108
FXUS63 KUNR 032322
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
522 PM MDT FRI JUL 3 2020
DISCUSSION
(THIS EVENING THROUGH FRIDAY)
ISSUED AT 1234 PM MDT FRI JUL 3 2020
PAC NW UPPER TROUGH WILL REMAIN ANCHORED IN THE PERIOD,
SUPPORTING ACTIVE SW FLOW OVER THE REGION AT TIMES, AS DEEP
MOISTURE WAVERS OVER THE REGION. WEAK SUBSIDENCE ONGOING ACROSS
THE REGION TODAY BEHIND A DEPARTING IMPULSE. MOISTURE HAS BEEN
DEPLETED SOME FROM YESTERDAYS IMPULSE, BUT STILL ENOUGH AROUND
TO SUPPORT 1000-2000 J/KG OF ML CAPE, HIGHEST IN NW SD WHERE THE
STRONGEST CAPPING IS IN PLACE. ANOTHER SHORTWAVE TROUGH WILL
ROTATE TOWARD THE REGION FROM THE FOUR CORNERS, SUPPORTING ISOLD
SHOWERS AND THUNDERSTORMS BY LATE AFTERNOON EVENING, MAINLY ACROSS
THE SW THIRD WHERE DIURNAL HEATING WILL SUPPORT THE WEAKEST CIN.
OTHER ISOLATED TS WILL BE POSSIBLE OVER THE NORTHERN AND CENTRAL
BLACK HILLS, MAINLY THE HIGHER ELEVATIONS THIS AFTERNOON.
AFOREMENTIONED SUFFICIENT CAPE WILL BE IN PLACE FOR A FEW STRONGER
CELLS, HOWEVER DEEP LAYER SHEAR WILL BE LACKING. THIS WILL SETUP
A PULSE ENVIRONMENT WITH COLLAPSING CORES CAPABLE OF PRODUCING
GUSTY WINDS AND SMALL HAIL, POTENTIALLY OVER 50 KNOTS IN SOME
AREAS GIVEN CLASSIC INVERTED V PROFILES. MAIN FORCING COMPONENT
AND OVERLAP OF INSTABILITY AND SHEAR WILL REMAIN WELL NW OF THE FA
IN MT AND ND WHERE THE BEST SEVERE THREAT WILL BE. HOWEVER, THE
SOUTHERN PERIPHERY OF AN EXPECTED TS COMPLEX MAY CLIP THE FAR NW
ZONES BEING DRIVEN BY A LLJ OVERNIGHT IF CAPPING CAN BE OVERCOME.
SOUTHERN FA ACTIVITY WILL PUSH NE AND WANE THIS EVENING, WITH ONLY
THE FAR NORTH EXPECTING ANY ACTIVITY AFTER MIDNIGHT. IMPULSE
DRIVEN LLJ WILL SUPPORT A BREEZY NIGHT INVOF OF THE BLACK HILLS
TONIGHT WITH FAVORED DOWNSLOPE AREAS SEEING 20 TO 30 MPH WINDS
POTENTIALLY AT TIMES, ESP THE NORTHERN FOOTHILLS. MORE OF THE SAME
TOMORROW AND SUNDAY AS ACTIVE SW FLOW SUPPORTS ANOTHER SET OF
IMPULSES WHICH WILL TIME WITH DIURNAL INSTABILITY AND A SFC TROUGH
INVOF OF THE REGION, COUPLED WITH TYPICAL BLACK HILLS DRIVEN
EARLY AFTERNOON CONVECTION IN A CONDITIONALLY UNSTABLE
ENVIRONMENT. DEEP LAYER BULK SHEAR WILL BE A LITTLE BETTER EACH
DAY, POTENTIALLY SUPPORTING AN INCREASED SEVERE THREAT WITH TIME
GIVEN SUFFICIENT CAPE. OTHERWISE, CONVECTION WILL BE POSSIBLE
NEARLY EVERY DAY IN THE REMAINDER OF THE PERIOD AS A SFC TROUGH
WAVERS OVER THE REGION IN UNSETTLED SW FLOW WITH SEASONALLY WARM
TEMPS.
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 520 PM MDT FRI JUL 3 2020
MAINLY VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. THE
EXCEPTION WILL BE THUNDERSTORMS THAT DEVELOP THIS AFTERNOON AND
EVENING, RESULTING IN LOCAL MVFR CONDITIONS AND GUSTY/ERRATIC
WINDS. MORE THUNDERSTORMS WILL BE POSSIBLE SATURDAY AFTERNOON AND
EVENING ACROSS NORTHEAST WY AND WESTERN SD.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...JC
AVIATION...13
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