947 FXUS63 KDDC 212025 AFDDDC Area Forecast Discussion National Weather Service Dodge City KS 225 PM CST Thu Feb 21 2019 ...Updated Long Term... .SHORT TERM...(This afternoon through Friday night) Issued at 1115 AM CST Thu Feb 21 2019 Strong SW flow aloft over SW KS as of midday, with variable amounts of cirrus, as a powerful, large closed low spins over the southern Great Basin. There will be some lower mid clouds this afternoon and attendant sprinkles across the NE zones, but models have really backed off on this idea. With zero QPF from 12z NAM, certainly not expecting anything more than sprinkles. Strong SE winds will be elevated and gusty this afternoon, gusting well over 30 mph at times, in response to surface pressures continuing to fall to the west. Temperatures will climb well into the 40s with the aid of modest warm air advection, with lower 50s across zones adjacent to Oklahoma. Tonight...Moist SEly upslope boundary flow will lead to widespread stratus development after midnight. Also included areas of fog in the grids. Short term models are not suggesting widespread 1/4 mile visibility (dense fog advisory criteria) but am confident that at least areas of advection fog will materialize in the persistent moist SE upslope flow. With the clouds and continued moisture advection, temperatures will be noticeably milder tonight, only falling to lower 30s for many zones. Friday...Clouds will prevail amid continued moist SE upslope. Kept areas of fog in the grids for at least the first half of the day. Areas of drizzle or light rain will focus across the eastern zones Friday, as gulf moisture continues to flow in on SE winds. Main synoptic trough begins its ejection across Arizona on Friday, encouraging leeside cyclogenesis in SE Colorado, and keeping the SE winds persistent and gusty. Accepted guidance with afternoon temperatures primarily in the 40s, with some 50s across the SW zones where some sunshine is more probable. Friday night...The interesting weather begins, as the much advertised powerful closed low ejects through northern New Mexico and begins to take on a negative tilt. Dynamic lift will increase rapidly over SW KS, especially after midnight. Widespread rain is expected, and included some thunder in the grids for the southern and SE zones to catch any convection that propogates in from the TX/OK panhandles. Consistent ECMWF runs spread the heaviest rain into the SW zones after midnight, and increased pops to the definite category for these zones. Some heavy rain is likely. Rain/snow line is expected to begin its march into the far western zones early Saturday morning. .LONG TERM...(Saturday through Thursday) Issued at 225 PM CST Thu Feb 21 2019 ...Intense Winter Storm Taking Aim on SW Kansas... Have issued a winter storm watch for much of SW Kansas, running from 6 am Saturday through midnight Saturday night. Model consensus continues to indicate a high impact, but quickly moving, intense winter storm affecting SW Kansas. The worst conditions remain focused on the Saturday daylight hours. The past 3-4 runs of ECMWF have shown little if any variability in the track, speed and amplitude of this incoming storm. WPC has discounted 12z GFS as a northern outlier, and have noted the new GFS-FV3 sets up its heavy snow band further south along the lines of 12z NAM/ECMWF/Canadian. As such, we also removed the GFS and forecast builder grids from the Saturday time frame, and followed a blend of WPC/ECMWF guidance on QPF/snow amounts. Rain with embedded thunder will be widespread at sunrise Saturday, in response to intense dynamic lift/diffluence aloft ahead of negatively-tilting closed 500 mb low near Clovis. The rain/snow line is expected to be entering the far western zones around sunrise Saturday, and subsequently march eastward across SW Kansas during the daylight hours. We have high confidence this thermodynamic phase change will occur from west to east. But exactly how fast it progresses, and how much QPF we lose as rain, will be critical in determining how much snow falls, and where. Without a warm layer aloft, the rain to snow transition should be quick, and snow production after the phase change should be dramatic. Whereever the strongest forcing/moisture/cold air align, a few hours of 1-3"/hour snowfall rates are possible. At this time, it appears this heaviest snow will fall from within 50 miles of Garden City northeastward through the NE zones. Here, a widespread 6-9 inches is forecast. This will be a wet, compacted snowfall, with high water content, and marginally cold temperatures within a few degrees of 30. As such, snow will stick easily to trees and powerlines. This poses a problem, as we are expecting wind gusts near 60 mph behind the departing storm during the midday/afternoon hours Saturday. Power outages and down tree limbs are a concern on Saturday. Given the current storm track, lesser snow amounts of 3-6 inches are likely for most other zones. Very progressive nature of parent cyclone should prevent snow amounts from exceeding 10 inches or so for most locations. It is emphasized, however, that this storm is more than the snow amounts you see on paper. This will be a strongly dynamic storm with an intense pressure gradient response during the day Saturday. Loaded the strongest consmos wind guidance into the grids, added a few mph to it, and hope it is enough. Wind grids show NW wind gusts as high as the 55-65 mph range. These winds will crank up while the heavy snow rates are occurring, which will reduce visibility to near zero at times. Despite the wet snow character, and falling on wet ground from previous rains, placed blowing snow and near blizzard conditions in the grids. Models remain consistent, pulling the storm quickly away, with no snowfall after 6 pm Saturday. Allowed the winter storm watch to continue through midnight to capture lingering affects on likely highly impacted roadways, but much improved weather is expected Sunday and beyond. What could go wrong? The models remain highly consistent on impacts aligning across Kansas on Saturday, once the northward and progressive nature of the operational GFS is discounted. As the large powerful closed low is sampled by the upper air network across the SW U.S. tonight and tomorrow, a southward storm track adjustment may occur, as jet energy on the back side of the trough is better sampled. This evolution may push the zone of highest (blizzard) impacts further south in the CWA. But a strong enough southward track adjustment that would take impacts out of Kansas is highly unlikely. Currently, expect the SE zones to remain mostly rain (why Comanche/Barber counties were excluded from the winter storm watch). But if a southward adjustment occurs, so will the heaviest snowfall totals. A northward track correction is very unlikely. A southward correction lured by latent heat release from West Texas convection has occurred in the past, and short term/high resolution models will be watched carefully over the next 24 hours to monitor for this possible southward trend. At this point with the model agreement, a strongly worded winter storm watch seems prudent for the majority of SW Kansas. A long stretch of dry weather is expected after this storm's passage, with no pops in the grids Sunday onward. && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 1035 AM CST Thu Feb 21 2019 VFR will continue through about 06z Fri, with variable amounts of cirrus. SE winds will be strong at all airports through this afternoon, gusting in the 28-32 kt range. Winds will subside somewhat around 00z Fri, but remain SE and somewhat elevated tonight. After 06z Fri, high confidence that flying conditions will degrade rapidly, as moist SEly upslope yields widespread LIFR stratus cigs and reduced visibility in BR/areas of fog. At all airports, brought vis down to 1/2 sm and cig down to 300 ft AGL by 12z Fri. Areas of drizzle likely to develop from near DDC to near HYS by 18z Fri. && .PRELIMINARY POINT TEMPS/POPS... DDC 32 45 35 35 / 10 10 70 100 GCK 30 46 30 32 / 0 10 80 100 EHA 28 55 27 39 / 0 0 80 100 LBL 32 51 32 39 / 0 10 80 100 HYS 31 40 31 31 / 10 30 50 100 P28 32 43 38 44 / 10 30 60 100 && .DDC WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch from Saturday morning through Saturday evening for KSZ030-031-043>046-061>066-074>081-084>088. && $$ SHORT TERM...Turner LONG TERM...Turner AVIATION...Turner