807
ACUS01 KWNS 200601
SWODY1
SPC AC 200600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT FRI JUN 20 2025
VALID 201200Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY...
..SUMMARY
SEVERE THUNDERSTORMS ARE LIKELY THIS AFTERNOON INTO TONIGHT FROM FAR
EASTERN MONTANA EASTWARD ACROSS THE NORTHERN PLAINS AND INTO THE
UPPER MISSISSIPPI VALLEY. TORNADOES, WITH ONE OR TWO POTENTIALLY
STRONG, WINDS GREATER THAN 75 MPH, AND HAILSTONES GREATER THAN 2
INCHES IN DIAMETER WILL BE POSSIBLE. MARGINALLY SEVERE STORMS WILL
ALSO BE POSSIBLE ACROSS PARTS OF THE NORTHEAST NEW MEXICO AND
SOUTHEAST COLORADO.
..NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY
A MID-LEVEL SHORTWAVE RIDGE WILL MOVE EASTWARD TODAY FROM THE
NORTHERN PLAINS INTO THE UPPER MISSISSIPPI VALLEY. IN THE WAKE OF
THE RIDGE, A SHORTWAVE TROUGH WILL MOVE QUICKLY EAST-NORTHEASTWARD
ACROSS THE NORTHERN PLAINS. AT THE SURFACE, A LOW WILL DEEPEN OVER
NORTHWESTERN SOUTH DAKOTA. TO THE NORTH AND NORTHEAST OF THE LOW, AN
EAST-TO-WEST AXIS OF LOW-LEVEL MOISTURE WILL TAKE SHAPE BY
AFTERNOON, ALONG WHICH SURFACE DEWPOINTS WILL BE IN THE LOWER TO MID
70S F. IN RESPONSE TO SURFACE HEATING, MODERATE TO STRONG
INSTABILITY IS EXPECTED TO DEVELOP ACROSS MUCH OF THE NORTHERN
PLAINS BY AFTERNOON. CONVECTION IS FIRST EXPECTED TO INITIATE IN FAR
EASTERN MONTANA LATE THIS AFTERNOON. FROM THIS CONVECTION,
THUNDERSTORMS ARE FORECAST TO RAPIDLY GROW UPSCALE INTO A
FAST-MOVING LINEAR MCS, WITH THE TRACK OF THE MCS MOVING EASTWARD
ALONG A SHARP GRADIENT OF INSTABILITY.
RAP LATE AFTERNOON FORECAST SOUNDINGS ALONG THE PROJECTED TRACK OF
THE MCS IN SOUTHEASTERN NORTH DAKOTA HAVE MLCAPE AROUND 4500 J/KG,
WITH 0-6 KM SHEAR NEAR 60 KNOTS. LAPSE RATES ARE FORECAST TO BE NEAR
8 C/KM, AND 0-3 KM STORM RELATIVE HELICITY IS FORECAST TO BE BETWEEN
350 AND 400 M2/S2. THIS ENVIRONMENT SHOULD BE FAVORABLE FOR ALL
HAZARDS, INCLUDING TORNADOES, LARGE HAIL AND WIND DAMAGE. TORNADOES
WILL BE MOST LIKELY WITH SUPERCELLS AND ALONG THE LEADING EDGE OF
BOWING SEGMENTS. A STRONG TORNADO OR TWO WILL BE POSSIBLE. THE MORE
DOMINANT SUPERCELLS WILL ALSO BE CAPABLE OF PRODUCING HAILSTONES
GREATER THAN 2 INCHES IN DIAMETER. A WIND-DAMAGE THREAT SHOULD EXIST
ALONG THE ENTIRE NORTH-SOUTH LENGTH OF THE MCS, WITH A FEW GUSTS
OVER 75 MPH POSSIBLE. THE SEVERE THREAT IS EXPECTED TO CONTINUE
THROUGH THIS EVENING AND INTO THE OVERNIGHT PERIOD AS THE MCS TRACKS
EASTWARD INTO THE UPPER MISSISSIPPI VALLEY.
FURTHER SOUTHWARD ACROSS MUCH OF THE UPPER MIDWEST, A FEW
WARM-ADVECTION-RELATED THUNDERSTORMS WILL BE POSSIBLE EARLY IN THE
DAY. ALTHOUGH THESE CELLS MAY BE ELEVATED, A MARGINAL SEVERE THREAT
WILL BE POSSIBLE, WITH A POTENTIAL FOR ISOLATED SEVERE GUSTS AND
HAIL.
..NORTHEAST NEW MEXICO/SOUTHEAST COLORADO
SOUTHWEST MID-LEVEL FLOW WILL BECOME ESTABLISHED ACROSS THE SOUTHERN
AND CENTRAL ROCKIES TODAY. AS SURFACE TEMPERATURES WARM, ISOLATED TO
SCATTERED THUNDERSTORMS ARE EXPECTED TO DEVELOP IN THE HIGHER
TERRAIN. THESE STORMS WILL MOVE INTO THE LOWER ELEVATIONS LATE THIS
AFTERNOON INTO THIS EVENING. ALTHOUGH INSTABILITY WILL BE WEAK,
LOW-LEVEL LAPSE RATES WILL BE VERY STEEP, AROUND 9.5 C/KM IN SOME
AREAS. THIS COULD BE ENOUGH FOR ISOLATED SEVERE GUSTS, ASSOCIATED
WITH LOW-PRECIPITATION CELLS.
..BROYLES/MOORE.. 06/20/2025
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