Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 192017
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
217 PM MDT TUE MAY 19 2015

.SHORT TERM...THIS EVENING THROUGH WEDNESDAY NIGHT
ISSUED AT 139 PM MDT TUE MAY 19 2015

WATER VAPOR SATELLITE SHOWS PLUME OF MOISTURE MOVING NORTHWARD
TOWARD FORECAST AREA AHEAD OF UPPER LOW OVER GREAT BASIN...WITH
RAIN AND SOME SNOW OVER MUCH OF WESTERN NE MOVING NORTHWARD. PRECIPITATION
NOT MAKING MUCH HEADWAY INTO SOUTH DAKOTA AS IT IS ENCOUNTERING
DRIER AIR FROM THE SURFACE RIDGE OVER THE EASTERN DAKOTAS.
DEFORMATION ZONE BETWEEN GREAT BASIN SYSTEM AND SHORT WAVE TROF
MOVING ACROSS ND AIDED BY A JET STREAK FROM CANADA WILL GIVE A
SHARP GRADIENT FROM PRECIP TO DRY CONDITIONS OVER NORTHWESTERN SD.
850HT TEMPS ARE WARMER ON 12Z MODELS...BUT FORECAST SOUNDING SHOW
TEMPERATURES COLD ENOUGH FOR SNOW OVER SOUTHWESTERN SD OVERNIGHT...WITH
A MIX OVER NORTHEASTERN WY AND THE NORTHERN BLACK HILLS...AND RAIN
OVER SOUTH CENTRAL SD. HEAVIEST PRECIP STILL OVER FAR NORTHWESTERN
NE AND INTO SOUTHWESTERN SD...SO WILL LEAVE THE FLOOD WATCH IN
EFFECT FOR NOW. MODELS HAVE ALIGNED IN WEAKENING UPPER LOW AS IT
JOINS THE NORTHERN STREAM WAVE...AND PRECIP ENDS FROM WEST TO EAST
WEDNESDAY. TEMPERATURES WILL BE COOLER WHERE CLOUDS LINGER OVER
SOUTHERN SD.

.LONG TERM...THURSDAY THROUGH TUESDAY
ISSUED AT 139 PM MDT TUE MAY 19 2015

MEDIUM RANGE MODELS STILL SHOWING UNSETTLED WEATHER
THROUGH THE PERIOD AS A LARGE TROUGH OVER THE WRN CONUS CONTINUES TO
EJECT SYSTEMS ACROSS THE ROCKIES AND THE NORTHERN/CENTRAL PLAINS.
WEAKER SHORT-WAVE TROUGHS IN SOUTHWEST FLOW ALOFT WILL BRING MOSTLY
LOW CHANCES FOR SHOWERS AND THUNDERSTORMS LATE THURSDAY INTO FRIDAY
...WITH THE BEST CHANCES ACROSS THE SOUTHERN CWA. A STRONGER SYSTEM
IS PROGGED TO MOVE INTO THE REGION OVER THE WEEKEND. THERE ARE SOME
DIFFERENCES ON THE TIMING...TRACK...AND STRENGTH OF THE
SYSTEM...THUS CONFIDENCE IS RELATIVELY LOW AT THIS POINT ON WHERE
AND WHEN HEAVIEST RAIN WOULD FALL WITH THE SYSTEM...BUT THERE SHOULD
BE SOME DECENT AMOUNTS IN SPOTS. WILL KEEP MOSTLY BROADBRUSHED
HIGHER CHANCE POPS FOR SHOWERS AND STORMS OVER THE WEEKEND. ENOUGH
SHEAR AND CAPE FOR SOME SEVERE STORMS ON SATURDAY...ESPECIALLY
ACROSS THE SRN CWA. WITH REGARD TO TEMPERATURES...THEY SHOULD STAY
BELOW AVERAGE THROUGH THE WEEKEND...WITH HIGHS MOSTLY IN THE MID 50S
TO UPPER 60S. TEMPS SHOULD FINALLY RISE TO NEAR AVERAGE DURING THE
FIRST PART OF NEXT WEEK AS LOW-AMPLITUDE RIDING DEVELOPS OVER THE
WRN CONUS.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY
ISSUED AT 139 PM MDT TUE MAY 19 2015

LOW PRESSURE OVER THE CNTRL ROCKIES WILL MAINTAIN LOW
CLOUDS AND SHOWERS OVER NERN WY AND SWRN SD TODAY...SPREADING ACROSS
SRN SD TNGT. THIS WILL PRODUCE MVFR/IFR CIGS...WITH SOME MVFR/IFR
VSBYS IN HIGHER ELEVATIONS WERE SNOW OCCURS. VFR CONDITIONS ARE
EXPECTED FOR THE NERN HALF OF THE AREA. THIS WILL CONTINUE OVERNIGHT
WITH GRADUAL CLEARING FROM NORTH TO SOUTH ON WED.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...FLOOD WATCH FROM 6 PM MDT THIS EVENING THROUGH LATE WEDNESDAY
     NIGHT FOR SDZ042-043.

WY...NONE.
&&

$$

SHORT TERM...55
LONG TERM...BUNKERS
AVIATION...BUNKERS



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