Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 181658 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1158 AM CDT Tue Jul 18 2017 .UPDATE...
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Issued at 1158 AM CDT Tue Jul 18 2017 Showers and storms which affected parts of the forecast area continued to diminish late this morning. Will keep some low POPs for a few more hours in our far southeast counties, then attention turns to the northwest. We could see some storms later this afternoon and evening in northeast Nebraska. Shear and instability suggest a few storms could be strong to severe. Experimental HRRR and 12Z NAM are not overly aggressive with development though. Trended POPs down a little for much of the area into mid afternoon. Made some minor changes to temps and winds. UPDATE Issued at 614 AM CDT Tue Jul 18 2017 Bumped up Pops in southeast NE where numerous showers/isolated storms will exist this morning.
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&& .SHORT TERM...(Today through Thursday) Issued at 321 AM CDT Tue Jul 18 2017 Ongoing convection was noted in north central NE to southeast SD, as well as in central NE. Subjective 00Z upper-air analysis indicates broad upper-level ridging across the central US, with an embedded weak shortwave trough in central NE. Upper-level trough was noted in the Canadian prairie provinces. Upper-level jet up to 90kt was noted across MT-ND to northern MN. An 850mb low was centered in northern ON, with trailing front extending toward the ND-MN border through central SD. Ahead of the boundary, 850mb dewpoints of 12C+ had pooled across the Plains to upper Midwest. Elongated surface low at 07Z extended from southeast WY/western NE panhandle through eastern CO, with another low center in northern ON and a trough axis extending through northern MN/northeast to southwest SD. Main forecast concern is convective potential today, then heat Wednesday through Friday. Ongoing thunderstorms in central NE should move into eastern NE this morning as the associated shortwave trough slowly ambles eastward. Activity is likely to decline diurnally in the mid to late morning. However, have some concerns that the morning showers/storms and remnant clouds will temper temperatures today, offsetting increasing dewpoints and keeping heat indices below advisory thresholds for one more day. Surface cold front will sag through MN/SD into IA/NE this afternoon, potentially reinforced by convective outflow, and likely inducing a few thunderstorms along the front in the late afternoon to evening. Northwest Iowa would be most likely to see storms, closer to the shortwave trough in MN, but isolated to scattered storms could extend back along the front through eastern NE as it progresses southward through Tuesday evening. Instability will be greatest from central into eastern NE, but so will potential capping, while deep-layer shear around 30-40kt is possible in northeast NE to northwest IA, closer to the upper- level shortwave sliding across SD to MN. Thus, the potential for strong to severe storms will be higher toward the northeast but may skim the northernmost CWA. Given warm/moist profile and only modest deep-layer shear, think hail will be tough to find, with gusty winds more of a threat. The front is progged to wash out somewhere near the KS-NE/IA-MO borders by late Tuesday night, with reestablished southerly surface winds across the area by midday Wednesday. Upper-level high centered over KS-OK will extend into NE, with 500mb heights around 594-596dm. This should drive the ridge-riding troughs north and out of the area, with dry weather on Wednesday and temperatures able to soar. Mixing may improve on Thursday as surface to 850mb winds veer a bit more southwesterly, though 500mb heights may come back down a bit. The northernmost NE counties into northwest IA may just get skimmed wtih some convection on the periphery of the upper-level high, but with 850mb temperatures into the upper 20s C, a few sites may reach that triple digit mark. Convection may encroach on the northern CWA again on Thursday night, but the southern 2/3 of the CWA, at least, should remain just as hot on Friday. .LONG TERM...(Thursday night through Monday) Issued at 321 AM CDT Tue Jul 18 2017 As an upper-level low digs into the Great Lakes through the weekend, and the upper-level ridge is pushed west, the resulting northwesterly flow will bring lower temperatures. Also, with a surface to mid-level boundary floating around the area through Monday, chances for precipitation should increase for the weekend through Monday. Temperatures should dip to near- to below-normal readings for the weekend, responding to both the lower mid-level temperatures and the potential for clouds and showers/storms. && .AVIATION...
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(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1158 AM CDT Tue Jul 18 2017 Generally expect VFR conditions, outside of any TSRA. Chances are too low to mention in TAFs at this time.
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&& .OAX WATCHES/WARNINGS/ADVISORIES... NE...Excessive Heat Watch from Wednesday afternoon through Friday evening for NEZ015-033-034-042>045-050>053-065>068-078- 088>093. IA...Excessive Heat Watch from Wednesday afternoon through Friday evening for IAZ043-055-056-069-079-080-090-091. && $$ UPDATE...Miller SHORT TERM...Mayes LONG TERM...Mayes AVIATION...Miller

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