Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 151911
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
111 PM MDT TUE APR 15 2014

.SHORT TERM...THIS EVENING THROUGH WEDNESDAY NIGHT
ISSUED AT 108 PM MDT TUE APR 15 2014

THE LATEST WATER VAPOR IMAGES SHOWED A SHORT-WAVE TROUGH MOVING
ACROSS THE NWRN CONUS...TOWARD WY. A JET STREAK WAS ROUNDING THE
BASE OF THE TROUGH...AND THUS THE TROUGH IS EXPECTED TO INTENSIFY.
THIS TROUGH WILL MOVE ACROSS THE FORECAST AREA TONIGHT AND
WEDNESDAY MORNING...BRINGING A MIX OF RAIN AND SNOW.

FOR THE REST OF THIS AFTERNOON CLOUDS WILL BE INCREASING AND IT WILL
REMAIN MILD AS A LOW-LEVEL THERMAL RIDGE IS OVER THE AREA. THE
LEADING EDGE OF THE Q-VECTOR CONVERGENCE WILL REACH ERN WY BY 00Z.
THIS EVENING THE FAST-MOVING...COMPACT...BUT STRONG TROUGH WILL
SPREAD RAIN ACROSS THE NWRN HALF OF THE AREA. LOW-LEVEL THERMAL
PROFILES AND SREF/NAM/GFS/RAP MODEL GUIDANCE SUGGESTS THAT BY 06Z
SNOW WILL BE OVER THE HIGHEST BLKHLS AND HIGHER TERRAIN OF NERN WY.
PRECIPITATION AMOUNTS WILL BE TEMPERED BY THE FAST MOVEMENT OF THE
SYSTEM...YET...PRECIP RATES WILL BE ENHANCED BY STEEP LAPSE RATES
(NEAR MOIST-NEUTRAL) AND STRONG Q-VECTOR CONVERGENCE AND UPSLOPE
FLOW OVER THE NWRN BLKHLS. THIS IS EXPECTED TO BRING 1-3 INCHES OF
SNOW FOR THE HIGHEST ELEVATIONS TONIGHT.

RAIN WILL MIX WITH SNOW OVER THE WRN SD PLAINS LATE TONIGHT...BUT
THE FAST MOVEMENT OF THE TROUGH COMBINED WITH TEMPERATURES IN THE
LOWER 30S WILL PRECLUDE SNOWFALL ACCUMULATIONS. AT MOST 1-2 INCHES
OF SNOW MAY ACCUMULATE IN THE HIGHER TERRAIN OF THE NERN WY PLAINS.
ON WEDNESDAY MORNING THE WAVE AND Q-G FORCING WILL MOVE EAST EARLY
AND WILL BE FOLLOWED BY GUSTY NORTHWEST WINDS (850-MB WINDS OF 20-40
KT). STEEP LAPSE RATES...CYCLONIC FLOW ALOFT...AND RESIDUAL MOISTURE
OVER THE AREA WILL RESULT IN A CONTINUED CHANCE OF RAIN/SNOW SHOWERS
...WITH SNOW CONFINED MOSTLY TO THE BLKHLS...NERN WY...AND NWRN SD.
ON WEDNESDAY NIGHT IT WILL BE MOSTLY DRY...BUT A WEAK SHORT-WAVE
TROUGH MAY BRING ADDITIONAL SCATTERED SHOWERS TO THE AREA.

&&

.LONG TERM...THURSDAY THROUGH TUESDAY
ISSUED AT 108 PM MDT TUE APR 15 2014

UNSETTLED CONDITIONS WILL CONTINUE ON THURSDAY AS UPPER TROF
WORKS THROUGH THE NRN PLAINS...WITH STEEP LAPSE RATES RESULTING IN
SCT PCPN FOR THE REGION. TEMP FCST REMAINS TRICKY WITH WARM
ADVECTION SETTING IN FOR THE WRN 2/3RDS OF CWFA...AND HAVE
UNDERCUT GUIDANCE A BIT GIVEN EXPECTED CLOUD COVER AND PCPN. MUCH
WARMER TEMPS THEN EXPECTED FOR FRI AS SHORT WAVE RIDGE CROSSES THE
NRN PLAINS. ANOTHER QUICK MOVING DISTURBANCE ROTATES THROUGH
FRIDAY NIGHT FOR ANOTHER BRIEF PCPN EVENT...ALTHOUGH TEMPS LOOK TO
BE WARM ENOUGH FOR MOSTLY LIQUID. FLAT UPPER RIDGE THEN BUILDS
INTO THE PLAINS FOR THE WEEKEND AND EARLY NEXT WEEK...WITH DRY
WEATHER AND WARMER TEMPERATURES.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON
ISSUED AT 108 PM MDT TUE APR 15 2014

VFR CONDITIONS WILL CONTINUE THROUGH THIS AFTN. A CDFNT WILL MOVE
THROUGH THE AREA TONIGHT. WDSPRD MVFR/IFR CIGS WILL DEVELOP BEHIND
THE CDFNT ALONG WITH GUSTY NW WINDS. RAIN WILL ALSO DEVELOP
TONIGHT...CHANGING TO SNOW OVER NERN WY AND THE BLKHLS LATE
TONIGHT...WITH A RAIN/SNOW MIX POSSIBLE VERY LATE TONIGHT ON THE
SD PLAINS. IFR CONDITIONS IN SNOW EXPECTED OVER NERN WY AND THE
NRN BLKHLS FROM LATE TONIGHT INTO WED MRNG.

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

$$

SHORT TERM...BUNKERS
LONG TERM...JOHNSON
AVIATION...JOHNSON






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