Flash Flood Warning 27, NWS Denver/Boulder, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
241 PM MDT WED SEP 11 2013

.SHORT TERM...TONIGHT AND THURSDAY...LITTLE CHANGE IN THE PATTERN
OVER THE NEXT 24 HOURS. UPPER LEVEL LOW CENTERED NEAR LAS VEGAS WILL
SLOWLY LIFT NORTH OVER THE NEXT 24 HOURS. A VERY MOIST SOUTH-
SOUTHWEST FLOW ALOFT WILL CONTINUE. A SHORT WAVE TROUGH EMBEDDED IN
THE FLOW ALOFT IS OVER SOUTH CENTRAL/SOUTHEAST COLORADO. THIS IS
BRING RAIN SHOWERS TO EASTERN AND NORTHEAST COLORADO AT THIS TIME.
THE WAVE WILL CONTINUE TO MOVE NORTH-NORTHEAST AND PUSH THE
WIDESPREAD SHOWERS EAST OF THE AREA. THERE IS SOMEWHAT DRIER AIR
BEHIND THE WAVE AND THERE ARE PARTIAL BREAKS IN THE CLOUDS. THESE
BREAKS HAVE ALLOWED SOME LOCATIONS CLIMB TO AROUND 70 DEGREES.
EXPECT SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO REDEVELOP
BEHIND THIS WAVE DUE TO SOME INSTABILITY.

HEAVY RAIN WILL BE THE BIGGEST CONCERN THE STRONGER SHOWERS AND
THUNDERSTORMS. AIRMASS IS VERY MOIST WITH PRECIPITABLE WATER VALUES
AROUND 1.25 INCHES AND DEW POINTS IN THE UPPER 50S AND LOWER 60S.
WHERE TEMPERATURES CLIMB TO AROUND 70 DEGREES CAPES WILL BE AROUND
700 J/KG. NOT ENOUGH FOR SEVERE WEATHER...BUT PLENTY OF MOISTURE AND
INSTABILITY FOR VERY HEAVY RAIN OUT OF THUNDERSTORMS. RAINFALL RATES
OUT OF THE THUNDERSTORMS MAY REACH AN INCH IN 20 TO 30 MINUTES.

SHOWERS ARE EXPECTED TO DECREASE OVERNIGHT AND THUNDERSTORMS WILL
END. THE FORECAST AREA WILL BE BETWEEN WAVES SO ONLY EXPECT
SCATTERED TO ISOLATED SHOWERS OVERNIGHT. THE NEXT WAVE WILL ROTATE
INTO SOUTHERN COLORADO THURSDAY AFTERNOON. THIS IS EXPECTED TO BRING
ANOTHER ROUND OF RAIN SHOWERS AND ISOLATED THUNDERSTORMS. AIRMASS TO
REMAIN VERY MOIST...SO HEAVY RAIN WILL AGAIN BE A THREAT. HIGHS WILL
BE COOL OVER NORTHEAST COLORADO WITH HIGHS IN THE MID 60S ALONG THE
FRONT RANGE TO LOWER 70S OVER THE EASTERN PLAINS.

.LONG TERM...THE UPPER LOW WILL REMAIN ANCHORED OVER THE GREAT
BASIN THROUGH SATURDAY...THEN SLOWLY EJECT EASTWARD ACROSS THE
ROCKIES SUNDAY AND MONDAY. AHEAD OF THIS LOW THE AIRMASS OVER
COLORADO WILL CONTINUE TO BE MOIST AND MARGINALLY UNSTABLE WITH
OCCASIONAL TROUGHS LIFTING ACROSS THE STATE. FRIDAY LOOKS LIKE
ANOTHER DAY WITH A GOOD CHANCE OF AFTERNOON AND EVENING SHOWERS
AND THUNDERSTORMS...SATURDAY LOOKS A BIT DRYER AND WARMER. ON
SUNDAY A COLD FRONT IS EXPECTED TO DROP ACROSS NORTHEAST COLORADO.
THIS WILL INCREASE LOW LEVEL UPSLOPE FLOW...DROP TEMPERATURES A
FEW DEGREES...AND INCREASE THE CHANCE OF SHOWERS AND
THUNDERSTORMS.

THE PATTERN WILL CHANGE EARLY NEXT WEEK WITH SOUTHWEST FLOW
DEVELOPING OVER COLORADO...AND A LEE SURFACE TROUGH IN EASTERN
COLORODO. THIS WILL RESULT IN WARMER TEMPERATURES. THERE MAY BE A
FEW THUNDERSTORMS OVER THE MOUNTAINS EARLY NEXT WEEK BUT THE
PLAINS SHOULD REMAIN DRY.

&&

.AVIATION...CEILINGS WILL GENERALLY REMAIN BETWEEN 3000 TO 6000 FEET
ACROSS THE DENVER AREA FOR THE REST OF THIS AFTERNOON AND EVENING.
CEILING MAY OCCASIONALLY BE HIGHER. AT BJC...CEILINGS WILL BE
LOWER...AT 1000 TO 3000 FEET DUE TO UPSLOPE WINDS. CEILINGS WILL
FALL OVERNIGHT AGAIN TO 500 TO 1500 FEET. THERE IS A GOOD CHANCE
AGAIN FOR FOG AND CEILINGS OF 100 TO 500 FEET BETWEEN 10Z AND 15Z.

ISOLATED STORMS WILL BE POSSIBLE THROUGH 02Z. BRIEF HEAVY RAIN WILL
BE ACCOMPANY THE STRONGER STORMS. LOW CLOUDS AND RAIN SHOWERS WITH A
FEW EMBEDDED AFTERNOON STORMS ARE EXPECTED TO PREVAIL ONCE AGAIN
THURSDAY.

&&

.HYDROLOGY...RAINFALL OVER THE PAST FEW DAYS HAVE SATURATED SOILS IN
SPOTS. A FEW STREAMS ARE RUNNING HIGH BUT NO FLOODING HAS BEEN
REPORTED. THE HEAVIER RAIN SHOWERS ARE PRODUCING RAINFALL RATES OF A
QUARTER TO A HALF INCH PER HOUR...NOT A BIG CONCERN. HOWEVER THE
THUNDERSTORMS THAT FORM COULD PRODUCE RAINFALL RATES OF 1 INCH IN 20
TO 30 MINUTES...WHICH COULD CAUSE LOCALIZED FLOODING ISSUES.

RAIN SHOWERS WITH EMBEDDED THUNDERSTORMS WILL CONTINUE THROUGH
FRIDAY. IT WILL DRY OUT SOME THIS WEEKEND BUT AFTERNOON AND EVENING
THUNDERSTORMS ARE EXPECTED.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

SHORT TERM...MEIER
LONG TERM....RTG
AVIATION...MEIER

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
1056 AM MDT WED SEP 11 2013

COZ030>051-121700-
JACKSON COUNTY BELOW 9000 FEET-
WEST JACKSON AND WEST GRAND COUNTIES ABOVE 9000 FEET-
GRAND AND SUMMIT COUNTIES BELOW 9000 FEET-
SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/
NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET-
SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/
GILPIN/CLEAR CREEK/SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE
9000 FEET-LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET-
JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR
CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET-
CENTRAL AND SOUTHEAST PARK COUNTY-
LARIMER COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY-
BOULDER AND JEFFERSON COUNTIES BELOW 6000 FEET/WEST BROOMFIELD
COUNTY-
NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND
ARAPAHOE COUNTIES/EAST BROOMFIELD COUNTY-
ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES ABOVE 6000 FEET-
NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD COUNTY-MORGAN COUNTY-
CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES-
NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN
COUNTY-
SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN COUNTY-
LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS COUNTY-
1056 AM MDT WED SEP 11 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL
COLORADO.

.DAY ONE...TODAY AND TONIGHT

SHOWERS AND A FEW THUNDERSTORMS WILL OCCUR TODAY AND CONTINUE INTO
THE EVENING HOURS. RAINFALL AMOUNTS UP TO AN INCH IN TWO TO THREE
HOURS MAY OCCUR IN A FEW LOCATIONS WHERE HEAVIER SHOWERS DEVELOP.
UNDER THE STRONGER THUNDERSTORMS...UP TO AN INCH OF RAIN WILL BE
POSSIBLE IN 20 MINUTES TO THIRTY MINUTES. SCATTERED RAIN SHOWERS
WILL LINGER THROUGH THE NIGHT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

UNSEASONABLY COOL AND MOIST CONDITIONS WILL PERSIST FOR ONE MORE
DAY ON THURSDAY WITH SHOWERS AND THUNDERSTORMS ACROSS MOST OF THE
OUTLOOK AREA. SOME STORMS DURING THE AFTERNOON AND EVENING HOURS
MAY PRODUCE HEAVY RAINFALL AND POSSIBLY SOME SMALL HAIL...POSSIBLY
RESULTING IN LOCALIZED FLOODING. THE HIGHER MOUNTAIN PEAKS MAY
ALSO SEE SOME LIGHT SNOW. THERE WILL BE A BIT MORE SUNSHINE FRIDAY
AND SATURDAY...BUT SCATTERED SHOWERS WILL STILL BE POSSIBLE
ESPECIALLY IN THE AFTERNOON AND EVENING. SUNDAY A COOL FRONT
PUSHES INTO NORTHEAST COLORADO INCREASING CHANCES FOR
PRECIPITATAION ONCE AGAIN. DRYER AND WARMER WEATHER FINALLY
ARRIVES IN NORTHEAST COLORADO BY TUESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE DENVER CO
536 PM MDT WED SEP 11 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0212 PM     HEAVY RAIN       GENESEE                 39.69N 105.27W
09/11/2013  M4.15 INCH       JEFFERSON          CO   TRAINED SPOTTER

            48 HOUR RAINFALL TOTAL

&&

JK

PRELIMINARY LOCAL STORM REPORT...SUMMARY
NATIONAL WEATHER SERVICE DENVER CO
636 PM MDT WED SEP 11 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0628 PM     HEAVY RAIN       ERIE                    40.03N 105.05W
09/11/2013  M2.50 INCH       WELD               CO   BROADCAST MEDIA

            PAST TWO HOURS.

0614 PM     HEAVY RAIN       LYONS                   40.22N 105.27W
09/11/2013  M1.90 INCH       BOULDER            CO   BROADCAST MEDIA

            PAST 24 HOURS

0212 PM     HEAVY RAIN       GENESEE                 39.69N 105.27W
09/11/2013  M4.15 INCH       JEFFERSON          CO   TRAINED SPOTTER

            48 HOUR RAINFALL TOTAL

&&

JK