Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 170321

Area Forecast Discussion
National Weather Service Sioux Falls SD
1021 PM CDT Thu Mar 16 2017

.SHORT TERM...(This evening through Friday)
Issued at 420 PM CDT Thu Mar 16 2017

H5 ridging will move across the Northern Plains tonight with a warm
nose of +4 to +12C at H85 pushing into the CWA.  Some of that
warming will go to continuing to melt snow but that coupled with
cloud cover will help keep temps at or above freezing in most areas

Right on the heels of this ridge is a cold front from an associated
low crossing Saskatchewan and Manitoba.

Winds will become northwesterly tonight, as the front/boundary
pushes east off of the CWA, giving way to a windy Friday across the
region. The main impact on Friday will be strong northwesterly
winds, but it is expected to remain below the headlines criteria.
Leaned to CONMOS for winds by late morning through early evening,
and increased gusts a few readings during this time frame. Overall,
winds to 20 to 30 mph, with gusts to 30-40 mph are expected.

.LONG TERM...(Friday night through Thursday)
Issued at 420 PM CDT Thu Mar 16 2017

Brisk winds will continue much of Friday night within cold advection
and tight gradient on southwest flank of deepening low pressure over
the Great Lakes. A period of stratocumulus should wrap through
mainly southwest MN, but overall skies should be largely clear
before increasing higher clouds from the west late night. With
skinny surface ridge building through the James valley late night,
rapid decrease in winds should allow temps to approach the upper
teens in the mid James valley, but should generally settle into the
20s over the remainder of the area.

Ridge of high pressure wanders eastward through Minnesota and Iowa
on Saturday, lingering some cooler air across areas east of I-29
which are likely to see little change from Friday readings. Brisk
southerly winds will develop by Saturday afternoon west of the James
river, and south central areas will warm into the lower 60s, with
some afternoon humidity dropping to around 25 percent, and a very
high fire danger is likely to result for Lower Brule areas.

On Saturday night, strong southerly winds will spread through the
remainder of the area, keeping temperatures milder. There is a
threat that some moisture will streak northward on low-level jet
into eastern Nebraska and northwest Iowa by Sunday morning.  While
NAM is likely overdone, even the ECMWF and GFS suggestive of having
a least a broken area of stratus into midday to early afternoon
through parts of northwest Iowa. Gradually, a strong wave will knock
down the ridge over the northern plains by later Sunday, and a
frontal boundary will move into central SD toward midday, and
approach the lower Missouri valley by early evening. This will set
up likelihood of a narrow tongue of warm air surging northward ahead
of the advancing front, which could push temperatures into at least
the mid 70s through the Missouri valley. Winds will be shifting
northerly behind the boundary in the afternoon, with low humidity
again presenting an enhanced fire weather risk Sunday afternoon.

As strong trough drives along the International border toward the
Great Lakes Sunday night, trailing a tail of QG lift forcing and mid-
level moisture through the CWA through Monday morning. Could be a
little bit of light precip, but at this point no better than a
minimal chance with drying fairly significant through lower levels.
Cooler high pressure will build southward into the plains through
Tuesday with dry conditions, before warm advection strengthening
Tuesday night and Wednesday will likely push a band of snow to rain
eastward across the CWA. Plenty of clouds and gradually warming off
surface temperatures will keep diurnal ranges reduced through
midweek.  Wednesday night and Thursday there is at least a decent
amount of consistency in indicating a more significant trough
pushing into the central Plains. Structure of system is up in the
air at this point, but a fairly widespread swath of warm advection
will likely be in place over the CWA. Ensembles have almost no
members with 850 hPa temps below zero, and a mean across the CWA
from 3 to 8C, suggesting strongly at face value that should be
primarily a liquid event. Could even suggest a threat for some
convection into southern area around KYKN/KSUX/KSPW.
At this point, have only a little snow on the periphery due to the
temperature forecast which is likely a bit low even with wet bulb


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1016 PM CDT Thu Mar 16 2017

VFR conditions expected through the period. Gusty winds are
expected tomorrow afternoon at all TAF sites.




SHORT TERM...Sally/05
LONG TERM...Chapman
AVIATION...Ferguson/08 is the U.S. government's official web portal to all federal, state and local government web resources and services.