Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 182039
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
239 PM MDT SAT APR 18 2015

.SHORT TERM...THIS EVENING THROUGH SUNDAY NIGHT
ISSUED AT 213 PM MDT SAT APR 18 2015

UPPER LEVEL ANALYSIS HAS CUT OFF LOW OVER EASTERN COLORADO WITH
NORTHERN STREAM SHORTWAVE DIVING INTO NORTHERN MONTANA. RIDGE IS
SLOWLY MOVING ONSHORE ALONG THE WEST COAST. SKIES ARE MOSTLY
CLOUDY ACROSS THE FORECAST AREA AS MAIN BAND OF CLOUDS AND RAIN
ARE LIFTING THROUGH THE CWA. MAIN BAND OF RAIN STRETCHES FROM
NORTHWEST SD THROUGH NORTHEAST WY. AT THE SURFACE...MAIN LOW IS
SITUATED IN WESTERN KS WITH COLD FRONT APPROACHING THE CWA FROM
THE NW. VERY WEAK RIDGING OBSERVED IN BETWEEN. TEMPERATURES ARE IN
THE 50S OUTSIDE THE PRECIP AREAS...AND IN THE 40S WHERE PRECIP IS
FALLING. WINDS ARE LIGHT.

RAIN/RAIN SHOWERS WILL CONTINUE FROM NORTHWEST SD INTO NORTHEAST
WY THIS EVENING AS THE UPPER LOW OVER CO MOVES SLOWLY EAST.
ISOLATED EVENING THUNDERSTORMS WILL BE POSSIBLE AS WELL...ACROSS
SOUTHERN SD AS THEY ADVECT IN FROM NEBRASKA...AND ACROSS NORTHWEST
SOUTH DAKOTA IN ADVANCE OF THE COLD FRONT. COLD FRONT PUSHES
THROUGH THE CWA THIS EVENING...BRINGING GUSTY NORTHWEST WINDS.

COLD FRONT AND UPPER SHORTWAVE WILL HELP TO ACCELERATE THE UPPER
LOW OUT OF CO AND PUSH IT QUICKLY ACROSS THE CENTRAL PLAINS
LATE TONIGHT AND SUNDAY MORNING. SHOWERS WILL TAPER OFF GRADUALLY
FROM WEST TO EAST TONIGHT...WITH MOST OF THE ACTIVITY OVER WITH BY
LATE TONIGHT. A LIGHT ACCUMULATION OF SNOW IS POSSIBLE OVER THE
BLACK HILLS BEFORE THE PCPN ENDS OVERNIGHT. GUSTY NORTHWEST WINDS
CAN BE EXPECTED BEHIND THE PASSAGE OF THE FRONT...BUT THE
STRONGEST WINDS SHOULD BE RATHER SHORT-LIVED.

A COOL AND MUCH DRIER AIRMASS WILL BE IN PLACE FOR SUNDAY AS HIGH
PRESSURE APPROACHES THE NORTHERN HIGH PLAINS. BEFORE IT DOES...A
TIGHT PRESSURE GRADIENT WILL REMAIN OVER THE WESTERN DAKOTAS...
RESULTING IN STRONG NORTHWEST WINDS FOR MUCH OF THE DAY. A WIND
ADVISORY WILL LIKELY BE NEEDED FOR AT LEAST THE NORTHWEST AND
WEST CENTRAL SD PLAINS DURING THE DAY...AS WINDS COULD GUST TO
AROUND 50 MPH. HIGHS WILL BE IN THE LOW TO MID 50S ACROSS MUCH OF
THE PLAINS...WITH 40S IN THE BLACK HILLS. WINDS WILL DIMINISH
TOWARD SUNSET AND SKIES WILL BECOME MOSTLY CLEAR OVERNIGHT. LOWS
SUNDAY NIGHT WILL BE IN THE 20S AND LOWER 30S.

.LONG TERM...MONDAY THROUGH SATURDAY
ISSUED AT 213 PM MDT SAT APR 18 2015

MONDAY THROUGH WEDNESDAY WILL FEATURE UPPER LOW OVER SOUTHEAST
CANADA/GREAT LAKES AND TROUGH OVER THE EASTERN PACIFIC. CWA WILL
BE INBETWEEN WITH WEAK RIDGING/BLOCKING PATTERN EXPECTED. DRY
WEATHER FORESEEN WITH SEASONABLE TEMPERATURES.

SOUTHEAST CANADA UPPER LOW SHIFTS WEST SOME AS EASTERN PACIFIC
TROUGH MOVES EAST FOR THE END OF THE WEEK. RESULT WILL BE A BACK
DOOR FRONTAL BOUNDARY PUSHING WEST ACROSS THE CWA...WHICH WILL BE
THE FOCUS FOR ANY PRECIPITATION AS SEVERAL WEAK WAVES MOVES ACROSS
THE NORTHERN ROCKIES INTO THE PLAINS. MODELS ARE NOT IN VERY GOOD
AGREEMENT WITH DETAILS.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z SUNDAY
ISSUED AT 213 PM MDT SAT APR 18 2015

A SLOW MOVING UPPER LOW WILL KEEP RAIN/ISOLATED TS ACROSS THE
AREA THIS AFTERNOON/EVENING. MVFR CIGS/VSBYS WILL OCCUR EXCEPT
ACROSS FAR NORTHWEST SD/NORTHEAST WY. LOCAL LIFR CIGS/VSBYS
EXPECTED OVER THE HIGHER TERRAIN OF THE BLACK HILLS. CONDITIONS
WILL IMPROVE FROM NORTHWEST TO SOUTHEAST BEGINNING THIS EVENING AS
A COLD FRONT MOVES THROUGH TONIGHT. GUSTY NORTHWEST WINDS ARE
EXPECTED BEHIND THE FRONT.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
WY...NONE.
&&

$$

SHORT TERM...15
LONG TERM...HELGESON
AVIATION...HELGESON



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