textproduct: Goodland

KEY MESSAGES

- Occasional shower chances through the rest of the week.

- Severe storms are possible across eastern Colorado Thursday afternoon and evening. Large hail, a tornado or two and damaging winds are all possible.

- Repeated rounds of showers and storms are possible overnight Thursday into Friday morning leading to a 20-30% chance of low lying and street flooding..

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 124 PM MDT Wed May 20 2026

500mb troughing is seen via 16Z RAP analysis and is helping lead to widespread cloud cover across the area. At the surface an inverted trough was located over the area and was responsible for the rain showers from the morning. As the afternoon goes on am anticipating a brief break in the cloud cover as some slightly drier lair in the low levels moves in from the southwest. This potential is what is driving the high temperature forecast to remain in the upper 50s to mid 60s across the area. This evening and overnight 500mb vorticity associated with with another shortwave is forecast to move through the area and collocating with some bands of isentropic ascent in the 290K level which suggests that additional showers have around a 50- 60% chance to redevelop this evening and overnight with locations along and south of Interstate 70 favored. Mainly showers associated with the isentropic lift would be favored across northern portions of the area. Moisture advection is also forecast to increase through the night in the 850mb level leading to some fog potential across Cheyenne (CO), Kit Carson, Greeley, Wichita and Wallace counties Thursday morning. With the deep saturation in place, dense fog could also be possible. The caveat to any dense fog would be if any showers would still be ongoing or not. 12Z HREF has a 20% chance of visibilities less than one half mile. With forecast winds being around 10-15 mph that further puts my doubts towards any dense fog potential so am opting to leave fog out of the forecast for now.

Thursday, 850mb moisture advection is forecast to continue through the day as dew points rise into the mid to upper 50s and even potentially low 60s. This does put some concern into the high temperature forecast for the day as highs are currently forecast in the upper 50s to low 60s across the area. If clouds are able to break especially across eastern Colorado then highs could reach the upper 60s to low 70s.

Shower and storm potential is forecast to increase starting across eastern Colorado during the mid afternoon as a shortwave moves across eastern Colorado and a departing 250mb jet puts the area in the right entrance region of the said jet. A stationary boundary is forecast to set up across Yuma county based on 15Z RAP data. With the proximity of the shortwave in the area am anticipating some convection to occur in the proximity of Yuma county and is supported by most if not all of convection allowing models. Should this scenario pan out then a tornado and significant hail threat with hail sizes around 2 inches could develop due to shear being more than sufficient for supercells along with low LCL's due to the moisture advection. RAP and HRRR along the boundary also do support the tornado threat along this boundary with high EBWD and SRH along with steep 0-1km lapse rates and plenty of 0-3 CAPE. Right mover motion is also to the east-southeast which would also support the residency time of tornado potential should this pan out. There are some failure points as well to this potential with the strong 850mb moisture advection clouds may remain thick throughout the day and not enough destabilization could occur as temperatures could also remain lower. The NAM is also a few hours slower than the RAP and the HRRR on the moisture advection which is notable as the NAM normally has a more moist bias to it. Further south additional showers and storms are forecast to develop due to a low pressure system being in place as well with a further threat for severe weather, confidence is a bit lower in this area for severe weather due to being further away from the synoptic forcing of the shortwave.

Showers and storms are forecast to continue to develop overnight due to the forcing of the low due to the lack of CAPE and and lesser lapse rates but hail around quarter size may still be possible. Do have some concern for Gravity Wave Associated Convection (GWAC) with the overnight convection which could lead to repeated rounds of convection. 12Z NAM shows a 250mb jet in place on the northern periphery of the MUCAPE axis along with lapse rates of 7-7.5 c/km and Effective Bulk Wind Difference exceeding 40 knots. The 06Z and 12Z HRRR also interestingly shows similar characteristics to GWAC with even spacing between convection. If this does occur then some low lying and urban flooding potential could occur with PWATS around 1 to 1.1 inches. The overall flooding potential doesn't appear to be overly high with very fast storm motions and place but if the repeated rounds does occur then localized hydro concerns could develop Thursday night. A cold front is forecast to move through the area as well early Friday morning bringing another potential round of rain to the area but with rainfall diminishing Friday morning.

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 /00Z TAFS THROUGH 00Z FRIDAY/

Issued at 442 PM MDT Wed May 20 2026

SSE winds are forecast to continue through the majority of this TAF period. Showers and isolated storms are developing across eastern Colorado and are forecast to gradually move towards each terminal this evening; have PROB30 groups in to account for this. Moisture and warm air advection are forecast to overspread the area overnight leading to additional showers and low stratus with ceilings eventually falling to IFR. Airport minimums may be met with the low ceilings and occasional rain showers through the night and Thursday morning. MVFR to IFR ceilings are forecast to continue through the end of this TAF period for each terminal.

GLD WATCHES/WARNINGS/ADVISORIES

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