Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KFSD 271103
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
603 AM CDT THU AUG 27 2015

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 401 AM CDT THU AUG 27 2015

AN MCS HAS DEVELOPED OVER WESTERN AND CENTRAL SOUTH DAKOTA AND WILL
HAS BEGUN MOVING INTO OUR WESTERN FORECAST AREA. THIS COMPLEX HAS A
HISTORY OF VERY STRONG WINDS WITH MIDLAND SD REPORTING 79 MPH GUSTS
AS IT MOVED OVERHEAD. GIVEN THAT THIS COMPLEX IS SHOWING SIGNS OF
WEAKENING AS IT MOVES EAST...THINK THAT THE SEVERE WIND THREAT WILL
BE GREATEST IN OUR SOUTH CENTRAL SD COUNTIES. HRRR SUGGESTS THAT IT
WILL SIGNIFICANTLY WEAKEN BY THE TIME IT HEADS EAST OF THE JAMES
RIVER.

THINK THIS THIS INITIAL WAVE OF SHOWERS AND THUNDERSTORMS WILL
APPROACH I29 SHORTLY AFTER SUNRISE AND WEAKEN FURTHER AS IT MOVES
THROUGH SW MN AND NW IA THROUGH MIDDAY.  THERE WILL LIKELY BE SOME
SORT OF BREAK IN ACTIVITY BEHIND THIS COMPLEX...BUT THIS WILL BE
SHORT LIVED. SURFACE LOW PRESSURE SLIDING EASTWARD ALONG THE
MISSOURI RIVER AHEAD OF THE MAIN UPPER LOW DIGGING INTO CENTRAL
SD...WILL IGNITE FURTHER CONVECTION LATER THIS AFTERNOON AS WARM AIR
AND MOISTURE CONTINUES TO ADVECT INTO THE REGION. THIS INITIAL
ACTIVITY WILL LIKELY BE FOCUSED IN THE NORTHWEST FORECAST AREA LATE
AFTERNOON WITH SHOWERS AND THUNDERSTORMS BECOMING WIDESPREAD THIS
EVENING ACROSS THE BULK OF THE CWA AS THE LOW LEVEL JET INTENSIFIES.
THIS SYSTEM SLOWLY TRUDGES EASTWARD OVERNIGHT WITH THE BEST CHANCES
FOR PRECIPITATION MAINLY ACROSS THE I29 CORRIDOR AND POINTS
EASTWARD.

PRECIPITABLE WATER VALUES REMAIN ABOVE NORMAL TODAY AND TONIGHT...SO
RAINFALL WILL LIKELY TO BE MODERATE TO HEAVY AT TIMES. FLASH
FLOODING WILL BE A CONCERN...BUT GIVEN THE HIGH FLASH FLOOD GUIDANCE
ON THE ORDER OF 2 TO 3 INCHES PER 3 HOURS IN THE CENTRAL AND EASTERN
FORECAST AREA WHERE THE HEAVIEST AMOUNTS ARE EXPECTED...WILL NOT
ISSUE ANY HEADLINES AT THIS POINT. BUT WILL NEED TO MONITOR THIS
POTENTIAL THIS EVENING AND TONIGHT. FORECAST SOUNDINGS SUGGEST THAT
SEVERE WEATHER THREAT WILL RATHER LOW THIS AFTERNOON AND
EVENING...BUT GIVEN THE STRONG DYNAMICS OF THE UPPER WAVE THERE IS A
SMALL THREAT FOR MARGINAL HAIL OR WINDS...MAINLY NEAR THE MO VALLEY.
BY LATE EVENING THIS THREAT DROPS SIGNIFICANTLY...AS WILL THE
POTENTIAL FOR MUCH THUNDER AT ALL. HIGHS TODAY WILL BE HAMPERED A
BIT BY THE CLOUDS AND RAIN TODAY...BUT WILL BE MILD IN THE MID 70S
TO LOWER 80S.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 401 AM CDT THU AUG 27 2015

SIGNIFICANT WEATHER CONTINUES TO BE FRONT WEIGHTED AT THE START OF
THE LONGER RANGE. DEEPENING UPPER LEVEL WAVE SHOULD BE FAIRLY CLOSE
TO BEING CENTERED RIGHT OVER THE FSD CWA AT 12Z FRIDAY...BUT STILL
DEALING WITH A COUPLE DISTINCT COMMUNITIES OF SOLUTIONS...ONE A BIT
MORE NORTHWARD CONSISTING OF MOST OF THE DETERMINISTIC MODELS...AND
ONE MORE SOUTHWARD CONSISTING OF THE CANADIAN AND WRF-ARW/WRF NMM.
SOME HINTS IN THE WATER VAPOR EARLY THIS MORNING SUGGEST A BIT MORE
CREDENCE SHOULD BE GIVEN TO THIS SUBSET...WITH STRONGER OF THE WAVES
MOVING THROUGH SOUTHERN UTAH AND WHAT IMPACT THE CURRENT MCS WILL
HAVE ON BOUNDARY LOCATION. WHEREVER THE EXACT UPPER LOW SETS UP BY
EARLY FRIDAY...THE EASTERN CWA WILL REMAIN IN A PRECIPITATION
FAVORED DYNAMIC SET UP.

ONE THING THAT MAY BE A CHALLENGE IS GETTING A GREAT COVERAGE OF
THUNDER...WITH MOST PROFILES SIDING CLOSER TO MOIST NEUTRAL NEAR AND
BEHIND THE UPPER LOW. CONTINUE TO SHOW TRAJECTORY WRAPPING MID LEVEL
FRONTAL SUPPORT AND PRECIPITATION BEHIND SYSTEM...SO WILL CONTINUE
WITH A PERIOD OF CATEGORICAL PRECIPITATION DURING THE MORNING ACROSS
SOUTHWEST MINNESOTA...BUT ON A GRADUAL DECLINE FROM WEST TO EAST.
EVEN IF PRECIPITATION DOES END OVER MOST OF THE AREA BY EARLY TO MID
AFTERNOON...WILL CONTINUE TO HAVE FAIRLY WIDESPREAD CLOUDINESS
LINGER OVER MOST OF THE AREA TO IMPACT HEATING. WILL LIKELY HOLD
TEMPS IN THE UPPER 60S IN THE FAR EAST...AND SOME LATE DAY SUNSHINE
SHOULD PUSH TEMPS CLOSER TO 80 IN THE WEST.

CONCERN GOING INTO FRIDAY NIGHT WITH UPPER LOW CONTINUING TO SLOWLY
PULL EASTWARD IS JUST HOW MUCH PUSH THE STRATUS FIELD WILL GET
BEFORE FLOW WEAKENS WITH BUILDING RIDGE. MOST OF THE CWA TRAJECTORY
WOULD FAVOR DRYING...BUT THE FAR SOUTHEAST COULD SEE STRATUS LINGER
INTO MUCH OF THE NIGHT. EVEN NOT IMPOSSIBLE FOR THERE TO BE SOME
AREAS OF FOG WITHIN THE SURFACE RIDGE AXIS TOWARD THE I29 CORRIDOR.

FLOW WILL CONTINUE TO TREND TOWARD SOUTHERLY OVER THE REMAINDER OF
THE AREA AS WE MOVE THROUGH SATURDAY...AND THIS SOUTHERLY FLOW WILL
BE A FEATURE OF THE FORECAST FOR THE REMAINDER OF THE EXTENDED.
FEATURES...IN FACT...ARE FAIRLY STABLE THROUGH THE PERIOD WITH A
COUPLE OF WAVES PUSHING OVER A POSITIVELY TILTED RIDGE. POTENTIALLY
COULD GET A WEAK FRONTAL BOUNDARY TO LAY DOWN ACROSS THE AREA TOWARD
TUESDAY/WEDNESDAY...BUT FOR NOW WITH THE WARMISH TEMPS ALOFT AND
DISTINCT LACK OF CONVERGENCE ANYWHERE NEAR THE AREA...HAVE REMOVED
ATTEMPT BY BLENDED INITIALIZATION FOR SEVERAL PERIODS OF LOWER
PRECIPITATION CHANCES. OTHERWISE...TEMPS APPEAR TO HAVE A BIT OF A
COOL BIAS IN THE BLEND AND HAVE PUSHED MOST DAYTIME READINGS UP A
COUPLE DEGREES BY TUESDAY AND WEDNESDAY. TEMPTED TO DO MORE...BUT
INCREASED MOISTURE IN THE LOWER LEVELS AND WARMING TEMPS ALOFT
SHOULD KEEP SURFACE TEMPS BELOW MAXIMUM MIXING. READINGS IN THE WEST
WILL OCCASIONALLY PUSH INTO THE LOWER 90S...WHILE GENERALLY 80S
PREVAIL EACH DAY CENTRAL AND EAST. OVERNIGHT LOWS WILL MAINLY HOLD
IN THE LOWER TO MID 60S.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 557 AM CDT THU AUG 27 2015

COMPLEX OF SHOWERS AND THUNDERSTORMS MOVING SLOWLY EASTWARD ACROSS
SOUTHEAST SD AND NORTHEAST NEBRASKA WILL CONTINUE TO DISSIPATE AS
IT MOVES THROUGH AREAS EAST OF I29 THIS MORNING. SCATTERED SHOWERS
AND STORMS WILL REMAIN POSSIBLE TODAY BEHIND THIS BAND...BUT THE
BETTER CHANCES FOR PRECIPITATION ARRIVE AFTER 21Z IN THE NORTHWEST
AND EXPAND ELSEWHERE THIS EVENING. EXPECT MAINLY VFR CONDITIONS
TODAY WITH THE EXCEPTION OF SOME LOWER VISIBILITIES UNDER SHOWERS.
OTHERWISE...AS THE RAIN EXPANDS THIS EVENING AND
OVERNIGHT...MVFR/IFR CEILINGS AND VISIBILITY WILL BECOME MORE
LIKELY...PARTICULARLY AFTER MIDNIGHT.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...
LONG TERM...CHAPMAN
AVIATION...


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.