180
ACUS01 KWNS 180536
SWODY1
SPC AC 180535
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1235 AM CDT FRI APR 18 2025
VALID 181200Z - 191200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN
PLAINS TO THE GREAT LAKES...
..SUMMARY
SCATTERED SEVERE THUNDERSTORMS ARE POSSIBLE FROM PARTS OF THE
SOUTHERN PLAINS NORTHEASTWARD TOWARD THE UPPER GREAT LAKES FROM LATE
AFTERNOON INTO EARLY SATURDAY MORNING. LARGE HAIL AND ISOLATED
SEVERE GUSTS WILL BE THE MAIN HAZARDS, ESPECIALLY ACROSS THE
SOUTHERN PLAINS WHERE STORMS WILL BE MORE CONCENTRATED.
..DISCUSSION
STRONG 500MB SPEED MAX IS CURRENTLY DIGGING SOUTH ACROSS THE
NORTHERN INTER-MOUNTAIN REGION. THIS FEATURE WILL ENCOURAGE A
PRONOUNCED UPPER TROUGH TO EVOLVE OVER THE SOUTHWESTERN U.S. BY THE
END OF THE PERIOD. A BROAD ZONE OF STRONG MID-LEVEL FLOW WILL EXTEND
ACROSS NORTHERN MEXICO-SOUTHERN PLAINS-GREAT LAKES AS HEIGHT FALLS
GRADUALLY SPREAD INTO THIS CORRIDOR OF THE CONUS. AS THIS TROUGH
DEEPENS INTO LOWER LATITUDES, SURFACE PRESSURES WILL RISE IN THE LEE
OF THE ROCKIES OVER THE PLAINS, AND A SHARP COLD FONT WILL SURGE
INTO WESTERN IA-SOUTHERN KS-OK PANHANDLE BY THE START OF THE PERIOD.
THIS BOUNDARY WILL LIKELY SERVE AS A FOCUS FOR ROBUST CONVECTION
THROUGH THE PERIOD, AND IT SHOULD EXTEND FROM EASTERN WI-WESTERN
MO-NORTHERN TX PANHANDLE BY EARLY EVENING.
LATEST MODEL GUIDANCE DOES NOT ALLOW THE UPPER MIDWEST/GREAT LAKES
REGION TO DESTABILIZE APPRECIABLY AS BUOYANCY WILL BE SOMEWHAT
LIMITED ACROSS THIS REGION. EVEN SO, STRONG FLOW/SHEAR WARRANT SOME
CONCERN FOR CONVECTIVE ORGANIZATION, AND SOME RISK FOR WIND/HAIL
WILL ACCOMPANY FRONTAL/PRE-FRONTAL STORMS AS THE BOUNDARY ADVANCES
EAST THROUGH THE PERIOD.
OF MORE CONCERN IS THE AIR MASS ACROSS THE SOUTHERN PLAINS. STRONG
BOUNDARY-LAYER HEATING IS EXPECTED ACROSS THE HIGH PLAINS FROM
EASTERN NM INTO NORTHWEST TX, JUST SOUTH OF THE FRONT. THE NORTHEAST
EXTENT OF THIS STEEP LOW-LEVEL LAPSE RATE PLUME WILL LIKELY EXTEND
INTO CENTRAL OK. LATEST MODEL GUIDANCE SUGGESTS STRONG SBCAPE WILL
EVOLVE EAST OF THE DRYLINE, AND SOUTH OF THE FRONT. AS TEMPERATURES
WARM THROUGH THE MID 80S CONVECTIVE TEMPERATURES WILL BE BREACHED
ALONG THE DRYLINE, LIKELY BY 21Z. FORECAST SOUNDINGS SUPPORT THIS
AND SUPERCELLS ARE EXPECTED. THIS ACTIVITY SHOULD GROW UPSCALE AND
SPREAD NORTHEAST ALONG THE FRONTAL ZONE. A CONSIDERABLY AMOUNT OF
POST-FRONTAL ELEVATED CONVECTION IS ULTIMATELY EXPECTED, AND STEEP
MID-LEVEL LAPSE RATES FAVOR HAIL WITH THE ELEVATED STORMS. WHILE THE
FRONTAL ZONE WILL PROVE SHARP, WITH SIGNIFICANT UNDERCUTTING OF
UPDRAFTS, THERE IS SOME RISK FOR TORNADOES PRIOR TO THIS OCCURRING.
LATEST NAM GUIDANCE HAS 500MB TEMPERATURE COOLING TO -15C AT FSI BY
04Z, THUS VERY LARGE HAIL CAN BE EXPECTED WITH SUPERCELLS. COLD
FRONT WILL GRADUALLY SAG SOUTHEAST DURING THE OVERNIGHT HOURS, BUT
AN EXTENDED CONVECTIVE EVENT IS LIKELY FROM WESTERN OK INTO THE
MID-MS VALLEY DUE TO THE EVOLUTION OF THE LONGER-WAVE PATTERN.
..DARROW/WENDT.. 04/18/2025
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