April 14th, 2012 Plains High Risk

[hm8]

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1243 AM CDT SAT APR 14 2012

VALID 141200Z - 151200Z

...THERE IS A HIGH RISK OF SVR TSTMS TODAY ACROSS MUCH OF CENTRAL

AND EASTERN NEBRASKA AND PARTS OF ADJACENT NORTH CENTRAL

KANSAS/WESTERN IA...

...THERE IS A HIGH RISK OF SVR TSTMS LATE THIS AFTERNOON AND EVENING

ACROSS PARTS OF SOUTH CENTRAL KANSAS INTO NORTH CENTRAL OKLAHOMA...

...THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK AREA

ACROSS THE REMAINDER OF CENTRAL AND EASTERN NEBRASKA...WESTERN

IOWA...NORTHWEST MISSOURI...CENTRAL AND EASTERN KANSAS...AND PARTS

OF NORTHERN AND CENTRAL OKLAHOMA...

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MODERATE RISK

AREA ACROSS A LARGE PORTION OF THE CENTRAL AND SOUTHERN PLAINS...

..SYNOPSIS

MODELS ALL INDICATE THAT A STRONG MID/UPPER JET STREAK...NOW DIGGING

INTO THE BASE OF A LARGE-SCALE UPPER TROUGH OVER THE WESTERN

U.S...WILL CONTINUE EASTWARD ACROSS THE SOUTHERN PLATEAU

TODAY...BEFORE NOSING NORTHEASTWARD ACROSS THE SOUTHERN ROCKIES INTO

THE CENTRAL PLAINS BY LATE TONIGHT. THIS IS EXPECTED TO INCLUDE A

90-100+ KT 500 MB JET CORE...WHICH MAY BE PRECEDED BY ANOTHER

SIGNIFICANT SPEED MAXIMUM ACROSS THE SOUTHERN ROCKIES/ CENTRAL

PLAINS REGION DURING THE DAY. GUIDANCE SUGGESTS THAT ASSOCIATED

FORCING WILL CONTRIBUTE TO RAPID INTENSIFICATION OF A SURFACE

CYCLONE TO THE LEE OF THE CENTRAL ROCKIES...WITH A 1000 MB LOW

CENTER DEEPENING BELOW 990 MB ACROSS EASTERN COLORADO INTO SOUTHWEST

NEBRASKA BETWEEN 14/12Z AND 15/00Z. WITHIN ITS WARM SECTOR...A

SOUTHERLY LOW-LEVEL JET WILL STRENGTHEN ACROSS THE SOUTHERN INTO

CENTRAL PLAINS /50+ KT AT 850 MB BY LATE AFTERNOON...INCREASING UP

TO 70 KT DURING THE EVENING/. THIS WILL CONTRIBUTE TO THE

CONTINUING NORTHWARD ADVECTION OF INCREASINGLY RICH MOISTURE

RETURNING OFF THE WESTERN GULF OF MEXICO...BENEATH AT LEAST MODESTLY

STEEP LAPSE RATES. MIXED LAYER CAPE IS EXPECTED TO EXCEED 2000 J/KG

WITHIN A CORRIDOR ACROSS CENTRAL TEXAS THROUGH MUCH OF OKLAHOMA AND

CENTRAL/EASTERN KANSAS...INTO THE VICINITY OF A WARM FRONTAL ZONE

EXTENDING EAST OF THE LOW ACROSS NEBRASKA INTO THE MISSOURI VALLEY.

THIS ENVIRONMENT IS EXPECTED TO BE CONDUCIVE FOR A SIGNIFICANT

OUTBREAK OF SEVERE STORMS...THAT MAY IMPACT PORTIONS OF THE CENTRAL

AND SOUTHERN PLAINS THROUGH MUCH OF THE PERIOD. THIS MAY INCLUDE

SEVERAL TORNADIC SUPERCELLS...AND PERHAPS...BY TONIGHT... THE

EVOLUTION OF A SUBSTANTIAL SQUALL LINE.

..NEBRASKA

NORTH AND EAST OF THE DRY LINE WRAPPING INTO THE DEEPENING SURFACE

CYCLONE...INTO THE VICINITY OF THE WARM FRONT...CONDITIONS APPEAR

LIKELY TO BECOME VERY CONDUCIVE TO THE FORMATION OF DISCRETE

TORNADIC SUPERCELLS...AS THE EXIT REGION OF THE CYCLONIC MID/UPPER

JET OVERSPREADS THE REGION. THIS COULD OCCUR AS EARLY AS

18-21Z...IF NOT BEFORE...ACROSS PARTS OF SOUTHWEST INTO CENTRAL

NEBRASKA...BEFORE DEVELOPING EASTWARD AND INCREASING IN COVERAGE

ACROSS CENTRAL INTO EASTERN NEBRASKA THROUGH THE REMAINDER OF THE

AFTERNOON. THIS IS WHERE LOW-LEVEL HODOGRAPHS ARE EXPECTED TO

BECOME LARGE AND CLOCKWISE CURVED...AND SUPPORTIVE OF LONG-LIVED

SUPERCELLS CAPABLE OF PRODUCING STRONG TORNADOES.

..KANSAS AND OKLAHOMA INTO NORTH CENTRAL/NORTHWEST TEXAS

BARRING COMPLICATIONS FROM RESIDUAL EARLY DAY CONVECTIVE

DEVELOPMENT...THE WARM SECTOR ENVIRONMENT AHEAD OF THE DRY LINE

ACROSS MUCH OF CENTRAL/EASTERN KANSAS AND OKLAHOMA PROBABLY WILL

STILL BE CAPABLE OF SUPPORTING LONG-LIVED SUPERCELLS CAPABLE OF

PRODUCING STRONG TORNADOES. HOWEVER...CONCERN EXISTS THAT THE

POTENTIAL COVERAGE OF DISCRETE SUPERCELL STORMS MAY REMAIN SOMEWHAT

SPARSE...PRIOR TO SQUALL LINE EVOLUTION THIS EVENING AS A COLD FRONT

OVERTAKES THE DRY LINE AND SURGES EASTWARD ACROSS THE PLAINS. ONCE

THIS OCCURS...DAMAGING WIND AND LARGE HAIL MAY BECOME THE PRIMARY

SEVERE THREAT.

..KERR/LEITMAN.. 04/14/2012

[Superstorm93]

45%

[Memphis Weather]

45% tor risk in the north

Nailed it! LOL

Still sounds like SPC very leery of the KS/OK risk. Wondering still if it weren't for the initial Day 2 that it wouldn't be MDT right now...

[Stebo]

I wonder if we will see a rare 60% later today, I think that has only been used once. I think if everything holds suit and any sort of uncertainties are ironed out we will see a 60%.

[andyhb]

Earliest greater than 30% tor probs ever issued now too.

[Superstorm93]

I don't think there's room for a 60% lol

Pretty compact as of now.

[andyhb]

That 45% area is larger in areal coverage than 4/27 or 5/24 of last year.

[hm8]

IIRC the last 60% tor prob was issued when tornadoes were already in progress. To have an actual 60% before initiation would be remarkable. Think about it like this, if you live in an area in a 60% prob area, that means chances are literally better than not that your area (within 25 miles) will be hit by a tornado.

[baroclinic_instability]

I doubt there will be a 60% for tomorrow, but then again I am usually wrong.

[Thundersnow12]

Yeah I doubt we will see a 60% tomorrow, but then again i didn't think we would see a 45% with the first day 1.

[andyhb]

The convection ongoing over the southern part of the risk area doesn't appear to be very restrictive looking (I.E. there's no giant MCS ongoing that could otherwise hamper destabilization later in the day).

[Minnesota Meso]

I think with the next update you will see the northern extent of the tornado risk move slightly to the north. At this time they only have a 2% chance for SW MN, but I think that will increased with the next update to a 15% chance or better. Time will tell.

[Buckeye05]

The convection ongoing over the southern part of the risk area doesn't appear to be very restrictive looking (I.E. there's no giant MCS ongoing that could otherwise hamper destabilization later in the day).

Could produce boundaries though.

[andyhb]

Could produce boundaries though.

I'm fairly sure it will.

[tmagan]

00Z RGEM at tau=24

Helicity

Lifted Index

Dew Point

Wind Shear

[Thundersnow12]

The 4km WRF which is usually a few hours too fast, agrees with the NE play.

[baroclinic_instability]

Pretty stark differerences in the numerical models w.r.t. DMC initiation along I35.

I will say one thing though...GGEM and RGEM have absolutely led the way with this event w.r.t. the general upper level config and cyclogenesis.

[baroclinic_instability]

NAM 4 km simulated IR.

[Thundersnow12]

NAM 4 km simulated IR.

def a few monsters in the southern risk area.

[baroclinic_instability]

def a few monsters in the southern risk area.

Yeah definitely some big boys in there. Going to be an interesting day tomorrow watching all this evolve.

[andyhb]

def a few monsters in the southern risk area.

And some ridiculous looking action in NE and Northern KS.

[David Reimer]

Here I am sitting at the hotel getting ready to hit the sack and I happen to pull up the radar. Notice my SpotterNetwork position on this graphic relative to a well-defined hook echo and a weak, but obvious low level circulation. This was around 1:30 AM CDT. I went outside and observed a decent wall cloud with rapid rising motion then was assaulted by the wet RFD that had fairly good winds. Mind you this is all out my hotel door in my pajamas. Considering the look the El Reno supercell is displaying right now, I think I'm going to wait up and make sure I don't need to take protective action for it.

[Thundersnow12]

Yeah definitely some big boys in there. Going to be an interesting day tomorrow watching all this evolve.

We are leaning to the NE play but it just takes one to go down south.

[Jim Marusak]

to those chasing tomorrow, be safe.

[OHweather]

After looking at models I'm in agreement with the northern high risk area...there will be morning convection to deal with but the warm sector should be capped and convection free south of the warm front, so moderately unstable air should make it into NE although the northern edge of the high risk might be borderline depending on how quickly the ongoing convection and subsequently the warm front can lift north. Left exit portion of 120kt H25 jet steak will move over head by 21z along with nose of 100kt H5 jet streak near dark. Hodos are shown to be very curved with near 90 degrees of turning from the surface through 500mb near the warm front...should see several discrete cells fire capable of long trackers in that environment with 21z-3z likely being the best window given timing of jet streak and likely development of low level inversion after dark. Storms will likely initiate over central NE along dry line and warm front near the triple point and rapidly surge ENE through the warm sector...potentially posing some tornadic threat in southern MN and IA overnight. Given strong LLJ transporting moisture and high theta-e air northward, tornado threat will likely exist as far west as the surface low late afternoon into this evening.

As for farther south, they will be in the right-exit quadrant of the jet streak which will probably limit storm coverage until after midnight when the rest of the jet streak swings overhead and the cold front pushes east. However, capping will erode by mid afternoon and moderate to strong instability will be in place. Modeled negative vertical velocities indicate convection should begin to initiate along the dryline between 18-21z in KS/OK. 50kt low lvl jet which should increase near dark combined with a backed low level flow supporting curved hodos will support supercellls capable of producing tornadoes through the evening. Likely isolated coverage combined with shear vectors running more perpendicular to the dry line should prevent things from quickly going linear until the cold front starts surging eastward. Storm coverage will likely be isolated but a couple-few storms will probably put down decently long tracked tors in northern-central OK into central KS...the high might be borderline there based on lack of coverage but a particularly strong tornado or two may evolve in the southern high risk.

The presence of -VV's should indicate convection firing near dark (if not sooner based on the cooling mid level temps and erosion of the cap several hours prior to dark)

700mb temps...

And this is really impressive turning, especially up in NE:

[tmagan]

KOMA RUC BUFKIT forecast sounding for 23Z April 14^th.

[nwburbschaser]

Just got to Des Moines, and I think Nebraska is my play. I think the Southern target will be a zoo, but I am waiting till about 8 this morning before I commit.

[David Reimer]

BULLETIN - EAS ACTIVATION REQUESTED

TORNADO WARNING

NATIONAL WEATHER SERVICE NORMAN OK

224 AM CDT SAT APR 14 2012

THE NATIONAL WEATHER SERVICE IN NORMAN HAS ISSUED A

* TORNADO WARNING FOR...

EXTREME NORTHWESTERN OKLAHOMA COUNTY IN CENTRAL OKLAHOMA...

EXTREME NORTHEASTERN CANADIAN COUNTY IN CENTRAL OKLAHOMA...

EXTREME SOUTHWESTERN LOGAN COUNTY IN CENTRAL OKLAHOMA...

* UNTIL 300 AM CDT

* AT 222 AM CDT...NATIONAL WEATHER SERVICE METEOROLOGISTS DETECTED

A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS

DANGEROUS STORM WAS LOCATED 1 MILES NORTHEAST OF PIEDMONT...MOVING

NORTHEAST AT 20 MPH.

* THIS TORNADIC THUNDERSTORM WILL REMAIN OVER MAINLY RURAL AREAS

OF EXTREME NORTHWESTERN OKLAHOMA...EXTREME NORTHEASTERN

CANADIAN AND EXTREME SOUTHWESTERN LOGAN COUNTIES

[andyhb]

Impressive meso and reflectivity signature on that cell near Piedmont.

[Stebo]

These 2 cells Near Edmond and NE of Guthrie really getting their act together again, both tornado warned. The one NE of Guthrie has a 80kt GTG at 4000'