Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 190908
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
408 AM CDT Tue Mar 19 2024

.KEY MESSAGES...

- High to very high fire danger expected this afternoon between
  11 AM and 4 PM, especially across portions of northeast
  Nebraska

- A cold front moving through the region tonight will bring much
  cooler temperatures into the region, with highs through the
  end of the forecast period after today in the 40s and low 50s.

- A more active weather pattern develops later this week with
  precipitation chances from Thursday into the weekend. Light
  wintry mix will be possible across east-central and northeast
  Nebraska, and southwest Iowa Thursday morning with more
  widespread rain chances across the entire region Friday
  morning.

- Medium range guidance suggests a strong storm system will
  impact the region towards the end of the forecast period. The
  most likely time frame for impacts will be Sunday and Monday
  with snow becoming increasingly likely across portions of
  northeast Nebraska and western Iowa. Uncertainty regarding
  details of system evolution is still high.

&&

.DISCUSSION...
Issued at 245 AM CDT Tue Mar 19 2024

...Today and Tomorrow...

Surface analysis this morning shows a surface trough extending
from western Nebraska into central Minnesota. Ahead of this
feature, southwesterly winds will advect warmer air into the
region. Furthermore, regional METAR stations are observing
winds ranging from 10 to 20 mph. This will help mix the
nocturnal boundary layer limiting the effects of radiative
cooling. As such, low temperatures this morning will largely
remain near freezing, which is 15 to 20 degrees warmer than
yesterday. By 10 AM, the surface trough out west is expected to
have moved through the area and into Missouri/Iowa. Behind this,
winds will become northwesterly at the surface. The airmass
behind the surface trough will be relatively dry with dew points
in the upper 20s and low 30s. The dryness of the airmass in
conjunction with clear skies and adiabatic compression of air
advecting off the High Plains will allow temperatures to rise
well above average across the region. Forecast highs today range
from the mid 60s across northeast Nebraska and southwest Iowa
to near 70 degrees across southeast Nebraska.

Forecast soundings also show a deep PBL developing over the
course of the day, with the associated inversion reaching
heights of 1 to 2 km across short term guidance solutions. This
will aid in the downward mixing of higher momentum air aloft
and allow winds to strengthen to 15-25 mph this afternoon. Wind
gusts as high as 30 mph will be possible, particularly between
11 AM and 4 PM across northeast Nebraska. Due to the low dew
points and above average afternoon highs, minimum relative
humidities this afternoon will range between 20 and 30 percent.
Low relative humidities and gusty winds this afternoon will
result in high to very high fire danger across the region,
particularly across northeast Nebraska.

Further north into Canada, a surface low will track east-
southeast across southern Ontario. Behind this system an arctic
high pressure will build into the northern Plains and the upper
Midwest. Ahead of this high pressure system, a cold front will
push south-southwest across the Midwest and central Plains,
moving through our region tonight. This will shift winds from
northwesterly to out of the northeast. This front is expected
to stall out and become a stationary front south of our area,
likely extending from southeast Wyoming into northeast
Kansas/northwest Missouri. This will bring much cooler high
temperatures tomorrow afternoon, ranging from the mid 40s across
western Iowa to the low 50s in southeast Nebraska. The
baroclinic zone that will set up across the Plains from this
stationary front will be an important source of energy for more
active weather which is anticipated going into this weekend and
next week.

...Thursday and Friday...

By Thursday, model guidance suggests ridging is likely across
the western CONUS and troughing is likely across the eastern
CONUS. Embedded in northwesterly flow aloft, a shortwave trough
is expected to eject into the central Plains. Divergence aloft
and forcing for ascent ahead of this disturbance will result in
surface cyclogenesis in the central High Plains. Most likely
location for the surface low to develop is in northeast
Colorado/southeast Wyoming. This surface low pressure is
expected to remain relatively weak as it traverses east across
the central Plains. Nonetheless, flow immediately above the
boundary layer across our area (850 to 700 mb) will become
south-southwesterly, advecting an elevated layer of warm air
into the region. Weak synoptic lift ahead of this disturbance
will promote widespread cloud cover and a low potential (15-25
percent chance) of light precipitation Thursday morning, likely
after 6 AM. Forecast soundings show temperatures in the boundary
layer will largely remain below freezing, as will the vertical
temperature profile above the boundary layer at the onset of
light precipitation. This will favor flurries/light snow as the
dominant precipitation type beginning Thursday morning.
Forecast soundings do show a robust dry layer near the surface
which will significantly limit the amount of precip that will
make it to the ground. Nonetheless, through the morning,
flurries/light snow, transitioning to sprinkles/light rain by
noon cannot be ruled out, especially along and east of the
Missouri river, north of Interstate 80. Late morning (9 AM
through noon), ice pellets may mix into the light precipitation
as the above freezing layer aloft becomes more robust in the
warm air advection ahead of this disturbance. Any light precip
that is able to reach the surface should move east of the region
by noon.

Thursday night into Friday morning, a more robust mid-level
disturbance is expected to move across the northern Plains and
into the upper Midwest. This will bring a more substantial
chance (50-80%) of precipitation across the region Friday
morning. At the surface, a reinforcing cold front is expected
to move southeast across the region Friday morning. Thursday
night ahead of the cold front, temperatures are expected to
remain above freezing. Furthermore, the surface front is
expected to lag behind the bulk of the precipitation associated
with this system. This will likely result in most, if not all
precip Friday morning to fall as rain. Between 8 AM and noon,
temperatures across far northeast Nebraska will approach and
temporarily fall below freezing. This will support a transition
from rain to a rain-snow mix late Friday morning. Little to no
snow accumulations are expected at this time. Precipitation is
expected to move east of the region by 1 PM Friday. Friday night
behind the cold front, temperatures are expected to fall into
the lower 20s and upper 10s.

...Saturday through Monday...

Medium range guidance continues to suggest a deep upper level
trough will slowly work its way into the western CONUS by the
end of the forecast period. Strong forcing for ascent and PVA
that will move into the Great Plains over the strong baroclinic
zone along the stationary front is expected to induce strong
surface cyclogenesis in the central High Plains. The majority of
ensemble and deterministic model solution resolve a surface low
with pressure below 990 mb in the central High Plains by Sunday
evening. However, there is still substantial uncertainty in the
exact position and timing of this system, and where it will
track across the Plains by the end of the forecast period.
Medium range models also diverge substantially in surface
temperature forecasts. Spread amongst models range anywhere from
15-25 degrees for any given location and time across our area
Sunday and Monday. As such, will refrain from more detailed
discussion on precip type and amounts. Nonetheless, there is
enough confidence in saying widespread light to moderate
precipitation will be likely (70-90%) across the entire region
Sunday into Monday. Snow will also be increasingly likely with
northward extent, with the most likely area to see snow being
northeast Nebraska and western Iowa along and north of US
highway 30.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1030 PM CDT Mon Mar 18 2024

VFR conditions expected through the period with southwest winds
overnight at 10 to 15 kts turning clockwise to northwesterly and
gusting 20 to 25 kts by Tuesday morning. Winds will begin to
weaken and become more northerly by late afternoon/early
evening. Otherwise, expect some low level wind shear into the
early morning hours, with westerly winds at 45 to 50 kts around
1500 ft agl.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.

&&

$$

DISCUSSION...Darrah
AVIATION...CA


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