textproduct: Goodland

KEY MESSAGES

- A few severe storms are possible across eastern Colorado late this afternoon and evening, mainly between 5-10 pm MDT. Large hail, damaging winds and a brief tornado are possible.

- There is a 30% chance that several rounds of thunderstorms may lead to localized flooding in low lying areas and small streams tonight and early Friday morning.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 255 AM MDT Thu May 21 2026

Through Mid-Afternoon: Ongoing convection (at 07Z) associated with modest DPVA attendant a deamplifying upper level disturbance lifting northeastward across the Tri-State Area and low/mid-level warm advection on the eastern periphery of an associated lee cyclone in southeast CO is expected to wane/dissipate around or shortly after sunrise (~12Z) as the disturbance lifts northeast of the region and the associated lee cyclone weakens/dissipates. Little, if any, precipitation is expected thereafter, from the late morning through mid- afternoon, when forcing will largely be absent (aside from very weak low-level warm advection) and thick, pervasive low stratus (4000-8000 ft in depth, deepest at lower elevations in the east) maintains a cool/capped airmass across the majority of the area. Expect highs in the upper 50's to mid 60's, warmest in Cheyenne County CO where low ceilings/stratus will be relatively shallow and more likely to lift/scatter out during the afternoon.

Late Afternoon and Tonight: Shortwave energy over eastern Idaho and western Montana at 08Z this morning will dig southeastward into western WY by early afternoon (~18Z) then slowly track east across the Nebraska Panhandle this evening and overnight. A loosely associated lee trough/cyclone in south- central and southeast CO this aft-eve will weaken as it drifts southeastward to the OK Panhandle tonight. Very similar to yesterday's pattern albeit with richer low-level moisture (from persistent SE low- level flow) and comparatively stronger diurnal destabilization (~1000-1500 J/kg mlcape compared to ~250 J/kg on Wed. Disagreement persists w/regard to the eastern extent of the instability axis; the HRRR suggests that moderate destabilization will occur over eastern CO and far western KS whereas the NAM NEST indicates a sharp instability gradient over eastern CO. While both models indicate low-level moisture / surface to 850 mb dewpoints of similar magnitude, a forecast sounding comparison reveals a few notable differences; the HRRR indicates steeper mid-level lapse rates (7.5-8.0 C/km compared to ~7.0 C/km on the NAM NEST) *and* suggests that low stratus in far western KS may be shallow enough to scatter-out during the late afternoon. As of 08Z this morning, mid-level lapse rates were ~6-6.5 C/km in eastern CO and western KS. At any rate, several focal points for convective development are possible upstream of the Goodland CWA late this afternoon, [1] the Cheyenne Ridge, [2] the Palmer Divide [3] enhanced low-level convergence invof the lee cyclone in southeast CO (La Junta area). Low confidence in convective coverage during the afternoon and early evening hours. Any sufficiently deep convection that develops in eastern CO will be capable of producing hail/wind and possibly a brief tornado late this aft- eve (~5-9 pm MDT). Confidence in convective development and coverage increases substantially tonight, when the aforementioned upper wave progresses eastward from WY into the NE Panhandle (in close proximity to the Goodland CWA). -Vincent

Friday: In wake of the cold front on Friday, stable air forecast to be in place limiting the precipitation potential for most of the day as the sun is forecast to return and temperatures warm back into the 60s and 70s. Another shortwave is forecast to move off of the Rockies Friday evening bringing another round of showers to the area. Since the cold front from that morning shunted all of the instability out of the area severe weather is not currently anticipated with this activity.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 211 PM MDT Wed May 20 2026

***Synopsis***

Troughing at 500-mb looks to be moving in overhead throughout the day Saturday. This would favor a weak low to the south of the county warning area (CWA), producing modest southerly to southeasterly return flow across the area. Southerly surface winds look to persist through the end of the forecast period as ridging moves in overhead Sunday, and troughing sets up across the Western United States.

***Saturday***

As the southerly return flow sets up on Saturday, conditions across the Tri-State area look to warm up, with current high temperatures forecast in the upper 60s to mid 70s. GEFS mean- spread guidance is also consistent with an 850-mb low in Mexico, and an 850-mb high across the Southeastern United States, which would favor moisture returning to the area as well. Dew points in the low to mid 40s could support shower or thunderstorm development across the region at least through the afternoon, and possibly into the evening and overnight hours. Both LREF and NBM guidance are consistent with a few hundred J/kg of CAPE (a measure of atmospheric instability) across the CWA Saturday afternoon and evening. Even so, most of this activity looks to be associated with lighter rain, as most areas have less than a 30% chance to receive greater than 0.1 inches of rain from this activity. As such, the most likely scenario would be associated with localized light showers. Current guidance would suggest that activity is unlikely to be severe. According to the LREF, the mean 500-mb wind is favored to be around 25 kts, with a reasonable maximum around 35 kts. In order for wind shear to be sufficient for supporting severe thunderstorms, the higher end of this range would need to be experienced.

***Sunday-Tuesday***

Warmer conditions look to continue Sunday through Tuesday as ridging overhead and troughing across the west allows the southerly surface flow to persist. Highs are forecast in the 80s all 3 days. A more southwesterly component to this flow may promote slightly drier conditions Sunday afternoon, though relative humidities (RH) are not expected to drop below critical fire weather criteria (15% or less). LREF guidance suggests less than a 20% chance across the CWA that this condition will be met. Additionally, even if RH values can meet critical fire weather criteria, wind gusts are forecast to be less than 20 mph across the area, which would not support the hazard. Winds may be stronger on Tuesday as troughing from the west approaches and lee cyclogenesis begins to occur across the Rockies. Current forecast guidance suggests that wind gusts may reach the 45- 50 mph range in some areas, particularly across Eastern Colorado. However, RH values forecast above 25% should once again limit the risk for critical fire weather conditions.

Afternoon and evening showers may be experienced once again on Monday and Tuesday, though NBM 48 hr precipitation guidance would suggest at best a 25% chance to see greater than 0.1 inches of precipitation between Monday and Tuesday's activity. Similar to Saturday, light, localized showers would seem to be the favored scenario Monday and Tuesday.

***Wednesday***

Warm, wet conditions look to continue Wednesday, with forecast temperatures in the upper 70s to mid 80s, and dew points as high as the low 60s according to LREF 90th percentile guidance. This could support 1500-2500 J/kg of CAPE, allowing convection to become thunderstorms as opposed to localized showers. There is some uncertainty regarding whether these storms would be severe, as model guidance shows some inconsistency on the timing of the incoming trough. A faster progression may promote a modest 40-45 kt jet streak at 500-mb to overspread portions of the CWA, which could support thunderstorms becoming severe. However, only 10% or less of GEFS and GEPS members show 500-mb wind speeds near or on par with this jet streak, keeping confidence of severe weather less than 10%.

AVIATION /12Z TAFS THROUGH 12Z FRIDAY/

Issued at 527 AM MDT Thu May 21 2026

Aviation impacts are set to overspread the Tri-State area quickly in the forecast period. VFR conditions will give way to low stratus and periodic rain through the day on Thursday.

Expect light rain to develop quickly this morning with ongoing low CIGs seen at K2V5 and K3K7 to continue to filter north and east. Rain should accompany this if not follow shortly with IFR conditions expected until closer to early afternoon when some modest improvement is possible in the southwest. Another round of rain and even potentially thunderstorms will arrive tonight and overnight. Main concerns with any convection will be briefly heavy rain bringing IFR/LIFR visibilities to go with the < 500 ft ceilings. Some improvement is possible towards the end of the period but confidence is limited.

GLD WATCHES/WARNINGS/ADVISORIES

KS...None. CO...None. NE...None.