Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 032310
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
510 PM MDT FRI JUL 3 2015

.SHORT TERM...THIS EVENING THROUGH SATURDAY NIGHT
ISSUED AT 209 PM MDT FRI JUL 3 2015

THE 20Z SURFACE ANALYSIS HAD A 1016MB HIGH OVER CENTRAL NEBRASKA
DRIFTING SOUTHEAST. THE FLOW AROUND THE HIGH HAS RESULTED IN
SOUTHERLY WINDS ACROSS MOST OF THE CWA. A CU FIELD HAS DEVELOPED
ACROSS THE BLACK HILLS AND WESTERN SOUTH DAKOTA...AND THERE ARE A
COUPLE OF WEAK SHOWERS OFF OF THE BLACK HILLS. IN ADDITION TO
SCATTERED CONVECTION NEAR THE BLACK HILLS...MODELS INDICATE
CONVECTION FIRING OFF THE BIGHORNS AND HIGH TERRAIN OF NORTH
CENTRAL WYOMING LATER THIS AFTERNOON AND MOVING ACROSS PARTS OF
CAMPBELL AND WESTON COUNTIES. NONE OF THE CONVECTION TODAY IS
EXPECTED TO BE SEVERE.

TONIGHT...THE LLJ STRENGTHENS OVER PART OF THE CWA AND MODELS INDICATE
SOME CONVECTION DEVELOPING AROUND 6Z. ELEVATED INSTABILITY OVERNIGHT
IS RATHER WEAK...BUT HAVE INCLUDED ISOLATED POPS TO ACCOUNT FOR
THE POSSIBILITY OF STORMS.

FOR INDEPENDENCE DAY...MOST OF CWA WILL BE IN A WARM AND MOIST SOUTHERLY
FLOW AHEAD OF A BROAD SURFACE LOW. MODEL GUIDANCE SHOWS VERY
WEAK...IF ANY...FORCING ALOFT AND ONLY A WEAK SURFACE TROUGH IN
WESTERN SOUTH DAKOTA. WHILE STORM CHANCES WILL BE VERY LIMITED
ACROSS THE CWA...THE BEST CHANCE FOR ANY CONVECTION WILL BE NEAR
THE BLACK HILLS WHERE OROGRAPHIC EFFECTS COULD HELP INITIATE A
STORM OR TWO IN THE AFTERNOON. OUTSIDE OF THE BLACK HILLS...MODEL
GUIDANCE HINTS AT ISOLATED CONVECTION FIRING OFF ALONG THE SURFACE
TROUGH IN WESTERN SOUTH DAKOTA AS THE CAP SLOWLY ERODES BY LATE
AFTERNOON. WITH CAPE FORECAST TO BE BETWEEN 2000-3000 J/KG...AND
0-6KM SHEAR APPROACHING 40 KNOTS...ANY CONVECTION THAT DOES FORM
COULD BE SEVERE. CONVECTION IN THE EASTERN PART OF THE CWA COULD
PERSIST DURING THE OVERNIGHT HOURS DUE TO THE LLJ STRENGTHENING AND
ELEVATED INSTABILITY.

.LONG TERM...SUNDAY THROUGH FRIDAY
ISSUED AT 209 PM MDT FRI JUL 3 2015

A STRONG SHORTWAVE AND A COLD FRONT WILL CROSS THE NORTHERN
PLAINS ON SUNDAY. EXACT TIMING OF THESE FEATURES IS A BIT
UNCERTAIN...ESPECIALLY THE POST FRONTAL SHORTWAVE. ECMWF IS SLOWER
THAN THE NAM...WITH THE GFS COMING MORE IN LINE WITH THE ECMWF. IN
GENERAL...WILL KEEP THE BEST CHANCES FOR PCPN DURING THE AFTERNOON
AND EVENING HOURS. THE OVERALL THREAT FOR SEVERE WEATHER WILL BE
SOMEWHAT DEPENDENT ON TIMING...BUT AREAS SOUTH AND EAST OF THE
BLACK HILLS IN A BETTER SHEAR AND INSTABILITY ENVIRONMENT SHOULD
HAVE THE BETTER POTENTIAL FOR SEVERE STORMS.

THE SYSTEM WILL EXIT LATE SUNDAY NIGHT...WITH DRIER WEATHER
EXPECTED INTO AT LEAST EARLY TUESDAY. FLOW ALOFT WILL BECOME MORE
ZONAL BY MIDWEEK...WITH INCREASING CHANCES FOR SHOWERS AND STORMS
LATER TUESDAY THROUGH WEDNESDAY. BEYOND THAT...A TROF IS FORECAST
TO DEVELOP ALONG THE WEST COAST LATE IN THE WEEK...WITH FLOW ALOFT
HERE EVENTUALLY BECOMING SOUTHWESTERLY. WILL KEEP LOWER CHANCES
FOR SHOWERS AND THUNDERSTORMS IN THE FORECAST FOR LATE NEXT WEEK.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 505 PM MDT FRI JUL 3 2015

VFR CONDITIONS GENERALLY EXPECTED THROUGH THE PERIOD. SMOKE FROM
CANADIAN WILDFIRES MAY REDUCE VISIBILITIES TO MVFR AT
TIMES...MAINLY TO THE NORTHEAST OF THE BLACK HILLS. ISOLATED TO
WIDELY SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE THIS
EVENING AND OVERNIGHT...MAINLY ACROSS NORTHEAST WY AND THE BLACK
HILLS AREA. AFTERNOON THUNDERSTORMS WILL THEN BE POSSIBLE OVER
MUCH OF WESTERN SOUTH DAKOTA SAT AFTERNOON. LOCAL MVFR CONDITIONS
ARE POSSIBLE WITH ANY HEAVIER SHOWERS.

&&

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

$$

SHORT TERM...MCKEMY
LONG TERM...26
AVIATION...JC



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