Area Forecast Discussion
Issued by NWS Omaha/Valley, NE

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000 FXUS63 KOAX 270501 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 1201 AM CDT WED JUL 27 2016 .UPDATE... Issued at 955 PM CDT Tue Jul 26 2016 The latest SWO has the marginal risk for severe storms into northeast Nebraska. Late this evening...a line of severe storms was rolling through parts of South Dakota and northern Nebraska. The instability and moisture are most favorable where the storms are now/western Nebraska. The eastern end of the line toward Verdel is weaker. As a weak shortwave moves into the area...0-3km shear increases, moisture will accompany it, and there will be some favorable deep layer shear and downdraft CAPE. Gusty winds will be possible with the storms. The 00Z NAM takes the bulk of the storms west of the area...meanwhile the ESRL HRRR/Operational HRRR bring the storms a little farther east before weakening 10-12Z. && .SHORT TERM...(tonight through Friday) Issued at 326 PM CDT Tue Jul 26 2016 High pressure is still dominating the area, with quiet and mild to seasonable temperatures. Subjective 12Z upper air analysis indicates mainly zonal flow across the northern tier of the US, with a few weak embedded shortwaves, including one in MT and another from MN through IA/MO. Weak upper-level flow was noted, with upper-level jet well north into Canada toward New England. At 850mb, a dry air intrusion was noted from MN into the mid- to lower MO River valley, with moisture returning through KS toward the High Plains of NE/SD/ND. Surface high at 19z was centered in eastern IA, with return flow finally sneaking into central to northeast NE. Main forecast concern is shower/thunderstorm potential tonight through Friday. Thunderstorms are ongoing in SD, and RAP/HRRR have some of the better current handling of the storms in both their coverage and their weakening trend. Meanwhile, storms also are developing from the Black Hills to the foothills. The more westerly batch of convection is the one associated with the shortwave analyzed in MT at 12Z and is more likely to impact our area tonight. Still seems like precipitation will hold off until after 06Z and may struggle to move into the drier air over eastern NE/western IA. Have limited the southward extent of precip mention tonight and really focused mention on northeast NE into Wednesday morning. There may be something of a lull in activity for most of the area on Wednesday as a weak front moves into the area, with convective development in eastern NE/western IA on Wednesday afternoon and expansion through the evening. Have tightened coverage of higher POPs through the afternoon and evening, particularly to clear the northwestern CWA more quickly and to delay onset in the southeastern CWA until evening. Think the marginal severe weather outlook from SPC is about right, with weak shear and some instability, but with a front becoming increasingly baroclinic through the evening and perhaps providing some focus for storms. Most models are now on the drier side on Thursday, with stabilized air and high pressure moving in behind the front. Have reduced POPs and also cooled temperatures a touch. Confidence remains quite low for Friday, with some signals for precipitation but not much in the way of focus, other than the presence of northwesterly flow and the tendency for periodic shortwaves. Have kept a mention on Friday for now, again with temperatures on the cooler side. .LONG TERM...(Friday night through Tuesday) Issued at 326 PM CDT Tue Jul 26 2016 Northwesterly flow continues into Saturday, before rising 500mb heights and a building ridge over the central US send the "ring of fire" northward. Held onto slight chance pops in at least some part of the CWA into Saturday, with lingering slight chances in the southern CWA into Sunday. Temperatures will moderate through the period, and by Monday and Tuesday, will again reach the 90s with increasing humidity, pushing heat indices toward the 100s. && .AVIATION...
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(For the 06Z TAFS through 06Z Wednesday night) Issued at 1151 PM CDT Tue Jul 26 2016 VFR conditions outside of any thunderstorm activity. Thunderstorms are weakening and included showers and some thunder a norfolk and these should weaken enough not to mention at KOMA and KLNK. Did mention some gusty winds as well. The next shortwave in the parade of disturbances in northwest flow would affect the taf sites Wednesday afternoon and Wednesday night. For now included a PROB30...but will need to hone in on timing with future forecasts.
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&& .OAX Watches/Warnings/Advisories... NE...None. IA...None. && $$ UPDATE...Zapotocny SHORT TERM...Mayes LONG TERM...Mayes AVIATION...Zapotocny

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