301 FXUS63 KTOP 080529 AFDTOP Area Forecast Discussion National Weather Service Topeka KS 1129 PM CST Mon Jan 7 2019 ...Update to aviation forecast discussion... .SHORT TERM...(This evening through Tuesday) Issued at 313 PM CST Mon Jan 7 2019 Westerly winds were dominating the region this afternoon behind a Pacific cold front. High clouds associated with a weak shortwave trough were moving across the state this morning into the mid- afternoon and water vapor imagery indicates another wave moving east-southeast out of central Montana. Clear skies and a modest surface ridge axis should allow for rapid cooling this evening, but a cold front of more northern origin quickly passes through the state late tonight as the Montana wave moves across the northern Plains. West to northwest winds will increase somewhat with northwest 925 mb winds in the 35-45 knot range producing strong cold-air advection, though the previous state of the boundary layer should inhibit strong mixing to occur. Deeper mixing takes place behind the front Tuesday and some notable gusts will likely return. Lows tonight are somewhat tricky depending on mixing behind the front but highs Tuesday will be much cooler than recent days with 850-925 mb temps around 7 C colder than today. .LONG TERM...(Tuesday night through Monday) Issued at 313 PM CST Mon Jan 7 2019 Upper ridging builds into the Rockies Tuesday night into Wednesday night with light winds along a cool surface ridge axis. High clouds should increase Wednesday though cloud cover should thicken more substantially Wednesday night into Thursday as modest mid- level warm-air advection accompanies a weak mid-level trough and subsequently the breaking-down of the western ridge. Temperature expectations for these periods remain to be lows in the 20s and highs in the 40s. There is fairly strong model agreement with a southern branch upper wave maintaining some intensity as it encounters the ridge and moves east-northeast across the central and southern Plains. South-southwest flow ahead of an inverted surface trough should provide enough moisture for at least some light precipitation to develop by late Friday. Many questions remain on temperature profiles and precip duration at this range but there is a strong enough signal for an introduction of chance PoPs for the late week and early weekend. Although the upper pattern takes on a more blocky appearance late in the weekend, there should be enough progression for the system to exit by Sunday with near-normal temperatures continuing into Monday. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1129 PM CST Mon Jan 7 2019 LLWS will be the main concern for the terminals through 13Z as a cold front moves through and winds increase near 1500 ft to around 45 or 50 kts in the 06-09Z time period. Northwest winds around 15 kts with gusts to near 23 kts will be common from 12Z through 23Z then decrease to around 10 kts after 00Z. VFR conditions are expected through the period. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...65 LONG TERM...65 AVIATION...53