032 FXUS63 KLBF 072154 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 354 PM CST Sat Dec 7 2019 .SHORT TERM...(This evening through Monday) Issued at 243 PM CST Sat Dec 7 2019 Impacts/Highlights and Confidence: Highs 5-15 degrees above seasonable temperatures Sunday will be followed by a cold front and chances for snow. Best chances across northern NE towards central NEB. Thinking chances for southwestern NEB to see measureable snowfall is low at this time. Limited impacts are possible with total snowfall forecast under an inch across far northwest NEB and north central NEB. Discussion: Latest Day Snow-Fog RGB imagery shows increasing thick clouds across northwestern NEB with a few swaths of thin high clouds elsewhere. Water vapor imagery shows zonal flow aloft overhead with an upper-level trough upstream offshore the West coast. Upper trough will evolve and advance to Northern High Plains to the Central Great Basin by late Sunday. Northern positive PV anomaly is expected to move from MT into the region Sunday night, along with associated strong cold front crossing the area. Concern turns snow chances Sunday night as transient lower tropospheric frontogenesis evolves and moves southeastward. Best forcing looks across northern into central NEB thus where highest PoPs are. Thinking p-type will be predominantly snow and given setup will be light snow. Best snowfall looks to favor the north, and with light amounts. System appears somewhat slower so did adjust timing and delayed onset. Forcing and chances move quickly through by Monday morning. .LONG TERM...(Monday night through Saturday) Issued at 243 PM CST Sat Dec 7 2019 Impacts/Highlights and Confidence: Below seasonable temperatures with quite a contrast, and the coldest on Tuesday. Highs Tuesday a few degrees to as much as 15 degrees below seasonable normals that range from the upper teens across extreme north central NEB to near 40 degrees over the extreme Southwest. Largely dry conditions expected, outside low-end chances Friday with low confidence at this time. Discussion: A deep upper trough will extend over the central CONUS across the Southern Rockies early Monday night with a closed low near the Southampton and Coats Islands. Elsewhere, an amplified upper ridge will be positioned across the West Coast. A weak cold front pushes into much of the area Monday night. This will provide somewhat of weak reinforcement to colder air after Sunday night’s frontal passage. Albeit, 850 hPa temperatures ranging from -3 to -6 C at 850 hPa at 12 UTC is at best approaching the 25th percentile (~5 C) per SPC Sounding Climo at LBF. Likewise, NAEFS and ECMWF ensemble systems don’t show that cold of a temperature forecast aloft at 850 and 700 hPa compared to climo with the more anomalous and colder temperatures to our northeast. The area will remain under southwest flow through Tuesday night wherein the western CONUS ridge breaks down as the next upper- level trough moves onshore late Tuesday. This will prompt a change in the pattern with the upper trough moving into the region by Wednesday night. Of which, differences in phase and amplitude grow in the large scale pattern Wednesday night on thus there is increasing uncertainty/decreased confidence. Guidance appears to support largely quasi-zonal to northwest flow at the end of the long term. Of which, this will help promote conditions for seasonable to mild temperatures. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1226 PM CST Sat Dec 7 2019 VFR conditions will continue the next 24 hrs across western and north central Nebraska. Stronger west winds just off the surface could create favorable low-level wind shear conditions through late this afternoon, especially across north central Nebraska. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...ET LONG TERM...ET AVIATION...Taylor