174 
FXUS63 KUNR 192046
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
246 PM MDT TUE MAR 19 2013

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 234 PM MDT TUE MAR 19 2013

20Z SFC ANALYSIS SHOWS HIGH PRESSURE OVER THE NORTHERN PLAINS.
UPPER ANALYSIS SHOWS UPPER RIDGE OVER THE WEST COAST WITH AN
UPPER TROUGH OVER THE MIDWEST. UPPER JET ENERGY ALONG THE BOUNDARY
IS ENHANCING LIFT AND COMBINING WITH STEEP LOW LEVEL LAPSE RATES
TO PRODUCE ISOLD-SCT -SHSNRA OVER NORTHEASTERN WYOMING...THE BLACK
HILLS AND SOUTHWESTERN SOUTH DAKOTA. THE SHOWERS ARE EXPECTED TO
END LATE THIS AFTERNOON OR EARLY THIS EVENING AS THE JET STREAK
PASSES OFF TO THE SOUTH.

TONIGHT/WEDNESDAY...THE UPPER RIDGE WILL BUILD OVER THE AREA
LEADING TO DRY AND QUIET WEATHER WITH TEMPERATURES ON THE COOL
SIDE OF GUIDANCE.

WEDNESDAY NIGHT...UPPER TROUGH MOVES INTO THE NORTHERN ROCKIES WITH 
ROBUST PRESSURE FALLS/LOW LEVEL JET DEVELOPING AHEAD OF IT. LIFT 
WILL OVERRIDE NORTHWEST/SOUTHEAST ORIENTED BAROCLINIC ZONE IN PLACE 
OVER THE CWA. ONCE DRY AIR IS OVERCOME...FORECAST SOUNDINGS AS WELL 
AS PROBABILISTIC GUIDANCE SUGGESTS -SN MIXED WITH -FZRA POSSIBLE 
OVERNIGHT.

&&

.LONG TERM...(THURSDAY THROUGH TUESDAY)
ISSUED AT 234 PM MDT TUE MAR 19 2013

FORECAST SOUNDINGS CONTINUE TO SUGGEST THE POSSIBILITY FOR FREEZING 
RAIN INTO THURS MORN AS SHORTWAVE TROF CONTINUES ITS APPROACH FROM 
THE WEST. FREEZING RAIN THREAT DIMINISHES BY AFTERNOON AS TEMPS 
WARM. CHANCES FOR RAIN/SNOW CONTINUE THRU THE DAY WITH CHANCES FOR 
SNOW CONTINUING INTO THE EVENING AS SECONDARY TROF SLIDES THRU. 
MODELS THEN TRY AND KEEP PERSISTENT TROF OVER THE REGION INTO THE 
WEEKEND...THEN DIVERGE ON A SOLUTION TO START THE WORK WEEK. AT ANY 
RATE...WITH THE ACTIVE PATTERN WILL KEEP POPS IN THE FORECAST 
THROUGH MOST OF THE PERIOD WITH COOLER TEMPS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 234 PM MDT TUE MAR 19 2013

ISOLD/SCT -SHRASN OVER NERN WY AND WRN SD MAY BRING BRIEF PERIODS
OF MVFR CIGS AND IFR VIS THRU THIS AFTERNOON. OTHERWISE...VFR CONDITIONS
ARE EXPECTED. GUSTY N/NWRLY WINDS OVER THE SD PLAINS WILL CONTINUE
THROUGH THIS AFTERNOON BEFORE DIMINISHING BY EARLY EVE.

&&

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

$$

SHORT TERM...10
LONG TERM...77
AVIATION...77