Absolute Vorticity

***April 13, 2022 - Possible Severe Threat Late Wednesday and Overnight***

We have a slight risk for severe wx mainly for Wed night as a cold front works thru the region. Damaging winds is the primary hazards. Highest threat is West. Trend is for a weakening line to move in during the overnight. Do we see any junk activity Wed morning to mess up future instability? All questions to be answered in the next couple of days.

Latest SPC Outlook:

12z 3km NAM only goes out to 8pm WED....but at this time radar looking nasty over in Indiana. Almost looking like a bow forming just south of IND.

Euro and really most models) are bringing the cold front thru with a small line of heavy rain / wind around 1 or 2am Wed night / Thurs morning. Wish the timing was better so we'll at least avoid the worst of the severe threat. I am favoring a line coming in with isolated strong winds possible.

Currently looking like my cousins in O'Fallon, MO (near St Louis) are in the Enhanced risk, an aunt and some cousins in Anderson, IN near the Enhanced / Slight boundary and nephew, his fiancee / her folks and their friends are near the Enhanced / Slight boundary, too.

The Enhanced Risk is closer but still thankfully to our West.

6Z NAM and esp the 6Z HRRR looking interesting for a couple of bowing segments coming thru the area which would mean damaging winds for the primary threat for us Wed evening and overnight. These short range models have elevated convection with the warm front, Wed morning then warm sectored from about 3-4pm on. Strong to severe storms move into the NW around 8-9pm and Cincinnati around 11pm to 1am range then SE Crew there after. HRRR has two distinct bowing segments from about Cincy on south then coming thru Northern sections from NW to SE via Indiana. So an opportunity really for everyone to get 60-70 mph wind gusts out of this system. I won't rule out a brief spin up but I think that threat is largely to the West and SW of us. High winds are my concern mostly with this system. Luckily trees aren't all fully leafed out and previous rainfall amounts have been light. We have that going for us for power / flooding concerns.

I'm not seeing a lot of SB CAPE though. NAM only has maybe a couple hundred J/kg and HRRR has 500-700 range in most places. I'd love to see one thousand to really get these storms going but the warm frontal convection is going to limit how much instability we'll receive so this event will have its limits.

BG StormTalk! https://www.wave3.com/2022/04/12/stormt ... pdate-412/

Good Morning and just back into the thick of things here and yes some interesting weather headed this way but will this involve severe weather is the question. Wednesday has a lot going on and what happens earlier in the day can help form what happens later in the day and evening. Looks like a nice area of rainfall Wednesday afternoon and how long does this hang around will play a part concerning severe weather. If the rain stops earlier in the afternoon then we have time for the atmosphere to sort of reload and we have a better shot of severe weather. If we still have rain going on between 4-6pm then the atmosphere will have a harder time to reload and the severe threat will be less but not zero. Going to be windy all day and not surprise to see some winds over 30 mph and that is without a thunderstorm. Main severe items will be straight line winds and heavy rain though a random tornado or two is not out of the question especially west of here. Like most severe threats the closer we get to the actual event the better the forecast will be concerning the best locations for the severe weather.

Glad to see you back Tim! Currently West of I-65 is kind of where the line begins to slowly weaken as it heads our way. Like you said, it'll be a nowcast tomorrow once we see how long it takes for the midday junk to get out of the way.

12Z HRRR is faster, bringing it in here around 10pm where the 12Z NAM is closer to midnight for Cincinnati.

tron777 wrote: ↑Tue Apr 12, 2022 10:57 am 12Z HRRR is faster, bringing it in here around 10pm where the 12Z NAM is closer to midnight for Cincinnati.

Les those 2 hours can make a difference the severe threat further east.

Hey Tim and welcome back, bro!

Looks like relatives of mine in IN, MO and western TN are in the Enhanced zone.

GFS shows a lot of junk rain / clouds and elevated convection so the storms would likely weaken rapidly as they head in here. Isolated strong winds still possible. Timing is going to make all the difference. How much heating do we get?

SPC has introduced a MOD risk out in western KY, SW Indiana, S Illinois down to NE Louisiana for tomorrow.

The 12z run of the HRRR has a line of storms moving through the area in the 8p-11p timeframe WED evening. Damaging winds look to be the main threat. There is quite a bit of helicity out ahead of this line, so if any cells can pop out ahead then tornado spin up potential is there as well.

SPC Discussion for our area, which is what we've said... instability is a big question for us.

...Mid-MS/lower OH river valleys...
Thunderstorms are expected to develop along the cold front by the
mid morning hours across parts of southern MO/northern AR. Mean
storm motions along the front will favor a quick transition from
quasi-discrete cells to more linear storm modes. Convection will
continue to grow upscale as it approaches the mid-MS river valley
amid increasing low-level moisture and daytime heating. Increasing
low-level flow (up to 50-60 knots between 925-850 mb) will likely
support bowing segments and the potential for widespread damaging
winds. The potential for multiple 65+ knot wind reports and/or
significant wind damage support an upgrade to a wind-driven Moderate
risk for portions of the mid-MS/lower-OH river valleys. Elongated
0-3 km hodographs ahead of the line will also support embedded
circulations. The warm advection regime and broad scale ascent ahead
of the line may support a few more discrete cells across the lower
OH river valley by mid to late afternoon. This potential may be
conditional on the degree of destabilization that can occur behind
early-morning rain/weak thunderstorms that should exit the region by
early afternoon. However, if discrete convection can become
established, all hazards will be possible, including the potential
for large hail and strong tornadoes.

MVWxObserver wrote: ↑Tue Apr 12, 2022 12:53 pm Hey Tim and welcome back, bro!

Looks like relatives of mine in IN, MO and western TN are in the Enhanced zone.

Hey Eric,nice to be home. Looking forward to baseball as always.

From the boys:

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
A mid-level shortwave advancing northeast in deep southwesterly
flow provides the impetus for showers and thunderstorms
Wednesday... starting in the mid-morning over the Tri-State
region and reaching central Ohio by late afternoon. Guidance
generally agrees there will be a brief respite into the early
evening hours, following by pre-frontal convection. Highs
Wednesday will reach well into the 70s. Winds may gust to
around 30-35 mph during peak heating.

For Wednesday late evening into the overnight, there remains
plenty of uncertainty on timing of a band of pre-front storms.
Earlier timing such as the 12Z HRRR depicts would increase the
chance of damaging wind gusts due to better instability. For
now, have indicated a broad period of PoPs to cover this
instability, and also have kept mention of damaging wind gusts
due to clear indication on all the CAMs of a linear mode along
with shear of 40-50 knots. Also kept mention of isolated tornado
potential in the HWO due to expected QLCS-nature of the
convection.

Frontal passage is likely to occur after midnight behind the
thunderstorm activity. This leads to dropping dewpoints and lows
dipping into 40s by early Thursday morning.

Good morning all! Mid 60s and humid to start our day. It's all about timing today. When does the rain get here later this morning / midday and how long do we get util the line comes this evening for instability prospects? We shall watch it unfold together. No changes this morning from the SPC's earlier outlooks.

Rain / storms are developing over S ILL, SKY, and TN heading NE towards us. This is associated with another warm front. That activity should be in here late this morning into the early afternoon hours. Then once we are in the warm sector, we will keep our eyes focused to the West for a line of storms associated with the cold front for this evening into the early overnight hours.

Seeing some light rain here already. HRRR doing a great job matching up well with the radar. NAM seems a bit too slow at bringing the rain in. We should be done by 2pm if the HRRR is correct to give the atmosphere time to recharge. That's the kicker. Do we quit that early or keep raining until 4 or 5pm? That makes a huge difference for t-storm fuel later on tonight.

BG StormTalk! https://www.wave3.com/2022/04/13/stormt ... pdate-413/

tron777 wrote: ↑Wed Apr 13, 2022 7:30 am Seeing some light rain here already. HRRR doing a great job matching up well with the radar. NAM seems a bit too slow at bringing the rain in. We should be done by 2pm if the HRRR is correct to give the atmosphere time to recharge. That's the kicker. Do we quit that early or keep raining until 4 or 5pm? That makes a huge difference for t-storm fuel later on tonight.

started raining steady here about 9am, still at it. I for one will be fine if we snuff out the severe potential on this one. Doesn't look like a great one anyway, and with it coming at night I'd prefer to pass. If there's to be something to see, I want to be able to see it.

HRRR keeps going back and forth on the rain. 12z has rain until 6p, but then wants to bring a couple of lines through at 1-2a.