- Day Three
acus01 kwns 191252
Storm Prediction Center ac 191251
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0751 am CDT Wed Jun 19 2019
Valid 191300z - 201200z
..there is an enhanced risk of severe thunderstorms
north-Central/Northeast Texas...northwest la...southwest Arkansas...
..there is a slight risk of severe thunderstorms Lee of the Big
Horn Mountains to the Black Hills...
Severe thunderstorms are most likely across north-Central/Northeast
Texas and The Ark-la-tex region during the late afternoon and
evening. Destructive hail and wind, along with a few tornadoes are
..TX to the MS/OH/TN valleys...
Complex forecast with multiple episodes of severe storms anticipated
during the period. Primary changes are to increase damaging wind
(including sig) probabilities for the enhanced slight risk, expand
marginal and slight risk areas in parts of la/MS/TX, and expand
tornado probabilities into the lower/mid-MS valleys. An upgrade to
moderate risk via wind and/or hail may be needed in later outlooks.
A decaying mesoscale convective system is ongoing, recently splitting into two active areas
of convection in the Ozarks and Ark-la-tex. Reintensification is
possible with The Ark-la-tex complex as boundary-layer heating
increases. Even if full decay occurs, redevelopment along remnant
outflows is likely towards midday/early afternoon downstream of both
areas across the lower/mid-MS valleys as the downstream air mass
characterized by upper 60s to mid 70s surface dew points
destabilizes. 25-35 kt 500-mb westerlies will support several
multicell clusters with scattered damaging winds as the primary
hazard this afternoon into the Ohio and Tennessee valleys.
Remnant west/east-oriented outflow boundary in the wake of the
morning mesoscale convective system should drift north across north-Central/Northeast Texas
into perhaps southeast OK by late afternoon. South of this boundary,
intense diabatic heating coupled with a plume of 70s surface dew
points over East Texas will support a strong to extremely unstable air
mass with MLCAPE in excess of 3500 j/kg. By late afternoon, ascent
should increase downstream of a minor mid-level impulse that is
currently approaching from the southern rockies. This should aid in
convective initiation along the outflow boundary, as well as near
the dryline bulge in the Texas Big Country. 40-50 kt effective shear
with pronounced speed shear in the mid to upper-levels will support
a risk for very large hail with initial supercells. This activity
should consolidate into yet another mesoscale convective system during the evening, aided by
a strengthening southwesterly low-level jet, with an increasing
threat for severe wind gusts (a few could be significant given the
large buoyancy). Tornado risk should be maximized during the first
couple hours of supercell formation in a relatively narrow corridor
near the outflow boundary.
Later tonight, this mesoscale convective system may spread east or separate clusters will
develop east as warm advection strengthens eastward into the Tennessee
Valley. An isolated threat for severe hail/wind may persist along
the eastern periphery of the elevated mixed-layer.
Near the confluence of the MS/Ohio rivers, in the wake of early-day
convection, a separate cluster of severe storms may develop towards
early evening. This region will lie south of the primary surface
cyclone that should consolidate and gradually deepen as it tracks
east along the I-70 corridor. If adequate boundary-layer heating can
occur in the absence of substantial overturning from the morning
convective activity, a few supercells are possible with a risk for
..northern Wyoming to western South Dakota...
Have upgraded to slight risk given the potential for a couple
long-track supercells this evening into tonight.
A shortwave trough will amplify from British Columbia across the
northern rockies as a 50-60 kt mid-level jet spreads east across the
northwest. This will strengthen forcing for ascent and yield
sustained thunderstorm development by late afternoon along the Wyoming/Montana
border. While boundary-layer moisture will be limited and the
boundary-layer will not be particularly warm, increasingly elongated
hodographs will favor potential for splitting supercells, a couple
of which could be long tracked. A swath of severe hail with
localized severe wind gusts appears possible.
acus11 kwns 191111
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 191110
Mesoscale discussion 1132
National Weather Service Storm Prediction Center Norman OK
0610 am CDT Wed Jun 19 2019
Areas affected...portions of East Texas into northwestern la
Concerning...severe potential...watch unlikely
Valid 191110z - 191245z
Probability of watch issuance...20 percent
Summary...an ongoing line of storms may pose an isolated
strong/gusty wind threat in the short term. Watch issuance remains
Discussion...two previously separate lines of storms (one from
southern OK and the other from north-central tx) have recently
merged across East Texas. A corresponding increase in radar
reflectivity and cooling cloud tops have recently been noted. Strong
inbound velocities are also present across East Texas along the apex of
this line per kshv radar. These storms are encountering mainly
elevated instability, with MUCAPE likely ranging from 1000-2000 j/kg
from latest mesoanalysis estimates. However, the low-level inversion
across East Texas and northwestern la is likely shallow (about 800-1000
ft agl) based on rap forecast soundings. There is some potential for
strong/gusty downdraft winds to breach the low-level inversion and
reach the surface given the strong velocities occurring on radar.
Observed gusts from various stations have generally ranged from
35-40 kt across East Texas over the past hour or so. But, isolated
strong to perhaps damaging winds could still occur. Watch issuance
remains unlikely in the short term, but convective trends will
continue to be monitored.
..please see www.Spc.NOAA.Gov for graphic product...
Latitude...Lon 32009535 32289490 32709449 32989431 32989339 32839273
31919270 31459326 31329427 31799532 32009535