174 FXUS64 KAMA 201739 AFDAMA Area Forecast Discussion National Weather Service Amarillo TX 1139 AM CST Wed Nov 20 2019 .AVIATION... 18z TAF Issuance...VFR conditions are expected through the TAf period at all three sites. Showers are expected to continue to move east northeast with KAMA as likely a site to see light rain showers. KDHT/KGUY have the chance for some vicinity showers, along with a light shower. Precipitation chances will be ending around 21z for KDHT and 00z for KAMA/KGUY. Winds are from the southwest today and will be breezy this afternoon with gusts up to 25 to 30 knots possible through 00z. Winds will turn to the north overnight between 06z to 09z as a cold front pushes south across the TAF sites. Winds will remain from the north through the period with wind speeds of 10 to 15 knots. Skies will remain BKN to SCT today with the precipitation, but quickly clear out overnight before another deck of clouds move in tomorrow morning behind the front. Rutt && PREV DISCUSSION... /Issued 341 AM CST Wed Nov 20 2019/ SHORT TERM...Today and Tonight... Current satellite reveals transient ridging across the Plains with an upper trough deepening a bit as it heads northeastward from the Colorado River delta. Southwesterly flow aloft is in place across the Panhandles between these features, with a series of shortwaves extending from the northern Gulf of California into eastern New Mexico as evidenced by increasing amounts of mid level cloudiness and an area of showers pushing east-northeast from a HOB-MAF line as of 08z. Across the Panhandles, temperatures range from the mid 40s in the northwest to the mid 50s in the southeastern Texas Panhandle with dew points in the 30s. Across the South Plains, temperatures were around 60 with dew points in the upper 40s. Observations also indicate southerly or south- southwesterly winds across the majority of both regions. With the relatively moist - by November standards - air mass currently advecting northward, expect showers to occur across the Panhandles ahead of the approaching wave. The big remaining two-part forecast question: will thunderstorms develop and, if so, will any of them be severe? RAP/NMM are most aggressive with up to 1000 J/kg of MUCAPE while the NAM/GFS/HRRR/ARW depict up to around 500 J/kg. This is largely due to the RAP/NMM being more aggressive with surface destabilization. Given the expected cloudy conditions across the forecast area, coupled with the fact that the majority of available guidance is less agressive, am leaning toward the lower instability solution and not thinking anything more than isolated thunderstorm coverage will occur. As for severe weather, progged 0- 6km bulk shear values midday Wednesday are on the order of 40-50 knots but hodographs suggest a largely unidirectional shear profile. Storm motion vectors are around 40-45 knots in magnitude and progged 850mb winds are 35-50 knots, so a stray severe wind gust is not out of the question should thunderstorms develop. Finally, while temperatures aloft are cold - it is the latter part of fall after all - CAPE in the -10 to -30 layer is negligible, so current thinking is that only if the more unstable RAP/NMM solution bears out will severe hail be possible. No matter what occurs, the southern Texas Panhandle will have the relatively higher chance for thunderstorms today. Precipitation should move out quickly Wednesday evening with a cold front pushing south overnight, with temperatures dropping largely into the 30s. Ferguson LONG TERM...Thursday through Tuesday... Models in good agreement that closed mid-level low over southern Nevada early Thursday morning will maintain its identity through the day, with a slow drift to the northeast. During the night on Thursday, main center of circulation becomes established over eastern Colorado, with rich moisture returning to Texas and Oklahoma Panhandles. Cold post-frontal surface high pressure ridge builds into the Panhandles Thursday and Thursday night, with modest isentropic lift setting up. Strong dynamics from mid- level low and modest upslope flow will lead to increasing chances for precipitation Thursday afternoon and Thursday evening. Expect that northwest part of forecast area, generally north of a line from Dalhart to Beaver, will cool sufficiently for light snow to be possible during the day on Thursday, with remaining sections receiving rain. As cold air deepens and spreads southeast Thursday evening, a transition zone of rain and snow is expected to also spread southeast. By midnight Thursday night, areas roughly along Highway 60 could experience mixed precipitation, with areas north of a line from Boys Ranch to Lipscomb becoming all snow. By sunrise Friday, all sections expected to be cold enough for snow or a rain/snow mix, but strong dynamics expected to quickly exit Friday morning, with mid-levels drying. All precipitation expected to end by noon Friday. Still appears that northwest part of forecast area, generally north of a line from Hartley to Liberal, will have the best opportunity for accumulating snow. Current forecast is in the 1 to 3 inch range in this area, with much lighter amounts elsewhere. Dry and mild weekend expected. Cold front Monday and Monday night brings a chance for light precipitation Monday night and Tuesday with Tuesday highs below normal. Cockrell && .AMA Watches/Warnings/Advisories... TX...None. OK...None. && $$ 23/9