120
ACUS03 KWNS 220647
SWODY3
SPC AC 220646
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0146 AM CDT THU AUG 22 2019
VALID 241200Z - 251200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER THE
NORTHERN PLAINS...
..SUMMARY
AT LEAST ISOLATED SEVERE STORMS ARE POSSIBLE OVER PARTS OF THE
NORTHERN PLAINS SATURDAY.
..SYNOPSIS
STRONG CYCLONIC FLOW ALOFT WILL DEVELOP SOUTHEASTWARD INTO THE
NORTHERN ROCKIES, PROVIDING INCREASED DEEP-LAYER SHEAR AND COOLING
ALOFT TO THE NORTHERN HIGH PLAINS. A WEAK SHORTWAVE TROUGH WILL
PRECEDE THIS LARGER-SCALE WAVE, AIDING LIFT OVER THE DAKOTAS AND MN
DURING THE DAY.
AT THE SURFACE, LOW PRESSURE WILL DEEPEN OVER THE NORTHERN HIGH
PLAINS, ENHANCING SOUTHERLY SURFACE WINDS AND MAINTAINING A PLUME OF
60S F DEWPOINTS FROM KS TO SOUTHERN MANITOBA. CONVERGENCE ALONG A
COLD FRONT WILL INCREASE OVERNIGHT AND INTO SUNDAY MORNING FROM
EASTERN MT TOWARD THE BLACK HILLS, PROVIDING LIFT.
ELSEWHERE, A MOIST AND UNSTABLE AIR MASS WILL REMAIN OVER THE
SOUTHERN PLAINS AND LOWER MS VALLEY, WITH VARIOUS AREAS OF STORMS
AND OUTFLOW BOUNDARIES THROUGHOUT THE PERIOD. ANY POTENTIAL MARGINAL
THREAT AREA HERE FOR WIND GUSTS IS CURRENTLY UNPREDICTABLE.
..NORTHERN PLAINS
STORMS ARE LIKELY TO BE ONGOING ACROSS THE CENTRAL DAKOTAS, AND
POSSIBLY INTO NORTH-CENTRAL NE SATURDAY MORNING, NEAR THE EASTERN
INSTABILITY GRADIENT WHERE SOUTHWESTERLY 850 MB WINDS OF 30-40 KT
WILL PROVIDE LIFT VIA WARM ADVECTION. MARGINAL HAIL CANNOT BE RULED
OUT EARLY.
LATER IN THE DAY, HEATING WILL REMOVE CIN OVER THE CENTRAL AND
WESTERN DAKOTAS, AND REDEVELOPMENT IS POSSIBLE NEAR THE TAIL END OF
THE DEPARTING LEAD WAVE OVER ND. VEERING WINDS WITH HEIGHT WILL
FAVOR A SUPERCELL OR TWO, WITH SEVERE THREAT DEPENDENT ON HOW MUCH
INSTABILITY CAN DEVELOP NEAR AN AXIS OF 200-300 M2/S2 EFFECTIVE SRH.
ISOLATED CELLS ARE ALSO POSSIBLE AT PEAK HEATING OVER WESTERN SD.
OVERNIGHT, LARGE-SCALE LIFT WILL INCREASE FROM MT INTO THE WESTERN
DAKOTAS. STEEP LAPSE RATES ALOFT AND STRENGTHENING DEEP-LAYER SHEAR
WILL CONDITIONALLY FAVOR SEVERE STORMS, HOWEVER, IT IS UNCLEAR HOW
MUCH MOISTURE AND INSTABILITY WILL EXIST OVERNIGHT THAT FAR WEST.
PARTS OF THE AREA MAY REQUIRE A CATEGORICAL UPGRADE IN FUTURE
OUTLOOKS SHOULD INSTABILITY INCREASE.
..JEWELL.. 08/22/2019
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