textproduct: Goodland

KEY MESSAGES

- Threat for heat related stress will be high Today with a Heat Advisory in effect for portions of the area.

- Late afternoon-evening storm chances return by mid-week.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 1247 AM MDT Mon Jul 20 2026

05Z Water vapor imagery and RAP H4 analysis indicates strong upper level ridge remains firmly in place across the central High Plains. The anticyclonic center has moved to the southeast somewhat from 24 hours ago, with center located near Flagler Colorado. At the surface a low was centered across western SD with weak frontal zone draped from southern WY to northeast SD.

Today-Tonight...The heat will continue to be the primary concern as H85 temps warm another 3 to 4C from yesterday as persistent, strong H5 ridge remains centered over the area. A weak surface pressure gradient will keep winds light and somewhat variable through the day, before cold front sweeps across the area overnight shifting winds to the northeast and increasing to the 15 to 25 mph range. Frontal timing will likely be after midnight, so do not anticipate any significant impacts as it passes. While front may provide some focused ascent, very stable airmass ahead of this front would make any storm development very unlikely.

Primary concern will be magnitude of heat today and how fast things will recover/cool tonight. Temperatures will continue to climb today and based on observed temperatures yesterday, confident several locations will climb into the low 100s. While heat indices may very close to the observed temperature and hover in the 100-105 degree range this afternoon and may struggle to hit legacy Heat Advisory criteria, both Wet Bulb Globe Temperature (WBGT) and NWS Heatrisk data indicate much of current advisory seeing 4-6 hours of "high" impacts due to heat. With lots of sun, little wind and hot temperatures extra precautions to stay hydrated and prevent heat exhaustion will be needed.

Tuesday-Tuesday night...Cold front will still be pushing south across the area around sunrise, ushering in gusty northeasterly winds and slightly cooler temperatures. Magnitude of cooldown will be primarily a function of how fast front advances to the south, with a 10 degree cooldown likely near KMCK, but only a few degrees cooler at KTRB. Narrow axis of 500-900 j/kg CAPE will develop during the afternoon with fairly weak capping. While not impossible to see a storm form along this front, concerned that instability actually more on the cool side of it in area that may see more downward motion due to near surface frontogenesis circulation with lift being more focused on the warm and dry side. More likely area of storms developing will be over higher terrain in eastern Colorado. While this normally would be a favorable initiation location, steering flow is actually very weak and out of the west so storms will definitely struggle to make much eastward movement. Area of strong WAA will develop overnight in response to weak short wave trough rounding the top of large ridge. While forcing for precipitation will certainly be in place, uncertainty remains with respect to lift being sufficient enough to saturate parcels and realize the limited potential instability. Comparing various operational models 315K isentropic surface forecast, parcel saturation is at least in realm of possible given the magnitude of forcing although little consensus on where this area of saturation will occur. Initially am skeptical about overnight showers along northern/eastern zones based on these concerns, although GEFS has been very consistent with high probabilities of > 0.01 24 hour precip so cannot discount it either. CAPE and shear appear very limited so if storms develop, not anticipating any severe weather.

Wednesday and Wednesday Night...Strongest part of lingering H5 ridge will be well to the south of area, with main concern being how much warm front lifts to the north in response to developing low across CO. Large differences in placement of front, timing and magnitude of disturbance moving atop the ridge and potential impact of morning precipitation makes forecast highly uncertain with temperature forecasts 15 degrees or more different from one another. Uncertainty aside, with ridge shifting to the south and southeasterly flow reestablishing at least weak instability expect thunderstorm chances to increase, especially overnight as strong shortwave trough moves onto the High Plains. Currently instability and shear appear to be on the weak side so severe weather potential appears low at this time.

LONG TERM /THURSDAY THROUGH SUNDAY/

Issued at 246 PM MDT Sun Jul 19 2026

The long term period opens on Wednesday with a distinct shift in the mid to upper level pattern. The persistent 500 mb ridge centered over the Rockies/Central Plains early in the week will suppress southward into the desert southwest. This is driven by a robust shortwave trough digging southeastward out of central Canada into the Great Lakes and Ohio River Valley, carving out a broader eastern CONUS trough.

As the ridge flattens, the Tri State area falls under weak west to northwest flow aloft. At the surface, a progressive cold front will push south to southwestward through the forecast area on Wednesday. East to southeasterly post frontal winds will establish a shallow upslope flow pattern, maintaining steady boundary layer moisture advection. By Friday and Saturday, the upper level ridge over the four corners area reamplifies somewhat, leaving the high plains in a northwest flow pattern aloft.

The post frontal airmass transition is reflected in the latest NBM probabilistic guidance with the probability of maximum temperatures exceeding 95 degrees dropping noticeably on Wednesday and Thursday to between 20-40 and 40-60 percent, respectively, for eastern communities (e.g., Hill City and McCook) and falls below 40 percent across eastern Colorado. Ensemble guidance yields a 25th to 75th percentile spread of just 4-6 degrees for daytime highs on Wednesday, signaling high model consensus regarding the timing and strength of the post frontal cooling. Highs will hover near or slightly below seasonal normals, generally in the upper 80s to lower 90s. A wider 8-12 degree NBM spread returns for Thursday into Saturday, introducing some uncertainty regarding how quickly the western ridge builds back eastward. Overnight lows will remain somewhat comfortable, dipping into the low to mid 60s, with some upper 50s possible in eastern Colorado.

Convective coverage peaks on Wednesday and Thursday evenings as the surface front interacts with a moist, moderately unstable airmass. While surface convergence will be robust along a stalled frontal boundary and associated surface low pressure system across the region, organized severe weather appears limited by weak dynamic support. Deep layer vertical wind shear is progged to top out around 20-30 knots as the main jet core remains well to our north. However, storm motion vectors look on the weaker side, averaging 15-20 mph or less. Given anomalous atmospheric moisture (precipitable water amounts exceeding the 75th percentile threshold for July) and slower storm cell propagation, localized heavy rainfall and minor flooding could occur.

For Friday through Saturday, pops taper off into the 15-25 percent range, reverting to a standard diurnal convective cycle. Scattered afternoon and evening activity will rely heavily on surface heating and localized topographic features (Palmer Divide) to break any potential inversion. While weak shear should limit widespread severe setups late in the week, steep low level lapse rates (inverted V soundings) mean any collapsing multicell clusters could produce localized microbursts and gusty outflows.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 1108 PM MDT Sun Jul 19 2026

VFR conditions will prevail as skies remain generally clear and winds remain light. A cold front will bring gusty northerly winds, but confidence is high that will not occur until after 06Z Tuesday.

GLD WATCHES/WARNINGS/ADVISORIES

KS...Heat Advisory from 7 AM this morning to 1 AM CDT Tuesday for KSZ001>004-014>016. CO...None. NE...Heat Advisory from 6 AM MDT /7 AM CDT/ this morning to midnight MDT /1 AM CDT/ tonight for NEZ079>081.