Area Forecast Discussion

FXUS63 KOAX 151729
Area Forecast Discussion
National Weather Service Omaha/Valley NE
1129 AM CST Fri Dec 15 2017
.SHORT TERM...(Today through Sunday)
Issued at 328 AM CST Fri Dec 15 2017
Relatively mild to start the weekend, then cooler with a small 
chance for precip on Sunday.
Mid level trough was exiting the Plains this morning, tracking 
southeast through southern Missouri. Heights are forecast to rise 
the next couple of days behind this wave and ahead of next shortwave 
ejecting into the region from mean trough position in the 
southwestern U.S. Much warmer airmass under the building height 
regime should put temperatures well into the 50s by Saturday over 
much of our area. 850 temps rise from sub-zero this morning to near 
5C this afternoon then 10C on Saturday. Favorable west to 
southwest surface winds this afternoon and decreasing cloud cover 
suggest highs should reach the 45 to 50 degree range.
Saturday will likely be warmer, especially in our south, given 
warming temperatures aloft. However weak surface front is forecast to 
settle across eastern Nebraska and southwest Iowa, turning winds to 
northeast to the north of the front and shaving several degrees off 
potential warming. So despite plenty of sunshine, expect highs in 
northeast Nebraska to hold in the middle 40s while southeast 
Nebraska should reach the upper 50s.
Shortwave ejecting from the southwest Saturday night and Sunday 
morning is expected to track across Missouri, with bulk of deeper 
moisture drawn north on the east side of path from eastern Texas 
into the Ohio Valley. However weak lift and mid level moisture 
associated with minor potential vorticity anomaly will skirt our 
southeast CWA Sunday morning. Models have been advertising light 
precipitation there, and continue the trend this morning. Forecast 
soundings suggest nose of warm air over top of cooler near-freezing 
surface temperatures could provide a mix of precipitation types for 
a few hours Sunday morning. However given light QPF and short 
duration of any precipitation, expect impacts will be minimal in 
southeast Nebraska and southwest Iowa.
Cooler temperatures will follow this system Sunday afternoon as 
northeast surface flow and more cloud cover hold temperatures closer 
to normal.
.LONG TERM...(Sunday night through Thursday)
Issued at 328 AM CST Fri Dec 15 2017
Another major pattern shift still looks likely by the end of the 
week, bringing much colder air to the region. Leading up to it, 
mainly northwest to west mid level flow will dominate the weather 
across the Plains through mid week as upper trough/low in the 
southwest U.S. gradually fills and tracks across the South. 
Meanwhile a deep low drifting through the Gulf of Alaska will 
creep southeast and eventually settle into the Rockies and 
Northern Plains by Thursday. 
Ahead of this system we should continue to see above-normal 
temperatures with only minor perturbations nudging temps one way or 
the other Monday and Tuesday. Wednesday looks to be the warmest day 
as stronger southerly flow develops ahead of approaching strong 
trough, then much colder air and a chance for precipitation will 
arrive Thursday. GFS and ECMWF have shown decent consistency in 
timing and precipitation placement the last few runs, so forecast 
confidence is increasing. Expect generally falling temperatures 
much of the day Thursday, with precipitation expanding across all 
of eastern Nebraska and southwest Iowa. Current indications point 
to mainly snow in our north and rain changing to snow in the south
through the day. 
.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1128 AM CST Fri Dec 15 2017
VFR conditions are expected through the TAF cycle. Mid-level
clouds will continue to exit, leaving skies with clear to 
scattered cirrus (25kft) conditions. Southwest winds around 
10-15kt this afternoon will diminish to 5-8kt by sunset, then 
become light and variable or light and northwesterly by Saturday 
LONG TERM...Dergan