Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000
FXUS63 KOAX 181729
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1229 PM CDT Fri May 18 2018

.UPDATE...
Issued at 1000 AM CDT Fri May 18 2018

Convection across central through Northeast NE is the primary
concern today, and whether any of that can hold together to move
into extreme east central NE this afternoon. ESRL HRRR/HRRR/Rap
all suggest a few showers could remain from the remnants, as far
east as the Missouri River, but it wouldn`t be anything more than
sprinkles by then given the very dry mid and low layers.

&&

.SHORT TERM...(Today through Sunday)
Issued at 335 AM CDT Fri May 18 2018

The main forecast concerns are in regards to thunderstorm chances,
potential for severe storms and possible areas of heavy rain.

Large scale pattern at 500 mb last evening featured a trough from
the northern Rockies down into southern CA, a weak ridge from
west TX up into KS and a trough from IA and MO down into the Gulf
coast region. We will be in southwest mid level flow the next few
days. Models show a closed low developing over eastern CO tonight,
then that opens up and lifts northeast across NE through Saturday
night.

For today and tonight, highest chance of severe storms should
stay mostly southwest of our of area - from parts of southwest NE
into central and western KS where instability should be highest.
Precipitation chances should be highest across northeast NE where
remnants of MCS that formed over western NE last evening are
tracking northeastward early this morning. Storms should lose
intensity as they get farther east. Most areas should see high
temperatures in the lower to mid 80s but portions of northeast NE
may only reach 75 to 80. Tonight, storms should develop mostly to
our west and then track into the area. These are expected to reach
farther east, compared to what is happening this morning.

Precipitation should linger Saturday morning, but coverage is
forecast to decrease in the late morning and early afternoon. The
latest Day 2 SPC Outlook has an enhanced risk of severe storms
for southeast NE and parts of southwest IA. This would be mostly
from mid to late afternoon through the evening. That seems
reasonable, but the details could change depending on how much
convection occurs or lingers earlier in the day on Saturday. With
temperatures reaching the mid 70s to lower 80s in the Slight and
Enhanced risk areas, expect 0-1km ML CAPE values up to near 3000
J/kg. There will also be adequate 0-6km shear - with values from
30 to 50 knots. This will be adequate for supercells and all modes
of severe weather, with very large hail and a few tornadoes with
main hazards. Chances are expected to be highest ahead of the
surface low and near the warm front. In addition, PW (precipitable
water) values reach around 1.5 inches so there will be some areas
of heavy rain.

Precipitation chances linger Sunday, but severe threat at least
for now expected to be much lower than on Saturday. Highs Sunday
should only be in the 60s across most of northeast NE, with 70s
for southeast NE and southwest IA.

.LONG TERM...(Sunday night through Thursday)
Issued at 335 AM CDT Fri May 18 2018

A fairly strong trough will be digging over CA Sunday night with a
closed low forming. That is expected to linger into Tuesday, while
our area is mainly in nearly zonal flow. Our pattern should turn
more active by Tuesday/Wednesday as several shortwaves track from
southwest to northeast across the Central Plains. Highs should
average 75 to 85 with lows averaging in the mid 50s to lower 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1225 PM CDT Fri May 18 2018

Outflow boundary of 27015g25kt from weakening convection to the
west is affecting KLNK/KOMA for the next hour or so. Otherwise,
showers have moved east of KOFK, but could affect KLNK 18-20z, and
KOMA 19-20z. Then additional thunderstorms expected at all TAF
sites later in the period. Lower MVFR ceilings developing late in
the period as well, and even down to IFR at KOFK.

&&

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

$$

UPDATE...DeWald
SHORT TERM...Miller
LONG TERM...Miller
AVIATION...DeWald



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