Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 230523 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1123 PM CST Wed Nov 22 2017 .SHORT TERM...(Tonight through Saturday) Issued at 310 PM CST Wed Nov 22 2017 Relatively mild temperatures are expected over the next few days, with at least breezy conditions behind a cold front on Friday. After morning lows in the teens and even some single digits, temperatures have rebounded nicely this afternoon into the 30s and lower 40s due in large part to plenty of sunshine and a return to south and southwest winds on back side of surface high pressure. Those southwest winds will continue into this evening before a weak cold front slides through the Plains overnight. Strongest cold advection should remain well northeast of our area behind the front, with main weather change here being a period of light northwest low level flow. Surface winds turn westerly on Thanksgiving Day as pressures lower in the lee of the Canadian through central Rockies in response to strong shortwave rounding top of western U.S. ridge extending from the Baja to southwestern Canada. We will feel the affects of this system on Friday when shortwave trough sweeps through the Plains and drives a cold front through Nebraska/Iowa and eventually into the southeast U.S. this weekend. Ahead of the front, downsloping southwest low level flow will increase Thursday night into Friday morning when 850 temps surge into the mid and upper teens across our CWA. Thus overnight lows should be halted in the 40s. Frontal passage is expected to clear southeast Nebraska and southwest Iowa by noon or so Friday, turning winds to the northwest and knocking 850 temps back into the 5-10C range by late in the day. Despite this cold advection regime, temperatures should still rebound into the 60s by early afternoon before brunt of cooling is felt. Windy conditions are also likely behind front as strong cold advection under 40-50kt 850 winds sets in. While not the most ideal momentum transfer regime is forecast, with low level lapse rates generally low and flow not as unidirectional with height as I`d like to see, still expecting top-of-boundary-layer winds to mix to the surface for several hours Friday afternoon, with gusts around 40 mph possible. With surface high pressure building into the region Friday night into Saturday, expect winds to diminish quite a bit by midnight. Meanwhile mid level heights will begin to rebound, indicating a warmer pattern is setting up for the latter part of the weekend. Saturday will feature plenty of sunshine, helping temps top our mid 40s normals, with highs in the 50s and light northwest winds. .LONG TERM...(Saturday night through Wednesday) Issued at 310 PM CST Wed Nov 22 2017 Warm temperatures are still expected into the beginning of the work week, with colder temps and a small chance for precipitation coming with and behind a cold front for Tuesday and Wednesday. Mid level flow pattern will feature building heights over the middle of the country through Sunday before deep trough begins to approach the region on Monday. As seems to be the case most of the time, the GFS is a bit slower than the Canadian which is a bit slower than the ECMWF in regards to trough progression. As such, the spread in attendant cold frontal passage spans from Monday afternoon as per GFS to Tuesday morning as per ECMWF. Our going forecast is a nice blend of these timing differences, bringing cold front through the area Monday night. Thus for Sunday and Monday we will keep warm temperatures going as 850 temps surge into the upper teens by Monday morning on increasing southwest low level flow. Highs Monday could reach 70 in parts of our south given this airmass and downslope flow regime. As cold front passes, post-frontal precipitation will be driven by mid level dynamics associated with trough/low. And again, models vary on degree of moisture/lift, but there is some consistency in showing best chances will reside from northern Nebraska northward Tuesday morning. And then again Wednesday as a secondary wave rolls through the region. Still, amounts should remain light if precip were to occur in our area, so no real impacts are expected. But will have to watch the Wednesday forecast when ECMWF wraps up surface low across eastern Nebraska and produces potentially accumulating snows in northeast Nebraska. Temperatures will be cooler, however, with Tuesday looking the coldest when 850 temps drop well below 0C. Some rebound is expected Wednesday as heights start to build into the region once again, but if ECMWF proves correct, highs will be well below our current 40s forecast. && .AVIATION...
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(For the 06Z TAFS through 06Z Thursday night) Issued at 1119 PM CST Wed Nov 22 2017 VFR conditions will prevail thru the fcst pd.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ SHORT TERM...Dergan LONG TERM...Dergan AVIATION...DEE is the U.S. government's official web portal to all federal, state and local government web resources and services.