Area Forecast Discussion
Issued by NWS North Platte, NE

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000 FXUS63 KLBF 240447 AFDLBF Area Forecast Discussion National Weather Service North Platte NE 1047 PM CST Sun Feb 23 2020 .SHORT TERM...(This evening through Monday night) Issued at 259 PM CST Sun Feb 23 2020 Concerns in the near-term revolve around the potential for rain/snow and snow chances Monday into Tuesday with the next disturbance moving into the area. The period begins with relatively zonal flow aloft as a compact h5 cut-off trough currently ejecting onto the Southern Plains moves into southeast Colorado and parts of southwest Kansas into the OK/TX Panhandles. This feature has been well advertised for a few days now with concerns that the area could see impacts from its northern fringes of precipitation. Light echos have been prevalent on radar much of the daytime as modest fgen is thrown north from the main trough. This fgen has generally weakened as it lifts now, however, has managed to produce a few pockets of perhaps sprinkles across southwest Nebraska. Inherited forecast contained "Slight Chance" and "Chance" PoPs across these areas but these were removed owing to the abundance of dry air in the lowest 2 km. Both the RAP and HRRR were quick to pick up on this and thus supported the decision to remove and replace with just a mention of sprinkles. Dew point depressions of nearly 40 degrees Fahrenheit and cloud bases of 9k feet AGL or greater back up this thought. Expect these light echoes and possible sprinkles to linger for areas along and south of Interstate 80 through the evening before moving off the south and east, following the stronger mid-level fgen bands. Weak surface high pressure will approach from the north late tonight with a strengthening low pressure further south towards the KS/OK border. Lows tonight will fall into the 20s to near 30 in proximity to the Pine Ridge. Attention quickly turns to the quick approaching shortwave trough moving out of the Pacific Northwest and onto the Central Plains during the day on Monday. Biggest forecast-to-forecast change has been to slow the arrival of precipitation to the area as strongest height falls and vorticity advection look to occur post-sunrise on Monday. Lee-cyclogenesis will begin across western South Dakota during the morning hours, leading to increasing southerly flow across much of western Nebraska. As this low develops and treks east along Interstate 90, an attendant surface cold front will sweep through the region from west to east. It`s this feature and associated lift coincident with it that`ll lead to increasing PoPs through the morning hours into the afternoon. These PoPs will be greatest for areas north of Interstate 80 through Monday evening. Daytime highs will climb into the upper 30s to 40s, with thoughts that any precipitation should be rain or a rain/wet snow mix. Dry air at the surface will also need to be overcome as this system isn`t bringing much moisture with it and residual dry air from Sunday will remain in place. General thoughts are little to no QPF is expected during the day on Monday. Winds behind this frontal boundary will increase out of the west with gusts as high as 35 mph for portions of the eastern Panhandle and 30 mph or less for further east. Elevated winds will continue into Tuesday as h85 flow remains elevated with 30 to 40 knots of flow through the event. The approaching trough will begin cutting off immediately upstream and with this occurring will slow its progression Monday evening into Tuesday, becoming centered over western Nebraska by early Tuesday morning. Strong isentropic ascent, particularly on the 290-295K surfaces, along with peaking differential vorticity advection will lead to increasing precipitation towards sunrise on Tuesday. By this time, temperatures will be well cold enough to support all snow across the region as h85 temperatures approach -8 degrees C and h7 temperatures approaching -20. The main h5 cutoff will have shifted south and east of the area by late morning Tuesday, with subsidence behind the departing wave and downglide across the lowest isentropic surfaces. This should bring a quick end to precipitation through the afternoon and into the evening. Current thinking is the heaviest precipitation will be confined to areas north of Highway 2 with generally 1-3" of snowfall expected and localized amounts closer to 4" possible. Did discuss potential for Winter Weather Advisory with neighbors considering expected snow totals and strong winds, but opted to defer to later forecasts for now given lingering uncertainties with where heaviest snowfall occurs. Tuesday will be well below-normal for temperatures with highs in the 20s and 30s and lows in the single digits to teens. Combined with strong winds, feels-like temperatures will remain in the single digits to teens all day making it feel very raw for late February. .LONG TERM...(Tuesday through Sunday) Issued at 259 PM CST Sun Feb 23 2020 Beginning 12z Wednesday. The extended period begins with highly amplified northwesterly flow as the area is caught between the departing trough and developing ridge along the west coast. Both the ECMWF and GFS advertise a weak clipper-like system moving through the area sometime in the Thursday/Friday timeframe. Both model outputs are similar in thinking with respect to this potential disturbance, although they differ on timing by 6 to 12 hours. Because of this, opted to leave the forecast as is which has a small coverage area of "Slight Chance" PoPs across north central Nebraska Thursday. That appears to be the only blemish on an otherwise dry forecast as the aforementioned ridging pushes eastward onto the Plains by the weekend. This will allow temperatures to climb Wednesday through Friday from the 20s/30s to 30s/40s. Then, as the main ridging arrives overhead by Saturday, temperatures will jump back into the 40s/50s with potential for some 60s on Sunday and dry conditions. For the start of next week, another stout trough will move onshore and approach the region in the Monday/Tuesday time frame. Some uncertainty remains with where the greatest impacts will be seen from this system as the GFS and ECMWF have vastly different evolutions. Either way, be mindful of potentially active weather for next week. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 1044 PM CST Sun Feb 23 2020 VFR conditions will rule through noontime Monday. Mid and high clouds will prevail with light winds. A cold front will move into the area Monday afternoon with winds shifting to the northwest with gusts up to 25 kt. In addition some scattered light rain or snow will be possible. An area of MVFR ceilings will accompany the front across northern portions of Nebraska including the KVTN terminal during the afternoon and evening hours Monday. Light snow will become more widespread across northern Nebraska Monday evening. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Jurgensen LONG TERM...Jurgensen AVIATION...Taylor

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