Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 302010
AFDOAX

Area Forecast Discussion
National Weather Service Omaha/Valley NE
310 PM CDT Sat May 30 2020

.DISCUSSION...
Issued at 310 PM CDT Sat May 30 2020

The main forecast issues are precipitation chances the next few
days and then temperatures for next week.

Upper air charts from 12Z this morning had the following features
of interest. At 300 mb there was a jet segment extending southeast
from Saskatchewan into the Great Lakes region, with a max of
around 115 knots over northern MN. Also another segment punching
northeast across parts of CA. At 500 mb, there was an impressive
closed low with 12 hour height falls of at least 170 meters moving
into CA. Water vapor loop showed that the center was in the San
Francisco area as of 3 pm. Thermal ridge at 700 mb extended from
AZ into UT. Locally, at the 700 mb level we were in an area of
warm air advection. Isentropic upglide was noted to be strongest
in the 305K to 310K layer. Surface analysis early this afternoon
showed a ridge of high pressure from southern Manitoba into IA,
with low pressure back over CO. A warm front stretched from parts
of MT and WY into northeast CO, then east/southeast across KS.
Temperatures south of the front in KS were in the 80s or 90s (the
90s were in southwest KS where southerly winds were gusting to
above 30 mph).

Tonight into Sunday night.
Current showers have been decreasing in coverage and should
mostly end later this afternoon/evening. However, we remain in
somewhat of a warm air advection pattern with isentropic upglide
in the 300K to 310K layer. Used a blend of ESRL HRRR/HRRR and
RAP13 for precipitation trends tonight. We should see some
isolated to scattered showers develop later tonight, somewhat in
association with increase of a low level jet, which stays mostly
farther west at least in regards to low level wind shear. Look for
lows tonight in the 50s. Some showers could linger into Sunday
morning, shifting mostly into western IA after about 10 am and
then decreasing in coverage. Look for highs Sunday ranging from
the lower 80s in our western zones to lower and mid 70s in
southwest IA. Will have a slight chance of showers for parts of
the area Sunday night, generally east of Norfolk to north east of
Omaha. Expect anything that does occur to be spotty and light.

Monday through Tuesday.
This will probably be our warmest period over the next 7 days and
it looks mainly dry. Southwest surface winds will be brisk and
gusty at least during the daytime, and downslope component is
expected to help with warming. 850 mb temperatures these two days
should be mostly 22 to 30 C. Look for daytime highs in the upper
80s to mid 90s. Lows should vary mainly from the mid 60s to the
lower 70s.

Tuesday night into Saturday.
Temperatures through this period should remain above normal with
highs in the 80s to lower 90s. A weak cold front will try to drop
through the area Tuesday night and Wednesday. Depending on cloud
cover and rain coverage, highs that we have forecast may be a bit
on the optimistic side. But stayed with a model blend for now.
There will be off and on chances for showers and thunderstorms in
this period, but models have some variance in timing the highest
chances. In general, the 12Z GFS was wetter than the ECMWF,
probably too wet.

500 mb ridge over the area Tuesday will start to flatten a bit
with main westerly flow across the northern 1/3 of the US mid
week. Toward the end of the week, we could see a mid level ridge
increasing again over the Central Plains as another low moves from
CA into NV and UT.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1208 PM CDT Sat May 30 2020

Expect mainly VFR conditions through the period, except for
MVFR visibilities in precipitation. Some MVFR ceilings are
possible but thought chances low enough to keep ceilings above
3000 feet for now. Showers will decrease in coverage this
afternoon, but chances will return again for tonight. Thunder
possible tonight with a bit of elevated instability, but for now
with just probably isolated thunder, did not include in TAFs.

&&

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

$$

DISCUSSION...Miller
AVIATION...Miller


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