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 012334
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
634 PM CDT FRI MAY 1 2015

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 354 PM CDT FRI MAY 1 2015

QUIET CONDITIONS EXPECTED THE REMAINDER OF THE AFTERNOON AND TONIGHT
AS WEAK SURFACE RIDGE DRIFTS ACROSS THE CWA. LOW LEVEL MOISTURE HAS
BEEN A BIT SLOWER TO CLEAR THAN EARLIER ANTICIPATED. AREAS NORTHWEST
OF THE SLOW MOVING SURFACE BOUNDARY HAVE SEEN A SHARP DROP IN DEW
POINTS DURING THE EARLY PART OF THE AFTERNOON...WHILE ALONG AND
SOUTH OF THE BOUNDARY DEW POINTS REMAIN IN THE UPPER 40S TO LOWER
50S AS OF 20Z. MODELS IN FAIRLY GOOD AGREEMENT HANGING ONTO THE
HIGHER MOISTURE LEVELS ACROSS THE SOUTHEAST CWA THROUGH THE NIGHT AS
THE BOUNDARY WASHES OUT AND THE SURFACE RIDGE MOVES IN...WHICH SEEMS
REASONABLE GIVEN THIS AREA WAS FORTUNATE TO RECEIVE MORE APPRECIABLE
RAINFALL THIS MORNING. WITH THE LIGHT WINDS AND HIGHER HUMIDITY...
COULD SEE SOME PATCHY FOG DEVELOP ACROSS OUR SOUTHEAST FORECAST AREA
LATE TONIGHT/TOWARD DAYBREAK. HOWEVER ANTICIPATE A LITTLE MORE CLOUD
COVER SPREADING INTO OUR SOUTH FROM CENTRAL PLAINS SYSTEM AS WELL...
SO CONFIDENCE IN FOG NOT TOO HIGH AND WILL LEAVE THE MENTION OUT FOR
NOW.

SOMEWHAT DEEPER MOISTURE REMAINS IN PLACE ACROSS THE SOUTHERN PARTS
OF THE CWA INTO SATURDAY...WHILE SHALLOWER MOISTURE ACROSS NORTHERN
AND FAR WESTERN AREAS APPEARS MORE LIKELY TO ALLOW DRIER AIR FROM
ALOFT TO MIX DOWN TO THE SURFACE IN THE AFTERNOON. BETTER MOISTURE
IN OUR SOUTHEAST IS LEADING TO MODEST INSTABILITY...WITH FORECAST
SOUNDINGS SHOWING LITTLE CAPPING BY MID-LATE AFTERNOON ALONG A WEAK
CONVERGENCE AREA. GOING FORECAST ALREADY HAD A LOW CHANCE POP OVER
MAINLY NORTHWEST IOWA SATURDAY AFTERNOON...AND SEE NO CONVINCING
ARGUMENT TO REMOVE AT THIS POINT. NOT AS CONFIDENT ABOUT CHANCES
ENTERING OUR FAR WEST GIVEN MUCH DRIER MOISTURE PROFILES IN THAT
AREA AND HAVE TRIMMED POPS FROM OUR AREAS WEST OF THE JAMES RIVER
LATE SATURDAY AFTERNOON. STILL LOOKS LIKE A VERY WARM DAY IN MOST
AREAS...WITH HIGHS RANGING FROM THE UPPER 70S IN OUR FAR SOUTHEAST
TO MID 80S WEST. THE WARM TEMPERATURES...LOWER HUMIDITY LEVELS...AND
SOUTHERLY WINDS AVERAGING 10-20 MPH WILL LEAD TO VERY HIGH GRASSLAND
FIRE DANGER FOR OUR FAR NORTHWEST AREAS...WITH HIGH DANGER ELSEWHERE
ACROSS THE FORECAST AREA.


.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY)
ISSUED AT 354 PM CDT FRI MAY 1 2015

A STRONG SOUTHERLY FLOW CONTINUES ACROSS THE REGION ON SATURDAY
NIGHT AS LOW PRESSURE/FRONTAL BOUNDARY APPROACHES FROM THE WEST.
THIS WILL RESULT IN A VERY MILD NIGHT WITH LOWS ONLY DROPPING INTO
THE MID AND UPPER 50S. THINK IT WILL REMAIN PRIMARILY DRY THROUGH
MUCH OF THE NIGHT...AND LOWERED POPS EVEN MORE IN OUR FAR WEST
DURING THE EVENING...IN SPITE OF SOME MODELS SPITTING OUT A
LITTLE QPF...AS MOISTURE LOOKS TO BE EXTREMELY LIMITED.

THE LOW PRESSURE AND COLD FRONT WILL PUSH ACROSS THE CWA DURING THE
DAY ON SUNDAY. MAY SEE SOME CONVECTION THROUGH THE MORNING OVER
SOUTHWESTERN MINNESOTA WITH CONVERGENCE ON THE LOW LEVEL JET.
OTHERWISE THE BETTER CONVECTION WILL MOST LIKELY WAIT UNTIL
AFTERNOON DURING THE HEATING OF THE DAY AS MID/UPPER LEVEL FORCING
INCREASES AS A SHORTWAVE TRACKS THROUGH THE REGION. WHILE IT WILL BE
UNSTABLE IN THE AFTERNOON WITH MUCAPE VALUES OF 1000 TO 1500 J/KG
OUT AHEAD OF THE FRONT...BULK SHEAR IS NOT OVERLY IMPRESSIVE AT
AROUND 20 TO 25 KTS...BUT CANNOT RULE OUT A COUPLE OF SEVERE STORMS
WITH LARGE HAIL IN PORTIONS OF SOUTHWESTERN MINNESOTA AND NORTHWEST
IOWA DURING THE AFTERNOON. ONE THING OF NOTE FROM PREVIOUS MODEL
RUNS IS THAT ALL THE LATEST MODEL RUNS HAVE THE FRONT THROUGH TWO
THIRDS OF OUR CWA BY 18Z...WHICH IS FASTER THAN PREVIOUS RUNS. IF
THIS TREND CONTINUES THE BETTER CHANCE OF SEVERE WEATHER MAY BE
PUSHED OFF TO THE EAST. IT STILL LOOKS LIKE A VERY WARM DAY OUT
AHEAD OF THE FRONT WHERE 850 MB TEMPERATURES WILL BE IN THE UPPER
TEENS C...AND LOOKING AT HIGHS IN OUR SOUTHEAST OF LOWER AND MID
80S...TO UPPER 70S BACK TO THE NORTH AND WEST.

IT WILL BE COOLER FOR SUNDAY NIGHT AND MONDAY WITH THE PASSAGE OF
THE SYSTEM...AS A NORTHEASTERLY LOW LEVEL FLOW DEVELOPS ACROSS THE
REGION AS HIGH PRESSURE SLIDES INTO THE NORTHERN PLAINS AND UPPER
MISSISSIPPI VALLEY. LOWS ON SUNDAY NIGHT LOOKING TO BE IN THE MID
40S TO LOWER 50S...WITH HIGHS ON MONDAY JUST EITHER SIDE OF 70.
THERE ARE MODEL DIFFERENCES WITH REGARD TO RAIN CHANCES IN OUR SOUTH
ON MONDAY WITH A WARM FRONT TO OUR SOUTH AND A SHORTWAVE TRACKING
THROUGH NEBRASKA. DID LEAVE A SMALL CHANCE OF SHOWERS/ISOLATED
THUNDERSTORMS THROUGH THE LOWER MO RIVER VALLEY INTO NORTHWESTERN
IOWA WITH THE BETTER POTENTIAL CONFINED TO THERE.

RAIN CHANCES LOOK TO INCREASE THROUGH THE REMAINDER OF THE WEEK AS AN
UPPER LEVEL TROUGH OVER THE WESTERN CONUS NUDGES SLOWLY EASTWARD.
WHILE THERE ARE STILL SOME MODEL DIFFERENCES DURING THE
PERIOD...CONSENSUS WOULD PUT THE BETTER RAIN CHANCES ON WEDNESDAY
INTO THURSDAY. TEMPERATURES THROUGH THE EXTENDED DO APPEAR TO BE
JUST ABOVE NORMAL WITH HIGHS GENERALLY IN THE LOWER 70S AND LOWS IN
THE UPPER 40S AND 50S.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 634 PM CDT FRI MAY 1 2015

VFR CONDITIONS EXPECTED TO DOMINATE ACROSS THE FORECAST AREA THROUGH
THE TAF PERIOD. WITH THE MORNING RAINFALL...AND LIGHT/VARIABLE WINDS
EXPECTED TONIGHT...COULD SEE PATCHY MVFR VISIBILITY IN FOG DEVELOP
ACROSS NORTHWEST IOWA. AT THIS TIME...GIVEN SHALLOW SURFACE-BASED
INVERSION OF 100-300FT AND 15-20KT WINDS JUST ABOVE THE INVERSION...
THINK THERE MAY BE ENOUGH BOUNDARY LAYER MIXING TO KEEP VISIBILITY
FROM DROPPING TOO FAR. THUS CONFIDENCE IN SUB-VFR CONDITIONS AT KSUX
IS LOW AND HAVE MAINTAINED VFR FORECAST THERE FOR NOW. SOUTH WINDS
ABOVE THE INVERSION NOT STRONG QUITE STRONG ENOUGH TO INTRODUCE LOW
LEVEL WIND SHEAR...THOUGH CONDITIONS MAY BE MARGINAL AT KSUX GIVEN
EXPECTED SURFACE WIND FAVORING EAST-SOUTHEAST ENHANCED BY LOCALIZED
MISSOURI RIVER EFFECT.

ISOLATED SHRA/TSRA POSSIBLE IN NORTHWEST IOWA AFTER 18Z SATURDAY...
BUT THREAT TOO SPOTTY TO INTRODUCE INTO KSUX TAF AT THIS TIME.

&&

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

$$

SHORT TERM...JH
LONG TERM...JM
AVIATION...JH



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