609 FXUS63 KOAX 301039 AFDOAX Area Forecast Discussion National Weather Service Omaha/Valley NE 539 AM CDT Wed Sep 30 2020 ...Updated Aviation Forecast Discussion... .DISCUSSION... Issued at 322 AM CDT Wed Sep 30 2020 Forecast Summary: Gusty north to northwest winds today will usher in much cooler air which will remain in the area through the weekend. In fact, freezing temperatures and areas of frost are likely Friday morning. The only real chance for precipitation comes Saturday. A rebound in temperatures still looks probable early next week. Today: Strong northwest mid level flow remained overhead this morning, in between pronounced ridge in the West and trough from eastern Canada through the Appalachians and into the northeast Gulf. A broad area of mid level clouds from eastern South Dakota into northeast Nebraska and much of Iowa was the result of mid level warm advection ahead of a shortwave diving southeast. As that shortwave passes through today, strong cold advection will follow this morning and afternoon. 850 temperatures are forecast to drop a good 10C from the mid and upper teens early this morning to near 8C this afternoon. After morning cloud cover in our north spreads east, more sunshine is expected for the afternoon, offering some help to offset strong cool advection. Expect highs only to rebound into the 60s north and lower 70s south today. Strong northwest winds are also forecast given tight pressure gradient and potent pressure rises behind cold front, generally in the 20 to 35 mph range across much of eastern Nebraska and western Iowa. And despite cooler temperatures than Tuesday, lower dew points will still result in minimum afternoon humidities between 20 and 25 percent. This dry air combined with the strong winds will result in near-critical fire weather conditions. Our fire weather fuels status remains non-critical overall, but given the prolonged drought in northeast Nebraska and west central Iowa, there are likely pockets of grasses that could support erratic fire behavior if starts occur. The strong winds should diminish rather quickly early this evening with loss of daytime heating and cool advection subsides. Thursday through Sunday: Another reinforcing shot of cooler air is scheduled to arrive between midnight and sunrise Thursday. 850 temps will likely drop below 0C in our north by Thursday morning with that cold airmass overhead through Thursday night. Temperatures Thursday afternoon may not reach 60 in much of our area. Then diminishing winds and mainly clear skies should allow for radiational cooling regime overnight. There may be a few more high clouds than our forecast suggests, which may limit cooling somewhat. Still we should see widespread frost Friday morning, with some spots dropping to or below freezing. Southerly winds return on Friday as surface high slides east and pressures fall to our west with the approach of a potent shortwave dropping through the Northern Plains. We will likely gain a few degrees over Thursday's highs for Friday afternoon, but still well below normal. Moisture profiles are rather paltry for the arrival of strong shortwave scheduled Saturday morning. Models in general have backed off a bit on extent of potential precipitation Saturday, but most all guidance produces some precipitation. Therefore, will maintain our chances for showers on Saturday under mainly cloudy skies and cool east to northeast winds. Cool temperatures remain overhead for Sunday behind exiting shortwave, with Sunday's highs in the 50s. Monday and Tuesday: We should see a nice warming trend to begin next week as mid level heights rise behind exiting shortwave. A couple of weak shortwaves riding through west to northwest mid level flow Monday and Tuesday will bring short bouts of warm then cool advection, but overall the warm advection pattern will win out. Expect highs back into the 70s by Tuesday. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 537 AM CDT Wed Sep 30 2020 Strong and gusty northwest winds 20 to 32kt are expected to develop between 14Z and 17Z at all eastern Nebraska TAF sites as a cold front sweeps through the region. Expect those winds to continue through 00Z before settling back to under 12kt by 02Z. Only scattered to briefly broken mid level clouds near FL120 are forecast through 18Z, then clear skies are expected. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...None. IA...None. && $$ DISCUSSION...Dergan AVIATION...Dergan