Name: Dense Fog in California, May 16, 2015
Start: 2015-05-16T05:50
End: 2015-05-16T08:50
Location: California

The toll

Deaths: 0
Injuries: 0
Property damage: None recorded
Crop damage: None recorded
Events: 1

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.

What happened

The episode as NWS PSR wrote it up.

An unseasonably strong upper level low pressure system produced showers and thunderstorms across the lower elevations of southeast California during the day on May 15th. The wet conditions allowed for the formation of patchy dense fog along the lower Colorado River Valley during the morning hours on May 16th; dense fog was reported at the airport at Blythe California. No accidents or injuries were reported due to the sharply reduced visibilities in dense fog.

What forecasters said that day

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 Phoenix, AZ wrote its last area forecast discussion before the first event at May 16, 5:05 AM MST, 45 minutes earlier.

Area forecast discussion, May 16, 5:05 AM MST, 45 minutes before

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
505 AM MST SAT MAY 16 2015

.UPDATE...TO AVIATION DISCUSSION...

&&

.SYNOPSIS...
THE PACIFIC LOW PRESSURE SYSTEM THAT BROUGHT WIDESPREAD RAIN TO THE
REGION...WILL MOVE INTO EASTERN ARIZONA AND WESTERN NEW MEXICO THIS
AFTERNOON...RESULTING IN DRY WEATHER IN ALL BUT THE MOUNTAINS OF
EASTERN ARIZONA. AFTERNOON TEMPERATURES ON THE LOWER DESERTS TODAY
WILL RANGE FROM 75 TO 80 DEGREES...OR 15 DEGREES BELOW NORMAL. DRY
AND WARMER WEATHER IS EXPECTED SUNDAY...HOWEVER ANOTHER PACIFIC LOW
PRESSURE SYSTEM IS FORECAST TO MOVE INTO THE REGION
MONDAY...RESULTING IN GUSTY WINDS...AND A SLIGHT CHANCE OF SHOWERS.
DRY AND WARMER WEATHER WILL RETURN NEXT TUESDAY THROUGH FRIDAY.

&&

.DISCUSSION...

TODAY AND TONIGHT...THE COLD PACIFIC LOW PRESSURE SYSTEM THAT MOVED
THROUGH SOUTHWEST AND SOUTH CENTRAL AZ...AND PRODUCED RECORD RAIN
FOR THE DAY IN PHOENIX AND YUMA...AND A RECORD LOW AFTERNOON HIGH
TEMPERATURE IN YUMA OF 69 DEGREES FOR MAY 15TH...PREVIOUS RECORD WAS
75 IN 1894...WAS MOVING INTO EASTERN AZ AT 2 AM MST. ONLY ISOLATED
LIGHT SHOWERS WERE NOTED AT THIS TIME OVER OUR FORECAST AREA FROM
PHOENIX EAST. A SLIGHT CHANCE OF SHOWERS WILL CONTINUE OVER THE
GREATER PHOENIX AREA THIS MORNING...WITH A CHANCE IN THE MOUNTAINS
OF SOUTHERN GILA COUNTY ZONE 24 EAST OF PHOENIX THE REMAINDER OF THE
DAY.

ON ANOTHER NOTE...THE HEAVIEST RAIN IN THE STATE WAS CENTERED IN
SOUTH CENTRAL ARIZONA FROM PHOENIX NORTHEAST INTO THE ADJACENT
MOUNTAINS AND FOOTHILLS. VALUES RANGED FROM 0.93 AT SKY HARBOR
AIRPORT...1.39 INCHES AT SUNFLOWER...AND 1.42 INCHES IN SCOTTSDALE.

FOR TONIGHT...WITH MODELS FORECASTING SIGNIFICANT BOUNDARY LAYER
DRYING...AND WITH CONSIDERABLE HIGH CLOUDS SPREADING IN FROM THE
WEST...FOG SHOULDNT BE AN ISSUE ON THE DESERTS.

SUNDAY...A MUCH WARMER AND DRIER AIRMASS WILL MOVE INTO THE AREA
WITH AFTERNOON TEMPERATURES REBOUNDING INTO THE UPPER 80S...BUT
STILL 6 TO 8 DEGREES BELOW NORMAL.

MONDAY...ANOTHER PACIFIC LOW PRESSURE SYSTEM IS FORECAST TO MOVE
INTO THE REGION MONDAY. GUSTY SOUTHWEST WINDS AHEAD OF THE COLD
FRONT SHOULD SPIKE DESERT TEMPERATURES INTO THE LOWER 90S.
ADDITIONALLY...500/300 HEIGHT FALLS ARE FORECAST TO BE MODERATELY
STRONG...AND ENOUGH TO WARRANT A SLIGHT CHANCE OF SHOWERS ACROSS
PARTS OF SOUTHEAST CA MONDAY MORNING/EARLY AFTERNOON...THEN ACROSS
THE GREATER PHOENIX AREA LATE MONDAY AFTERNOON AND EVENING.
NUMERICAL MODEL PRECIP PROBABILITIES HAVE INCREASED INTO THE 12 TO
17 PERCENT RANGE FROM YUMA TO PHOENIX.

TUESDAY THROUGH FRIDAY...DRY AND WARMER SOUTHWEST FLOW ALOFT IS
FORECAST. DESERT TEMPERATURES WILL REMAIN STEADY STATE NEAR 90
DEGREES...OR 5 DEGREES BELOW NORMAL. THERE IS A HINT THAT ANOTHER
WEAK PACIFIC TROF MAY MOVE INTO THE REGION FRIDAY AND SATURDAY...
HOWEVER DETAILS ARE LACKING THIS FAR IN ADVANCE.

&&

.AVIATION...
SOUTH-CENTRAL ARIZONA INCLUDING KPHX...KIWA...AND KSDL...
BULK OF THE HEAVIEST RAIN SHOWER ACTIVITY HAS ENDED ACROSS THE
PHOENIX METRO IN THE LAST FEW HOURS. ONLY ISOLATED SHOWERS DRIFTING
THROUGH THE AREA FROM WEST TO EAST SO MAINTAINED VCSH FOR THE
TERMINALS THROUGH LATE-MORNING. RAIN-SOAKED SURFACES AND ELEVATED
BOUNDARY LAYER MOISTURE WILL SUPPORT THE DEVELOPMENT OF SCT-BKN CIGS
IN THE 2-4KFT RANGE...ESPECIALLY AFTER SUNRISE. VALLEY WEBCAMS AND
OBS FROM KSDL AND KIWA ALREADY INDICATE THE LOWER CLOUD FIELDS
MOVING ACROSS THE CITY. LOWERED CIGS/CLOUD FIELDS SHOULD DISSIPATE
TOWARDS THE MID TO LATE MORNING. FOR THE REST OF THE AFTERNOON...SCT-
BKN CU FIELDS 5-7KFT. WINDS WILL BROADLY FAVOR WESTERLY HEADINGS
THROUGH LOW TO MID LEVELS...WHILE AM SFC WINDS WILL BE MORE VARIABLE
IN HEADINGS WITH SPEEDS GNLY 6KTS OR LESS.

SOUTHEAST CALIFORNIA AND SOUTHWEST ARIZONA INCLUDING KIPL AND
KBLH...
CLEARING SKIES...COOLER TEMPERATURES AND AMPLE BOUNDARY LAYER
MOISTURE WILL PERSIST AREAS OF MIST/FOG ACROSS THE LOWER ELEVATIONS
OF SOUTHEAST CA AND FOR THE TERMINALS INTO THE LATE AM. CONDITIONS
TO GRADUALLY CLEAR BY LATE MORNING AS FURTHER DRYING AND SUBSIDENCE
TRANSITIONS INTO THE REGION. LIGHT AM WINDS TO GIVE WAY TO W-SW
HEADINGS FOR BOTH KIPL AND KBLH WITH SPEEDS 10KTS OR LESS.

AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.

&&

.FIRE WEATHER...
MONDAY THROUGH FRIDAY...
A COUPLE OF FOLLOW-ON SYSTEMS WILL MOVE THROUGH THE DESERT SOUTHWEST
DURING THE NEXT WORK WEEK. THIS WILL KEEP TEMPERATURES BELOW NORMAL
AND THERE WILL BE BREEZY CONDITIONS AT TIMES. THESE SYSTEMS ARE NOT
EXPECTED TO BE AS MOIST AS THE PRECEDING SYSTEM AND THUS MINIMUM
HUMIDITIES WILL GENERALLY BE IN THE 10-15 PERCENT RANGE ON THE
LOWER ELEVATIONS. HOWEVER...NO CRITICAL CONDITIONS ARE EXPECTED.

&&

.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&

VISIT US ON FACEBOOK...TWITTER...AND AT WEATHER.GOV/PHOENIX

DISCUSSION...VASQUEZ
AVIATION...NOLTE
FIRE WEATHER...AJ

Event by event

1 dense fog. Local standard time, as filed.

Dense Fog, Lower Colorado River Valley

When: May 16, 5:50 AM MST to 8:50 AM MST
Where: Lower Colorado River Valley forecast zone
Reported by: ASOS

An unseasonably strong upper level low pressure system led to wet conditions along the lower Colorado River valley during the morning hours on May 16th. As a result, patchy and locally dense fog developed which affected the airport at Blythe California. At 0552PST the ASOS weather station at Blythe reported visibility reduced to one quarter of a mile. No accidents or injuries were reported due to the dense fog. A Dense Fog Advisory was issued for the area due to the reported low visibility.

What these are

Dense Fog: Fog reducing visibility to a quarter mile or less, filed where it caused accidents or disruption.

After NWS Directive 10-1605, the rules offices file Storm Data by.

The same day elsewhere

More

Every storm in California in 2015 Every state in 2015 This day in weather history Warnings in California, May 2015

Sources

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: 575733.