Day 1 Severe Weather Outlook

USA Weather — Severe Weather Division

This outlook is expired and is no longer valid.

Issued
14:51Z Fri, Aug 5
Valid
12Z Fri, Aug 5 - 12Z Sat, Aug 6
Forecaster
Wyatt Huber

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTH-CENTRAL MINNESOTA INTO CENTRAL SOUTH DAKOTA...

...SUMMARY...

DAMAGING WINDS, LARGE HAIL, AND PERHAPS A TORNADO OR TWO WILL BE POSSIBLE THIS EVENING ACROSS THE FAR NORTHERN TIER. A FEW DAMAGING WIND GUSTS ARE ALSO POSSIBLE OVER THE MID-ATLANTIC, SOUTHEAST, AND THE FOUR CORNERS REGION INTO NEVADA.

...NORTHERN TIER...

DEEP MOISTURE PRESENTLY ADVECTING NORTHWARD INTO THE REGION IS OBSERVED IN THE LATES (14Z) OBSERVATIONS. DEWPOINTS INCREASING INTO THE LOW-MID 60S AND FAVORABLE THETA-E ADVECTION IS NOTED. FAVORABLE MOISTURE TRANSPORT DUE TO STRENGTHENING LOW-LEVEL WINDS OF 35 TO 50KTS IS NOTED. ALL OF THESE FACTORS SUPPORT HIGHLY UNSTABLE AND MODERATE TO STRONG WIND SHEAR ACROSS THE REGION TODAY, SUPPORTING A SEVERE WIND AND ATTENDENT LARGE HAIL THREAT.

THUNDERSTORMS WILL INITIATE LATE THIS AFTERNOON INTO EARLY EVENING ALONG A SURFACE COLD FRONT. INITIAL ACTIVITY SHOULD BEGIN OVER THE SOUTH DAKOTA REGION AND MOVE QUICKLY NORTHEAST. STRONG INSTABILITY AND STEEP 8-9 C/KM LAPSE RATES SUPPORT A VERY LARGE HAIL POTENTIAL WITH ANY STORM THAT DEVELOPS. IN ADDITION, DCAPE VALUES OF 1000-1600 J/kg SUPPORT DAMAGING DOWNDRAFTS AND OUTFLOW WINDS. STORMS QUICKLY INITIATE TO THE NORTH, AND DAMAGING WINDS/HAIL WILL BE POSSIBLE AT TIMES. BOUNDARY INTERACTIONS INCREASING SRH LOCALLY TO 250m2/s-2 IS POSSIBLE, AND AN ISOLATED TORNADO CANNOT BE RULED OUT.

AS THUNDERSTORMS RAPIDLY DEVELOP AND TRAIN TO THE NORTHEAST COMBINED WITH LOSS OF SURFACE HEATING, AVALIBLE INSTABILITY WILL DECREASE WHILST INHIBITION INCREASES. THIS SHOULD BEGIN TO END THE SEVERE THREAT BY 05-06Z. 

...MID-ATLANTIC AND SOUTHEAST...

LESS MOISTURE WILL RENDER MORE ISOLATED TO SCATTERED THUNDERSTORMS. HOWEVER, DRY MID-LEVELS INCREASES DCAPE TO 800-1500 J/kg AND STEEP LOW-LEVEL LAPSE RATES. THEREFORE ANY STORM THAT DEVELOPS IN THIS REGION HAS THE POTENTIAL TO PRODUCE BRIEFLY SEVERE WIND GUSTS AND LARGE HAIL. HOWEVER, LACK OF DEEP LAYER SHEAR RENDERS LIMITED ORGANIZATION, AND PROBABILITIES ARE NOT ADDED ATTM. 

...FOUR CORNERS INTO NEVADA REGION...

MONSOON TROUGHING AND FAVORABLE MOISTURE TRANSPORT DUE TO LOW LEVEL WINDS CONTINUE TO FEED DEEP MOISTURE INTO THE REGION. NUMEROUS THUNDERSTORMS DURING AFTERNOON TO EVENING HOURS IS LIKELY, AND A FEW STRONG WET MICROBURSTS WILL BE POSSIBLE. HOWEVER, THE OVERALL SEVERE THREAT REMAINS TOO ISOLATED AND THUS PRECLUDES PROBABILITIES TO BE ADDED ATTM.