199
FXUS63 KUNR 091104
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
504 AM MDT SUN AUG 9 2020
DISCUSSION
(TODAY THROUGH SATURDAY)
ISSUED AT 240 AM MDT SUN AUG 9 2020
CURRENT SURFACE ANALYSIS SHOWS ONE FRONTAL BOUNDARY JUST SOUTH
AND EAST OF THE REGION, WITH A COLD FRONT OVER MT ALSO APPROACHING
THE AREA. UPPER LEVEL ANALYSIS SHOWS LOW PRESSURE OVER CENTRAL
CANADA SHIFTING SLOWLY NORTHEASTWARD, WITH NEAR ZONAL FLOW ACROSS
THE NORTHERN PLAINS. SHORTWAVE ENERGY THAT BROUGHT STORMS
YESTERDAY AFTERNOON AND EVENING IS MOVING ACROSS EASTERN PORTIONS
OF THE NORTHERN PLAINS. A FEW SHOWERS AND STORMS LINGER OVER PARTS
OF SOUTHWEST INTO SOUTH CENTRAL SD EARLY THIS MORNING. SKIES ARE
CLEARING ELSEWHERE TO THE NORTH AND WEST WITH TEMPS MOSTLY IN THE
60S AND LOWER 70S. WINDS ARE VARIABLE ACROSS THE AREA BETWEEN THE
TWO FRONTAL BOUNDARIES.
COLD FRONT TO THE NORTHWEST WILL PUSH THROUGH THE AREA TODAY,
BRINGING BREEZY NORTHWESTERLY WINDS TO MOST AREAS BEHIND IT. HIGHS
WILL RANGE FROM THE MID TO UPPER 70S OVER PORTIONS OF NORTHEAST WY
AND THE HIGHER BLACK HILLS TO THE LOW TO MID 90S OVER FAR SOUTHERN
SD. THE FRONT LOOKS TO BE DRY AS IT CROSSES MOST OF THE AREA.
HOWEVER, AS THE FRONT REACHES CENTRAL SD IN THE AFTERNOON, STORMS
ARE EXPECTED TO DEVELOP ALONG AND AHEAD OF IT. A STORM OR TWO COULD
CLIP FAR SOUTH CENTRAL SD DURING THE LATE AFTERNOON AND EARLY
EVENING. THE BETTER INSTABILITY FOR STRONGER STORMS WILL BE SOUTH
AND EAST OF THE AREA BY THIS TIME, BUT SHEAR LOOKS TO BE SUFFICIENT
FOR A POSSIBLE SEVERE STORM LATE IN THE DAY OVER THE TRIPP COUNTY
AREA. A POST FRONTAL SHORTWAVE WILL MOVE ACROSS THE AREA LATER
SUNDAY NIGHT, WITH A CHANCE FOR SHOWERS AND A FEW THUNDERSHOWERS
OVER A GOOD PORTION OF THE FORECAST AREA, BUT ESPECIALLY FROM THE
BLACK HILLS TO SOUTH CENTRAL SD.
MONDAY LOOKS TO BE A PLEASANT DAY WITH SKIES BECOMING MOSTLY SUNNY
AND HIGHS IN THE MID 70S TO MID 80S. A WEAK DISTURBANCE, COMBINED
WITH DEVELOPING LOW LEVEL JET AND THETA-E ADVECTION OVER THE AREA,
WILL LIKELY BRING AT LEAST ISOLATED SHOWERS AND STORMS MONDAY NIGHT
INTO EARLY TUESDAY.
BUILDING RIDGE OVER THE PLAINS MIDWEEK WILL BRING HOTTER CONDITIONS
BACK TO THE REGION. HIGHS WILL BE IN THE UPPER 80S AND 90S ACROSS
MUCH OF THE PLAINS WEDNESDAY AND THURSDAY. WEAK DISTURBANCES MOVING
THROUGH THE RIDGE MAY BRING A FEW STORMS AT TIMES, ESPECIALLY LATE
DAY INTO THE EVENING, BUT MANY AREAS COULD STAY DRY. ANOTHER UPPER
LEVEL SYSTEM IS PROGGED TO TRACK ACROSS SOUTHERN CANADA LATE WEEK,
EVENTUALLY DRAGGING A COLD FRONT ACROSS THE NORTHERN PLAINS, LIKELY
FRIDAY AND FRIDAY NIGHT. NEAR AVERAGE TEMPERATURES SHOULD RETURN FOR
THE WEEKEND.
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 502 AM MDT SUN AUG 9 2020
PATCHY FOG ACROSS PORTIONS OF NORTHWEST SOUTH DAKOTA WILL BRING
SOME LOCAL IFR CONDITIONS. FOG WILL DISSIPATE EARLY THIS MORNING
AS A COLD FRONT MOVES THROUGH. GUSTY NORTHWEST WINDS WILL SPREAD
ACROSS THE PLAINS OF WESTERN SOUTH DAKOTA BEHIND THE FRONT...WITH
GUSTS TO AROUND 35 MPH. WINDS WILL DIMINISH LATE THIS
AFTERNOON/EARLY EVENING.
FIRE WEATHER
ISSUED AT 240 AM MDT SUN AUG 9 2020
A COLD FRONT WILL PASS THROUGH NORTHEAST WYOMING AND NORTHWEST
SOUTH DAKOTA THIS MORNING AND THE REST OF THE AREA DURING THE
MIDDAY AND AFTERNOON HOURS. BREEZY CONDITIONS WILL DEVELOP ACROSS
MUCH OF THE AREA, ESPECIALLY THE NORTHWEST AND WEST CENTRAL SD
PLAINS. MINIMUM RELATIVE HUMIDITIES WILL DROP TO AROUND 20 PERCENT
ACROSS FIRE ZONES 317, 322, AND INTO 326.
NEAR TO BELOW AVERAGE TEMPERATURES WILL PREVAIL FOR MONDAY INTO
TUESDAY, BEFORE HOT AND DRIER CONDITIONS RETURN FOR MID TO LATE
WEEK. RELATIVE HUMIDITIES WILL LIKELY DROP TO NEAR OR BELOW 15
PERCENT FROM NORTHEAST WYOMING INTO PARTS OF SOUTHWEST SOUTH DAKOTA
WEDNESDAY THROUGH FRIDAY. WINDS AT THIS TIME LOOK TO BE BELOW RED
FLAG CRITERIA, AT LEAST ON WEDNESDAY AND THURSDAY.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...26
AVIATION...7
FIRE WEATHER...26
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