May 2024 - General Weather Discussion

[jn1780]

I think confidence is pretty high from Norman up into Kansas that the cap will break hence the High risk being issued. NWS Norman page currently has a graphic with a note saying that strong tracked tornados could occur in any risk area.

Also, the most southern storm that successfully breaks the cap could potentially be the worse since it won't be choked off from a storm to its south.

[John1744]

When’s the next SPC guidance? 11ish CST?

[FighttheGoodFight]

When’s the next SPC guidance? 11ish CST?

11:30am then 3pm I believe.

[kukblue1]

Still only 68 outside as of 10am HUM

[jn1780]

https://twitter.com/NWSNorman/status...08862515613976

They are not expecting clouds or cap to prevent storm development this afternoon or evening.

[NikonNurse]

Satellite shows a line of mostly clearing just west of okc. Then a fast moving line of heavy clouds than NONE.

Am I looking at this correctly?

[C_M_25]

Yeah starting to wonder about the cap breaking myself. Heavy cloud cover and cool. I know the parameters are such that it shouldn’t matter, but I feel like heavy cloud cover and cool temperatures reduces the risk more often than not. I dunno. Still lots of time for the clouds to clear out.

[SoonerDave]

Yeah starting to wonder about the cap breaking myself. Heavy cloud cover and cool. I know the parameters are such that it shouldn’t matter, but I feel like heavy cloud cover and cool temperatures reduces the risk more often than not. I dunno. Still lots of time for the clouds to clear out.

The language in the forecast seems to mitigate the highest end development in SW OK because the forcing isn't as substantial. I think that's why there's so much emphasis or discussion about the I-40 corridor. That informally seems to be a very rough and by no means carved in stone boundary between the "highest" risk area and the "less highest risk" area, if that makes sense.

[OKCMallen]

[SEMIweather]

Satellite shows a line of mostly clearing just west of okc. Then a fast moving line of heavy clouds than NONE.

Am I looking at this correctly?

Looking at satellite imagery, I see mostly cloudy skies as far west as the easternmost tier of counties in the Texas Panhandle at the moment, with the clearing line moving east (however, the dryline isn’t far behind). That being said, would expect the low clouds to slowly decrease in coverage as the day goes on (you can already see this happening if you loop the satellite for a couple of hours).

[FighttheGoodFight]

SPC at 11:00am

...NE/KS/OK to north TX...
Water-vapor imagery late this morning shows a potent mid- to
upper-level trough/low over the central Rockies with a speed max
moving through the base of the trough and into the southern and
central High Plains. This negatively tilted mid level trough will
continue northeast to near the Black Hills by this evening while its
southern portion overspreads the KS/OK corridor. The 12z Amarillo,
TX raob showed the leading edge of stronger 700-600 mb southwesterly
flow nosing eastward into the High Plains. A cyclone near the NE
Panhandle this morning will deepen as it moves north-northeast to
the SD/ND border early Tuesday morning. An associated Pacific front
will push east into the High Plains and overtake the northern
portion of the dryline across parts of the central High Plains this
afternoon into this evening. Farther south, a dryline will mix east
into western OK by late this afternoon with a broad moist/unstable
warm sector across the southern Great Plains and becoming
increasingly pinched in spatial width farther north into the
north-central Great Plains. An attendant warm front will advance
northward from OK into the lower MO Valley by early evening and
later into the mid MS Valley.

Visible satellite imagery shows considerable low stratus and
stratocumulus from north TX into the central Great Plains. The 12z
Fort Worth, TX raob sampled the richer low-level moisture (15 g/kg
lowest 100mb mean mixing ratio) compared to areas farther north.
Surface analysis late this morning shows rapid northward transport
of moisture into OK with 65-70 deg F dewpoints advecting northward
through OK to the KS border. This plume of richer moisture will
continue northward today beneath an EML and lead to moderate
destabilization over NE with a very to extremely unstable airmass
forecast to develop farther south over the southern half of KS into
OK and adjacent north TX.

Initial thunderstorm development is likely as the upper forcing
impinges on the northwestern periphery of the moist/unstable sector
across the central High Plains (western KS/NE) and northward into SD
with time. Steep 700-500 mb lapse rates and strengthening flow
becoming more meridional with time will favor organized storms,
including supercells and bands of storms with an associated isolated
to scattered risk for hail/wind and perhaps a few tornadoes.
Farther south, the erosion of the cap is expected initially over the
KS portion of the dryline and perhaps into northwest OK by the mid
afternoon. Strengthening flow through the column combined with
strong to extreme buoyancy (2500-4500 J/kg MLCAPE) --from I-70 in
central KS to I-40 in central OK-- will strongly favor supercell
development. Strong upper-level diffluence across the central Great
Plains and intensifying southwesterly to westerly 250-mb flow, which
will result in very long hodographs, will strongly favor discrete
storm modes, at least initially. Large to giant hail (3-4 inches in
diameter) is possible with the more robust supercells. The LLJ is
forecast to be strongest over KS northward into the north-central
Plains through 21z. During the 21-00z timeframe, the flow
associated with the LLJ will strengthen over OK acting to enlarge
hodographs. Climatologically large combinations of deep-layer
shear, buoyancy, and SRH will result in extreme values of composite
indices (STP 6-12) during the 22z-06z timeframe across the Moderate
to High Risks. Several discrete supercells are expected to traverse
across a large portion of the Moderate and High-Risk equivalent
tornado probabilities. Tornadoes, some of which can be intense
(EF3+), are forecast late this afternoon and well into the evening.
Some model guidance shows regenerative supercell development across
central OK this evening. Have extended the High Risk slightly
farther south to account for this possibility.

[kukblue1]

Yeah starting to wonder about the cap breaking myself. Heavy cloud cover and cool. I know the parameters are such that it shouldn’t matter, but I feel like heavy cloud cover and cool temperatures reduces the risk more often than not. I dunno. Still lots of time for the clouds to clear out.

Clouds are starting to thin. NWS brought this up also Visible satellite imagery shows considerable low stratus and
stratocumulus from north TX into the central Great Plains. The 12z
Fort Worth, TX raob sampled the richer low-level moisture (15 g/kg
lowest 100mb mean mixing ratio) compared to areas farther north.
Surface analysis late this morning shows rapid northward transport
of moisture into OK with 65-70 deg F dewpoints advecting northward
through OK to the KS border. This plume of richer moisture will
continue northward today beneath an EML and lead to moderate
destabilization over NE with a very to extremely unstable airmass
forecast to develop farther south over the southern half of KS into
OK and adjacent north TX.

First tornado watch for Nebraska/Kansas about ready to be issued. 11:15 central

[bison34]

Is OKC likely to even see rain or hail from this? I've mostly seen this as a northern and NW Oklahoma storm. Has it shifted at all?

[Bunty]

Yeah starting to wonder about the cap breaking myself. Heavy cloud cover and cool. I know the parameters are such that it shouldn’t matter, but I feel like heavy cloud cover and cool temperatures reduces the risk more often than not. I dunno. Still lots of time for the clouds to clear out.

Hopefully day staying cloudy means smaller risk for F4 or 5 tornadoes and baseball sized hail. But a F3 tornado is plenty bad.

[OKCMallen]

Is OKC likely to even see rain or hail from this? I've mostly seen this as a northern and NW Oklahoma storm. Has it shifted at all?

Certainly appears so. Worst tornado threat is to the NW of OKC, but the metro will be dodging supercells all night, I think.

[OKCMallen]

Hopefully day staying cloudy means smaller risk for F4 or 5 tornadoes and baseball sized hail. But a F3 tornado is plenty bad.

Right as you all were discussing, it got notably brighter downtown, even through the clouds.

[Zuplar]

I've noticed in the past 10 minutes it getting sunnier outside my location in Southwest OKC.

[jn1780]

Is OKC likely to even see rain or hail from this? I've mostly seen this as a northern and NW Oklahoma storm. Has it shifted at all?

Risk is still there. They just talk about Northern Oklahoma because that will initiate first.

Edit: They actually expanded high risk further south and east in the 11:30 outlook.

[SoonerDave]

Risk is still there. They just talk about Northern Oklahoma because that will initiate first.

Edit: They actually expanded high risk further south and east in the 11:30 outlook.

Part of me wonders if they opted to expand that at least in part because not including Norman in an area affecting/including the Metro might be drawing too fine a line of distinction. I know they also made reference to some other model guidance about other initiation later.

[PoliSciGuy]

PDS Tornado watch coming this afternoon https://x.com/NWSSPC/status/1787524998804164785

[okatty]

Oklahoma County Courthouse closing at 2 PM today which is pretty unusual.

[PoliSciGuy]

NWS Norman issued a pre-emptive EMS activation. Never seen that before:

https://mesonet.agron.iastate.edu/wx...e=202405061658

[SoonerDave]

School districts across the region are announcing early closures and/or canx of all pm activities. Some schools are allowing teachers who live outside their district to leave early. Ugh.

[jn1780]

Part of me wonders if they opted to expand that at least in part because not including Norman in an area affecting/including the Metro might be drawing too fine a line of distinction. I know they also made reference to some other model guidance about other initiation later.

Maybe, I think its a good call and would cause too much splitting of hairs to not. There has a been a couple of models showing the worse storm pretty near the metro. Just a little bit further south and a storm pretty much guaranteed to be a right turner would put Norman in the cross hairs.

[yukong]

The state has ordered non-essential offices and services to close at 4.