Area Forecast Discussion
Issued by NWS Rapid City, SD

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910
FXUS63 KUNR 052038
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
238 PM MDT THU MAY 5 2016

.SHORT TERM...THIS EVENING THROUGH FRIDAY NIGHT
ISSUED AT 220 PM MDT THU MAY 5 2016

AFTN SFC ANALYSIS SHOWS SOUTHERLY WINDS HAVE DEVELOPED MUCH OF THE
REGION DUE TO THE PRESSURE GRADIENT BETWEEN HIGH PRESSURE OVER THE
CENTRAL CONUS AND LOW PRESSURE EXTENDING FROM CENTRAL MANITOBA
ACROSS MONTANA AND THEN INTO THE FOUR CORNERS REGION. SUNNY SKIES
AND SUBSIDENCE ASSOCIATED WITH THE UPPER RIDGE HAS HELPED TO PUSH
TEMPERATURES INTO THE UPPER 70S TO MID 80S OVER THE FORECAST AREA.
MODELS ARE SHOWING 500-1000J/KG CAPE OVER THE BLACK HILLS AND
PARTS OF THE WESTERN SOUTH DAKOTA PLAINS HOWEVER SUBSIDENCE AND
RELATIVELY WARM AIR ALOFT WILL KEEP ANY THUNDERSTORMS FROM
DEVELOPING THIS AFTN/EVE.

TONIGHT...A 35-45KT LOW LEVEL JET WILL DEVELOP FROM SOUTHWESTERN
INTO NORTHEASTERN SOUTH DAKOTA. THERE MAY BE SOME BREEZY
CONDITIONS OVER THE HIGHER ELEVATIONS OF THE BLACK HILLS TONIGHT. THETA-E
ADVECTION WILL REMAIN RATHER WEAK HOWEVER SOME ACCAS MAY
FORM...BUT WITH RATHER DRY LOWER LEVELS EXPECT ONLY VIRGA TO
RESULT.

ON FRIDAY...THE UPPER RIDGE WILL MOVE OFF TO THE EAST AS A COLD
FRONT DROPS SOUTHWARD INTO THE FORECAST AREA. MOISTURE POOLING
ALONG BOUNDARY DURING PEAK HEATING...ESPECIALLY OVER SOUTHERN HALF
OF CWA...WILL RESULT IN 500- 1000J/KG MLCAPE AND WEAK 0-6KM BULK
SHEAR. MLCIN WEAK ENOUGH TO ALLOW TSRA TO DEVELOP IN THE AFTERNOON
AHEAD OF SHORTWAVE MOVING ACROSS CO INTO WY...WHICH IS AHEAD OF
UPPER LOW SPINNING OVER CA/NV. TEMPERATURES WILL BE TRICKY WITH
CLOUD COVER/PRECIPITATION COVERAGE AFFECTING EVENTUAL READINGS.

FRIDAY NIGHT...TSRA ACTIVITY QUIETS DOWN SOME WITH -SHRA BECOMING
MORE PREVALENT UNDER FAIRLY MOIST EAST/NORTHEAST BOUNDARY LAYER
FLOW. FORCING AHEAD OF UPPER LOW WILL BE FOCUSED OVER SOUTHWEST
THIRD OF CWA WHERE HIGHEST POPS WERE PAINTED. LOWS WILL BE NEAR
GUIDANCE.

.LONG TERM...SATURDAY THROUGH THURSDAY
ISSUED AT 220 PM MDT THU MAY 5 2016

A LARGE UPPER LEVEL LOW LIFTS OUT OF THE DESERT
SOUTHWEST INTO THE CENTRAL ROCKIES BY SUNDAY. THEN IT SLOWLY DRIFTS
EASTWARD ACROSS THE CENTRAL PLAINS ON MONDAY AND TUESDAY. ANOTHER
LOWS PUSHES SOUTHEASTWARD INTO THE NORTHERN ROCKIES BY MONDAY. THIS
WILL LEAD TO AN UNSETTLED AND WET WEATHER PATTERN...WITH DAILY
CHANCES FOR SHOWERS AND SOME ISOLATED THUNDERSTORMS. NEAR SEASONAL
TEMPERATURES ARE EXPECTED THROUGH THE EXTENDED PERIOD.

&&

.AVIATION...FOR THE 18Z TAFS THROUGH 18Z FRIDAY
ISSUED AT 220 PM MDT THU MAY 5 2016

VFR CONDITIONS ARE EXPECTED THROUGH THE FORECAST PERIOD.
A STRONG COLD FRONT WILL ENTER THE NORTHERN AND WESTERN PORTIONS OF
THE FORECAST AREA FRIDAY MORNING...WITH SURFACE WINDS SWITCHING TO
THE NORTH AND INCREASING TO 25 KTS.

&&

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

$$

SHORT TERM...10
LONG TERM...15
AVIATION...15



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