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Posts posted by andyhb
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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.
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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.
QuoteDay 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
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Predictably, the 00z HRRR is insane.
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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.
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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).
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Early 3 km NAM runs certainly don't do anything to suppress this potential. Impressive parameter space across the entire warm sector.
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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.
QuoteHowever, 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.
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Huge D3 enhanced/30 hatched area issued.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
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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.
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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.
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12z GFS/GEFS is also incredible in the Tuesday-Wednesday window next week.
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00z Euro for 4/4, holy mother of god...
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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.
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500 mb presentation on the Euro is a classic for a significant severe event in the Midwest.
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CSU MLP is going off for Friday with a massive 45% hatched area.
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That’s a very large 30% in the D5.
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Strong tornado ongoing WNW of Tuskegee AL.
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00z models look nasty for Friday in portions of the sub-forum. A couple of them have what would probably be a significant severe weather outbreak from the Mid MS Valley to the western Lakes.
Some very high end solutions here in the GEFS.
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And now up to 21...
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7 dead per county coroner in Sharkey Co. MS (Rolling Fork area).
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That was a devastating hit on the northern portion of Amory.
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Absolutely violent tornado heading for Amory, and that is not a small town.
Severe Weather 4-4-23 and 4-5-23
in Lakes/Ohio Valley
Posted
30% D6 issued, with some pretty strong wording (understandably) for being that far out.