FXUS63 KUNR 112045
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
243 PM MDT SUN MAY 11 2008

.DISCUSSION...20Z SFC ANALYSIS SHOWS A SFC HIGH PRESSURE RIDGE OVER
ERN SD/NEB WITH FALLING PRESSURE OVER MONTANA IN REPONSE TO AN
APPOACHING UPPER TROUGH.

THE UPPER TROUGH WILL MOVE FROM THE ROCKIES INTO THE CENTRAL PLAINS
TONIGHT AND MONDAY...ALLOWING A COLD FRONT TO CROSS THE FORECAST
AREA. POST FRONTAL PRECIPITATION CHANCES WILL INCREASE AS SYNOPTIC
LIFT INCREASES AHEAD OF THE UPPER TROUGH. TEMPERATURES BEHIND THE
FRONT ON MONDAY ARE GENERALLY EXPECTED TO BE IN THE 50S...BUT
DEPENDING ON THE TIMING OF THE FRONT...TEMPERATURES MAY RISE INTO
THE LOWER 70S AHEAD OF THE TROUGH OVER SOUTH CENTRAL SOUTH DAKOTA ON
MONDAY AFTERNOON. THE WARM TEMPERATURES COMBINED WITH LIFT ALONG THE
FRONTAL BOUNDARY WOULD CREATE ENOUGH INSTABILITY FOR A CHANCE OF
AFTN AND EVENING THUNDERSTORMS OVER THAT AREA. TEMPERATURES ALOFT
WILL BE COLD ENOUGH ON MONDAY NIGHT FOR SOME SNOW IN THE HIGHER
ELEVATIONS OF THE BLACK HILLS...BUT ACCUMULATION WOULD BE MINOR. ON
TUESDAY...LINGERING MORNING RAIN SHOWERS...MIXED WITH SNOW SHOWERS
IN THE WEST...WILL GIVE WAY TO DECREASING CLOUDS AS DRIER AIR AND
SYNOPTIC SCALE SUBSIDENCE MOVES INTO THE REGION BEHIND THE DEPARTING
UPPER TROUGH.

EXTENDED...CYCLONIC FLOW ALOFT WILL BRING A VARIETY OF WEAK
DISTURBANCES ACROSS THE AREA THROUGH THURSDAY...BRINGING A DAILY
CHANCE OF PRECIPITATION AND SLIGHTLY BELOW AVERAGE TEMPERATURES. A
PROLONGED DRIER AND MILDER PATTERN IS EXPECTED TO RETURN BY THE END
OF THE WEEK.

&&

.AVIATION...VFR CONDITIONS WILL PREVAIL THROUGH THIS EVENING.
ISOLATED SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE GENERALLY NORTH
OF THE BLACK HILLS OVERNIGHT AS AN UPPER LEVEL TROF STARTS TO
APPROACH THE AREA...THOUGH CIGS AND VIS ARE EXPECTED TO REMAIN VFR.

&&

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

$$