High-based thunderstorms associated with a weak disturbance produced strong outflow winds.
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The episode as NWS GJT wrote it up.
High-based thunderstorms associated with a weak disturbance produced strong outflow winds.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Grand Junction, CO wrote its last area forecast discussion before the first event at Jul 28, 2:54 PM MST, 13 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 354 PM MDT Sat Jul 28 2018 .SHORT TERM...(Tonight through Sunday night) Issued at 354 PM MDT Sat Jul 28 2018 This morning's short wave...which brought a little more exciting weather than anticipated...is leaving some of the east-central CWA under subsidence and quiet conditions. However a moderately sheared atmosphere has been able to recover upstream of this and a second round of storms are likely to bring some gusty winds...small hail and heavy rainfall through the evening hours. Derived sat imagery is showing much drier air upstream and this will be source region for us as the pattern becomes more northerly over the Rockies by amplifying heights to the West. The upper jet will remain over the central Rockies due to the stronger thermal gradient aloft between the hot ridge to the West and cooler trough to the East. This jet is often under estimated for nocturnal convection due to the strong EML on the warm side of the jet and small waves passing through the flow. There is a hint of this happening again Sunday morning near the central CO/UT border. Not brave enough to mention this yet due to coverage being minimal and will bank on another batch of accas and virga. Plan on thunderstorms. Otherwise heating and residual moisture along with steep lapse rates likely to pop some isolated afternoon storms even though drier are will begin to invade from the NW. Expect more wind than rain as we dry out the PBL...and those with swamp coolers will be a bit happier as our dew points begin a downward trend through the first of the week. Afternoon temps push back above normal and with drier air cooler temps expected Sunday night under mainly clear skies. .LONG TERM...(Monday through Saturday) Issued at 354 PM MDT Sat Jul 28 2018 So we are basically in a trough-ridge-trough-ridge pattern from the E.Pac to the Atlantic seaboard. With the ridge dominating the western CONUS the monsoon has not had a direct attack into our region but rather recirculated around the high. With this pattern continuing through at least Tuesday...drier and warmer than normal conditions will persist. A small uptick in storms is possible by midweek as the E.Pac trough plows into the top of the ridge and we get a shot of recycled moisture and some cooler temperatures aloft. As this trough heads into the MidWest the ridge once again shift to the SW and drier air filters back in for the weekend. This trough however looks to dig farther east along the Mid Atlantic States. The RMOP shows some promise of a stronger Western trough as well so that the pattern becomes trough-ridge- trough across the CONUS by early next week. This could signal a more direct tap to the monsoon moisture region. Now this is way out there but we could use all the hope we can get at this point. Stay tuned. Oh and hot temperatures stay in place for much of this forecast. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1144 AM MDT Sat Jul 28 2018 Isolated to scattered storms today will threaten ILS breakpoints at TAF sites throughout the afternoon and early evening hours. Anticipating that a second line of storms will develop across eastern Utah later this afternoon and trek eastward late this afternoon. VFR will prevail at TAF sites in between storms. Gusty winds to 45 kts will be possible today with stronger thunderstorms, especially locations from KCNY-KMTJ-KGUC and northward. Less convection is expected on Sunday. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...15 LONG TERM...15 AVIATION...JAM
Hazardous Weather Outlook National Weather Service Grand Junction CO 551 AM MDT Sat Jul 28 2018 COZ001>014-017>023-UTZ022>025-027>029-291200- Lower Yampa River Basin-Central Yampa River Basin- Roan and Tavaputs Plateaus-Elkhead and Park Mountains- Upper Yampa River Basin-Grand Valley-Debeque to Silt Corridor- Central Colorado River Basin-Grand and Battlement Mesas- Gore and Elk Mountains/Central Mountain Valleys- Central Gunnison and Uncompahgre River Basin- West Elk and Sawatch Mountains-Flat Tops- Upper Gunnison River Valley-Uncompahgre Plateau and Dallas Divide- Northwest San Juan Mountains-Southwest San Juan Mountains- Paradox Valley/Lower Dolores River- Four Corners/Upper Dolores River-Animas River Basin- San Juan River Basin-Southeast Utah-Eastern Uinta Mountains- Eastern Uinta Basin-Tavaputs Plateau-Arches/Grand Flat- La Sal and Abajo Mountains-Canyonlands/Natural Bridges- 551 AM MDT Sat Jul 28 2018 This hazardous weather outlook is for eastern Utah and western Colorado. .DAY ONE...Today and Tonight More convection is expected today as daytime heating, moisture, and the jet stream aloft all aid in convective development. Gusty winds from any convection may reach 40 to 50 mph this afternoon and evening. Most storms and showers will die down shortly after sunset though a few may linger past then. .DAYS TWO THROUGH SEVEN...Sunday through Friday Dry conditions will move in Sunday through Wednesday causing a noticeable decrease in convection across the area. Even so, some showers and storms will likely fire over higher terrain. Coverage will be much less than we've seen lately. Moisture starts increasing Wednesday onwards which will cause convection to increase as well. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1026 AM MDT SAT JUL 28 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1000 AM DENSE FOG 1 N SILVERTON 37.82N 107.66W
07/28/2018 SAN JUAN CO CO-OP OBSERVER
VISIBILITY WAS ABOUT A TENTH OF A MILE FROM
SHORTLY AFTER MIDNIGHT UNTIL 9 AM MDT THIS
MORNING.
&&
JRPPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1124 AM MDT SAT JUL 28 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0241 PM HEAVY RAIN 4 S VALLECITO 37.33N 107.60W
07/25/2018 E0.47 INCH LA PLATA CO TRAINED SPOTTER
RAINFALL OCCURRED BETWEEN 2:26 PM AND 2:41
PM MDT.
&&
JRPPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
1200 PM MDT SAT JUL 28 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1150 AM HAIL CARBONDALE 39.40N 107.21W
07/28/2018 M0.25 INCH GARFIELD CO PUBLIC
TWITTER REPORT FROM BRYAN HANNEGAN FROM
DOWNTOWN CARBONDALE.
&&
JPFSpecial Weather Statement
National Weather Service Grand Junction CO
1244 PM MDT SAT JUL 28 2018
COZ010-012-281915-
Gore and Elk Mountains/Central Mountain Valleys CO-
West Elk and Sawatch Mountains CO-
1244 PM MDT SAT JUL 28 2018
...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN PITKIN COUNTY UNTIL
115 PM MDT...
At 1243 PM MDT, Doppler radar was tracking a strong thunderstorm near
Aspen, or 41 miles southeast of Glenwood Springs, moving southeast at
35 mph.
Wind gusts near 50 mph and significant pea sized hail accumulation
will be possible with this storm.
Locations impacted include...
Aspen and Independence Pass.
This includes Colorado 82 between mile markers 40 and 61.
PRECAUTIONARY/PREPAREDNESS ACTIONS...
Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.
&&
LAT...LON 3916 10655 3915 10656 3911 10656 3910 10659
3906 10658 3904 10660 3903 10660 3900 10662
3917 10686 3927 10678 3918 10651 3916 10651
TIME...MOT...LOC 1843Z 293DEG 32KT 3916 10673
15PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
144 PM MDT SAT JUL 28 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1254 PM HEAVY RAIN 1 NE EL JEBEL 39.41N 107.08W
07/28/2018 M0.24 INCH EAGLE CO MESONET
IRAWS STATION MEASURED 0.24 OF AN INCH OF
RAIN AND SMALL HAIL BETWEEN 12:03 AND 12:18
PM MDT. FLOWING WATER UP TO 6 INCHES DEEP
RAN ACROSS A USFS ROAD AS OF 12:54 PM MDT.
&&
JRPPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
146 PM MDT SAT JUL 28 2018
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0139 PM HAIL MEEKER 40.05N 107.89W
07/28/2018 M0.25 INCH RIO BLANCO CO NWS EMPLOYEE
&&
JPFThe Grand Junction radar (KGJX), 27 km away, was scanning. The volume nearest the first event began at 22:03 UTC.
2 thunderstorm wind. Local standard time, as filed.
A high-based thunderstorm produced strong outflow winds at the Grand Junction Regional Airport.
A trained spotter reported an estimated wind gust of 60 mph as a result of strong outflow from a high-based thunderstorm.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2018Every state in 2018This day in weather historyWarnings in Colorado, July 2018
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 760513, 766195.