Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 281720
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1220 PM CDT THU APR 28 2016

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 412 AM CDT THU APR 28 2016

UPPER LOW CENTERED OVER NORTHWEST IOWA EARLY THIS MORNING IS EXPECTED
TO TREK EAST TOWARDS THE WESTERN GREAT LAKES REGION.  AS UPPER LOW
WORKS TO THE EAST...PRECIPITATION ASSOCIATED WITH ISENTROPIC LIFT
SHOULD GRADUALLY DWINDLE THROUGHOUT THE DAY. COULD SEE SOME SNOW MIX
IN WITH PRECIPITATION ALONG THE BUFFALO RIDGE...BUT DO NOT THINK
RATE WILL BE STRONG ENOUGH TO SUSTAIN ANY ACCUMULATIONS. HAVE
HEAVIEST RAINFALL TODAY IN SOUTHWEST MN WHERE UP TO TWO TENTHS OF AN
INCH IS POSSIBLE. PRECIPITATION WILL KEEP TEMPERATURES DOWN ONCE
AGAIN TODAY. WITH 925 HPA TEMPS NEAR 0C...EXPECT HIGHS TO REMAIN IN
THE 40S.

CLOUD WILL HANG TOUGH THROUGH THE NIGHT THURSDAY NIGHT INTO FRIDAY
MORNING LIMITING THE FOG POTENTIAL.  ZERO STANDARD DEVIATION IN THE
MEN GUIDANCE FOR LOWS TONIGHT...SO STUCK WITH BLEND FOR LOWS.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 412 AM CDT THU APR 28 2016

OUR NEXT WELL ADVERTISED UPPER LOW BEGINS TO INFLUENCE OUR WEATHER
AS EARLY AS FRIDAY IT APPEARS. THE VARIOUS MODELS ARE IN GOOD
AGREEMENT IN BRINGING THE CENTER OF THE LOW INTO EASTERN COLORADO...
TYING IT WITH A SECONDARY UPPER LOW POSITIONED OVER THE PACIFIC
NORTHWEST. THEREFORE BASICALLY A LONG WAVE TROUGH IS CARVED OUT OVER
THE ENTIRE INTERMOUNTAIN WEST. THE NAM CONTINUES TO BE THE MOST
AGGRESSIVE MODEL IN BRINGING A SWATH OF LIGHT RAINFALL NORTHEASTWARD
TOWARD I 90 BY FRIDAY AFTERNOON. HOWEVER THE HIRES NMM AND ARW ARE
NOT FAR BEHIND WHILE THE GLOBAL MODELS ARE FURTHER SOUTH WITH THE
PRECIP. THE NAM IS KEYING ON SOME POSITIVE 850MB THETAE ADVECTION
WITH A MOISTURE PROFILE THAT IS MORE ROBUST IN THE MID LEVELS THAT
THE ECMWF AND GFS. THE NAM SOLUTION BEING SO CONSISTENT IS
INCREASINGLY HARD TO IGNORE...THEREFORE EXTENDED AT LEAST CHANCE
POPS FURTHER NORTHWARD TO AROUND I 90 BY FRIDAY AFTERNOON EXCEPT IN
SOUTHWEST MN WHERE THE AIR IS CERTAINLY DRIER. CONCERNING HIGHS...
BECAUSE OF THE EXTENSIVE CLOUD COVER AND EASTERLY WINDS...CONTINUED
THE TREND OF FOLLOWING THE COLDER GUIDANCE VALUES WHICH WERE
THE CONSENSUS RAW MODEL VALUES. THE ONE EXCEPTION IS IN OUR FAR
EASTERN ZONES FROM MARSHALL MN TO SPENCER IA...WHERE WE ADDED A
COUPLE OF DEGREES TO THE HIGHS BECAUSE OF DRIER AIR.

ON FRIDAY NIGHT AND SATURDAY...THE ENTIRE LONG WAVE TROUGH OVER THE
WESTERN U.S. PIVOTS COUNTER CLOCKWISE. THE LOW POSITIONED OVER THE
PACIFIC NORTHWEST DROPS SOUTHWARD TO THE SOUTHWEST U.S...BOOTING THE
LOW AFFECTING OUR AREA INTO NEBRASKA AND KANSAS. THEREFORE ANOTHER
ROUND OF WET WEATHER WILL OCCUR...ESPECIALLY FOR THE SOUTHERN HALF
OF OUR FORECAST AREA WHERE THE DEEPEST MOISTURE PROFILE RESIDES ALONG
WITH PERSISTENT THETAE ADVECTION. HEADING NORTH OF I 90...IT WILL BE
RAINY BUT QPF AMOUNTS WILL BE LIGHTER AS YOU GET EVER CLOSER TO THE
LIMITING STREAMLINES BETWEEN 850MB AND 700MB. NOW BY SUNDAY...THE
LOW FILLS WHILE IT WEAKENS WHEN IT MOVES INTO THE EASTERN PLAINS...
ALLOWING THE DRIER CANADIAN AIR TO MOVE SOUTHWARD. THEREFORE
PRECIPITATION WILL BECOME INCREASINGLY LIGHTER HEADING INTO SATURDAY
NIGHT AND THEN FINALLY INTO SUNDAY. IN FACT ONE CAN STATE A STRONG
CASE NOW THAT CONDITIONS WILL BE DRY BY SUNDAY AFTERNOON. FOR
TEMPERATURES FRIDAY NIGHT THROUGH SATURDAY NIGHT...DUE TO CLOUD
COVER KEPT THE DIURNAL RANGE VERY SMALL DURING THIS TIME FRAME. ONCE
AGAIN THE CONSENSUS RAW MODEL VALUES DID THE BEST JOB AT THIS
SCENARIO. WARMER TEMPERATURES ARE WARRANTED FOR SUNDAY...ALBEIT
STILL A LITTLE BELOW NORMAL...WITH RAINFALL FINALLY WANING.

EARLY AND MID WEEK NEXT WEEK...WE GET A PATTERN SHIFT STILL
ADVERTISED BY THE DETERMINISTIC MODELS WHICH INCLUDES A LARGE UPPER
RIDGE OVER THE WESTERN U.S...AND TROUGHING ACROSS THE EAST. THIS
WILL SETUP A MILD NORTHWEST FLOW ALOFT IN OUR AREA WITH FINALLY
DRIER WEATHER AND NORMAL TEMPERATURES. THOUGHT ABOUT A FOG POTENTIAL
DUE TO WET GROUND...HOWEVER THE SURFACE AND MIXED LAYER WINDS ARE
CONSISTENTLY WEST OR NORTHWEST MONDAY THROUGH WEDNESDAY...SO THAT
COULD HELP KEEP AT LEAST WIDESPREAD FOG AT BAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1220 PM CDT THU APR 28 2016

CEILINGS 1-3K FEET. PATCHY CEILINGS BLO 1K FEET THROUGH 20Z. SCT
-SHRA THROUGH 22Z. AREAS CEILINGS BLO 1K FEET DEVELOPING AGAIN
AFTER 29/09Z WITH AREAS VISIBILITY 3-5SM/BR. VISIBILITIES
IMPROVING TO P6SM AGAIN AFTER 29/15Z.

&&

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

$$

SHORT TERM...BT
LONG TERM...MJ
AVIATION...



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