999
ACUS48 KWNS 260843
SWOD48
SPC AC 260842
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0342 AM CDT WED AUG 26 2026
VALID 291200Z - 031200Z
..DISCUSSION
..D4/SATURDAY - NORTHERN PLAINS TO UPPER MIDWEST
A MID-LEVEL RIDGE WILL MOVE SLOWLY EAST ACROSS THE PLAINS WITH
SLIGHT SUPPRESSION THROUGH THE DAY. A LEE TROUGH WILL CONSOLIDATE
INTO A SURFACE LOW ACROSS THE NORTHERN PLAINS THROUGH THE DAY
SATURDAY. AHEAD OF THIS SURFACE LOW, STRONG INSTABILITY IS FORECAST
ACROSS SOUTH DAKOTA AND VICINITY. DESPITE THE FAVORABLE ENVIRONMENT
ACROSS THIS REGION, PRIMARY FORCING WILL BE FOCUSED ON THE NOSE OF
THE LOW-LEVEL JET ACROSS IOWA AND INTO WISCONSIN, WELL EAST OF THE
GREATEST INSTABILITY AND NEAR THE CANADIAN BORDER. THEREFORE,
LIMITED STORM COVERAGE PRECLUDES SEVERE WEATHER PROBABILITIES AT
THIS TIME, BUT GIVEN THE FAVORABLE ENVIRONMENT, IT WILL NEED TO BE
MONITORED CLOSELY.
..D5/SUNDAY - NORTH DAKOTA AND VICINITY
A MID-LEVEL SHORTWAVE TROUGH WILL MOVE FROM THE PACIFIC NORTHWEST TO
THE NORTHERN PLAINS SATURDAY/D4 AND SUNDAY/D5. 00Z GUIDANCE HAS COME
INTO FAIRLY CONSISTENT AGREEMENT WITH THE LOCATION AND AMPLITUDE OF
THIS TROUGH ACROSS EASTERN MONTANA AT 00Z SUNDAY EVENING. HOWEVER,
THERE IS CONSIDERABLE DISAGREEMENT WITH THE DEGREE OF
DESTABILIZATION ACROSS NORTH DAKOTA, WHERE FORCING WILL BE GREATEST.
THE GFS DRY BIAS ACROSS MOST OF THE PLAINS HAS SEVERELY LESSENED THE
INSTABILITY. HOWEVER, DESPITE THIS CHALLENGE, IT IS APPARENT THAT
MOST OF THE INSTABILITY SIGNIFICANTLY SOUTHEAST OF THE UPPER-LEVEL
FORCING. THE GFS-PARA SEEMS TO HAVE A MORE REALISTIC HANDLE ON
LOW-LEVEL MOISTURE/INSTABILITY MAGNITUDE BUT IT ALSO SHOWS A
SIGNIFICANT DISCONNECT BETWEEN WHERE THIS INSTABILITY IS LOCATED AND
THE DEEPER FORCING.
THE DETERMINISTIC ECMWF FORECAST SHOWS A POTENTIALLY SIGNIFICANT
SEVERE WEATHER EVENT ACROSS NORTH DAKOTA WITH STRONG INSTABILITY AND
SHEAR AHEAD OF A ROBUST CONVECTIVE QPF SIGNAL. THIS IS SUPPORTED BY
THE AI-ECMWF WHICH SHOWS A SIMILAR EVOLUTION. HOWEVER, THE
EC-ENSEMBLE MEAN OF INSTABILITY SHOWS AT LEAST SOME TREND TOWARD THE
GEFS WITH PRIMARY INSTABILITY SOUTHEAST OF THE BEST FORCING.
IT IS ALSO WORTH NOTING THAT THE WAVE IS FORECAST TO EJECT ACROSS
NORTH DAKOTA RELATIVELY LATE (~06Z) WHICH MAY BE A SOMEWHAT LIMITING
FACTOR TO A GREATER THREAT. THIS POTENTIAL TIMING DISCONNECT,
COMBINED WITH SOME HINT OF LIMITED OVERLAP BETWEEN THE GREATEST
INSTABILITY AND THE PRIMARY UPPER FORCING, CAST ENOUGH UNCERTAINTY
TO PRECLUDE SEVERE WEATHER PROBABILITIES AT THIS TIME. HOWEVER, IT
IS WORTH NOTING THAT IF A SOLUTION SIMILAR TO THE ECMWF
MATERIALIZES, A SIGNIFICANT SEVERE WEATHER EVENT IS POSSIBLE.
..D6 AND BEYOND
BY EARLY NEXT WEEK, THE PRIMARY MID-LEVEL RIDGE APPEARS TO CENTER
AROUND THE SOUTHERN APPALACHIANS WITH BROAD SOUTHWESTERLY FLOW FROM
THE SOUTHWEST TO THE GREAT LAKES. WITHIN THIS AREA OF SOUTHWESTERLY
FLOW, MULTIPLE EMBEDDED MID-LEVEL SHORTWAVE TROUGHS ARE FORECAST.
PREDICTABILITY OF THESE SMALLER SCALE FEATURES IS RELATIVELY LOW AT
THIS RANGE, BUT SOME CONTINUED SEVERE WEATHER THREAT WILL LIKELY
PERSIST AROUND THE PERIPHERY OF THE RIDGE FROM THE PLAINS TO THE
GREAT LAKES AND POTENTIALLY INTO THE NORTHEAST.
..BENTLEY.. 08/26/2026
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