Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 222327
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
627 PM CDT WED APR 22 2015

.SHORT TERM...(THIS EVENING THROUGH THURSDAY)
ISSUED AT 355 PM CDT WED APR 22 2015

THE SURFACE RIDGE AXIS WILL SLIDE SOUTHWARD ACROSS THE REGION
TONIGHT...AND AS IT DOES SO BREEZY CONDITIONS IN OUR EAST WILL
SUBSIDE DURING THE EVENING AS THE ATMOSPHERE DECOUPLES AND THE
GRADIENT CONTINUES TO RELAX. WITH THE VERY LIGHT WINDS...IT WILL
AGAIN BE A COLD NIGHT ACROSS THE AREA...THOUGH NOT QUITE AS COLD
THROUGH SOUTH CENTRAL SD AND THE LOWER JAMES RIVER VALLEY WITH SOME
MID CLOUDS MOVING INTO THE AREA IN CONJUNCTION WITH WEAK LOW LEVEL
WARM ADVECTION ON THE BACK SIDE OF THE HIGH PRESSURE. THE COLDEST
READINGS WILL BE THROUGH OUR NORTHEAST WITH LOWS IN THE MID
20S...AND KEPT THE FREEZE WARNING OVER THIS AREA INCLUDING EXPANDING
IT INTO OUR REMAINING SOUTHWESTERN MINNESOTA COUNTIES. BACK TO THE
SOUTH AND WEST LOWS LOOK TO BOTTOM OUT AROUND 30.

ON THURSDAY THE HIGH WILL PUSH OFF TO THE EAST WITH A SOUTHERLY LOW
LEVEL FLOW RETURNING TO THE AREA. IT WILL BECOME BREEZY WEST OF
INTERSTATE 29 DURING THE AFTERNOON WITH INCREASING MIXED LAYER WINDS
AND A TIGHTENING GRADIENT. LUCKILY...WITH INCREASING LOW LEVEL
MOISTURE THROUGH THAT AREA...AFTERNOON RELATIVE HUMIDITY SHOULD
REMAIN IN CHECK SO FIRE WEATHER CONCERNS SHOULD BE LIMITED AS
EXPLAINED BELOW. WITH WARMING THERMAL PROFILES HIGHS WILL TOP OUT IN
THE MID 50S OVER SOUTHWESTERN MINNESOTA TO THE MID 60S THROUGH SOUTH
CENTRAL SD.

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 355 PM CDT WED APR 22 2015

BROAD LOWER TO MID LEVEL ISENTROPIC LIFT DEVELOPS ON THURSDAY
NIGHT...NOT WASTING TOO MUCH TIME IN FOCUSING ALONG AND EAST OF
INTERSTATE 29 AFTER MIDNIGHT. SOME DRY AIR AT LOWER LEVELS TO
OVERCOME...BUT NOT ENOUGH TO PRECLUDE MENTION OF AT LEAST SOME
SCATTERED SHOWERS SPREADING IN FROM THE SOUTHWEST. JUST A BIT OF
NEUTRALITY TO MARGINAL INSTABILITY SNEAKS INTO THE SOUTHERN CWA...SO
OBLIGATED TO MAKE A MEAGER MENTION OF THUNDER THREAT BY LATER IN THE
NIGHT.

CHARACTERIZE FRIDAY INTO FRIDAY NIGHT AS A SITUATION WHERE DYNAMICS
TO A GREATER EXTENT ARE SPLITTING AROUND THE CWA...BUT CONTINUE TO
FIND BROAD WARM AIR ADVECTION AHEAD OF TROUGH. CONTINUED NEUTRALITY
TO MARGINAL WEAK INSTABILITY OVER EASTERN CWA SUGGESTS PERHAPS AN
ISOLATED RUMBLE OR TWO AT TIMES. AREAS OF QG FORCING WANDERS TOWARD
THE SOUTHEASTERN CWA LATE DAY...AND HAVE INCREASED MENTION TO LIKELY
POPS IN ACCORDANCE WITH INCREASED FORCING AND CLOSER PROXIMITY TO
LOWER LEVEL WARM FRONT. OVERALL...THE INCREASING MOISTURE AT LOW
LEVELS AND PRECIP WILL IMPACT HIGHS ON FRIDAY...EVEN A TOUCH COOLER
WET BULB POTENTIAL...WITH LOWER 50S EAST.

DYNAMICS WITH NORTHERN EDGE OF CENTRAL PLAINS CLOSED LOW GRADUALLY
SHIFT FOCUS TO THE SOUTH AND EAST LATER FRIDAY NIGHT/EARLY
SATURDAY...AND TRENDED GRADUALLY DOWN WITH RAINFALL CHANCES FROM
NORTHWEST TO SOUTHEAST FAIRLY QUICKLY. LOTS OF MOISTURE REMAINS AT
LOWER LEVELS...AND PERHAPS WILL END UP WITH ENOUGH SHALLOW LIFT TO
KEEP SOME VERY LIGHT RAIN/DRIZZLE IN THE MIX WELL INTO SATURDAY.
HOWEVER...WITH INCREASE IN SUBSIDENCE BY AFTERNOON AND IMPACT OF
DRYING EAST/NORTHEAST TRAJECTORY ALOFT...WILL KEEP AFTERNOON CLEAR
OF PRECIPITATION FOR NOW. DOES NOT APPEAR THAT OVERALL QPF AMOUNTS
WILL BE VERY SIGNIFICANT FOR EVENT...PERHAPS SOME QUARTER INCH
AMOUNTS IN PARTS OF NW IA...BUT MOST A TENTH OR LESS.

CLOSED LOW WILL WANDER THE SOUTHERN PLAINS AGAIN LATE IN THE WEEKEND
THROUGH EARLY NEXT WEEK...WITH NORTHERN PLAINS EITHER IN MINIMAL
FLOW ALOFT OR A BIT MORE TOWARD THE WEAK NORTHERN STREAM. EITHER
SCENARIO SPELLS FAIRLY BENIGN WEATHER FOR THE REGION. COULD EASILY
SEE FURTHER REMOVAL OF BUFFERING POPS ACROSS THE WEST AND NORTH FROM
SUNDAY THROUGH TUESDAY AS DRIER EASTERLY COMPONENT WEARS AT
APPROACHING NORTHERN STREAM WAVE ON MONDAY AND MONDAY NIGHT WITH
WEAK CONVERGENCE AND INCONSEQUENTIAL BOUNDARIES. DIURNAL RANGE TO
TEMPS WILL STRETCH OUT A BIT AS AIR MASS DRIES...BUT SHOULD SEE
TENDENCY FOR CLOSER TO AVERAGE TEMPS THROUGH THE PERIOD.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 626 PM CDT WED APR 22 2015

SOME MID LEVEL CLOUDINESS MAY DEVELOP TONIGHT ALONG AND WEST OF
INTERSTATE 29...HOWEVER CONDITIONS WILL BE VFR TONIGHT AND
THURSDAY.

&&

.FIRE WEATHER...
ISSUED AT 355 PM CDT WED APR 22 2015

A RED FLAG WARNING WILL REMAIN IN EFFECT THROUGH SOUTHWESTERN
MINNESOTA THROUGH THE REMAINDER OF THE AFTERNOON. OTHERWISE...THE
FIRE DANGER SHOULD LESSEN OVERALL ON THURSDAY AS THE LOWEST
RELATIVE HUMIDITY AND HIGHEST WINDS SHOULD NOT BE COLLOCATED. THE
LOWEST RH WILL BE FOUND GENERALLY EAST OF INTERSTATE 29 AT AROUND
25 PERCENT...THOUGH WINDS WILL BE RELATIVELY LIGHT OVER THAT AREA.
WINDS WILL BE STRONGER BACK TO THE WEST...THOUGH RH VALUES SHOULD
REMAIN AT OR JUST OVER 30 PERCENT.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...FREEZE WARNING FROM 3 AM TO 8 AM CDT THURSDAY FOR SDZ038>040-
     053>056-061-062-067.

MN...FREEZE WARNING FROM 3 AM TO 8 AM CDT THURSDAY FOR MNZ071-072-080-
     081-089-090-097-098.

     RED FLAG WARNING UNTIL 7 PM CDT THIS EVENING FOR MNZ900.

IA...FREEZE WARNING FROM 3 AM TO 8 AM CDT THURSDAY FOR IAZ001>003-
     012>014.

NE...NONE.
&&

$$

SHORT TERM...JM
LONG TERM...CHAPMAN
AVIATION...MJ
FIRE WEATHER...JM



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