STORM2K

http://www.spc.noaa.gov/products/outlook/day1otlk.html

http://www.spc.noaa.gov/products/outlook/day2otlk.html

Significant severe weather is likely on Thursday from KS into OK

High Risk for Thursday

If you have family and friends in NW OK and S & S Central KS they need to be weather aware which could be the difference between life and death. This is as serious as it gets folks.

The SPC has a very rare High Risk area across NW OK and S & S Central KS. A very dangerous life-threatening event will occur later this afternoon through tonight. I can't remember ever seeing a 30% hatch for tornadoes from the SPC.

I am currently in Wichita, Kansas going to go chase the storms today. I'll try and post photos later

StormingB81 wrote:I am currently in Wichita, Kansas going to go chase the storms today. I'll try and post photos later

Be safe and watch out for stupid drivers. Don't assume people will actually stop at stop signs.

StormingB81 wrote:I am currently in Wichita, Kansas going to go chase the storms today.

I really wish that was outlawed.

A rare high risk right in the heart of tornado alley. I notice the text of the discussion includes a "what could go wrong" section...perhaps since they've been burned so many times this year. These days really quicken the pulse rate. Hopefully everyone stays safe. This is fantastic chase territory so if things go down we should have access to excellent footage.

I've noticed the vast majority of the severe weather and tornado outbreaks have been in the Deep South according to the SPC.

psyclone wrote:A rare high risk right in the heart of tornado alley. I notice the text of the discussion includes a "what could go wrong" section...perhaps since they've been burned so many times this year. These days really quicken the pulse rate. Hopefully everyone stays safe. This is fantastic chase territory so if things go down we should have access to excellent footage.

I think it has more to do with the SPC realizing how many people read their discussions now. It's a communication tool now much like the TC discussions from NHC.

TheStormExpert wrote:I've noticed the vast majority of the severe weather and tornado outbreaks have been in the Deep South according to the SPC.

The best dynamics are lifting north as is typical as we get deep into May. The deep south often finds itself "below the fray" by this time. I recall growing up in northern Ohio, peak severe season was mid May to mid June with organized severe clusters (ridge riders) common through the Summer.

The atmosphere is incredibly unstable and will get more so. Impressive dynamics at play with this event.

EF-5bigj wrote:The atmosphere is incredibly unstable and will get more so. Impressive dynamics at play with this event.

There's no way you can have a huge snow event in the Rockies this late in the year and not pay rent in the plains. I'm expecting serious action but hopeful it will avoid people since there's abundant elbow room in the hot zone.

Not 100% convinced today will be that big of a tornado day. A lot of factors on the table. Wouldn't be surprised if the storm mode goes instantly linear once initiation starts.

HRRR continues to support early and widespread initiation that grows upscale. I'm very skeptical. I think it's eroding the cap too quickly.

From the Norman NWS

DISCUSSION...
Determining exactly when and where storms occur today remains a
challenge. Latest guidance overall has been suggesting an earlier
start for storm initiation with first storms forming across
southwestern Oklahoma and western north Texas around noon.

Overall, based on latest model guidance (particularly the
HRRR/RAP) and incoming data from a special 15 UTC KOUN sounding,
confidence is growing that storms will form earlier and somewhere
over southwestern Oklahoma or western north Texas around noon
today. The 15 UTC KOUN sounding depicted that the base of the low
level inversion has lifted about 40 mb (from around 900 mb to 860
mb) and low level moisture deepening below the inversion. Based on
latest HRRR/RAP guidance, this lifting is expected to continue in
the next few hours, which would allow for storms to form earlier
than previously expected once surface temperatures reach the
lower to mid 80s near or just east of the dryline across
southwestern Oklahoma and western north Texas. A weak mid level
disturbance may be causing the lift, though the exact cause for
the lift remains uncertain.

If these storms form around noon in southwestern Oklahoma and
western north Texas, they may at first be slighlty elevated with
giant hail as the main hazard. However, these storms would likely
become surface-based due to daytime heating no later than 3 pm as
they move northeast. This could increase the tornado potential
across western north Texas, southwestern and central Oklahoma this
afternoon and evening while slightly decrease the tornado
potential in northwestern Oklahoma. Again, the exact details
remain uncertain today.

The bottom line is that the combination of shear, instability,
and moisture support significant severe storms with giant hail
and tornadoes this afternoon and evening somewhere over the
western two thirds of Oklahoma and western north Texas

IMO, very good possibility that early initiation may also hinder the tornadic threat today.

Still see quite a few horizontally propagating gravity waves in SW OK/N TX. Doesn't exactly scream that initiation is imminent. HRRR has well-developed storms in 1 hour.

One of our members, StormingB81 is on a chase team in that area. I know he will give reports.

It doesn't look like it's initiating from what I've seen could be wrong but aren't models trending early convection?

From Norman, OK NWS:

FXUS64 KOUN 181726 AAA
AFDOUN

Area Forecast Discussion...UPDATED
National Weather Service Norman OK
1226 PM CDT Thu May 18 2017

.AVIATION...18/18Z TAF Issuance...
Very complicated aviation forecast today. Confidence is high that
thunderstorms will develop during the period, but there remains
much uncertainty in the timing and location of the initial
development in western Oklahoma and western north Texas.
Therefore, tried to keep the TAFs simple, using TEMPOs for TSRA at
all sites, with prevailing -TSRA during stretches where
confidence is highest. Ceilings and visibilities will likely vary
between MVFR and IFR at sites impacted by thunderstorms during
the period.

Kurtz

&&

.PREV DISCUSSION... /issued 1025 AM CDT Thu May 18 2017/

UPDATE...
Here is a mesoscale update.

DISCUSSION...
Determining exactly when and where storms occur today remains a
challenge. Latest guidance overall has been suggesting an earlier
start for storm initiation with first storms forming across
southwestern Oklahoma and western north Texas around noon.

Overall, based on latest model guidance (particularly the
HRRR/RAP) and incoming data from a special 15 UTC KOUN sounding,
confidence is growing that storms will form earlier and somewhere
over southwestern Oklahoma or western north Texas around noon
today. The 15 UTC KOUN sounding depicted that the base of the low
level inversion has lifted about 40 mb (from around 900 mb to 860
mb) and low level moisture deepening below the inversion. Based on
latest HRRR/RAP guidance, this lifting is expected to continue in
the next few hours, which would allow for storms to form earlier
than previously expected once surface temperatures reach the
lower to mid 80s near or just east of the dryline across
southwestern Oklahoma and western north Texas. A weak mid level
disturbance may be causing the lift, though the exact cause for
the lift remains uncertain.

If these storms form around noon in southwestern Oklahoma and
western north Texas, they may at first be slighlty elevated with
giant hail as the main hazard. However, these storms would likely
become surface-based due to daytime heating no later than 3 pm as
they move northeast. This could increase the tornado potential
across western north Texas, southwestern and central Oklahoma this
afternoon and evening while slightly decrease the tornado
potential in northwestern Oklahoma. Again, the exact details
remain uncertain today.

The bottom line is that the combination of shear, instability,
and moisture support significant severe storms with giant hail
and tornadoes this afternoon and evening somewhere over the
western two thirds of Oklahoma and western north Texas.

MBS

PREV DISCUSSION... /issued 639 AM CDT Thu May 18 2017/

DISCUSSION...
The 12Z aviation discussion follows....

AVIATION...
A large, powerful storm system will move through the southern
Plains today and tomorrow. A jagged deck of stratus will cover
much of central and eastern Oklahoma (also the Wichita Falls area
in Texas) this morning, then break up toward 18Z. Intense/severe
thunderstorms are forecast to develop quickly during the early
afternoon, probably between 19Z and 20Z, across western Oklahoma
and adjacent parts of Texas. The initial storms will mainly affect
KLAW, KCSM, KHBR, and KSPS, then spread/move east/northeast with
time. Then, a cold front will enter northern Oklahoma around
sunrise on Friday, bringing a minor wind shift and possibly some
very low stratus to far northern Oklahoma. At the same time, a
renewed deck of stratus will be advancing north across the Red
River.

CmS

PREV DISCUSSION... /issued 342 AM CDT Thu May 18 2017/

DISCUSSION...
The second shortwave trough in this week`s series is rounding the
base of the longwave trough, and is now centered near Salt Lake
City, Utah. At the same time, a surge in low-level moisture is
advancing quickly north across Oklahoma. High dewpoint
temperatures have extended to Ponca City, Oklahoma City, and
Lawton, and this humidification will extend across most of the
remainder of Oklahoma (and western north Texas) by this
afternoon.

The HRRRX model has been fairly consistent in breaking out the
initial convection early this afternoon over Texas, in the general
vicinity of Abilene, then spreading/expanding this area rapidly
north through the afternoon. In a general sense, this is probably
what will happen. Supercell thunderstorms are likely within the
expected environment, and the SPC has issued a "High Risk" of
severe storms for today for much of the northwest quadrant of
Oklahoma, with lesser risk areas covering the remainder of our
forecast area.

A cold front will move into northern Oklahoma on Friday, and by
evening, it should be near I-44. This will limit the risk of
severe storms to the north, but along and south of the front,
there will again be a risk of severe storms. There is more
question about what will happen tomorrow, since lingering early-
morning convection will alter the environment in unpredictable
ways.

Rainfall tomorrow may be quite heavy near the front. There is
still some uncertainty where the heaviest rain may fall, and
whether it will be enough to cause more than localized flooding,
so there is not yet justification for a flood watch. Nevertheless,
some urban and small stream flooding seems likely, if the expected
scenario is correct.

The front will continue its advance on Saturday and Sunday, as
rain/storm chances slowly diminish from the northwest. This will
bring a relatively quiet period for most of the weekend and into
early next week. Another wave sweeping south across the Plains
will, however, bring another chance of showers and thunderstorms
(with a lower risk of severe storms) for Tuesday and parts of
surrounding days.

&&

.PRELIMINARY POINT TEMPS/POPS...
Oklahoma City OK 66 78 58 70 / 60 80 90 20
Hobart OK 65 82 55 71 / 50 70 70 20
Wichita Falls TX 69 84 61 73 / 40 70 80 40
Gage OK 57 79 48 70 / 60 40 30 10
Ponca City OK 65 78 56 70 / 70 70 80 30
Durant OK 69 83 66 76 / 40 40 70 60

&&

.OUN WATCHES/WARNINGS/ADVISORIES...
OK...Flood Watch from 7 PM CDT this evening through Saturday morning
for OKZ005>048-050>052.

TX...Flood Watch from 7 PM CDT this evening through Saturday morning
for TXZ083>090.

&&

$$

17/25/04

PDS tornado watching coming soon.