NTXX99 PHEB 210200 TSTHEB primary-side test from PTWC IRC RZRZRZRZRZRZRZRZRZRZRZRZRZRZ RZRZRZRZRZRZRZRZRZRZRZRZRZRZ SOVD83 KWNB 210100 RRX KKYY 21096 0150/ 742368 087795 88870 83099 2//// 3//// 66292 20002 21027 99999 45186= KKYY 21096 0150/ 742491 087779 88870 83099 2//// 3//// 66292 20002 18038 99999 45187= KKYY 21096 0150/ 741892 087563 88870 83099 20001 31860 20003 31881 20005 31881 20007 31881 20009 31881 99999 45198= SNVG01 TUPJ 210200 AAXX 21014 78550 41581 30803 10277 20235 30150 40155 70182 82233 333 82820= NTXX98 PHEB 210201 PTWC PRIMARY-SIDE TEST FROM IRC PZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZ PZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZPZ ACUS11 KWNS 210201 SWOMCD SPC MCD 210201 KSZ000-COZ000-210400- Mesoscale Discussion 2320 NWS Storm Prediction Center Norman OK 0901 PM CDT Sun Sep 20 2026 Areas affected...portions of eastern Colorado and western Kansas Concerning...Severe Thunderstorm Watch 673... Valid 210201Z - 210400Z The severe weather threat for Severe Thunderstorm Watch 673 continues. SUMMARY...The initial severe threat has come to an end across the area. However, the region is being monitored for additional thunderstorm development, such as that suggested by latest numerical models. A new watch or the extension in space or time of the existing watch may become necessary before Severe Thunderstorm Watch #673 expires at 9:00 PM MDT. DISCUSSION...The long-track supercell that moved southeast across the Plains of Colorado this evening has dissipated bringing an end to the initial severe threat. This evolution was handled very well by high-resolution guidance. Attention is now focused on areas to the north where high-resolution guidance is indicating additional thunderstorm development is likely in the next 60-90 minutes. This scenario seems plausible given the persistent moist, easterly flow into the foothills expected this evening. Initial development may already be underway across portions of the Denver and Fort Collins metro areas based on MRMS CREF imagery. The overall environment will remain conducive for supercells with MUCAPE values in excess of 1000 J/kg, especially south and east of the Denver metro. Effective-layer shear remains more than sufficient for updraft rotation, with shear values between 40-55 knots across the Colorado Plains. Large hail and strong thunderstorm outflows will be possible with any sustained supercell this evening and overnight. Severe Thunderstorm Watch #673 is scheduled to expire at 9 PM MDT. The area will continue to be monitored for additional thunderstorm initiation and intensification. If it becomes apparent that additional severe thunderstorms are probable this evening, the region will either need a new Severe Thunderstorm Watch or an extension of Severe Thunderstorm Watch #673. A decision will be made regarding the need for a new watch, an extension of the existing watch, or cancellation of the existing watch within the hour. ..Marsh.. 09/21/2026 ...Please see www.spc.noaa.gov for graphic product... ATTN...WFO...DDC...GLD...PUB...BOU... LAT...LON 37620267 38560409 39030494 39620532 40110518 40290471 40250355 40110245 39960193 39750156 39360106 38750079 37890098 37630143 37620267 MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH MOST PROBABLE PEAK WIND GUST...55-70 MPH MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN BMBB99 TNCC 210200 THIS IS A GST WAFS SITE HEARTBEAT MESSAGE FROM TNCC.