Area Forecast Discussion
Issued by NWS Rapid City, SD

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428
FXUS63 KUNR 200431
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1031 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 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1026 PM MDT TUE MAY 19 2015

LOW PRESSURE OVER THE CNTRL ROCKIES WILL MAINTAIN LOW CLOUDS AND
SHOWERS OVER THE SOUTHERN HALF OF THE FA TONIGHT IN RAIN AND/OR
SNOW. MVFR/IFR CIGS CAN BE EXPECTED THERE. VFR CONDITIONS ARE
EXPECTED FOR THE NERN HALF OF THE AREA. PRECIP IS EXPECTED TO
SHIFT EAST EARLY WED MORNING...WITH DRY AIR SLOWLY SHIFTING BACK
SOUTH INTO THE FA WED. THIS WILL SUPPORT A TREND BACK TO VFR N-S.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...FLOOD WATCH THROUGH LATE WEDNESDAY NIGHT FOR SDZ042-043.

WY...NONE.
&&

$$

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



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