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Bevo
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New Day 1 Outlook is out (8 AM CST/9 AM EST)
The major update to this outlook is to remove the 10% hatched tornado risk across N.TX and OK. Let's hope it stays that way! (sorry chasers)
The second big adjustment to the new outlook is to expand and enhance the sig.severe hail threat. It now encompasses a much wider area, which reflects the more widespread hail sizes on the model soundings.
Wind risk is like "hey guys I'm still here"
SPC AC 221253
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0753 AM CDT Fri May 22 2020
Valid 221300Z - 231200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PORTIONS
OF NORTH-CENTRAL/NORTHEAST TEXAS AND SOUTHEASTERN OKLAHOMA...
...SUMMARY...
Severe storms are expected today from north Texas into the Ozarks.
...Synopsis...
In mid/upper levels, a longwave trough will persist over the western
CONUS, while a blocking pattern breaks down in the East. The latter
will be related to height falls across the Great Plains states,
shifting to the Mississippi Valley, contributing to the
northeastward ejection of a formerly cut-off low now near CVG. The
associated cyclone will fill gradually as it moves northeastward up
the Ohio valley, past PIT around 06Z, then eastward over the
southern PA/MD area.
To the west, as a cyclone over central AB weakens and shifts
northeastward, a strong shortwave trough now over the interior
Northwest will dig east-southeastward. This perturbation should
become a closed cyclone over southern ID and northwestern UT around
the end of the period. A shortwave trough -- now evident in
moisture-channel imagery over the central/southern High Plains --
will move east-northeastward across KS and northern OK, phasing with
MCVs produced by an ongoing MCS over portions of OK/KS. The
combined perturbation may develop a closed 500-mb low over IA by 12Z
tomorrow.
At the surface, a low was analyzed over sotuhern VA, with weak,
slow-moving cold front over eastern NC and coastal SC, becoming
quasistationary over central GA. This part of the boundary should
become more diffuse and retreat northward over GA and the Carolinas
through the day. The warm-frontal segment -- analyzed across
central AL, northern MS, southern AR and eastern OK, will be
overtaken over much of its OK extent (and perhaps some of AR) by an
extensive outflow boundary from an MCS now mostly covering southern/
eastern OK. A dryline -- analyzed initially from the TX Big Bend
region north-northeastward to just west of CDS, will mix eastward
today to parts of northwest/west-central TX, to northern Coahuila.
The dryline and outflow boundary may intersect this afternoon near
the Red River over northwest TX.
...North TX/Arklatex/Ozarks...
Except for an initially separate multicellular cluster over south-
central OK, near its southern flank, an extensive MCS that has
produced several measured severe gusts in central/northern OK
appears to be undergoing a general weakening trend while moving
east-southeastward astride the warm-frontal zone. See SPC watch 201
and related mesoscale discussions for near-term details.
The major influence on the convective/severe potential today will be
the MCS' outflow boundary. This complex has progressed farther/
faster than indicated by most progs used for the previous outlook
cycle, and it still bears a substantial pressure/theta-e
perturbation. This introduces more uncertainty regarding the
ultimate stalling position of the boundary, and therefore associated
severe probabilities, which still may need more shifting as
mesoscale trends warrant. Nonetheless, the boundary still should
focus the bulk of afternoon severe convective development, even if
more likely farther south near the Red River in north TX and
southeastern OK. This repositioning would displace the most robust
convection farther from stronger midlevel westerlies related to the
shortwave trough, in turn marginalizing deep shear somewhat.
Scattered thunderstorms are expected to form this afternoon along
the boundary, perhaps very rapidly, given the strong instability
expected on its south side. Convection should be isolated to widely
scattered farther southwest near the dryline. The moist sector
across southern OK, north-central/northeast TX, and AR south of the
warm front will be characterized largely by surface dew points in
the upper 60s to low 70s F. Where these preconvective conditions
persist, steep midlevel lapse rates and a deep troposphere will
contribute to peak afternoon MLCAPE in the 3500-4500 J/kg, locally
higher. The thermodynamic profiles favoring very intense updrafts,
combined with effective-shear magnitudes around 30-35 kt and
localized boundary-layer vorticity enhancement along the boundary,
indicate a mix of multicell and heavy-precip supercell modes, with
at least broken quasi-linear clustering ultimately occurring. Until
the mode gets too messy, considerable hail is likely, some of it
significant/ destructive in nature, along with severe gusts.
Storm-scale and boundary interactions still support a threat for a
few tornadoes as well. Isolated severe hail and gusts also will be
possible from convection near the dryline.
Pockets of somewhat drier and more readily mixed, lower-buoyancy air
may linger over portions of southern OK and western north TX,
advected from a convectively processed air mass now southwest
through west of the Metroplex, where mid-50s to low-60s F surface
dew points have been observed for a few hours. If maintained, this
air mass may affect severe potential over parts of northwest/north-
central TX, by making convection more high-based and outflow-
dominant.
...GA/Carolinas/eastern TN...
Isolated severe gusts and hail are possible across the outlook area
through this afternoon. An MCV and associated midlevel shortwave
trough -- currently associated with nonsevere convection across
portions of the Mid-South region into northern AL and mid TN, will
move eastward today. The associated field of large-scale ascent
will impinge on a boundary layer that will be destabilizing from
south-north across the outlook area, from a combination of diabatic
heating and theta-e advection. Scattered thunderstorms should move
eastward from the higher terrain of southeastern TN/northern GA,
into an airmass with around 1000-1500 J/kg MLCAPE. Additional
development may occur in a weakly capped warm sector over southern
parts of the outlook area. Deep shear should increase as the
mid/upper low pivots northeastward and the MCV/shortwave approaches,
with effective-shear magnitudes in the 30-40 kt range. A mix of
multicell and at least isolated supercell modes are possible.
..Edwards/Smith.. 05/22/2020
The major update to this outlook is to remove the 10% hatched tornado risk across N.TX and OK. Let's hope it stays that way! (sorry chasers)
The second big adjustment to the new outlook is to expand and enhance the sig.severe hail threat. It now encompasses a much wider area, which reflects the more widespread hail sizes on the model soundings.
Wind risk is like "hey guys I'm still here"