Special Weather Statement, NWS Denver/Boulder, CO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER/BOULDER CO
320 PM MDT WED AUG 3 2011

.SHORT TERM...SCATTERED CONVECTION CURRENTLY ACROSS MOUNTAINS AND
NORTHERN FOOTHILLS. ALSO SOME SHOWERS OVER FAR NORTHEAST CORNER
ASSOCIATED WITH EXITING TROUGH. IN BETWEEN...LITTLE OR NO CONVECTION
AS AIRMASS STILL STABLE...NOTED BY ACARS SOUNDINGS. LATEST GPS IPW
VALUES HOVERING AROUND 1.15 INCHES. FORECAST SOUNDINGS KEEP A BIT OF
A CAP ALONG URBAN CORRIDOR...SO CONVECTION THERE WILL PROBABLY NEED
HELP FROM ANY OUTFLOW BOUNDARIES. HARD TO FIND ANY SHORTWAVE IN THE
MOIST FLOW ALOFT TO INCREASE THE COVERAGE AND POPS ACROSS CFWA THIS
EVENING...SO WILL BE KEEPING THE CHANCE POPS GOING. FROM RADAR AND
SATELLITE LOOPS...CONVECTION MOVING A BIT QUICKER THAN YESTERDAY...
ROUGHLY AROUND 10KTS. WITH THE QUICKER MOVEMENT AND LOWER
PRECIPITABLE WATER VALUE...NOT ANTICIPATING A BIG FLOOD THREAT BUT
STILL THE POTENTIAL FOR BRIEF HEAVY RAIN. SHOULD SEE STORM ACTIVITY
ENDING AROUND MIDNIGHT DUE TO LACK OF ANY SHORTWAVE. BOUNDARY LAYER
WIND AND HUMIDITY PROGS SUGGEST SOME INCREASE IN LOW LEVEL MOISTURE
MAINLY EAST OF A STERLING TO LIMON LINE SO WILL ADD SOME PATCHY FOG
THERE LATE TONIGHT. ON THURSDAY...MODELS SHOW LITTLE CHANGE IN
OVERALL PATTERN WITH UPPER RIDGE ACROSS NORTHERN TEXAS AND WEAK TO
MODERATE SOUTHWEST FLOW ALOFT OVER CFWA. THERE IS SOME INCREASE IN
QG ASCENT OVER THE MOUNTAINS DURING THE AFTERNOON IN RESPONSE TO
SOME SORT OF SHORTWAVE MOVING IN FROM ARIZONA. THIS SHOULD HELP
INCREASE STORM CHANCES FOR THE MOUNTAINS. PRECIPITABLE WATER VALUES
RANGE FROM AROUND AN INCH ALONG FOOTHILLS TO ROUGHLY 1.3 INCHES FAR
EASTERN ZONES. SO POTENTIAL FOR BRIEF HEAVY RAIN STILL A
POSSIBILITY. TEMPERATURE AND THICKNESS PROGS AS WELL AS GUIDANCE
SHOW HIGHS IN THE 80S ACROSS PLAINS. CURRENT TEMPERATURE GRIDS IN
LINE WITH GUIDANCE...LITTLE CHANGES NEEDED. SO DENVER TO WAIT
ANOTHER DAY TO BEGIN THE 90 DEGREE STRING.

.LONG TERM...ON FRIDAY...THE BROAD UPPER LEVEL RIDGE WILL BE
STRETCHED ACROSS THE SRN U.S. WITH A WEAK SOUTHWESTERLY FLOW ALOFT
OVER COLORADO.  THE SUPTROPICAL MOISTURE PLUME WL BE MAINLY OVER THE
SRN HALF OF THE STATE...WITH A DRIER AIRMASS INTRUDING FROM THE
NORTH.   NAM12 SOUNDINGS INDICATE PRECIPITABLE WATER VALUES AROUND
0.6 INCHES AT DENVER WITH HIGHER VALUES NEAR 1.2 INCHES ALONG THE
ERN CO BORDER.  AS A RESULT...THE STORMS WILL BE HIGHER BASED ALONG
THE FRONT RANGE WITH GUSTY WINDS THE MAIN ISSUE.  WL CONTINUE THE
TREND OF WARMER AND DRIER INTO THE WEEKEND.  THE UPPER RIDGE WILL
RECENTER ITSELF OVER NORTHERN MX/DESERT SOUTHWEST BY MONDAY OF NEXT
WEEK.  A DRIER WEST TO NORTHWESTERLY FLOW WL BE OVER COLORADO.  A
COUPLE OF DISTURBANCES SLIDING ACRS THE NORTHERN PLAINS COULD BRING
A COLD FRONT AND SOME UPSLOPE TO THE NORTHERN PLAINS BY
TUESDAY/WEDNESDAY OF NEXT WEEK.

&&

.AVIATION...STORM CHANCES FOR LOCAL AIRPORTS ARE DECREASING AS ACARS
SOUNDINGS STILL INDICATING MODEST CAP. MAY NEED AN OUTFLOW BOUNDARY
OR TWO TO INITIATE STORM DEVELOPMENT THIS EVENING. WILL KEEP THE
VCTS IN CASE THERE IS SOME STORM DEVELOPMENT. IF A STORM DOES PASS
OVER THE AIRPORT MAY STILL SEE A BRIEF PERIOD OF GUSTY WINDS...SMALL
HAIL AND MODERATE RAINFALL. STILL VFR CONDITIONS TO PREVAIL WITH A
CHANCE FOR CEILINGS IN THE 5000-6000 FEET AGL RANGE WHICH COULD
AFFECT ILS APPROACHES. SOUTHEAST WINDS TO DECREASE AND SHIFT BACK TO
DRAINAGE BY 03Z. NOT EXPECTING ANY STRATUS AT AREA AIRPORTS. CHANCE
FOR STORMS AGAIN THURSDAY AFTERNOON...MAINLY WEST AND SOUTH OF AREA
AIRPORTS. CHANCE AGAIN FOR CEILINGS AROUND 6000 FEET AGL RANGE WHICH
COULD AFFECT ILS APPROACHES.

&&

.HYDROLOGY...THERE REMAINS A CHANCE OF THUNDERSTORMS THIS EVENING...
PARTICULARLY OVER THE MOUNTAINS AND FOOTHILLS. A FEW STORMS COULD
AFFECT THE BURN AREAS. THE STORMS LOOK TO BE FASTER MOVING...SO
THE FLASH FLOOD THREAT IS LOW. HOWEVER IF A STRONGER STORM DOES
AFFECT ONE OF THE BURN AREAS RAINFALL AMOUNTS COULD REACH UP TO ONE
INCH IN 30 MINUTES. MOST OF THE RAINFALL AMOUNTS SHOULD BE UNDER ONE
HALF INCH. CHANCE FOR STORMS AGAIN THURSDAY AFTERNOON AS A
DISTURBANCE APPROACHES FROM THE WEST. PRECIPITABLE WATER VALUES LOOK
TO DECREASE A BIT FROM TODAY...WHICH SHOULD LOWER THE THREAT FOR
FLASH FLOODING. STILL SOME STORMS COULD PRODUCE BRIEF HEAVY RAIN/

&&

.BOU WATCHES/WARNINGS/ADVISORIES...NONE

&&

D-L/COOPER

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1058 AM MDT WED AUG 03 2011

COZ030>051-041200-
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-
1058 AM MDT WED AUG 03 2011

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

.DAY ONE...TODAY AND TONIGHT

SCATTERED THUNDERSTORMS WILL DEVELOP ACROSS THE MOUNTAINS...
FOOTHILLS AND ADJACENT PLAINS THIS AFTERNOON WITH A CHANCE FOR
THUNDERSTORMS OVER THE REMAINDER OF THE PLAINS. THE STORMS WILL BE
CAPABLE OF PRODUCING BRIEF HEAVY RAIN...SMALL HAIL AND GUSTY WINDS.
THERE IS A SLIGHT CHANCE THAT A STORM ALONG THE URBAN CORRIDOR COULD
REACH SEVERE LIMITS...WITH HAIL TO ONE INCH IN DIAMETER. THE STORMS
WILL CONTINUE INTO THE EVENING BEFORE ENDING AROUND MIDNIGHT.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

MONSOONAL MOISTURE WILL REMAIN IN PLACE OVER THE STATE ON THURSDAY
ALONG WITH LIGHT WESTERLY WINDS ALOFT.  DAYTIME HEATING WILL PRODUCE
SHOWERS AND THUNDERSTORMS OVER THE MOUNTAINS BY EARLY AFTERNOON
WHICH WILL DRIFT OVER THE ADJACENT PLAINS BY LATE AFTERNOON.  STORMS
MAY BE SLOW-MOVING AND CAPABLE OF PRODUCING LOCALLY HEAVY RAINFALL.
FRIDAY AND SATURDAY...THE UPPER HIGH THAT HAS BEEN DOMINATING
WEATHER ACROSS THE SOUTHERN U.S. THE PAST SEVERAL WEEKS WILL BEGIN
SHIFTING WESTWARD...CUTTING OFF THE FLOW OF MONSOONAL MOISTURE TO
COLORADO.  DRIER CONDITIONS WILL RESULT WITH THE AMOUNT OF
THUNDERSTORMS DECREASING EACH DAY.  THIS WILL ALSO ALLOW
TEMPERATURES TO WARM UP THROUGH EARLY NEXT WEEK WITH A RETURN OF
AFTERNOON READINGS IN THE LOWER AND MID 90S ACROSS THE PLAINS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT BUT RAINFALL
REPORTS WILL BE APPRECIATED.

D-L/COOPER

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE DENVER CO
716 PM MDT WED AUG 3 2011

COZ040-041-043-045-040200-
CENTRAL AND SOUTH WELD COUNTY CO-
CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES CO-
NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE
COUNTIES/EAST BROOMFIELD COUNTY CO-
ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES ABOVE 6000 FEET CO-
716 PM MDT WED AUG 3 2011

THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A SIGNIFICANT
WEATHER ADVISORY FOR

  NORTH CENTRAL ARAPAHOE COUNTY
  CENTRAL ADAMS COUNTY
  NORTHEASTERN DENVER COUNTY
  SOUTH CENTRAL WELD COUNTY

AT 716 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
THUNDERSTORM CAPABLE OF PRODUCING PEA SIZE HAIL...AND WIND GUSTS TO
AROUND 50 MPH.  THIS STORM WAS LOCATED 5 MILES NORTH OF DENVER
INTERNATIONAL AIRPORT...OR 20 MILES NORTHEAST OF DENVER...MOVING
SOUTHEAST AT 15 MPH.

LOCATIONS IN THE ADVISORY INCLUDE BUT ARE NOT LIMITED TO D.I.A.
TERMINAL AND CONCOURSES...WATKINS...PROSPECT VALLEY...MANILA
VILLAGE...LOCHBUIE...KEENESBURG...HUDSON...BRIGHTON...BENNETT...BARR
LAKE...DENVER INTERNATIONAL AIRPORT...NORTHEASTERN COMMERCE CITY AND
NORTHEASTERN AURORA.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HEAVY RAINS MAY ALSO OCCUR WITH THIS STORM...WHICH MAY FLOOD
LOW-LYING AREAS SUCH AS DITCHES AND UNDERPASSES. DO NOT DRIVE YOUR
VEHICLE ON A FLOODED ROADWAY.

&&

LAT...LON 3999 10415 3963 10453 3988 10492 4031 10456
TIME...MOT...LOC 0116Z 317DEG 21KT 3991 10467