Area Forecast Discussion
Issued by NWS Rapid City, SD

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083
FXUS63 KUNR 151729
AFDUNR

AREA FORECAST DISCUSSION FOR WESTERN SD AND NORTHEASTERN WY
NATIONAL WEATHER SERVICE RAPID CITY SD
1129 AM MDT FRI MAY 15 2015

.UPDATE...
ISSUED AT 1123 AM MDT FRI MAY 15 2015

VERY LITTLE CHANGED TO THE FCST...MOSTLY TO ACCOUNT FOR CURRENT
CONDITIONS. STILL WATCHING FOR THE POTENTIAL FOR SVR STORMS THIS
AFTN/EVE. LOW CLOUDS ARE HANGING TOUGH ACRS THE CWFA...ALTHOUGH
SOME CLEARING NOTED OVER PARTS OF NCNTRL NEB. CLEARING WILL BE THE
KEY TO SFC BASED CONVECTION...AND ESPECIALLY FOR ANY TORNADIC
THREAT (SHEAR VALUES WILL BE SUFFICIENT). IF CLEARING DOES
OCCUR...THIS BEST THREAT FOR SVR CONVECTION AND POSSIBLE TORNADOES
WILL BE ACRS FAR SWRN AND SCNTRL SD. HEAVY RAINFALL THEN BECOMES
THE PRIMARY ISSUE FOR THIS EVENING AS STRONG SHORT WAVE ROTATES
NWD THROUGH THE CWFA. CURRENT FCST IS HANDLING THIS WELL.

&&

.SHORT TERM...TODAY THROUGH SATURDAY NIGHT
ISSUED AT 300 AM MDT FRI MAY 15 2015

CURRENT SURFACE MAP SHOWS HIGH PRESSURE RIDGE INTO NORTH
DAKOTA...WITH LOW ACROSS EASTERN COLORADO. AREAS FOG/DRIZZLE
LOCATED ACROSS MUCH OF WESTERN SOUTH DAKOTA. SCATTERED
SHOWERS/THUNDERSTORMS INCREASING IN COVERAGE ACROSS NORTHEAST
WYOMING INTO THE NEBRASKA PANHANDLE...LIFTING NORTHWARD INTO
SOUTHWEST SOUTH DAKOTA.

LARGE UPPER TROF LOCATED ACROSS THE FOUR CORNERS REGION...WITH
EMBEDDED SHORTWAVES. AS JET STREAK ROTATES AROUND UPPER TROF THIS
MORNING...LEAD SHORTWAVE LIFTS THROUGH EASTERN WYOMING/WESTERN
SOUTH DAKOTA. HI-RESOLUTION MODELS HAVE A DECENT HANDLE ON CURRENT
CONVECTION...SPREADING INTO WESTERN SOUTH DAKOTA THIS MORNING.
SECOND ROUND OF CONVECTION EXPECTED LATER THIS AFTERNOON/EVENING.
WITH ABUNDANT LOW CLOUDS AND EARLY CONVECTION...QUESTION WILL BE
HOW MUCH CLEARING OCCURS ACROSS SOUTHWEST/SOUTH CENTRAL SOUTH
DAKOTA FOR THIS AFTERNOON. WITH SURFACE LOW DEEPENING ACROSS
WESTERN NEBRASKA...BL-850MB MOIST EASTERLY FLOW WILL HELP KEEP
LOW CLOUDS THROUGH MUCH OF THE DAY. BEST CHANCE OF CLEARING WILL
BE ALONG NEBRASKA BORDER THIS AFTERNOON. MLCAPE INCREASES TO
1000-1500J/KG IN AREAS THAT CLEAR OUT. STRONG SHEAR WILL ALLOW FOR
ROTATING UPDRAFTS...WITH LARGE HAIL MAIN THREAT. GIVEN 0-1KM
SHEAR...ISOLATED TORNADOES POSSIBLE. LOCALLY HEAVY RAIN POSSIBLE
THIS AFTERNOON/EVENING.

FOCUS FOR PRECIPITATION SHIFTS NORTH AND WEST OF FORECAST AREA
TONIGHT/EARLY SATURDAY AS INITIAL SHORTWAVE LIFTS INTO MONTANA.
AS UPPER TROF/LOW LIFTS ACROSS THE ROCKIES ON SATURDAY...MORE
SHOWERS/THUNDERSTORMS EXPECTED ACROSS THE AREA. SEVERE
THUNDERSTORM POTENTIAL SHIFTS INTO CENTRAL SOUTH DAKOTA WITH BEST
INSTABILITY/SHEAR.

.LONG TERM...SUNDAY THROUGH THURSDAY
ISSUED AT 300 AM MDT FRI MAY 15 2015

MEDIUM RANGE MODELS IN GOOD AGREEMENT ON MOVING UPPER
LOW ACROSS THE DAKOTAS INTO NORTHERN MN SUNDAY AND SUNDAY NIGHT.
RAIN SHOWERS WILL BE MOST NUMEROUS ON SUNDAY ACROSS THE BLACK HILLS
INTO CENTRAL SD...WITH ISOLATED THUNDERSTORMS OVER EASTERN PORTIONS
OF THE CWA. A LITTLE LIGHT SNOW IS POSSIBLE ACROSS THE HIGHER
ELEVATIONS OF THE BLACK HILLS. STRONG NORTHWESTERLY WINDS ARE
EXPECTED TO DEVELOP ON SUNDAY ACROSS THE WESTERN SD PLAINS...
ESPECIALLY FROM 2WX TO RAP. SHOWERS WILL TAPER OFF FROM WEST TO EAST
DURING THE AFTERNOON AND EVENING....WITH WINDS ALSO DECREASING
SUNDAY EVENING.

A DRY DAY CAN BE EXPECTED MONDAY AS THE AREA WILL BE BETWEEN
SYSTEMS. THE NEXT SYSTEM WILL MOVE ACROSS THE WESTERN STATES MONDAY
NIGHT AND TUESDAY...WITH SOUTHWEST FLOW ALOFT DEVELOPING OVER THE
AREA AHEAD OF IT. CHANCES FOR SHOWERS WILL INCREASE FROM SOUTHWEST
TO NORTHEAST ACROSS THE CWA MONDAY NIGHT AND TUESDAY. WIDESPREAD
CHANCES FOR SHOWERS CAN BE EXPECTED TUESDAY AFTERNOON INTO WEDNESDAY
AS THE UPPER LOW TRACKS OVER THE AREA AND EVENTUALLY WEAKENS.
ANOTHER SYSTEM COULD DEVELOP OVER THE WESTERN STATES LATE IN THE
WEEK...WITH CHANCES FOR SHOWERS AND THUNDERSTORMS INCREASING AGAIN
TOWARD THE END OF THE WEEK. TEMPERATURES WILL MOSTLY BE BELOW
AVERAGE NEXT WEEK...WITH HIGHS IN THE 50S AND LOWER 60S MOST DAYS.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY)
ISSUED AT 1118 AM MDT FRI MAY 15 2015

FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING
ISSUED AT 536 AM MDT FRI MAY 15 2015

AN UPPER LEVEL LOW PRESSURE SYSTEM...AND MODERATELY UNSTABLE
AIRMASS OVER EASTERN WY AND WESTERN SD...WILL RESULT IN SHOWERS
AND THUNDERSTORMS DEVELOPING AND INCREASING IN COVERAGE THIS
AFTERNOON AS THEY MOVE NORTHWARD ACROSS THE AREA. UPSLOPE WINDS
AT THE SURFACE WILL ALLOW IFR/LIFR CONDITIONS TO PERSIST ACROSS
MUCH OF THE FORECAST AREA TODAY INTO TONIGHT. SHOWERS AND
THUNDERSTORMS WILL BECOME RATHER WIDESPREAD ACROSS THE FORECAST
AREA DURING THE MID AFTERNOON INTO EARLY EVENING HOURS. A FEW
STORMS COULD BECOME SEVERE...ESPECIALLY ACROSS SOUTHWEST AND SOUTH
CENTRAL SD THIS AFTERNOON AND EARLY EVENING...WITH LARGE HAIL AND
STRONG WIND GUSTS POSSIBLE. CONDITIONS MAY IMPROVE ACROSS
NORTHEAST WYOMING AND THE BLACK HILLS BY 12Z SATURDAY MORNING.


&&

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

$$

UPDATE...JOHNSON
SHORT TERM...7
LONG TERM...26
AVIATION...15



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