounts, then perhaps say 0.50-0.75" of rain. Otherwise, it looks great! We may also need to hit the wind wording in our posts a little harder too.

Yeah that's what I'm thinking. Kept 1" as the ceiling for now but will probably lower it.

Also, figured a thread name change was in order

12Z RGEM bombs the low to 976 MB over S Mich but then it weakens and transfers its energy to an EC Low. I have seen that solution a couple of times as of late but not on a lot of models to use that in my forecast. For rainfall about 0.75" or so for us with the heavy stuff west of us near the low track. That seems to be the theme so far today with regards to QPF anyway.

Trevor wrote: ↑Wed Jan 10, 2024 10:26 am

tron777 wrote: ↑Wed Jan 10, 2024 10:23 am

tpweather wrote: ↑Wed Jan 10, 2024 10:18 am Great forecast Trev. I do believe the winds could be worse than yesterday. My guess is you may lower the overnight lows next week if and of course if we get a decent snow Sunday/Monday. Busy is the key word over the next 1-2 weeks and hopefully in February as well.

The only comment I have is that if we see the rest of the 12Z data come in similarly with regards to rainfall amounts, then perhaps say 0.50-0.75" of rain. Otherwise, it looks great! We may also need to hit the wind wording in our posts a little harder too.

Yeah that's what I'm thinking. Kept 1" as the ceiling for now but will probably lower it.

Also, figured a thread name change was in order

No doubt! Changing the name of the thread makes perfect sense!

tpweather wrote: ↑Wed Jan 10, 2024 10:18 am Great forecast Trev. I do believe the winds could be worse than yesterday. My guess is you may lower the overnight lows next week if and of course if we get a decent snow Sunday/Monday. Busy is the key word over the next 1-2 weeks and hopefully in February as well.

Of course! If confidence increases that we will have at least SOME snow on the ground (and believe me it is increasing), a temp adjustment will be necessary.

12Z GFS is a hair stronger / NW of its 6Z run. It's a bit more moist with around an inch for most folks, rainfall wise.

Around 0.40" from the 12Z Euro. Euro seems to be coming in drier with each successive run. A nice deform band / TROWL showing up on the north and west side of the deepening cyclone. 973 MB over N Indiana at 60 hours.

At the very least, I expect wind advisories to be issued again area wide probably sometime tomorrow. Not sure if we'll make high wind warning criteria though. Also wondering if a strong t-storm is not out of the question for our S counties. SPC has a marginal risk out for our extreme SW forecast area for Day 3 (Fri afternoon and evening).

I don't really have a lot of change here with this storm. Models have the track ironed out pretty good now. Wet tomorrow with very windy conditions esp in the afternoon and overnight. Gusts to 50 mph are certainly possible. I cannot rule out a strong t-storm either. Rainfall amounts between 0.50-1" can be expected. Heavier west, lighter east. Then, we do get some snow showers on the back side later Fri night into Dat. Continued windy with falling temps. Highs barely hitting 30 on Sat. 1" or less for snow with the I-70 Crew having the best chance at seeing light accumulations. This is my final call on this system.

Overnight AFD from the boys. It's a good read and they are hitting the wind wording hard! Which makes sense of course.

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Weak mid-level ridging builds across the Ohio Valley this evening,
and weak surface high pressure quickly passes to the east by
Friday morning. Clouds temporarily decrease early this evening before
the vanguard WAA clouds increase ahead of the next system.

Mid level flow amplifies in response to system digging into the
Southern Plains. With the ridge shifting off to the east the
flow backs late tonight.

Deepening surface low ejects northeast from the Lower MS Valley
Friday morning to a position over northern Indiana by Friday
evening. Very strong southerly low level jet of 75-80 KTS
pivots into the area Friday. Precipitation may reach ILN/s far
western counties toward sunrise Friday and then overspreads the
entire area during the day. Pcpn may begin as a brief rain/snow
mix over the northwest and then quickly transition to all rain
in the strong WAA pattern.

Initial low level inversion will limit wind in the morning but
with better mixing during the afternoon expect wind gusts up to
40 mph. On the warm side of the system, highs to range from the
mid 40s northwest to the lower 50s southeast.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Active weather will be well underway at the start of the extended
forecast period, with some hazards and concerns continuing into next
week. The main concerns are wind on Friday night into Saturday
morning, cold wind chills heading into next week, and some uncertain
low-end chances for snow on occasion.

On Friday evening, a sharp mid-level trough will be rotating
northeast into the Great Lakes. An associated surface low (easily
sub-980mb) will be tracking northeast into the lower peninsula of
Michigan by early Saturday morning. A very tight pressure gradient
will be in place near the low, which will begin to have an occluded
frontal structure after 00Z as a cold front moves across the ILN
forecast area. This discussion will focus on the post-frontal
period, with strong WSW winds to the south of the low, aided by
steep lapse rates in the cold advection. Snow will be one concern to
contend with, as any precipitation will change to snow quickly after
frontal passage, though overall forcing looks broad and weak. Could
see some light accumulations across a decent portion of the forecast
area, but any outside chance of getting around an inch would likely
be confined to areas north of Interstate 70. Of course, the wind is
the bigger concern with this system, and the probability of gusts
over 40kts appears quite high for most of the ILN CWA. Ensemble wind
gust probabilities (NBM/LREF) also back up this idea. There is high
confidence in strong wind Friday night, likely to advisory criteria.
There is low confidence in the wind being strong enough to hit 50kt
warning criteria, though low is not zero. For now, will increase
wind gusts in the forecast (as high as 47kts in the northern part of
the forecast area) but in collaboration with surrounding offices to
the west, north, and east, no headlines will be issued on this shift.

Winds will only gradually subside on Saturday -- perhaps falling out
of advisory criteria by noon, but still remaining gusty well into
Saturday night. Any remaining light snow should eventually diminish
as well, but broad troughing over the Great Lakes will mean some
light snow could occur at times into Sunday as well.

Not sure what's going on with the Euro but it continues to decrease QPF with this system. 0.30" for CVG on the new 6Z run.

tron777 wrote: ↑Thu Jan 11, 2024 8:01 am Not sure what's going on with the Euro but it continues to decrease QPF with this system. 0.30" for CVG on the new 6Z run.

I have no way of knowing but the path was more to the west which would most likely decrease totals but also we just had the GOM unleash tons of precip and you wonder if there has been enough time to boost up precip totals.

What are your current thoughts on this system for tomorrow and Saturday? I have to travel to Indianapolis both days and have not seen any weather on tv. My phone had snow then no snow and reading here sounds like rain to snow if reading things right.
Thanks in Advance

Looks like the system will occlude quicker and that would also cut down on totals

Pepper wrote: ↑Thu Jan 11, 2024 9:10 am What are your current thoughts on this system for tomorrow and Saturday? I have to travel to Indianapolis both days and have not seen any weather on tv. My phone had snow then no snow and reading here sounds like rain to snow if reading things right.
Thanks in Advance

Looks like heavy rain and wind Friday switching to snow late and then Saturday some snow showers and though not a ton of moisture left over roads could get slick in spots and much of that will be determined how quickly the cold air comes in Friday night. Hopefully the wind can dry it out some but its going to be a close call.

tpweather wrote: ↑Thu Jan 11, 2024 9:11 am Looks like the system will occlude quicker and that would also cut down on totals

Being away from the heaviest precip will also increase our winds. I went 45-55 (isolated 60) in my FB update.

ILN is debating whether to go HWW or WA, but I suspect they may go WA and upgrade if needed. I would understand doing that.

Trevor wrote: ↑Thu Jan 11, 2024 9:17 am

tpweather wrote: ↑Thu Jan 11, 2024 9:11 am Looks like the system will occlude quicker and that would also cut down on totals

Being away from the heaviest precip will also increase our winds. I went 45-55 (isolated 60) in my FB update.

ILN is debating whether to go HWW or WA, but I suspect they may go WA and upgrade if needed. I would understand doing that.

I didn't get a lot of time to look but I agree... a further west track and a quicker occlusion of the low would absolutely be valid reasons why the QPF would get cut down. Definitely something to watch to see if this is a trend with the 12Z guidance today. Wonderful posts Tim!!!

I also agree with you Trev. We would get better mixing and any heavier shower would certainly be able to pull down stronger winds to the surface. I originally had 50 mph gusts, but if this ends up being true, 60 mph gusts wouldn't be a problem and that would fit high wind warning criteria. We know a wind advisory is a slam dunk and something should be issued with ILN's afternoon forecast package.

12Z NAM looks to be going the Euro route too with the earlier occlusion and reduction in QPF. 1/4 to 1/2" totals.

tron777 wrote: ↑Thu Jan 11, 2024 9:53 am 12Z NAM looks to be going the Euro route too with the earlier occlusion and reduction in QPF. 1/4 to 1/2" totals.

The 3km is much further east. Probably not correct.

12z GFS seems to stick with the ~1" idea.

IND went HWW so I bet that is what ILN will do as well soon.

LOU and JKL have wind advisories issued for their respective CWA's.

tron777 wrote: ↑Thu Jan 11, 2024 12:24 pm LOU and JKL have wind advisories issued for their respective CWA's.

Yes they do. I’d be shocked if ILN doesn’t go HWW. Even LOU may have to upgrade as well.