Area Forecast Discussion
Issued by NWS Amarillo, TX

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000 FXUS64 KAMA 191110 AFDAMA Area Forecast Discussion National Weather Service Amarillo TX 610 AM CDT Mon Apr 19 2021 .AVIATION... For the 12z TAFs: VFR conditions are expected through most of this cycle, but conditions will deteriorate this evening when a cold front blast through the Panhandles. This will result in a sharp wind shift and breezy/windy conditions along and behind the front. Additionally, ceilings will drop down to MVFR as moisture increase behind the front. There will also be a chance for light wintry precipitation in the form of snow and/or freezing drizzle. Not expecting much if any accumulations. Guerrero && .PREV DISCUSSION... /Issued 417 AM CDT Mon Apr 19 2021/ SHORT TERM (Today and tonight)... A lot of different potential hazards to talk about in the next 24 hours which mainly revolves around a strong cold front expected tonight. Potential Hazards: * Wind Advisory across the western TX Panhandle * Area-wide subfreezing temperatures * Light wintry precipitation (freezing drizzle/snow) Further Details: There isn`t much upper level dynamics with this event; therefore, overall forcing is weak and very progressive. This will lead to only light precipitation strongly rooted behind the frontal passage within a 700 mb layer of frontogenesis. Our moisture source is not ideal with this setup either as it comes oddly enough behind the front from the north. Part of the reason for this is the cut off low over northern Baja California blocking and steering any moisture from the south away from the Panhandles. That said, very strong cold air advection and lift associated with the frontogenetic band at 700 mb should lead to at least light accumulation of precipitation. We may see rain/drizzle initially, but this will quickly convert over to snow and freezing drizzle with the cold airmass. The precipitation will be closely rooted with the frontogenesis and quickly push south, so any precipitation window will be quick. The biggest question is whether or not we will see super cooled water droplets and/or ice crystal form in the cloud layer because this will be the difference between light snow and/or freezing drizzle. It may be a combination of these based on forecast soundings. Most of the models differ from one another on this, so its a rather difficult forecast regarding precip type. Luckily there isn`t much upper level dynamics and the frontogenesis passes quickly, so our window of opportunity is small. Therefore, any wintry precipitation whether it`s light snow or light freezing drizzle will be quick hitting and accumulations will be limited. Lee cyclogenesis will lead to a surface low developing in the vicinity of southeast Colorado/northeast New Mexico. As the surface low slides south and east, strong height rises are expected behind the front with 3-hr pressure changes on the order of 10-12 mb. This will result in a strong pressure gradient along the front and near the surface low. Even though the mixed layer near the surface is shallow, we still have strong winds at the top if this layer around 45 knots. A combination of these winds aloft, and the strong pressure gradient will lead to wind speeds around 30-35 mph with gusts around 45-50 mph across the western Texas Panhandle. A Wind Advisory will be in effect for this area from midnight tonight through 6am Tuesday morning. We officially started our issuance of frost/freeze products for the growing season today. With the Canadian airmass bringing strong cold air advection into the region, we will have area-wide subfreezing temperatures tonight. Due to the cold airmass, a Hard Freeze Warning and a Freeze Warning will be in effect from 1am tonight through 9am Tuesday morning. Guerrero LONG TERM...Tuesday through Monday... Forecast soundings suggest a few more hours with saturated shallow near surface layer across the southern Panhandles and a slightly deeper moist layer across the north Tue morning while strong upslope flow continues. At this point, the cloud layer is forecast to have cooled to at least -8 deg C across the entire area which would suggest P-type would mostly likely be all snow at that point. Given very light QPF (trace at best), have just introduced flurries to cover any remaining very light across the area Tue morning. With skies clearing, temps will actually rebound nicely into the 40s and 50s Tue aftn as winds decrease with SFC high pressure settling into CEN OK. The clearing skies will also allow temps to plummet again Tue night however and another combination of freeze and/or hard freeze is expected Wed morning areawide. We went ahead and matched up with the freeze watch issued by neighbors for Wed morning. The upper level pattern will remain rather amplified with strong ridging just west of N America (in the ERN Pac) and broad troughing across the CONUS, but a somewhat zonal orientation of a split jet across the southern US. Numerous S/WVs can be seen in models tracking through multiple jet branches through the weekend making for a complex forecast across the country. SFC winds will quickly turn southeast and increase Wed as high pressure shifts east and SFC low pressure begins to develop to the west in response to the next approaching S/WV which will move down the east side of the aforementioned ridge into NV. Models show solid H85-H5 theta-e advection as this system weakens and moves towards the across area and a potential for showers between 06Z and 18Z Thu. In fact the GFS forecast soundings even show a tad of elevated CAPE (around 200 j/kg) above warm nose located at around 5000 ft. After coordinating with surrounding WFOs, have included a slt chc for shra during this time frame using CONSALL rather than NBM POPS which remain dry. Strong H85 theta-e advection and SE (upslope) low level flow also suggest significant stratus potential Thu and we may struggle to break out of the low level cloud over in the eastern 2/3rds Thu and even into Fri as another S/WV quickly replaces the first across SRN CA. Models are not in great agreement on the evolution and track of this system as it tracks east but generally show it moving across the area in some form around Fri into Fri night. This system may have moisture depth issues as the Thu S/WV is forecast to scour out the moisture at H7 and above. For now will not disagree with the NBM not showing POPs on Fri, but have noted the operational 00Z GFS and GEM did both indicate some potential for precipitation (possibly TSTMS) late Fri as the S/WV and assoc cold front move across the region. So, would not be surprised if we ended up introducing POPs at some point again for this system for Fri. Again this cold front is forecast to be a quick hitter with winds quickly turning back to the south by Sun after less than 24 hours of NRLY flow behind the weak front on Sat. So, after another day of below normal temps on Sat, Sunday looks warm and breezy. Gittinger && .AMA Watches/Warnings/Advisories... TX...Hard Freeze Warning from 1 AM to 9 AM CDT Tuesday for the following zones: Carson...Dallam...Deaf Smith...Hansford... Hartley...Hutchinson...Lipscomb...Moore...Ochiltree... Oldham...Palo Duro Canyon...Potter...Randall...Roberts... Sherman. Freeze Watch from late Tuesday night through Wednesday morning for the following zones: Armstrong...Carson... Collingsworth...Dallam...Deaf Smith...Donley...Gray... Hansford...Hartley...Hemphill...Hutchinson...Lipscomb... Moore...Ochiltree...Oldham...Palo Duro Canyon...Potter... Randall...Roberts...Sherman...Wheeler. Wind Advisory from midnight tonight to 6 AM CDT Tuesday for the following zones: Dallam...Deaf Smith...Hartley...Moore... Oldham...Palo Duro Canyon...Potter...Randall...Sherman. Freeze Warning from 1 AM to 9 AM CDT Tuesday for the following zones: Armstrong...Collingsworth...Donley...Gray... Hemphill...Wheeler. OK...Hard Freeze Warning from 1 AM to 9 AM CDT Tuesday for the following zones: Beaver...Cimarron...Texas. Freeze Watch from late Tuesday night through Wednesday morning for the following zones: Beaver...Cimarron...Texas. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.