Scientific Forecaster Discussion
fxus63 koax 231948
Area forecast discussion
National Weather Service Omaha/valley NE
248 PM CDT Tue Jul 23 2019
Short term...(tonight through friday)
issued at 245 PM CDT Tue Jul 23 2019
The potential for fog tonight, precipitation chances (mainly for
Wednesday night) and temperatures the next few days will provide
the main forecast challenges.
A highly amplified pattern remains in place with a strong ridge
over the western US and a trough to the east. We remain in north/
northwest mid level flow. The center of a 500 mb ridge was near
the border of eastern Utah and northwest Colorado this morning. That is
expected to shift southward the next few days, as shortwave
energy move east from the Pacific northwest toward the northern plains.
Water vapor imagery early this afternoon showed a disturbance
pushing southeast through the northern plains. This will spread
some mid and high level cloudiness toward US, but it is not
expected to produce any precipitation for our area. Temperatures
bottomed out in the 50s at most locations this morning, and
tonight will be another cool night. Look for lows mainly in the
middle to upper 50s. A few low lying areas may be cooler. Normal
lows are in the middle and upper 60s. Fog appears possible again
tonight, mainly across parts of southwest Iowa and southeast NE
where winds will be nearly calm. It does not look like a big deal,
but will mention some patchy fog or areas of fog. This would be
most likely near any bodies of water or in river valleys.
For Wednesday, model soundings suggest a decent amount of cumulus
development, but probably not quite as much as today. Winds will
be a bit stronger from the south, as high pressure starts to slide
off to the east/southeast. Some showers and thunderstorms should
develop from parts of western and north central NE into South Dakota in the
evening, and some of these could slide into northeast NE later
Wednesday night. Kept chances mainly around 20 percent for now,
but that may need an increase later. A few showers could linger
into mid morning Thursday, but did not include in the gridded
forecast at this time. Precipitation chances for Thursday night
into Friday are a bit higher, but just outside of our area.
High temperatures should moderate from the lower and mid 80s
Wednesday to the upper 80s and lower 90s by Friday.
Long term...(friday night through tuesday)
issued at 245 PM CDT Tue Jul 23 2019
At the start of this period, there should be a closed low at
500 mb over western Ontario, and ridge centered over Arizona. A modest
trough will be pushing into western British Columbia and Washington state.
A blend of the 12z runs of the European model (ecmwf) and GFS suggest that the
ridge may retrograde westward briefly on the weekend, but then
move back to The Four Corners region by Monday/Tuesday. We will
not be totally dry in the long term period, will include some
thunderstorm chances for Saturday night and Sunday morning.
Chances will be highest across the northern half of the forecast
area. Have also included low chances for thunderstorms for at
least parts of the area for Sunday night and again Monday night.
High temperatures should be mostly in the upper 80s and lower 90s
for the weekend, with a slight cooling for Monday/Tuesday.
Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1204 PM CDT Tue Jul 23 2019
VFR conditions through this evening. Scattered cumulus clouds
have developed around 5000 feet this afternoon and will linger
through 22z Tuesday before clearing. Patchy fog is possible
overnight, especially at koma. May need to reduce visibility with
06z Wednesday taf.