Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 221952 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 252 PM CDT Sat Jul 22 2017 .SHORT TERM...
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(Tonight through Monday) Issued at 224 PM CDT Sat Jul 22 2017 Northerly winds have taken over the forecast area as of mid Saturday afternoon. Cooler temperatures have been filtering in as well, but have been slow to do so in southeast NE and southwest IA where heat indices in the 100-112 range persist. The good news is that the cool air advection will be persistent and eventually win out with lower dewpoints and temperatures gradually building into the area this evening. Widespread cloud cover has also overtaken most areas north of I-80 as the mid level moisture plume streams overhead. There have been a few showers and even a couple rumbles of thunder associated with this moisture but much of the precipitation evident in radar reflectivity imagery has not been reaching the ground as the airmass between 1000-12000 feet remains hot and quite dry. The potential for a few showers and even a thunderstorm will continue over western and southern parts of the forecast area. At this time, it appears that stronger surface based convection will be focused very near or more likely south of the NE/KS border as the surface-based cap strengthens quickly with northward extent. With that said, if surface based storms do develop within the forecast area, there is ample instability (on the order of 6000 J/kg) available and 20 to perhaps 30 kts of effective shear which could support periods of storm organization with an attendant damaging wind and hail threat. Should note that while the surface front and cumulus field extends across the northern tier of KS counties at 245 PM, the impressive instability field does extend north of the front and this low-end severe potential also extends about 80 miles to the "cool" side of the surface front. Any precipitation chances will gradually diminish and shift farther south overnight with low temperatures ranging from the mid 60s north to the low 70s south. Sunday, while cooler, will still be a few degrees warmer than normal with highs in the upper 80s to lower 90s. Heat indices will hold in the 90s though as the airmass will have much lower dewpoints. Monday will be near normal for temperatures with dry conditions expected both Sunday and Monday. .LONG TERM...(Monday night through Saturday) Issued at 224 PM CDT Sat Jul 22 2017 Tuesday into Wednesday are now looking to be the hottest days of the coming week but still with a consistent signal for conditions to NOT be as hot as this past week with maximum heat indices probably in the 100 degree range at times but unlikely to approach 110. Will also have some rain potential Monday night into Wednesday. First a small chance for showers or a few thunderstorms over primarily northeast Nebraska Monday night as a compact vorticity maximum is forecast by all large scale models to track near the NE/SD border on Monday evening. The main limiting factors with this system seem to be cap strength and presence of enough moisture for widespread convection. The better precipitation chances come late Tuesday into Wednesday as a strong short wave trough moves across the Great Lakes. This trough appears likely to be strong enough to have its effects felt well southwest circulation center where associated vertical motion will interact with the modified monsoonal moisture plume over the local area. This should result in one of the better chances for widespread thunderstorms this week...although far from a slam dunk at this point. The cold front associated with the Great Lakes short wave trough looks to be fairly strong and should push all the way through the forecast area. This will set up a good chance for a period with highs in the mid 80s and lows in the 60s, but also increases the likelihood for a dry end to the week and first half of the weekend.
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&& .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1211 PM CDT Sat Jul 22 2017 Low clouds and some patchy fog were slow to burn off this morning but VFR conditions will prevail through this TAF cycle. Northwest surface winds will become light and variable through the overnight hours as a weak are of high pressure moves overhead. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Heat Advisory until 7 PM CDT this evening for NEZ045-052-053- 065>068-078-088>090. Excessive Heat Warning until 7 PM CDT this evening for NEZ091>093. IA...Heat Advisory until 7 PM CDT this evening for IAZ055-056-069-079. Excessive Heat Warning until 7 PM CDT this evening for IAZ080- 090-091. && $$ SHORT TERM...Barjenbruch LONG TERM...Barjenbruch AVIATION...Kern

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