ACUS01 KWNS 072001

SWODY1

SPC AC 072000



Day 1 Convective Outlook  

NWS Storm Prediction Center Norman OK

0300 PM CDT Sun Jun 07 2026



Valid 072000Z - 081200Z



...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF

SOUTHEASTERN MONTANA...EXTREME NORTHWESTERN SOUTH DAKOTA...WESTERN

AND CENTRAL NORTH DAKOTA,...



...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF

SOUTHWESTERN MISSOURI AND FAR NORTHWESTERN ARKANSAS...



...SUMMARY...

A bow echo with 60-100 mph gusts appears likely over the northern

High Plains into the Dakotas this afternoon, with a few instances of

severe hail and isolated tornadoes also possible. A couple of

tornadoes and isolated damaging gusts are still possible across the

Ozarks region.



...20Z Update...

A Category 4/Moderate Risk was introduced to portions of the

northern High Plains. Confidence is increasing in a well-defined

cold-pool-driven bow echo MCS developing across portions of the

northern High Plains later this afternoon. A potentially dense swath

of 60-100 mph gusts appears likely, and a derecho may occur. Current

observations depict a near stationary surface boundary across far

southeastern MT northeastward into western ND along an elongated

surface trough. High-resolution deterministic and ensemble guidance

(including HREF, REFS, and some of the latest WoFS runs) all depict

a classic bow echo MCS traversing this surface boundary, accompanied

by a widespread severe wind swath and scattered 75+ mph gusts. The

MCS would benefit from localized vorticity along this boundary,

which in turn could support book-end vortices and the subsequent

development and sustenance of a rear-inflow jet, lending

plausibility to the guidance consensus. Latest mesoanalysis also

shows continued eroding MLCINH and 2500+ J/kg MLCAPE in place. Low-

to mid-level lapse rates are already exceeding 8 C/km in some spots,

coinciding with 50-60 kts of sfc-8 km bulk shear oriented normal to

the anticipated bow echo leading line, which is favorable for

derecho development. Alternatively, multiple severe-wind producing

multicellular clusters may occur, which would support higher

coverage of severe winds (with gusts occasionally exceeding 75 mph).





Otherwise, the previous forecast remains on track, with only minor

changes made to thunder and severe probabilities to reflect the

latest observations.



..Squitieri.. 06/07/2026



.PREV DISCUSSION... /ISSUED 1139 AM CDT Sun Jun 07 2026/



...MT/WY/Dakotas...

Water-vapor imagery late this morning shows a strong upper trough

over the northwestern CONUS and it is forecast to pivot eastward

through the northern High Plains through tonight.  Surface

mesoanalysis placed a low near the MT/ND/SD border with a frontal

zone draped southwest to northeast from northeastern WY into far

western ND.  Cyclogenesis and strong heating/moistening of the

boundary layer will favor storm development by mid afternoon in the

vicinity of the Big Horns.  Relatively steep low-level lapse rates

on the immediate cool side of the frontal zone and moderate CAPE

values will support a risk of large hail and severe wind gusts once

storms begin to mature.  A linear cluster is expected to evolve

during the late afternoon into potentially a bow echo during the

early evening with the severe-wind risk notably increasing and

becoming more widespread.  Have increased the intensity highlight

from southeast MT into western portions of ND where it seems

increasingly probable a swath of intense gusts ---possibly a bow

echo--- is progged by a diverse array of different model cores/runs

this morning.  This model signal appears reasonable given the

co-location of surface features, lapse rates, and upper-level

support.  It is within this mesoscale corridor that localized peak

gusts may range 85-100 mph.  Considered an upgrade to Moderate Risk

but will defer to the 20 UTC outlook for additional model run-to-run

continuity and confidence in mesoscale environmental features.  This

activity will sweep northeastward during the evening with a gradual

lessening of the wind/hail hazard towards the early overnight as it

moves east into the eastern half of the Dakotas late.  



...Ozarks...

A weak trough/low over the central US with embedded disturbances

from OK into IA continues to drift northeastward late this

morning.  An associated band of 30-40 knot southwesterly mid-level

winds and deep moisture will lie across the Ozark plateau this

afternoon.  The 12 UTC Springfield, MO raob sampled this belt of

stronger flow with 80-kt at 200 mb.  Heating of a very moist airmass

with some minor enlargement of low-level hodographs may result a few

weak supercells developing coincident with peak heating.  A couple

of brief tornadoes and isolated damaging gusts are possible with

this activity.



...Eastern VA/NC...

A weak surface cold front is sagging southward across central VA

this morning.  A combination of strong heating and frontal forcing

will lead to widely scattered thunderstorms this afternoon across

southeast VA and northeast NC.  The strongest of these cells could

produce gusty winds.



$$