andyhb

When the 3 km NAM comes in looking like the hyped up runs of the FV3/HRRR, you might have a problem. 18z run is crazy for the northern MDT/vicinity.

4 minutes ago, Chambana said:

Forgive my amateur question pertaining to severe wx, but could this be the highest threat to the region since 4/27/11?

I won't make any comparisons to such high end outcomes this far out, but the synoptics with this one are screaming major severe weather outbreak, to say the least. Still comes down to the mesoscale on the day of and day before, but the potential here is at a level rarely seen given the consensus from the 12z guidance.

Putting it another way for the long-timers, back in the day, this would be a level of threat that @CUmet would come out of the woodwork for.

Just now, SolidIcewx said:

Now imagine if this was May/June

Lol you don't have to imagine it, there's 2000-4000 CAPE across the entire warm sector with tornadic supercell wind profiles.

Unbelievable run again. All of those are occurring in environments favorable for strong/violent tornadoes.

Put it this way, I would be in favor of moving Tuesday's thread to the main board if this place wasn't so poorly organized. Feel like both C/W and GL/OV are going to be involved in some manner here.

These are some of the most dangerous model solutions I've seen in a very long time within reasonable range.

30% D6 issued, with some pretty strong wording (understandably) for being that far out.

Quote

As the western trough ejects on Day 6/Tuesday, potential significant severe thunderstorms will be possible far eastern OK toward southeast MO and vicinity. Rich boundary-layer moisture will be in place amid steep midlevel lapse rates courtesy of an EML advecting across the region from the Mexican Plateau. This will supply plenty of instability with stronger vertical shear accompanying the ejecting trough. There is some uncertainty among medium range guidance on the northern extent of better moisture return and hence severe potential. This is mostly driven by differences in surface low, dryline and warm front positions related to somewhat different ejection of the upper trough. However, guidance is in very good agreement with respect to the southern portion of the risk area. Supercells capable of all severe hazards, some potentially significant, will be possible.

Euro once again is a high end event for 4/4 (Tuesday). Massive trough with a wavelength of more than half the CONUS slams into a huge warm sector with mid-upper 60s dewpoints throughout. Other models definitely slowed so there is a bit of split now in the solutions.

Bimodal D2 MDT, one closer to the surface low with a 10 hatched tornado risk (wind driven), the other in the Mid South with a 15 hatched tornado risk.

Quote

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1257 AM CDT Thu Mar 30 2023

   Valid 311200Z - 011200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
   IOWA INTO NORTHWEST ILLINOIS...AND ACROSS NORTHEAST ARKANSAS...THE
   MISSOURI BOOTHEEL...EXTREME WESTERN KENTUCKY...WESTERN
   TENNESSEE...AND FAR NORTHWEST MISSISSIPPI...

   ...SUMMARY...
   Intense and widespread severe thunderstorms are expected Friday
   afternoon into the overnight hours across portions of the Middle
   Mississippi Valley and Mid-South vicinity, eastward to the Lower
   Ohio and Tennessee Valleys. Intense, damaging gusts and several
   tornadoes (some strong and long-track) are expected.

   ...A bi-modal regional outbreak of severe storms is expected on
   Friday from the Mid-Mississippi Valley into the Mid-South...

   ...Synopsis...

   An amplified large-scale upper trough will be oriented from the
   northern plains to the southern Rockies early Friday. The trough
   will continue to deepen as it shifts east toward the MS Valley by
   00z, and oriented from the upper Great Lakes to the TN Valley
   vicinity by Saturday morning. With time, a closed low is expected to
   develop over eastern SD/NE/IA and a 100+ kt 500 mb jet will
   overspread the Mid-MS/OH Valley region. Intense southwesterly
   low-level flow also will overspread the Mid-South through much of
   the Midwest, with an 850 mb jet around 65-80 kt forecast by late
   afternoon into the overnight hours.

   At the surface, a deepening low centered over eastern NE/western IA
   Friday morning will shift east across IA through the afternoon
   before lifting toward southern Ontario overnight. A trailing cold
   front will extend from the low into eastern KS/central
   OK/west-central TX at 12z, and shift east across much of the Midwest
   and Mid-South. Ahead of the eastward-advancing front, strong
   southerly flow will transport 60s F dewpoints northward. Near-60 F
   dewpoints are expected as far north as eastern IA into northern IL
   during the afternoon. The warm sector will become more
   narrow/pinched off with north and east extent toward the Ohio Valley
   during the evening/overnight hours. However, near 60 F dewpoints are
   still expected in a narrow corridor ahead of the surging cold front
   into far southern IN and central KY. Richer boundary-layer moisture
   will reside from the Mid-South into the Lower-MS/TN Valleys where
   low to mid 60s F dewpoints are forecast.

   ...Mid-Mississippi Valley Vicinity...

   The strongest forcing/DCVA will be located over northern portions of
   the Mid-MS Valley close to the surface low/triple point. The
   expectation is that rapid destabilization through the morning
   (1000-2000 J/kg SBCAPE) and arrival of stronger forcing by early
   afternoon will result in initial supercell development near the
   surface low. All severe hazards will be possible with these fast
   moving storms, including a couple of strong tornadoes, intense
   damaging gusts and large hail. Cellular activity should spread
   across eastern IA/northern MO and into northwest IL before tendency
   toward upscale growth into linear convection ensues with eastward
   extent as convection develops south and east ahead of the front from
   east-central MO into northern/central IL. Damaging gusts will become
   more prominent with linear convection, though QLCS tornadoes will
   also be possible. 

   Additional storms will likely form near/just north of the warm front
   and move into parts of far southeast MN and southern WI. This
   activity should remain elevated, posing a risk for large hail and
   strong gusts, though any cell rooting on the warm front will pose a
   tornado risk as well, though the better warm sector is expected to
   remain south of MN/WI. 

   ...Mid-South Vicinity...

   A concerning scenario appears to be developing across portions of
   the MO Bootheel, northeast AR, western TN/KY and far northwest MS
   vicinity during the afternoon/evening. At least mid-60s F dewpoints
   are expected beneath modest midlevel lapse rates. This will support
   1500-2000 J/kg MLCAPE amid intense vertical shear. Forecast
   soundings indicate 0-1 km SRH increasing to around 400 m2/s2 by
   early afternoon. Thunderstorms are expected to develop by early
   afternoon ahead of the cold front within a pre-frontal
   trough/low-level confluence zone. Storm motion near 50 kt with
   supercell wind profiles will support cells capable of significant
   and long-track tornadoes. With time, upscale growth into a QLCS is
   expected, and intense wind gusts will be possible in addition to
   mesovortex tornadoes.

   ...OH/TN Valley vicinity...

   Low-level moisture/instability will begin to wane with north and
   east extent into the nighttime hours. However forecast guidance has
   consistently shown a few hundred J/kg MLCAPE with little/no
   inhibition. Forecast guidance generally tends to under-forecast
   north/east extent of severe potential in strongly forced, intense
   shear system. As such, the ongoing outlook maintains a broad
   gradient from Enhanced to Slight risk across this region. Damaging
   gusts and a few QLCS tornadoes will be possible into the nighttime
   hours.

   ..Leitman.. 03/30/2023

Predictably, the 00z HRRR is insane.

6 minutes ago, WaryWarren said:

He's too busy posing for selfies in Rolling Fork.

To be fair, he also has raised a lot of money for the community. You can't fault him for that.

Come on, seriously now. You just don't see output like that from the 3 km NAM.

HRRR solutions later are likely going to be pretty nuts if the 3 km NAM is already this aggressive across the warm sector (with supercellular storm modes).

Early 3 km NAM runs certainly don't do anything to suppress this potential. Impressive parameter space across the entire warm sector.

Think we're going to need a specific thread for 4/4 given the potential magnitude of Tuesday's threat, but we have a large D7 15% area outlined in the latest D4-8.

Quote

However, on Tuesday, as the upper trough ejects
   east and spreads intense deep-layer southwesterly flow over the
   Lower/Mid-MS Valley to the Ohio Valley, a sharp cold front will
   surge east. Rich gulf moisture across a broad warm sector will
   supply plenty of instability, and potentially widespread severe
   thunderstorms will once again be possible across the Mid-MS/Lower OH
   Valley toward the Mid-South and TN Valley.

Quote

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0236 AM CDT Wed Mar 29 2023

   Valid 311200Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE MID-MISSISSIPPI VALLEY TO THE MID-SOUTH...

   ...SUMMARY...
   Potentially intense and widespread severe thunderstorms are expected
   Friday afternoon into the overnight hours across portions of the
   Middle Mississippi Valley and Mid-South vicinity, eastward to the
   Lower Ohio and Tennessee Valleys. Damaging gusts and tornadoes will
   be the main hazards with this activity.

   ...Arklatex to the Mid-MS Valley and eastward to the OH/TN
   Valleys...

   Widespread, regional episode of severe thunderstorms is possible on
   Friday.

   An intense mid/upper trough is forecast to eject eastward across the
   Plains to the central U.S. on Friday. Intense deep-layer
   southwesterly flow will accompany this system, with a 100+ kt 500 mb
   jet expanding over much of the Midwest. As the upper trough deepens
   during the afternoon and evening, a 60-70 kt southwesterly low-level
   jet will overspread much of the risk area. These flow fields will
   favor a fast-moving squall line shifting across the Mid-MS
   Valley/Mid-South toward the Lower OH and TN Valleys. 

   At the surface, strong southerly low-level flow will transport 60s F
   dewpoints northward. Near-60 F dewpoints are expected as far north
   as eastern IA to northern IL and then central IN as the surface low
   tracks east/northeast from IA early in the day, to southern Ontario
   by Saturday morning. While some questions remain regarding moisture
   with north and east extent into the OH Valley, forecast soundings
   indicate at least a few hundred J/kg MLCAPE will exist during the
   evening as far east as the I-65 corridor in KY/TN. Given intense
   flow fields, a threat for damaging gusts will persist from MO/IA
   into the Lower OH Valley.

   Across IA/MO, initial supercell development is possible near the
   surface low/triple point. Fast moving storms may produce possibly
   significant damaging gusts and tornadoes. Upscale growth into a QLCS
   is expected to occur rapidly given strong forcing/vertical shear.

   Further south into the Mid-South and vicinity, large-scale ascent
   will be somewhat weaker further removed from the upper trough.
   However, flow fields will remain intense and a mixed mode of
   supercells and linear convection is expected. All severe hazards
   (damaging gusts, tornadoes and isolated hail) are expected by late
   afternoon into the evening hours.

   ..Leitman.. 03/29/2023

Somehow the 00z Euro came in and outdid last night's 00z run in terms of insanity. A 971 mb low with plenty of moisture access. Absolute bomb.

Will just report my tweet here for the ensemble means, which all indicate that Tuesday could be a big day.

1 hour ago, CheeselandSkies said:

Also notable that the 00Z NAM forecast dewpoint in east-central Iowa for 21Z tomorrow is 7 degrees. In 48 hours that's supposed to be nearly 60.

In fact, last couple of NAM runs (especially 00Z) suggesting the northern end of this setup might struggle with moisture return moreso than previously thought. That cold high pressure tomorrow is really gonna wipe it out. OTOH it is the NAM so... And the precip fields even appear to be popping an arc of semi-discrete convection in that classic sweet spot just southeast of the surface low.
 

Probably because it's almost -20 degrees at 500 mb and below freezing at 700 mb yielding extreme 0-3 km CAPE and low-level lapse rates.

12z GFS/GEFS is also incredible in the Tuesday-Wednesday window next week.

00z Euro for 4/4, holy mother of god...

5 minutes ago, cyclone77 said:

I'll be down at Lake of the Ozarks Thu/Fri so no chasing for me with this.  Will definitely be following it though as it looks pretty interesting.  Nice to see a setup in the forecast.  

You could take a... "detour" to Eastern AR perhaps.

500 mb presentation on the Euro is a classic for a significant severe event in the Midwest.

CSU MLP is going off for Friday with a massive 45% hatched area.

That’s a very large 30% in the D5.

Strong tornado ongoing WNW of Tuskegee AL.