Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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FXUS63 KOAX 201758

Area Forecast Discussion
National Weather Service Omaha/Valley NE
1258 PM CDT Tue Mar 20 2018

.SHORT TERM...(Today through Thursday)
Issued at 318 AM CDT Tue Mar 20 2018

A weak mid-level vorticity lobe and attendant precipitation band
will translate through the area this morning with light rain
temporarily mixing with or changing to light snow before ending or
transitioning to drizzle as the stronger forcing for ascent shifts
east. The radar presentation as of 0800z is rather unimpressive
with highest precipitation rates (~0.02-0.05/hr) associated with
rain per surface observations. Based on current radar trends and
latest short-term model guidance, any snow accumulation should
remain low and generally less than a half an inch.

Lingering cloud cover and light precipitation (especially across
the eastern part of the CWA) will once again limit daytime heating
with highs today mainly in the lower to mid 40s. However by
Wednesday, decreasing clouds coupled with building mid-level
heights will yield warmer temperatures with afternoon readings in
the upper 40s to upper 50s.

Wednesday night into Thursday, model guidance suggests that warm
advection and isentropic upglide within the exit region of a low-
level jet will foster a swath of light rain across portions of
western into central IA, to the immediate north/northeast of a
weak surface warm front. Our southwest IA counties will be on the
western periphery of that precipitation where we will indicate
slight-chance PoPs. To the west of the front, south to southwest
low-level winds will allow temperatures to warm into the 60s with
mid to upper 50s forecast along and to the east/northeast of the
boundary from northeast NE into west-central IA.

.LONG TERM...(Thursday night through Monday)
Issued at 318 AM CDT Tue Mar 20 2018

Latest medium-range guidance continues to indicate an active
pattern over the mid-MO Valley through much of the extended
forecast period. These data suggest that an amplified ridge will
overspread the Great Plains Thursday night into Friday ahead of a
low-amplitude perturbation moving from the Rockies into the High
Plains. Strengthening warm advection ahead of that disturbance
will support a chance of light rain on Friday. By Friday night
into Saturday, it appears that the High-Plains disturbance will
amplify as it moves through the region, driving the deepening of a
surface low which is forecast to track to our south. Nonetheless,
steepening lapse rates and increasing moisture content will
support scattered showers and a few thunderstorms as the synoptic
system moves through the area.

On Sunday, a short-wave trough will traverse the northern Plains
with an associated surface cold front focusing precipitation
chances over the mid-MO Valley. By early next week, the GFS
progresses a low-amplitude trough through the central U.S.,
whereas the ECMWF and Canadian models depict broader troughing
lagging west over the Rockies. As such, forecast confidence is low
during that time frame.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1246 PM CDT Tue Mar 20 2018

Conditions will continue to improve to MVFR levels this afternoon,
as mixed precip moves east of the TAF sites. Some light drizzle
or rain will still be possible at KOMA through 20Z. Light
northwesterly winds will become variable, briefly, before shifting
to the south late Wednesday morning. Light winds in addition to
moist conditions near the surface will create the potential for
fog late tonight and into Wednesday morning, however left mention
out of the TAFs for now, until confidence improves.




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