Public Information Statement
Issued by NWS Denver/Boulder, CO

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PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE BOULDER CO
600 PM MDT WED APR 16 2014

AS WE SAW LAST SEPTEMBER...FLOODING CAN BE A MAJOR PROBLEM IN
COLORADO.

THE FLASH FLOODING IN SEPTEMBER DAMAGED A NUMBER OF STREAMS...AND
MITIGATION IS ONGOING TO REMOVE DEBRIS AND SHORE UP HEAVILY DAMAGED
AREAS ALONG THE STREAMS IN AND NEAR THE FOOTHILLS FROM LARIMER
COUNTY TO EL PASO COUNTY. THE SNOWPACK IN THE SOUTH PLATTE BASIN IS
ABOVE NORMAL SO THERE IS CONCERN WHEN THE MELT OCCURS THAT STREAMS
MAY NOT BE ABLE TO HANDLE A FAST MELT. THE RATE AT WHICH RUNOFF
OCCURS IS DEPENDENT ON A NUMBER OF FACTORS INCLUDING THE DEPTH OF
THE SNOW HOW FAST HOT TEMPERATURES DEVELOP AND WHETHER THUNDERSTORMS
DROP HEAVY RAIN ON THE SNOWPACK WITH RUNOFF COMBINING WITH FALLING
RAIN. IN 2011 WE HAD A SIMILAR HIGH SNOWPACK WITH MINIMAL FLOOD
ISSUES AS THE WARM DAYS AND COOL NIGHTS MODERATED THE RATE OF THE
SNOW MELT. THE PEAK SNOWMELT SEASON USUALLY EXTENDS FROM LATE MAY
THROUGH EARLY JUNE JUNE.

IN SEPTEMBER OVER 8 INCHES OF RAIN FELL OVER A LARGE AREA OF THE
FOOTHILLS FROM NORTHERN JEFFERSON TO NORTHERN LARIMER COUNTIES. ALL
THIS RAIN FILLED AREA CREEKS AND RIVERS CAUSING CONSIDERABLE FLASH
FLOODING. RUNOFF FROM AREA STREAMS COMBINED TO CAUSE MAJOR FLOODING
ALONG THE SOUTH PLATTE RIVER.

FLASH FLOODING RREFERS TO A DANGEROUS SUDDEN RISE IN WATER ALONG A
CREEK...RIVER...OR OVER A NORMALLY DRY LAND AREA. FLASH FLOODS
RESULT FROM HEAVY RAINFALL...SUDDEN BREAKS IN RIVER ICE JAMS...AND
DAM OR LEVEE FAILURES. FLASH FLOODS CAN OCCUR WITHIN A FEW MINUTES
OR HOURS...AND CAN MOVE AT SURPRISINGLY HIGH SPEEDS...STRIKING WITH
LITTLE WARNING. FLASH FLOODS ARE QUITE DESTRUCTIVE BECAUSE OF THE
FORCE OF THE MOVING WATER...AND THE DEBRIS THAT ACCUMULATES IN FLOOD
WATERS...SUCH AS TREES AND BOULDER...WHICH CAN DESTROY
ROADWAYS...BRIDGES AND BUILDINGS.

OTHER COMPLICATIONS IN COLORADO ARE RECENT FIRES WHICH RAISE THE
FLOOD THREAT WHEN LOCALLY HEAVY RAIN FALLS ON RECENTLY BURN SCARS.
RESIDENTS IN AND NEAR BURNED AREAS NEAR MANCOS, DEBEQUE OR IN THE
FRONT RANGE FOOTHILLS FROM LARIMER TO EL PASO COUNTIES SHOULD PLAN
AHEAD ON RESPONSE ACTIONS FOR FLOODING.

THE NATIONAL WEATHER SERVICE WILL DISCUSS FLOOD AND FLASH FLOOD
POTENTIAL IN DAILY HAZARDOUS WEATHER OUTLOOKS AND IN THE WEATHER
STORY ON NATIONAL WEATHER SERVICE WEBSITES. ON DAYS WITH A HIGH
THREAT FOR FLOODING YOU MAY HEAR...

A FLASH FLOOD OR FLOOD WATCH...WHICH MEANS THAT FLASH FLOODING OR
FLOODING IS POSSIBLE WITHIN THE WATCH AREA.

A FLOOD WARNING, WHICH MEANS THAT FLOODING IS IMMINENT OR HAS BEEN
REPORTED ALONG A RIVER.

A FLASH FLOOD WARNING...WHICH MEANS THAT FLASH FLOODING HAS BEEN
REPORTED OR IS IMMINENT. WHEN A FLASH FLOOD WARNING IS ISSUED FOR
YOUR AREA...ACT QUICKLY. IF ADVISED TO EVACUATE...DO SO IMMEDIATELY.
GO TO HIGHER GROUND OR CLIMB TO SAFETY BEFORE ACCESS IS CUT OFF BY
FLOOD WATERS.

AN URBAN FLOOD ADVISORY WILL BE ISSUED FOR IMPACT FLOODING THAT IS
NOT IN ITSELF LIFE THREATENING. IN AN URBAN AREA IF YOU WERE
COMMUTING DURING RUSH HOUR DURING A FLOOD ADVISORY YOU COULD EXPECT
SOME INTERSECTIONS TO BE UNDERWATER AND A MUCH LONGER COMMUTE. A
SMALL STREAM FLOOD ADVISORY MIGHT BE ISSUED WHEN FLOW IS BANKFUL
WITH MINOR LOWLAND FLOODING ALONG THE STREAM.

NEARLY HALF OF ALL FLASH FLOOD FATALITIES ARE VEHICLE RELATED. DO
NOT ENTER A FLOODED ROADWAY...INSTEAD TURN AROUND...DO NOT DROWN.
IN RAPIDLY RISING WATERS BACKING UP AWAY FROM WATER MAY BE SAFER.
ONE TO TWO FEET OF WATER WILL CARRY AWAY MOST VEHICLES AND YOU ALSO
CANNOT TELL IF THE ROAD IS DAMAGED BENEATH MOVING WATER.

COLORADO SEVERE WEATHER AWARENESS WEEK CONTINUES THROUGH THIS
SATURDAY.

WFO BOULDER



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