392
ACUS01 KWNS 171952
SWODY1
SPC AC 171951
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0251 PM CDT FRI JUL 17 2026
VALID 172000Z - 181200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
IDAHO INTO MONTANA...THE GREAT LAKES...AND THE OHIO VALLEY INTO THE
SOUTHEAST...
..SUMMARY
STRONG TO POTENTIALLY SEVERE STORMS ARE POSSIBLE TODAY ACROSS PARTS
OF WESTERN MONTANA AND NORTHERN IDAHO, AND ALSO ACROSS PARTS OF THE
UPPER MIDWEST AND NORTHERN GREAT LAKES. MORE ISOLATED STRONG TO
SEVERE STORMS WITH DAMAGING WIND GUSTS ARE POSSIBLE OVER PARTS OF
THE OHIO VALLEY AND SOUTHEAST.
..20Z UPDATE
THE PREVIOUS FORECAST REMAINS LARGELY ON TRACK BASED ON LATEST
TRENDS IN ENSEMBLE GUIDANCE. RECENT RUNS OF THE RRFS/HRRR
TIME-LAGGED ENSEMBLE CONTINUE TO SHOW SOME POTENTIAL FOR ORGANIZED
CONVECTION ACROSS NORTHERN WI AND INTO THE U.P. OF MICHIGAN LATER
THIS EVENING, AND LATEST TRENDS IN GOES IMAGERY SHOW BUILDING
CUMULUS THAT SEEM TO SUPPORT THESE SOLUTIONS. HOWEVER, THE OVERALL
ENSEMBLE SIGNAL FOR WIDESPREAD SEVERE CONVECTION ON THE U.S. SIDE OF
THE INTERNATIONAL BORDER REMAINS LIMITED. SIMILARLY, A CORRIDOR OF
MORE FOCUSED WIND POTENTIAL MAY EMERGE ACROSS WEST-CENTRAL MT THIS
EVENING, BUT GIVEN LOW ENSEMBLE PROBABILITIES FOR SEVERE WINDS,
COUPLED WITH MODEST LOW-LEVEL LAPSE RATES IN LATEST RAP MESOANALYSES
AND FORECAST SOUNDINGS, LIMITS CONFIDENCE IN A WIDESPREAD SEVERE
WIND THREAT. SEE THE PREVIOUS DISCUSSION BELOW AND MCD #1641 FOR
ADDITIONAL DETAILS.
..MOORE.. 07/17/2026
PREV DISCUSSION
/ISSUED 1130 AM CDT FRI JUL 17 2026/
..NORTHERN ROCKIES AND NORTHERN HIGH PLAINS
THE REGION WILL BE INFLUENCED BY AN INCREASINGLY PROGRESSIVE
SHORTWAVE TROUGH MOVING NORTHEASTWARD FROM OFF THE WASHINGTON COAST
AND OVER SOUTHERN BRITISH COLUMBIA. THE PRECEDING UPPER RIDGE WILL
FLATTEN/SHIFT EASTWARD PARTICULARLY NEAR THE INTERNATIONAL BORDER,
WITH A PLUME OF RICH MONSOONAL MOISTURE EXTENDING INTO THE REGION,
HIGHLIGHTED BY PREVALENT MIDDLE 50S TO LOWER 60S F DEWPOINTS ALONG
THE CONTINENTAL DIVIDE. OROGRAPHIC LIFT AND HEATING WILL PROMOTE THE
DEVELOPMENT OF SCATTERED THUNDERSTORMS THIS AFTERNOON, ESPECIALLY
ACROSS EASTERN/NORTHERN IDAHO AND WESTERN MONTANA. STEEPENED
LOW-LEVEL LAPSE RATES WILL POTENTIALLY YIELD STORMS CAPABLE OF
ISOLATED SEVERE WIND GUSTS BEGINNING THIS AFTERNOON AND CONTINUING
INTO MID-LATE EVENING. ISOLATED LARGE HAIL MAY OCCUR WITH THE
STRONGER THUNDERSTORM CORES, ESPECIALLY OVER NORTHWEST MONTANA WHERE
DEEP-LAYER SHEAR MAY EXCEED 30 KT.
..UPPER MIDWEST AND NORTHERN GREAT LAKES
A DECAYING CLUSTER OF STORMS CONTINUES TO SPREAD SOUTHEASTWARD
ACROSS NORTHERN MICHIGAN, AND SMOKE WILL CONTINUE TO BE A FACTOR
REGIONALLY, ALBEIT WITH SOME WEST-TO-EAST ABATEMENT LATER TODAY. A
COLD FRONT ASSOCIATED WITH THE UPPER WAVE WILL PUSH SOUTHEASTWARD
ACROSS THE UPPER MIDWEST AND PROVIDE A FOCUS FOR THUNDERSTORM
REDEVELOPMENT LATE THIS AFTERNOON, AND MORE SO INTO THIS EVENING.
FORECAST MODEL GUIDANCE SHOWS MODERATE BUOYANCY DEVELOPING TODAY
WITHIN A BELT OF 25-40 KT WEST-NORTHWESTERLY 500-MB FLOW AS UPSTREAM
SHORTWAVE TROUGH AMPLIFICATION OCCURS.
A FEW OF THE STRONGER THUNDERSTORMS COULD EVOLVE INTO SUPERCELLS AND
ORGANIZED MULTICELL CLUSTERS, ALTHOUGH UNCERTAINTY PERSISTS
REGARDING THE OVERALL MAGNITUDE/EXTENT OF TODAY'S SEVERE POTENTIAL.
ISOLATED LARGE HAIL AND DAMAGING GUSTS ARE THE PRIMARY HAZARDS,
ALTHOUGH A BRIEF TORNADO RISK MAY ALSO DEVELOP IN THE AREAS
SURROUNDING LAKE SUPERIOR. ONE OR MORE CLUSTERS OF STRONG TO SEVERE
STORMS MAY PERSIST INTO THE OVERNIGHT ALONG THE WARM FRONT.
..OHIO VALLEY TO THE SOUTHERN APPALACHIANS AND FLORIDA
A MOIST AND DIURNALLY DESTABILIZING AIRMASS WILL SUPPORT SCATTERED
TO NUMEROUS STORMS DEVELOPING BY THE MID AFTERNOON. SOME OF THE
STRONGER WATER-LOADED DOWNDRAFTS WILL POTENTIALLY BE CAPABLE OF
50-60 MPH GUSTS AND ISOLATED WIND DAMAGE.
..WEST-CENTRAL TEXAS
A WEAK MID- TO UPPER-LEVEL LOW OVER WEST TEXAS WILL MOVE LITTLE
DURING THE DAY WHILE A WARM/MOIST CONVEYOR PERSISTS ACROSS SOUTHERN
INTO CENTRAL PARTS OF TEXAS. DESPITE VERY MOIST LOW LEVELS AND SOME
ENLARGEMENT OF THE LOW-LEVEL HODOGRAPH, WEAK FLOW IN THE MID LEVELS
SHOULD LIMIT STORM ORGANIZATION AND MEANINGFUL SUPERCELL POTENTIAL,
MORE SO FAVORING A HEAVY RAIN THREAT.
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