Storm Prediction Center Forecast


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SPC - No watches are valid as of Mon Mar 30 13:40:01 UTC 2020

No watches are valid as of Mon Mar 30 13:40:01 UTC 2020.


SPC - No MDs are in effect as of Mon Mar 30 13:40:01 UTC 2020

No Mesoscale Discussions are in effect as of Mon Mar 30 13:40:01 UTC 2020.


SPC Mar 30, 2020 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook
      
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0749 AM CDT Mon Mar 30 2020

Valid 301300Z - 311200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
SOUTHERN HIGH PLAINS...AND FROM EAST TEXAS TO PARTS OF WEST-CENTRAL
MISSISSIPPI....

...SUMMARY...
Severe hail and wind are possible over parts of the southern High
Plains this afternoon and early evening.  This afternoon through
tonight, a few severe storms may affect a corridor from east-central
Texas into a portion of the lower Mississippi Valley.

...Synopsis...
A progressive upper-air pattern over the CONUS will feature three
predominant perturbations:
1.  The long-lived, but filling cyclone now centered over southern
ON, and forecast to move eastward across New England and over
adjoining Atlantic waters by 12Z tomorrow.
2.  A vigorous, southern-stream trough -- apparent in moisture
channel imagery over eastern portions of AZ/UT.  This feature will
move quickly, reaching the southern/central High Plains around 00Z,
and the Ozarks/Arklatex regions by 12Z.
3.  An elongated synoptic cyclone now moving southeastward offshore
from the Alaska Panhandle and BC coast, with a strong, basal
shortwave trough crossing coastal WA.  The shortwave trough will
cross the interior Northwest today and northern Rockies tonight,
while the bulk of the cyclone shifts inland across central/southern
BC and the Northwest overnight.

At the surface, a cold front related to the northeastern cyclone was
analyzed at 11Z offshore from the Carolinas, becoming
quasistationary across the FL/GA line and extreme southeastern LA,
across the middle TX Coast and over deep south TX.  This boundary
will shift northward over central/east TX and central/northern LA
today, and into central MS tonight.  Secondary/precip-reinforced
frontogenesis is expected from northwest-southeast today across
southwestern KS portions of the OK/TX Panhandles, to parts of
northwest and central TX, linking with the western limb of the
returning synoptic front over north TX this evening or tonight.  A
dryline should develop today as moisture returns inland, becoming
best-defined around 00Z into the evening from a frontal intersection
over northwest TX southward to near DRT.

...Southern High Plains...
Widely scattered to scattered thunderstorms are expected to develop
this afternoon, both in a roughly north-south corridor of
destabilization from extreme southeastern CO and southwestern KS
into the northern TX Panhandle, and in the low-level frontal zone
extending southeastward from there.  Damaging gusts and large hail
are the main concerns.  Storm motion will be variable:  at first
more northeastward as frontal convection moves over the
northeastward-tilted baroclinic zone (ahead of the upper trough),
then eastward or even southeastward as the trough itself draws
close.  The main damaging-wind threat should exist with convection
near the trough that can aggregate its outflow and push into
surface-based air (or nearly so), perhaps as far as western OK. 

As the trough approaches, the combination of very strong cooling/
DCVA aloft and a corridor of boundary-layer warming will contribute
to quick lower/mid-tropospheric destabilization this afternoon. 
Very steep lapse rates -- at times nearing dry-adiabatic from
surface to 500 mb -- will be accompanied by just enough low-level
moisture for thunderstorms.  Forecast soundings accordingly depict a
narrow plume of well-mixed, surface based parcels, underlying 500-
1000 J/kg MLCAPE -- just ahead of the convection, and near the
northwestern frontal limb.  Effective shear and SRH also will vary
widely over short distances due to the influences of the frontal
zone and quickly evolving flow geometry aloft.  Still, supercells
are possible for related storm-dynamics enhancement of hail size
locally.  The overall severe threat should diminish from west to
east this evening, although isolated hail will be possible into
tonight.

...East-central TX to parts of Delta region...
Convection will become more widespread along and north of the warm
front through the period, as strengthening large-scale ascent (warm
advection area-wide and DCVA in western parts late) overspread the
region, with destabilization aloft.  The most intense cores north of
the front could yield isolated marginal to subsevere hail, while the
gust potential will reside mainly in the near-surface frontal zone
southward over the adjoining warm sector.  Given the  intensifying
flow aloft, and related increase in deep shear, supercells are
possible, along with multicell convection, including organized
clusters and bowing segments.  As such, a tornado cannot be ruled
out, especially along and just south of the front, though
potentially messy mode and weak lapse rates will limit buoyancy
substantially.  Even in the warm sector, MLCAPE should be only
around 500 J/kg east of the Sabine River.

The severe threat is expected to be constrained:
1.  With northward extent by increasingly stable, less-buoyant air
north of the frontal zone, and
2.  With southward extent by weaker lift/convergence in the warm
sector, and the somewhat related issue of gradual storm maturation
as cells get closer to the frontal convergence max.
3.  Somewhat on the west side, as low-level streamline forecasts and
corresponding UVV progs suggest a zone of enhanced low-level
convergence will form in the warm sector over east TX and act as a
preferential convective genesis zone, in addition to the front
itself.  
The maximized outlook probabilities reflect these limits, with the
eastern extent representing a probable range of surface-based
strong-severe convective potential around the end of the period.

..Edwards/Mosier.. 03/30/2020

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