000 FXUS65 KPUB 131728 AFDPUB Area Forecast Discussion National Weather Service Pueblo CO 1128 AM MDT Thu May 13 2021 .UPDATE... Issued at 658 AM MDT Thu May 13 2021 Updated the forecast to include patchy dense fog over Pueblo and El Paso Counties this morning. Area observations, satellite imagery and looking out the window, show areas of dense fog. Reduced visibility is expected, mainly on Highway 50 and I-25. Reduce speeds and use low beams. Mozley && .SHORT TERM...(Today and tonight) Issued at 345 AM MDT Thu May 13 2021 Currently...satellite imagery this morning shows valley fog and low stratus over the upper Arkansas River basin and Wet Mountain Valley along with portions of El Paso County. Otherwise, generally clear conditions are prevailing across southern Colorado. Winds are relatively light across the region. Current temperatures are running in the lower to mid 40s across the Plains, while the San Luis Valley is seeing lower to mid 30s. Today and tonight...flat upper ridging over Utah into the Desert Southwest and troughing across the Central Plains will keep northwesterly flow across southern Colorado for the next 24 hours. Weak energy embedded in the flow may spark a few thunderstorms this afternoon over the southern Sangre de Cristo Mountains, east into the Raton Mesa region. Thunderstorms that do form, will quickly move southeast into New Mexico by late afternoon to early evening. Lightning and gusty outflow winds will be the main concerns with thunderstorms. There will be near critical fire weather conditions this afternoon, mainly over the La Garita range, mainly over Saguache County, into northwest portions of the San Luis Valley. Winds will be gusty this afternoon and humidity values low. Temperatures this afternoon will warm nicely across the region. Highs for today will reach into the lower to mid 70s for most of southern Colorado. Expect any thunderstorms that develop to shift southeast of the area or dissipate by this evening. Once this occurs, dry conditions are expected to prevail across the region. Across the Plains, a weak surface low will develop, with southerly winds advecting moisture northward near the Kansas border. Lows tonight will remain mild, with mid 40s across the Plains, and mid 30s across the San Luis Valley. Mozley .LONG TERM...(Friday through Wednesday) Issued at 345 AM MDT Thu May 13 2021 ...Active Severe Weather Pattern for Friday and Saturday and potentially into Sunday... ...Pattern shifts to a mix of more widespread stratiform/convective precipitation for Monday and Tuesday with potential for strong thunderstorms and burn scar flash flooding... Relatively flat upper ridging translates across CO for Friday with weak perturbations moving through the flow aloft evident in PV fields. Appears one wave moves through during the morning with another during the evening and overnight which won`t particularly jive with peak heating. However, east to southeasterly low level flow will advect higher dew points into the southeast plains along and east of a surface trough axis/dry line and a frontal boundary of sorts across El Paso county and points eastward. High res CAMs models show convective development occuring over the mountains in the afternoon in relatively high based moisture with storms intensifying as they move eastward into a more moist/unstable atmosphere. With deep layer shears running around 40 kts and CAPE values around 1000-1500 J/kg, conditions will be favorable for one or two severe storms across the southeast plains. The best axis for instability will be east of a line from La Junta to Kim which jives well with SPC day 2 outlook. Gusty winds and large hail look to be the primary risks as LCLs still look a little high this day. But any right movers could ingest sufficient helicity for supercell structures with a brief weak tornado potential if everything comes together just right. This risk looks to be on the lower side of the spectrum this day. Thunderstorm activity moves eastward into KS during mid to late evening hours which helps drive moisture back westward into the southeast plains aided by westward moving convective outflows. Saturday look to be a more active day for severe thunderstorms across most of the southeast plains as moisture axis and higher CAPE gets driven back into the I-25 corridor. CAPE in the 1500-2000 J/kg range will be in place across the southeast plains with deep layer shears in the 30-40 kt range which will be supportive of a few severe thunderstorms. Once again, large hail and damaging winds will be the primary threats. But given the stout CAPE and lower LCLs the potential for a tornado does increase, especially with any initial rapid development along boundaries. Where low level winds pull more easterly some enhanced low level helicity may be in place as well. While the southeast mountains and plains will see increasing chances for thunderstorms for Friday and Saturday, the San Luis Valley may see another period of critical to near critical fire weather conditions both days. Winds through the mixed layer look a little on the light side though do tap 20 kts at the top of the mixed layer during the late afternoon. Wild card will be high based convection which may help generate gusty outflow winds and increase afternoon gusts sufficiently for a brief period of critical fire weather conditions. Given the low end probability, have refrained from any fire weather highlights at this time as conditions look too localized and brief at this point. At last check with land management agencies, green up was starting to occur so this will give later shifts time to check on the status. Operational runs are in good agreement on the next closed low moving into southern CA/southern NV on Sunday. Northern stream trough moves across the northern U.S. Rockies Saturday night which will send a cold front through the plains with easterly low level flow advecting 40s to mid 50 dew points back westward towards the southeast mountains. High CAPE but perhaps weaker shear will be present this day as both GFS and EC show a distinct shortwave propagating through the upper ridge aloft. Although CAPE looks sufficiently high, deep layer shear may be on the weaker side as upper ridging ahead of western U.S. upper low may weaken the flow aloft this day. Burn scar flash flooding may be a primary concern as CAPE over the southeast mountains will increase, with perhaps a more isolated severe threat across the plains with multicell structures. Still some uncertainty here on the details. As the upper low moves across AZ and NM Monday and Tuesday, easterly low level flow will keep higher dew points and sufficiently high CAPE values across the southeast mountains and plains each day. As forcing increases as area comes under difluence aloft we should see more stratiform precipitation develop with embedded convection each afternoon and evening dependent on surface heating. Deep layer shears will be weaker both days as flow aloft weakens, which will decrease the severe risk (though perhaps not entirely eliminate it) but enhance the flash flood threat for burn scars across the southeast mountains both days. This system will not be as cold as the last with snow levels likely to remain above 10kft. Cells that do develop in higher CAPE may still be capable of some pulse severe type hail but details this far out are still murky. The interior mountains and valleys will see a good chance for showers and thunderstorms both days as well as mid level southerly flow advects moisture into the region ahead of the upper low. Temperatures will be cooler these days as well with highs topping out in the lower 70s across the plains...60s mountain valleys and 40s and 50s for the mountains. Still some residual moisture for showers and thunderstorms behind the system on Wednesday and Thursday, though with less instability and weaker flow aloft, severe threat appears lower. Will still be monitoring burn scar flash flood potential both days, but perhaps more so on Wednesday before drier air spreads in from the west. -KT && .AVIATION...(For the 18Z TAFS through 18Z Friday afternoon) Issued at 1125 AM MDT Thu May 13 2021 VFR conditions are expected during the next 24 hours at all 3 taf sites; KCOS, KPUB, and KALS. Winds will generally be light and diurnal. && .PUB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...MOZLEY SHORT TERM...MOZLEY LONG TERM...KT AVIATION...HODANISH