Area Forecast Discussion
Issued by NWS Sioux Falls, SD

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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

000
FXUS63 KFSD 190354
AFDFSD

Area Forecast Discussion
National Weather Service Sioux Falls SD
1054 PM CDT Mon Mar 18 2024

.KEY MESSAGES...

- Relative humidity (RH) recovers into the 30-40% range Tuesday
  afternoon. Winds will be northwesterly gusting to 25-30 mph.
  Grassland fire danger index will remain in the High to very
  high category, but due to the higher RH, no headlines are
  planned at this time.

- A push of cold air Tuesday into Wednesday will result int
  temperatures slightly below normal Wednesday through next
  weekend.

- Confidence is increasing in precipitation beginning late
  Wednesday night through into the early part of next week.

- Uncertainty remains high for the weekend and early week
  precipitation forecast. Those with weekend travel plans will
  want to continue to monitor the latest forecast for the most
  up to date information.

&&

.DISCUSSION...
Issued at 232 PM CDT Mon Mar 18 2024

THIS AFTERNOON: Some scattered high stratus will drift in from the
north this afternoon on the backside of a high pressure that moved
through the area today. A low pressure system over Manitoba will
drag a cold front through the area beginning late this evening into
the overnight hours. Lows for tonight will be in the 20-30s.

TUESDAY: Winds at the surface will turn to the northwest and will
increase with a push of CAA behind the front. Look for winds to be
around 10 mph increasing to 15-20 mph in the afternoon. Good mixing
will help us to tap into the stronger winds in the 850-800 mb level,
resulting in afternoon gusts 25-30 mph. Dew points recover overnight
and settle into the mid to upper 20s by afternoon. Relative Humidity
(RH) recovers on pace with dew points, with minimum RH for the
afternoon in the 30-40% range. Despite the CAA, highs will still
warm into upper 40s to 50s, with 60s along the Missouri River and
southward. Grassland fire danger index remains in the High to Very
High category, but thanks to the higher RH it does not look like we
will meet minimum requirements for a Fire Weather headline as of
this forecast package. Should we mix down more of the drier air
aloft, dew points and RH may decrease enough to warrant a headline.
This will need to be monitored throughout the afternoon.
Significantly cooler lows for Tuesday night, teens to 20s.

WEDNESDAY: Moisture flows in from the northwest for Wednesday,
increasing RH and easing grassland fire danger index into the
Moderate to High category. Continued CAA cools temperatures at the
850 mb level into the negative single digits Celsius. Highs for
Wednesday will be slightly cooler than average, in the 30 to
low 40s. Lows will be in the low to upper 20s, with the coldest
temperatures for both highs and lows across southwestern
Minnesota. Throughout the day an inverted trough will push into
the area from the northwest. This will set the stage for an
active pattern that will persist into early next week. Bufkit
soundings indicate the column will saturate from the top down
through the afternoon and evening hours Wednesday. Saturation in
the DGZ could spawn some light snow showers as early as
Wednesday evening. However, there is a stout dry layer beneath
the stratus deck, which will need to saturate out before we`ll
see anything reach the ground. Deterministic and ensemble
guidance are split on Wednesday evening light precipitation
chances, with the GFS and EC only indicating a 10-30%
probability of measurable precipitation (24 Hr QPF >= 0.01 in).

THURSDAY and BEYOND: Currently, it looks like full column saturation
will happen during the overnight hours into Thursday morning. Here
the guidance begins to converge on 80-100% probability of
precipitation beginning Thursday. The majority of this first wave of
precipitation will fall along and north of I-90, but as far south as
Highway 20 still has a 50-80% probability of measurable
precipitation. Thursday evening a short wave and surface low moves
out of Wyoming and into western South Dakota. This wave has a
much more focused area of frontogenesis, and therefore a higher
probability of producing precipitation. There remains slight
variance on the amplitude of the upper trough and surface low
track, but the three main models indicate high probability
(70-100%) of precipitation across the region for Thursday night
into Friday morning, with southwestern Minnesota having the best
probability (70-100%) to see QPF up to a tenth of an inch.

A lull follows Friday evening into Saturday morning before a strong
push of WAA triggers another round of precipitation Saturday evening
into Sunday. At the same time, a stronger upper wave digs south as
it moves onshore over the Pacific Northwest. A strong surface
low will then eject out onto the central plains out of New
Mexico and Colorado by late Sunday night. There is a fair amount
of variance in solutions, but guidance is in good agreement
that a stronger precipitation event will unfold for Monday and
Tuesday. Please note:
the systems responsible for the upcoming precipitation are still
off shore over the Pacific Ocean. There remains high uncertainty
in the details and there will be changes to this forecast in the
coming days as things move closer to shore and are better
sampled. But confidence is beginning to increase that we will
see multiple days of precipitation, likely in the form of snow,
possibly interspersed with mixed precipitation or rain south of
I-90.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1053 PM CDT Mon Mar 18 2024

VFR conditions will prevail at TAF sites through Wednesday.
Southwest winds shift northwest after 06z behind a passing cold
front. LLWS lingers through 09-11z as 40-50 kt a low level jet
max slides southeast through the region.

Northwest winds strengthen again Wednesday morning with gusts in
the 20s by Wednesday afternoon. Low to mid VFR stratus seep into
southwest MN, parts of east central SD and northwest IA by 12z.
Could see occasional MVFR ceilings in southwest MN before clouds
scatter out Tuesday afternoon.


&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...None.
MN...None.
IA...None.
NE...None.

&&

$$

DISCUSSION...AJP
AVIATION...BP


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