759 FXUS63 KOAX 130843 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 343 AM CDT Wed May 13 2020 ...Updated Forecast Discussion for Today through Tuesday... .DISCUSSION... Issued at 339 AM CDT Wed May 13 2020 Forecast Summary: A couple of shortwave troughs rolling through the Plains will bring rain and thunderstorm chances over the next several days, most notably tonight and Thursday, then again Friday night and Saturday. Then mid level ridging building into the region will swing temperatures to above-normal to start next week. Today through Saturday night: Shallow shortwave ridging was over the Plains this morning, but will translate east today and allow west-southwest flow to take over through Saturday night. A shortwave trough is forecast to eject from the Rockies into the High Plains late this afternoon, then move into eastern Iowa by Thursday morning. Surface cyclogenesis is expected in eastern Colorado this afternoon and strengthen this evening, inducing warm frontal boundary across northern Kansas by late evening. Increasing southerly low level flow across the Plains today will draw moisture into our area today, with 50s dew points expected all areas by this evening. Low clouds were already overspreading eastern Nebraska and western Iowa early this morning, and don't expect those to go anywhere today as weak lift under diffluent mid level flow will only thicken cloud cover. Also, areas of drizzle or light showers are likely as well, especially near and southeast of Interstate 80 where deeper moisture will reside. Low level jet is expected to strengthen into the 40 to 50kt range this evening ahead of advancing shortwave, shoving higher theta-e air over warm front along southern Nebraska border. Forecast soundings show 1500 J/kg of elevated CAPE along with 35kt of 0-6km shear and lapse rates near 8 C/km in southeast Nebraska, suggesting some elevated supercell storms are likely, with large hail a possibility. Activity should drift northward with warm front overnight, reaching I-80 corridor or just north before sunrise. There will be some potential for heavy rain given precipitable water values near 1.5" and southwest 850 flow feeding west end convection leading to training of storms. Convection should move east of our area during the morning leaving much of Thursday dry. However some additional development is possible in the afternoon along frontal boundary expected to lie from eastern Kansas into northern Missouri. Instability axis will be to our southeast, but some storms may affect southeast Nebraska and southwest Iowa. We should see a lull in rain chances Thursday night and Friday before next and stronger shortwave enters the Plains Friday night and Saturday. While low level dew points may be a few degrees higher than tonight, models maintain instability axis across Kansas into Missouri. Still, given cooler air aloft, steep lapse rates and 30-35kt of shear, would expect a few strong storms as surface low/front move through our CWA Saturday afternoon. Will have to fine tune this potential with time as there is plenty of model spread on exact evolution and timing. Sunday through Tuesday: The Sunday through Tuesday period looks dry with a warming trend as mid level heights rise in the central CONUS. Sunday may still be close to normal in the low to mid 70s with northerly low level flow in wake of Saturday system. Southerly flow returns for Monday and Tuesday with 850 temps approaching 20C in parts of our area. We should see plenty of 80s both days, and perhaps a 90 degree reading by Tuesday. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1146 PM CDT Tue May 12 2020 Ceilings will start to deteriorate over the TAF period. By 10Z, ceilings should be at MVFR, and by 13Z they'll be at IFR. IFR conditions are expected to last through the TAF period. Short range models are indicating possible some rain showers today beginning around 12Z. Confidence in this still is not high. With strong warm air and moisture advection, some drizzle could be expected with the low ceilings. Marginal instability could lead to severe thunderstorms beginning around 20Z. Storm potential exists until about the end of the TAF period and possibly beyond that. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Dergan AVIATION...Fajman