Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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831
FXUS63 KFSD 022256
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
556 PM CDT MON MAY 2 2016

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 309 PM CDT MON MAY 2 2016

DISTURBANCE ACROSS CENTRAL SOUTH DAKOTA SHOULD DROP SOUTHWARD INTO
THE CENTRAL PLAINS EARLY THIS EVENING. IN THE WAKE OF THIS
DISTURBANCE...SKIES SHOULD CLEAR LEADING TO GOOD RADIATIVE
CONDITIONS. ANY INSTABILITY SHOWERS IN THE EAST SHOULD DIE THIS
EVENING WITH SUNSET.

COLD FRONT WILL WORK THROUGH THE REGION TOMORROW AFTERNOON.  AS
PREVIOUS FORECASTER MENTIONED...SHALLOW INSTABILITY FROM 750 TO 650
MB MAY RESULT IN SOME INSTABILITY SHOWERS AS FRONT MOVES THROUGH
THE REGION.  FAIRLY DRY IN THE SUBCLOUD LAYER...SO AM NOT EXPECTING
MUCH IN THE WAY OF ACCUMULATING RAINFALL.  POCKET OF COOLEST AIR IN
IN THE EASTERN CWA TOMORROW AFTERNOON...SO CONFINED POPS TO THE
EASTERN 1-2 COUNTIES IN THE FORECAST AREA. STRONG COLD AIR
ADVECTION BEHIND THE FRONT WILL LIKELY LEAD TO INCREASED WINDS. 925
HPA WINDS INCREASE TO NEAR 30 KNOTS BEHIND THE FRONT...BUT WITH COLD
AIR ADVECTION...EXPECT BREEZY CONDITIONS TO CONTINUE THROUGH THE
EVENING HOURS ON TUESDAY.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 309 PM CDT MON MAY 2 2016

COLD FRONT DROPS SOUTH THROUGH THE AREA TUESDAY NIGHT...AND WITH
SHALLOW UNSTABLE LAYER NEAR THE FRONT...AND SLIGHTLY BETTER MOISTURE
EAST OF I-29...WILL CONTINUE SMALL POPS IN PARTS OF SOUTHWEST MN AND
NORTHWEST IA TUESDAY EVENING.

OTHERWISE MIDDLE PORTION OF THE FORECAST PERIOD CONTINUES TO LOOK
DRY AS STRONG UPPER RIDGE SHIFTS EAST ACROSS THE PLAINS. EASTWARD
SHIFT OF THE UPPER RIDGE AXIS WILL ALSO ALLOW FOR WARMING FROM OUR
SEASONABLE POST-FRONTAL HIGHS IN THE 60S ON WEDNESDAY...TO WELL
ABOVE NORMAL HIGHS IN THE UPPER 70S TO LOWER 80S BY FRIDAY.

WEEKEND BEGINS WITH AN ELONGATED UPPER WAVE ROTATING SOUTHWARD INTO
THE NORTHERN PLAINS AROUND A STRONG UPPER LOW IN EASTERN CANADA.
MODELS DIVERGE QUITE A BIT FRIDAY NIGHT THROUGH SATURDAY NIGHT IN
HOW STRONGLY THIS WAVE AND ASSOCIATED FRONT PUSH SOUTHWARD THROUGH
THE NORTHERN PLAINS. GEM IS BY FAR THE MOST AGGRESSIVE...PUSHING THE
BOUNDARY WELL SOUTH OF OUR FORECAST AREA BY MIDDAY SATURDAY. ECMWF
AND GFS ARE SLOWER/LESS AGGRESSIVE...WHICH SEEMS MORE REASONABLE
GIVEN THE STRENGTH OF THE UPPER RIDGE INTO WHICH THIS BOUNDARY/WAVE
WILL ATTEMPT TO BREAK DOWN...THOUGH EVEN THESE MODELS ARE SHOWING
SOME DISAGREEMENT...WITH ECMWF FARTHER SOUTH THAN THE GFS WITH THE
FRONT BY SATURDAY AFTERNOON. THIS LEADS TO SOME UNCERTAINTY WITH
REGARDS TO EVENTUAL BOUNDARY POSITION...AND ASSOCIATED TEMPERATURES
AND PRECIP CHANCE TIMING FRIDAY NIGHT THROUGH SATURDAY NIGHT...AND
FOR NOW HAVE MADE FEW ADJUSTMENTS FROM BROADER MODEL CONSENSUS. MAY
HAVE TO WATCH FOR SOME STRONGER STORM POTENTIAL SATURDAY...DEPENDING
ON BOUNDARY LOCATION...AS MODELS ARE FORECASTING  A FAIR AMOUNT OF
DEEP LAYER SHEAR NEAR/NORTH OF THE FRONT.

LATE WEEKEND INTO EARLY NEXT WEEK...WESTERN CONUS TROUGH BEGINS TO
TRANSLATE EAST AND FURTHER BREAK DOWN THE UPPER RIDGE. THIS LOOKS TO
PUT US BACK INTO A WETTER PATTERN AGAIN SUNDAY/MONDAY AS THE UPPER
LOW SLOWLY MOVES OVER THE REGION...THOUGH PERHAPS NOT AS PERSISTENT
NOR WIDESPREAD AS OVER THIS PAST WEEK. FORTUNATELY...TEMPERATURES
LOOK MORE SEASONABLE THAN WE SAW DURING OUR RECENT WET PATTERN...
WITH HIGHS IN THE 60S AND LOWS IN THE UPPER 40S TO LOWER 50S.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)
ISSUED AT 553 PM CDT MON MAY 2 2016

ISOLATED TO SCATTERED SHOWERS THROUGH THE WESTERN JAMES RIVER
VALLEY THROUGH EARLY EVENING...OTHERWISE VFR CONDITIONS EXPECTED
THROUGH THE TAF PERIOD. NORTHWESTERLY WINDS WILL PICK UP ON
TUESDAY AFTERNOON...GUSTING TO AROUND 20 KTS AT TIMES.

&&

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

$$

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



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