National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KFSD 240255
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
955 PM CDT WED JUL 23 2014

.UPDATE...
ISSUED AT 950 PM CDT WED JUL 23 2014

FORECAST FOR TONIGHT STILL LOOKS IN PRETTY GOOD SHAPE. THETAE
ADVECTION STILL PROGGED TO INCREASE TONIGHT...WITH THE COMBINATION OF
THIS INCREASING MOISTURE AND STEEPENING LAPSE RATES ALOFT RESULTING IN
INCREASING INSTABILITY. BASED ON SOUNDINGS...APPEARS LIKE CONVECTION
SHOULD BE BASED AROUND 700 MB. AS BY LATER TONIGHT...PARCELS FROM
THIS LAYER SHOULD BE UNCAPPED...AND REALIZE BETWEEN 1000 AND 1500
J/KG OF CAPE. THESE STORMS SHOULD BE BASED ABOVE THE BEST
SHEAR...HOWEVER RAP SOUNDINGS STILL SUGGEST THEY MAY BE ABLE TO TAP
INTO 30 TO 40 KTS OF EFFECTIVE SHEAR. THUS STILL SEEMS LIKE SMALL
HAIL WOULD BE A POSSIBILITY WITH ANY STORM...WITH A FEW OF THE
STRONGER ONES POSSIBLY PUSHING QUARTERS. LEANING TOWARDS THE
HRRR...RAP AND ECMWF FOR TIMING...BRINGING STORMS INTO THE WEST
AROUND 08Z TO 09Z...APPROACHING INTERSTATE 29 BY 12Z. DO THINK STORMS
WILL BE IN A WEAKINING STATE AS THEY APPROACH INTERSTATE 29 AND POINTS
EAST AS THE LOW LEVEL JET SLACKENS WITH DAYBREAK. THE 0Z NAM SEEMS
OFF AND AN OUTLIER SO WAS DISCOUNTED AT THIS TIME. NOT A SURE BET WE
SEE CONVECTION OVERNIGHT...AS THESE ELEVATED EVENTS ARE ALWAYS
TRICKY...SO WILL STAY BELOW LIKELY POPS...BUT AM DEFINITELY LEANING
TOWARDS US AT LEAST SEEING SCATTERED ACTIVITY.

&&

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 317 PM CDT WED JUL 23 2014

MAIN FOCUS OF THE SHORT RANGE FORECAST WILL BE LATE TONIGHT AND
THURSDAY MORNING. DEALING WITH A LOT OF THETAE WARM AIR ADVECTION
MOVING INTO...THEN ACROSS OUR FORECAST AREA...FIRST HITTING OUR FAR
WESTERN ZONES OVERNIGHT TONIGHT...THEN EXITING OUR EAST THURSDAY
AFTERNOON. THE THETAE ADVECTION IS MAXIMIZED IN THE 800-750MB LAYER
AT THE TOP OF THE INVERSION. THE INVERSION IS STRONG IN THE LOW
LEVELS...THEREFORE IT IS LIKELY THAT THE STRONG DIRECTIONAL WIND
SHEAR IN THE LOWEST 1.5KM WILL NOT BE TAPPED...LEAVING ELEVATED
SHOWERS OR STORMS WHICH WILL BE TOUGH TO HIT SEVERE CRITERIA LATE
TONIGHT AND EARLY THURSDAY WEST OF I 29. AS FAR AS POPS...STILL DID
NOT HAVE ENOUGH EVIDENCE TO GO LIKELY POPS AT ANY PARTICULAR
LOCATION FROM 06Z TO 18Z THURSDAY. THE VARIOUS HIRES MODELS ARE
SURPRISINGLY DRY...POSSIBLY DUE TO THE AFOREMENTIONED REASON OF THE
PRECIP BEING ELEVATED. THEREFORE ONLY THE GLOBAL MODELS ARE BULLISH
IN DEVELOPING CONVECTION RIGHT TO THE WEST OF THE MID LEVEL RIDGE
AXIS...WHICH DOES NOT LEAD TO A LOT OF CONFIDENCE IS GOING LIKELY OR
CATEGORICAL POPS YET. WILL JUST HAVE TO MONITOR HOW THIS MORPHS
OUT. AS THE PRECIP TRIES TO MOVE EASTWARD BY MIDDAY THURSDAY...LESS
MID LEVEL MOISTURE LOOKS TO BE AVAILABLE IN OUR EASTERN ZONES BY
THURSDAY AFTERNOON WITH WEAKER THETAE ADVECTION.

TEMPERATURES STILL LOOK PLEASANT TONIGHT. HOWEVER 850MB TEMPERATURES
ARE VERY WARM WEST OF THE JAMES RIVER VALLEY ON THURSDAY BEHIND THE
THETAE ADVECTION. THEREFORE AS SKIES CLEAR IN THE EVENING...STILL
LOOKING AT LOWER 90S APPROACHING CENTRAL SD...WITH A DRAMATIC DROP
OFF IN TEMPERATURES HEADING EAST OF THE THERE. IN FACT EAST OF THE
JAMES...WE ARE STILL LOOKING AT READINGS ONLY A COUPLE OF DEGREES
EITHER SIDE OF 80 AS THE COOL HIGH PRESSURE SYSTEM OVER THE GREAT
LAKES STILL GREATLY INFLUENCES THE WEATHER.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 317 PM CDT WED JUL 23 2014

A RIDGE FLATTENING SHORT WAVE MAY BRING SOME REDEVELOPMENT OF
STORMS THURSDAY NIGHT...ISOLATED WEST AND SCATTERED EAST...MAINLY
FAR EAST WHERE MOST MOISTURE AND INSTABILITY WILL LINGER.
HOWEVER...THIS MOISTURE AND INSTABILITY WILL BE LIMITED AND MOST
OF THE ACTIVITY SHOULD END LATE. ISOLATED STORMS STILL SEEM
POSSIBLE FAR EAST FRIDAY WITH SOME WEAK UPPER AND THERMAL SUPPORT
ASSOCIATED WITH THE LINGERING MOISTURE. ANOTHER SUCH WEAK SYSTEM
MAY BRING A FEW SHOWERS OR STORMS TO THE MISSOURI RIVER AREA LATE
FRIDAY NIGHT AND SATURDAY WHILE MOST OF THE AREA STAYS DRY.
TEMPERATURES FRIDAY AND SATURDAY SHOULD BE MODESTLY WARM AND CLOSE
TO NORMAL WITH 80S HIGHS.

WHAT I DESCRIBED YESTERDAY AS A SECONDARY SHORT WAVE IS NOR A
COOLING CANADIAN UPPER LOW WHICH WILL DIG TOWARD THE WESTERN GREAT
LAKES SUNDAY AND BEGIN TO CARVE OUT A LARGE SCALE TROUGH OVER THE
CENTRAL AND EASTERN USA. A FEW WEAK SHOWERS/STORMS SEEM POSSIBLE
NORTH AND EAST OF FSD SUNDAY AND WILL MENTION WITH SLIGHT CHANCE
POPS. SUNDAY WILL OF COURSE BE COOLER WITH MAINLY 70S HIGHS...80
OR SO SOUTHWEST. A MOSTLY DRY AND SOMEWHAT LASTING COOL PATTERN
THEN SEEMS IN STORE FOR THE AREA...BUT WENT WITH THE EXTENDED
GUIDANCE SLIGHT CHANCE OF STORMS FOR WEDNESDAY AS THE EC DOES SHOW
A SHORT WAVE WITH THE RIGHT TIMING...GFS BEING A LITTLE FASTER.
HOWEVER NOBODY IS GOING TO GET VERY MUCH RAIN WITH THE MOISTURE
VERY LIMITED.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 650 PM CDT WED JUL 23 2014

VFR CONDITIONS ARE EXPECETD THROUGH THE TAF PERIOD. SCATTERED
THUNDERSTORMS ARE EXPECTED TO MOVE INTO SOUTH CENTRAL SD LATE TONIGHT
AND SLOWLY TRACK EASTWARD ACROSS THE AREA THROUGH THE DAY THURSDAY.
EXPECT ACTIVITY IN THE KHON AREA FROM 09Z TO 12Z AND INTO THE I29
CORRIDOR AFTER 13Z. AGAIN...COVERAGE WILL BE SCATTERED HOWEVER DID
LEAVE TEMPO MENTION AT ALL 3 TAF SITES. THE HIGH BASED STORMS WILL
LIKELY KEEP CONDITIONS PREDOMINATELY IN VFR...BUT STRONGER GUSTS AND
VERY BRIEF MVFR CONDITIONS WILL BE POSSIBLE IN THE STRONGER STORMS.
BREEZY SOUTH SOUTHEAST WINDS PICK UP AFTER 12Z AND PERIST THROUGH
THE END OF THE TAF PERIOD.


&&

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

$$

UPDATE...CHENARD
SHORT TERM...MJ/
LONG TERM...
AVIATION...