Severe Thunderstorm Warning 45, NWS Denver/Boulder, CO

000 
WWUS55 KBOU 212304
SVSBOU

SEVERE WEATHER STATEMENT
NATIONAL WEATHER SERVICE DENVER CO
504 PM MDT MON MAY 21 2007

COC005-212314-
/O.CAN.KBOU.SV.W.0045.000000T0000Z-070521T2330Z/
ARAPAHOE CO-
504 PM MDT MON MAY 21 2007

...THE SEVERE THUNDERSTORM WARNING FOR CENTRAL ARAPAHOE COUNTY IS
CANCELLED...

THE THUNDERSTORM THAT PROMPTED THE WARNING HAS WEAKENED AND IS NO 
LONGER EXPECTED TO PRODUCE SEVERE WEATHER. 

LAT...LON 3972 10442 3956 10441 3957 10382 3974 10381

$$
ENTREKIN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
320 PM MDT MON MAY 21 2007

.SHORT TERM...UPPER TROUGH OVER GREAT BASIN WITH FAIRLY STRONG
SOUTHERLY FLOW ALOFT AHEAD OF TROUGH OVER THE CWA. BAND OF
CONVECTION CURRENTLY MOVING ACROSS MOUNTAINS...FOOTHILLS AND FRONT
RANGE. AIRMASS UNSTABLE ACROSS PLAINS WITH CAPES AROUND 1000 J/JG.
MARGINAL SEVERE POTENTIAL THIS EVENING...THOUGH A FEW STORMS COULD
BECOME SEVERE OVER THE FAR NORTHEAST PLAINS WHERE SHEAR AND MOISTURE
ARE A BIT BETTER AND CAPES OF 1500 J/KG A POSSIBILITY. LOOKS LIKE
HAIL AND GUSTY WINDS WILL BE THE MAIN THREATS. PRECIPITABLE WATER
VALUES HAVE BEEN STEADILY INCREASING ACROSS THE PLAINS THIS
AFTERNOON...CURRENTLY IN THE 0.60-0.70 INCH RANGE. COULD SEE SOME
HEAVY RAIN WITH A FEW OF THE STORMS. FLASH FLOOD THREAT LOOKS LOW
BASED ON CURRENT STORM MOTION OF AROUND 15 KTS. TROUGH AND SURFACE
FRONT EXPECTED TO MOVE ACROSS AREA OVERNIGHT. MODELS SHOW MOUNTAIN
OROGRAPHICS BECOME FAVORABLE FOR A SHORT TIME BETWEEN 06Z AND 12Z
WHEN AREA OF GQ ASCENT MOVES OVER REGION. COULD SEE A PERIOD OF
SNOWFALL ACROSS THE MOUNTAINS WHEN 7H TEMPS DROP TO -2 DEGREES
CELSIUS. WILL DROP THE MENTION OF RAIN IN THE HIGH COUNTRY
OVERNIGHT. MOST OF SNOW FALL TO MELT DUE TO FAIRLY WARM GROUND
EVENIN AT HIGHER ELEVATIONS...BUT WILL MENTION LIGHT ACCUMULATION.
AS FOR PLAINS...FRONT STILL EXPECTED TO MOVE ACROSS DENVER AROUND
09Z AND ACROSS REMAINDER OF PLAINS BY 12Z. COULD SEE SOME SHOWERS
OVERNIGHT DUE TO FRONTAL LIFTING AND QG ASCENT. WILL KEEP THE HIGHER
POPS NEAR EASTERN BORDER. UPPER TROUGH AND COOL AIRMASS WILL BE OVER
THE AREA DURING THE DAY TUESDAY. A BIT OF DISCREPENCY BETWEEN THE
NAM AND GFS IN TERMS OF POTENTIAL UPSLOPE BEHIND FRONT. GFS
INDICATES UPSLOPE DEVELOPING BY AFTERNOON WHILE THE NAM SHOWS
DOWNSLOPE THROUGH THE DAY. WILL LEAN TOWARD THE GFS AND THE
UPSLOPE...IN LINE WITH PREVIOUS FORECASTERS THINKING. THUS...
HIGHER POPS ALONG FOOTHILLS AND ADJACENT PLAINS AS UPSLOPE DEVELOPS.
FORECAST SOUNDING SHOWING MINIMAL CAPE...BUT WITH LAPSE RATES AROUND
8 C/KM AND SOME QG ASCENT...WITH KEEP THE MENTION OF THUNDER. AS FOR
MOUNTAINS...NAM CROSS SECTIONS SHOW DECREASING MOISTURE BY AFTERNOON
WHILE GFS SHOWS GOOD BATCH OF MOISTURE THROUGH THE DAY. WITH THIS
MUCH OF A DIFFERENCE...BEST NOT TO CHANGE FORECAST AT THIS TIME AND
WILL LEAVE CURRENT GRIDS AS IS.

.LONG TERM...ON TUESDAY NIGHT...A STRONG SOUTHWESTERLY JET IS
PROGGED OVER THE FORECAST AREA.  THE SOUTHWESTERLY FLOW ALOFT
DECREASES EARLY WEDNESDAY WITH THE UPPER TROUGH AXIS PUSHING OVER
THROUGH THE DAY.  WEDNESDAY NIGHT...STRONG NORTHWESTERLY FLOW ALOFT
BEHIND THE TROUGH AXIS IS PROGGED.  ZONAL TO SOUTHWESTERLY FLOW
ALOFT IS INDICATED ON THURSDAY AND THURSDAY NIGHT.  THE GFS AND NAM
DIFFER SOMEWHAT WITH THE SYNOPTIC SCALE ENERGY OVER THE FORECAST
AREA TUESDAY NIGHT AND WEDNESDAY.  THE NAM HAS DOWNWARD MOTION
INDICATED TUESDAY NIGHT...THE GFS HAS UPWARD.  ON WEDNESDAY...BOTH
HAVE UPWARD MOTION WITH DOWNWARD FORCING INDICATED WEDNESDAY NIGHT
THROUGH THURSDAY MORNING.  THE LOW LEVEL WIND AND PRESSURE FIELDS
HAVE SOME UPSLOPE FLOW IN THE BOUNDARY LAYER TUESDAY NIGHT AND
WEDNESDAY...BUT NOT SIGNIFICANT.  THE GRADIENT IS PRETTY WEAK
WEDNESDAY NIGHT THROUGH THURSDAY.  FOR MOISTURE...BOTH MODELS SHOW
FAIRLY DEEP MOISTURE FOR THE FORECAST AREA TUESDAY NIGHT AND
WEDNESDAY.  THERE IS SOME DRYING WEDNESDAY NIGHT...BUT AN INCREASE
AGAIN ON THURSDAY.  THE GFS AND NAM DIFFER WITH THE LOW LEVEL
MOISTURE OVER THE PLAINS.  THE NAM DROPS BOUNDARY LAYER DEW POINTS
BELOW 20 F TUESDAY NIGHT.  THE GFS DOES HAS UPPER 30S TO LOWER 40S
F.  BY THURSDAY THEY ARE BETTER AGREEMENT...AND BOTH SHOW FAIRLY DRY
LOW LEVEL AIR MASSES.  THE THETA-E AXIS ON THE GFS DOES COME BACK
LATE WEDNESDAY AND THURSDAY...THE NAM KEEPS IT AWAY.  THERE IS
ALMOST NO CAPE FOR THE FORECAST AREA TUESDAY EVENING...THEN LIMITED
AMOUNTS LATE DAY WEDNESDAY.  LATE DAY THURSDAY HAS LITTLE TO NONE.
THE GFS HAS A BIT MORE.   THE LAPSE RATES ARE NEVER VERY STEEP
THROUGH A DEEP LAYER FORM TUESDAY NIGHT THROUGH LATE THURSDAY...
THERE IS ALSO A DECENT STABLE LAYER SOMEWHERE.  THE QPF GRIDS DO
SHOW LIMITED PRECIPITATION TUESDAY EVENING THROUGH WEDNESDAY
EVENING.  THE GFS HAS MORE.  BOTH ARE DRY ON THURSDAY.  CURRENT
GRIDS LOOK ON TRACK WILL ONLY MAKE SLIGHT ADJUSTMENTS IN
CLOUDS/POPS/WEATHER.  THE SNOW MENTIONED IN THE HIGHER ZONES LOOKS
GOOD WITH THE FORECAST SOUNDINGS SHOWING WET BULB ZERO IN THE
6000-6500 FOOT RANGE TUESDAY NIGHT INTO WEDNESDAY.  MAY NEED MENTION
OF SNOW MIXED IN OVER THE PALMER RIDGE AS WELL.  FOR TEMPERATURES...
WEDNESDAYS HIGHS ARE 1-2 C COOLER THAN TUESDAYS ACCORDING TO THE
THICKNESS GRIDS ON BOTH MODELS.  THURSDAY WARMS UP 3.5-7.0 C FROM
WEDNESDAY.

FOR THE LATER DAYS...FRIDAY THROUGH MONDAY...THE MODELS GENERALLY
HAVE SOUTHWESTERLY FLOW ALOFT FOR THE FORECAST AREA WITH WEAK UPPER
TROUGHINESS TO OUR IMMEDIATE WEST.  SOME OF THESE WEAKEN AND PUSH
CROSS THE FORECAST AREA THROUGH THE LAST FOUR DAYS.  WHAT MOISTURE
FIELDS THAT ARE AVAILABLE SHOW ENOUGH AROUND TO KEEP LIMITED LATE
DAY SHOWERS AND STORMS IN FOR ALL THE FORECAST AREA.  TEMPERATURES
LOOK AT OR SLIGHTLY ABOVE SEASONAL NORMALS.
&&

.AVIATION...ISOLATED STORMS POSSIBLE AT DIA THROUGH 04Z...WITH GUSTY
WINDS ALONG WITH BRIEF HEAVY RAIN. COULD BRIEFLY SEE MVFR CONDITIONS
AS THE STORMS PASS THROUGH. THEN A SLIGHT CHANCE OF RAIN SHOWERS
OVERNIGHT. FRONT TO MOVE ACROSS DIA BETWEEN 08Z AND 09Z WITH WIND
SHIFT TO THE NORTHWEST. BY 18Z EASTERLY UPSLOPE FLOW EXPECTED WITH
SCATTERED LIGHT RAIN SHOWERS EXPECTED ALONG WITH A SLIGHT CHANCE OF
A STORM.

&&

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

DL/RJK

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1104 AM MDT MON MAY 21 2007

COZ030>051-221200-
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-
1104 AM MDT MON MAY 21 2007

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

.DAY ONE...TODAY AND TONIGHT

THUNDERSTORMS WILL CONTINUE TO DEVELOP OVER THE MOUNTAINS THIS
AFTERNOON. ACROSS THE PLAINS...SCATTERED THUNDERSTORMS ARE
POSSIBLE...MOST NUMEROUS ALONG THE PALMER DIVIDE AND OVER THE
NORTHEAST BORDER AREA. GUSTY WINDS AND BRIEF HEAVY RAIN CAN BE
EXPECTED WITH THE STORMS. A FEW STORMS ON THE PLAINS COULD BECOME
SEVERE LATE THIS AFTERNOON AND EVENING...WITH HAIL UP TO AN INCH IN
DIAMETER POSSIBLE. THE GREATEST THREAT FOR SEVERE WEATHER WILL BE
EAST OF LINE FROM BRIGGSDALE THROUGH BYERS TO KIOWA LINE. A COLD
FRONT WILL MOVE THROUGH THE AREA LATE TONIGHT...WITH SCATTERED RAIN
SHOWERS MIXING WITH WET SNOW AT ELEVATIONS ABOVE 9000 FEET.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

A PACIFIC STORM SYSTEM WILL BRING A COLDER MORE MOIST AIRMASS TO THE
FORECAST AREA ON TUESDAY INTO WEDNESDAY.   IT WILL BE COLD ENOUGH
FOR SOME SNOW IN THE MOUNTAINS AND A MIX OF RAIN AND SNOW SHOWERS IN
THE FOOTHILLS.  IT WILL BE DRIER AND WARMER THE REST OF THE PERIOD
WITH A SLIGHT CHANCE OF THUNDERSTORMS EXPECTED EACH DAY IN THE
AFTERNOON AND EVENING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED AFTER 2 PM.