Low level moisture trapped at the surface resulted in areas of dense fog.
Every event with a place to put it; 1 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS GJT wrote it up.
Low level moisture trapped at the surface resulted in areas of dense fog.
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 May 20, 2:42 AM MST, 3 hours 18 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 342 AM MDT WED MAY 20 2015 .SHORT TERM...(TODAY THROUGH THURSDAY) ISSUED AT 339 AM MDT WED MAY 20 2015 HEIGHTS WILL BE ON THE RISE TODAY AS THE OLD UPPER LOW CONTINUES TO LIFT OUT INTO THE PLAINS. SOME MOISTURE LINGERS EARLY IN THE DAY TO KEEP A FEW SHOWERS GOING ACROSS THE NORTHERN ZONES...MAINLY ANCHORED UP AGAINST THE PARK RANGE. WITH THE RISING HEIGHTS WILL ALSO COME RISING TEMPERATURES AND SFC READINGS WILL BE JUMPING 5 TO 10 DEGREES IN MOST AREAS...BUT STILL A TAD BIT BELOW NORMAL FOR THIS TIME OF YEAR. CONVECTIVE TEMPS WILL BE REALIZED OVER THE HIGH COUNTRY BY EARLY AFTERNOON AND THIS WILL WORK ON LINGERING LOW LEVEL MOISTURE TO INCREASE COVERAGE OF THE MORNING SHOWERS...ALTHOUGH THE FOCUS WILL BE OVER THE HIGH COUNTRY WITH WEAK STEERING FLOW FAILING TO DRIVE THEM OFF THE HILLS AND OVER THE VALLEYS. THE DIURNALLY DRIVEN SHOWERS DIMINISH EARLY THIS EVENING WITH DRY CONDITIONS EXPECTED OVERNIGHT AS THE RIDGE AXIS SLIDES EAST OF THE DIVIDE. BY THURSDAY...FLOW IS BACKING BACK AROUND TO THE SOUTH SOUTHWEST AS YET ANOTHER LOW DIGS ALONG THE CALIFORNIA COAST. MODELS DRIVE MORE MOISTURE NORTH NORTHWEST ACROSS WEST TEXAS AND EASTERN NEW MEXICO UP INTO OUR FORECAST AREA BY THURSDAY AFTERNOON. PRECIPITABLE WATER VALUES JUMP BACK TO OVER A HALF AN INCH BY LATE IN THE DAY. WITH MOISTURE RAPIDLY INCREASING AND SEVERAL WEAK WAVES IN THE SOUTHERLY FLOW LIFTING NORTH...EXPECT AN INCREASE IN SHOWERS AND THUNDERSTORMS THURSDAY AFTERNOON AND EVENING. BETTER STORM MOTION TRANSLATES INTO STORMS ROLLING OVER THE VALLEYS BY LATE IN THE DAY. STILL EXPECT PLENTY OF SUN EARLY ON WITH TEMPS CLIMBING ANOTHER 5 DEGREES TO BRING THE REGION MORE IN LINE WITH CLIMATOLOGY. .LONG TERM...(THURSDAY NIGHT THROUGH TUESDAY) ISSUED AT 339 AM MDT WED MAY 20 2015 MODELS CONTINUE TO AGREE THAT MOISTURE WILL BE STREAMING UP FROM THE SUBTROPICS THANKS TO THE LOW OFF THE CALIFORNIA COAST AND HIGH OFF THE GULF COAST. ATTM...THE SAN JUANS AND THE CONTINENTAL DIVIDE LOOK TO GET THE MOST PRECIP. BY FRIDAY MORNING...SOME DEFINITE TURNING OF THE WINDS AT THE 700MB LEVEL INDICATES A SHORTWAVE MOVING ACROSS THE CWA CAUSING A MODERATE INCREASE IN ACTIVITY. BY NOON...THE WAVE WILL HAVE LIFTED INTO WY BUT NOT MUCH REPRIEVE IN PRECIP AS THE LOW PRESSURE CONTINUES MOVING EWRD WITH MORE SHOWERY PRECIP FORECAST FOR THE HIGHER TERRAIN. DIFFERENCES START ARISING SATURDAY WITH THE GFS LIFTING THE LOW PRESSURE NORTHWARD FAIRLY QUICKLY WHILE THE EC KEEPS IT SOMEWHAT STATIONARY OVER THE CWA. THE GFS CONTINUES TO SHOW A DRY SLOT OVER THE AREA WHILE THE EC A BIT MORE AGGRESSIVE. THE CANADIAN ALSO KEEPS US DRY AS DOES THE NAM TO A CERTAIN EXTENT. WHAT IS CERTAIN WILL BE CLOUDS AND SHOWERY PRECIP WITH SOME AFTN CONVECTION. THE TRICKY BIT IS HOW MUCH...HOW LONG...AND WHERE. CHANCE TO SLIGHT CHANCE POPS STILL LOOK GOOD FOR NOW. BY SUNDAY...ANOTHER DAY OF OFF AND ON SHOWERS AS THE NEXT LOW PRESSURE QUICKLY DROPS DOWN FROM THE PACNW. A DEFORMATION AXIS LOOKS TO SET UP OVER UTAH AND COLORADO AND LOOKS TO BE THE FOCUS OF PRECIP AHEAD OF THE LOW PRESSURE SUNDAY AFTERNOON INTO THE OVERNIGHT HOURS. AMPLE MOISTURE AND WIDESCALE LIFT THANKS TO THE LOW PRESSURE WILL BRING EVEN MORE PRECIP MONDAY THROUGH TUESDAY. WE HAD A DRY WINTER...BUT THIS SPRING IS REALLY MAKING UP FOR IT. && .AVIATION...(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING) ISSUED AT 339 AM MDT WED MAY 20 2015 SOME CLOUDS LINGER THIS MORNING BUT ASIDE FROM THE GUNNISON BASIN...VFR CONDITIONS ARE IN PLACE. MORE CONVECTION AND SHOWERS EXPECTED AFTER 18Z WITH HIGHER ELEVATIONS BEING FAVORED. MOST AREAS WILL REMAIN VFR THOUGH SOME MVFR TO BRIEF IFR POSSIBLE UNDER AND NEAR THE STRONGER CELLS. SOME MTN TOPS WILL BE OBSCURED ESPECIALLY THOSE ALONG THE CONTINENTAL DIVIDE. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...NONE. UT...NONE. && SHORT TERM...JDC LONG TERM...TGR AVIATION...TGR
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
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
543 AM MDT WED MAY 20 2015
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0535 AM DENSE FOG 2 WNW GRAND JUNCTION 39.10N 108.60W
05/20/2015 E0.10 MILE MESA CO TRAINED SPOTTER
&&
EVENT NUMBER GJT1500752
MMSThe national radar mosaic for the moment the first event began.
1 dense fog. Local standard time, as filed.
Dense fog reduced visibility to one quarter mile or less for two hours at the Eagle airport. Dense fog was also seen on webcams on I-70 near Wolcott.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2015Every state in 2015This day in weather historyWarnings in Colorado, May 2015
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: 618620.