291
FXUS63 KUNR 150739
AFDUNR
AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
139 AM MDT SUN SEP 15 2019
DISCUSSION
(TODAY THROUGH SATURDAY)
ISSUED AT 133 AM MDT SUN SEP 15 2019
THE LATEST SURFACE ANALYSIS HAS A LEE TROUGH/WEAK WARM FRONT OVER
EASTERN WY. WATER VAPOR IMAGES AND THE RAP ANALYSIS SHOWED A
DIRTY, LOW-AMPLITUDE RIDGE OVER THE NORTHERN ROCKIES. SOME HIGH
CLOUDS WERE SWEEPING ACROSS THE CWA.
TODAY THROUGH MONDAY NIGHT, UPPER RIDGE BUILDS OVER THE MO RIVER
VALLEY IN RESPONSE TO DEEPENING UPPER TROUGH OVER THE WEST COAST.
STRONG THERMAL RIDGE BUILDS OVER THE CWA BRINGING HIGH TEMPERATURES
AROUND 10F ABOVE AVERAGE. THE HRRR-SMOKE SUGGESTS SMOKE WILL MOVE
OVER PARTS OF THE CWA TODAY FROM WESTERN CONUS WILDFIRES. A WEAK
SHORT-WAVE TROUGH WITH LIMITED FORCING AND MOISTURE MOVES THROUGH
TONIGHT WITH SOME CLOUDS. ANOTHER SLIGHTLY STRONGER SHORT-WAVE
TROUGH MOVES THROUGH MONDAY NIGHT, WITH LOW-LEVEL JET/850-700MB
THETA-E ADVECTION EXPECTED. SOME STORMS MAY FORM JUST EAST OF THE
CWA.
TUESDAY WILL BE A TRANSITION DAY AS A STRONGER SHORT-WAVE TROUGH
EJECTS NORTHEAST FROM THE WEST COAST UPPER LOW. MOISTURE WILL BE
LIMITED AHEAD OF THE WAVE, BUT SYNOPTIC FORCING, FRONTOGENESIS, AND
MIDLEVEL MOISTURE SHOULD BE SUFFICIENT FOR SCATTERED TSRA TUESDAY
AFTERNOON AND EVENING. THE MAIN THREAT APPEARS TO BE GUSTY WINDS
GIVEN UNIDIRECTIONAL HODOGRAPHS, A LINEAR STORM MODE, AND A DRY
BOUNDARY LAYER. A STRONG COLD FRONT THEN MOVES THROUGH WITH GUSTY
WEST/NORTHWEST WINDS TUESDAY EVENING LINGERING INTO WEDNESDAY
MORNING.
WEDNESDAY THROUGH SATURDAY, SOUTHWEST FLOW ALOFT TRANSITIONS TO A
LARGE UPPER TROUGH MOVING THROUGH THE NORTHERN PLAINS LATER FRIDAY
INTO SATURDAY. A COOLING TREND IS EXPECTED, ESPECIALLY FRIDAY AND
SATURDAY, ALONG WITH INCREASED PRECIPITATION CHANCES AT THE END OF
THE WEEK.
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1025 PM MDT SAT SEP 14 2019
VFR CONDITIONS CAN BE EXPECTED THROUGH SUNDAY EVENING.
FIRE WEATHER
ISSUED AT 133 AM MDT SUN SEP 15 2019
RELATIVE HUMIDITIES WILL DROP INTO THE TEENS OVER NORTHEASTERN
WY/FAR SOUTHWESTERN SD THIS AFTERNOON. FORECAST SOUNDINGS SHOW
DEEP MIXING WITH POTENTIAL GUSTS OF 20-25 MPH, JUST SHORT OF RED
FLAG CRITERIA.
UNR WATCHES/WARNINGS/ADVISORIES
SD...NONE.
WY...NONE.
DISCUSSION...BUNKERS
AVIATION...7
FIRE WEATHER...BUNKERS
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