SPC 0600Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
0100 AM CDT Thu Apr 08 2021

Valid 091200Z - 101200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR
NORTH-CENTRAL TEXAS EASTWARD INTO NORTHERN LOUISIANA AND
MISSISSIPPI...

...SUMMARY...
Scattered severe thunderstorms are forecast on Friday from parts of
Oklahoma and Texas eastward through the lower Mississippi Valley. 
Large to giant hail is possible across parts of Texas, and a swath
of damaging gusts and several tornadoes are possible from Texas east
into Mississippi.

...Synopsis...
A mid-level low will weaken and meander northward over the western
Great Lakes.  A more potent, upstream mid-level trough will move
from WY southeastward into eastern KS/OK by early Saturday morning. 
A lower-amplitude disturbance in the southern stream will move
eastward from southwest Texas into the lower MS Valley.  In the low
levels, an area of low pressure over western north-central TX will
develop eastward and reach the AR/MS/TN vicinity by daybreak
Saturday.  A dryline will extend southward near the I-35 corridor in
north-central TX.  A residual front will advance northward across
much of AR and western TN.

...Southern Great Plains...
A seasonably moist/unstable airmass sampled by Wednesday evening
raobs along the TX Gulf Coast, and an elevated mixed layer, will
overlap and result in a very unstable airmass developing across TX
east of the dryline with 3000 J/kg MLCAPE forecast.  Rather cold 500
mb temperatures (-15 to -16 deg C) will result in very large CAPE in
the -10 to -30 deg C layer.  A strong capping inversion will weaken
with localized erosion of the cap by the late afternoon via strong
heating, convergence near the dryline, and the aforementioned
disturbance moving east across TX.  Explosive updraft growth is
expected with isolated to widely scattered storms developing from
southern OK southward into east-central TX.  A veering and
increasing wind profile with height will strongly favor discrete
supercells, before additional storm development occurs during the
evening as storms move east into the Arklatex.  In addition to hail
and a tornado risk, the threat for damaging gusts will probably
increase during the evening as this activity moves east into the
Arklatex.  

---model discussion---
The 08/00z and 07/18z NAM runs exhibit a too-cool bias with surface
temperatures east of the dryline across north-central TX (low to mid
70s near DFW metro), specifically near the I-35 corridor.  Moreover,
it is likely strong heating will occur across central and north TX
during the day with temperatures at least 90 F west of the dryline
and into the middle 80s to the east in the warm sector.  As a
result, ARW-based convection-allowing models (based on the parent
ARW model) are likely misrepresenting thunderstorm potential across
TX during the 21z-03z period.  Conversely, the 08/00z and 07/18z GFS
runs are showing excessive boundary-layer mixing and a too-warm bias
across north-central TX with the dryline likely displaced too far
east compared to its likely position near I-35 by late afternoon. 
The 07/12z ECMWF appears superior to the NAM/GFS in this regard with
adequate boundary-layer mixing implied by the warmer surface
temperatures (mid 80s F).  This forecast across the southern Great
Plains coincides with model output similar to the ECWMF in recent
model runs.

...Northern Gulf Coast states...
A complex forecast is seemingly evident for this region and
concerning mainly the after-dark severe threat expected to develop
from LA eastward into MS/AL.  Models indicate a moisture-rich
boundary layer beneath steep lapse rates will be present during the
day.  Despite the presence of a capping inversion, isolated to
widely scattered storms are possible during the day with mainly an
associated hail hazard.  The stronger updrafts may acquire supercell
characteristics with some conditional tornado risk over southern AL.
 However, the primary severe threat will likely develop as the low-
to mid-level wind field strengthens during the evening into the
overnight.  Storms developing within the WAA regime and/or a
thunderstorm cluster growing upscale into an MCS are seemingly the
favored scenarios for storm development.  Severe gusts (some
significant; 65+ kt) and tornadoes will likely become the main
hazards as storms move east across northern LA eastward into MS and
into western AL by early Saturday morning.  

...Southern Appalachian states...
The northeastern periphery of richer low-level moisture (60s F
dewpoints) will probably include GA and perhaps extend northward
into the western Carolinas during the day.  Isolated to widely
scattered multicells are forecast to develop during peak heating
with an isolated hail/wind risk with the stronger storms.  This
activity will likely diminish by early evening.

..Smith.. 04/08/2021

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