Tornadoes and Hail in Colorado, May 3 to 7, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
310 PM MDT THU MAY 3 2007

.SHORT TERM...STRONG PACIFIC COLD FRONT CONTINUES TO CHARGE ACROSS
THE MOUNTAINS THIS AFTERNOON AND WILL PUSH ACROSS THE URBAN CORRIDOR
IN THE NEXT FEW HOURS.  INCREASING THUNDERSTORMS AHEAD OF THE FRONT
AND HAVE UPPED POPS THIS EVENING MOST AREAS...THEN DECREASE FROM
WEST TO EAST WITH HIGHER POPS FARTHER EASTERN ZONES LATER THIS
EVENING.  A THREAT FOR SEVERE STORMS REMAINS AND MAY YET SEE A WATCH
FOR PORTIONS OF THE NORTHEAST AS DEWPOINTS CONTINUE TO CREEP UPWARDS
AND THERE HAS BEEN PLENTIFUL SUNSHINE THIS AFTERNOON.  TEMPERATURES
THO DO REMAIN RATHER COOL FARTHER TO THE EAST AS A RESULT OF
OUTFLOWING COOL AIR FROM THE BIG MASS OF CLOUDS AND PRECIP IN KS/OK.
SHEAR IS QUITE STRONG AND MAY BE TOO MUCH FOR THE MOISTURE PRESENT
BUT AT ANY RATE WOULD EXPECT HAIL AND STRONG WIND POTENTIAL WITH
STORMS THIS EVENING GIVEN THE STRONG FORCING WITH THE PACIFIC FRONT
AND ASSOCIATED UPPER LEVEL WAVE.  THERE HAS BEEN A DENVER
CONVERGENCE ZONE THIS AFTERNOON BUT IT CONTINUES TO MOVE TO THE
WEST/NORTHWEST AND THIS HAS KEPT ANY DEEP CONVECTION FROM DEVELOPING
ALONG IT.  SO THE MAIN FOCUS FOR STORMS WILL BE THE FRONT.  VERY
RAPID COOLING BEHIND THE FRONT WITH A LOT OF SNOW REPORTS IN WESTERN
WY AND IN UT AND PUT A FEW INCHES IN THE HIGH COUNTRY OVERNIGHT.
TOMORROW A COOLER DAY AND KEPT THE POPS CURRENTLY IN THE FORECAST AS
WE GRADUALLY GET INTO LOWER LEVEL NORTHEAST FLOW AS PRESSURES FALL
TO OUR WEST AHEAD OF THE STRONG SYSTEM COMING FOR THE WEEKEND.  THIS
SHOULD ALLOW FOR A THREAT OF AFTERNOON SHOWERS AND THUNDERSTORMS
THOUGH THE AMOUNT OF MOISTURE PRESENT IS THE BIG UNCERTAINTY FOR
TOMORROW BEFORE THINGS GET REALLY INTERESTING OVER THE WEEKEND.

.LONG TERM...MDLS CONTINUE TO DEPICT A LARGE UPPER LEVEL SYSTEM
ENTERING THE FOUR CORNERS REGION OVER THE WEEKEND.  AS IT MOVES
SOUTHEAST FM NRN UTAH...A DISTURBANCE WILL EJECT FROM THE PARENT UPR
LOW FRIDAY NIGHT INTO SATURDAY.  12Z MDLS...GFS IN PARTICULAR...
SPLITS QUITE A BIT OF ENERGY FM THE UPR SYSTEM AS THE LEAD
DISTURBANCE QUICKLY MOVE NORTHEAST INTO WY SATURDAY. ALTHOUGH IT IS
DIFFICULT TO LATCH ONTO TOO MANY DETAILS WITH THESE SPLITTING
TROFS...AM INCLINED TO BELIEVE BEST CHC FOR PRECIPITATION WILL
INITIALLY BE DURING THE FRIDAY NIGHT INTO SATURDAY TIMEFRAME.  HAVE
INCRSD POPS TO LIKELY IN THE MTNS WITH SCT POPS ELSEWHERE.

MEANWHILE AT THE SFC...CDFNT IS EXPECTED TO SLIDE INTO THE PLAINS
DURING THE AFTN.  TEMPS WILL BE QUITE COLD FOR THIS TIME OF YEAR
WITH TEMPS SATURDAY ONLY REACHING THE 40S ALG THE FNT RANGE.  DITTO
FOR SUNDAY.  THIS WOULD TRANSLATE INTO SOME PRETTY LOW SNOW LEVELS
...ARND 6000 FEET EXPECTED AT THIS TIME.  BUT LATER SHIFTS MAY NEED
TO ADJUST FOR LOWER SNOW LVLS AS THE TREND IS TWD COOLER TEMPS ALF.

UPPER LOW WL STALL OUT OVER THE FOUR CORNERS AS IT RMNS DIVORCED
FROM JET STREAM.  STILL LOOKING FOR AN EXTENDED PERIOD OF CLOUDY
SKIES...COOL TEMPS AND SCATTERED SHOWERS THROUGH MONDAY.  CHOSE TO
TRIM TEMPS BACK A LITTLE IN THE EXTENDED FORECAST BASED ON ALL THE
CLDS.  BY WEDNESDAY...STUBBORN TROUGH WL BE OUT OF THE AREA AND
WARMER TEMPERATURES ARE EXPECTED TO RETURN.

&&

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

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HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE DENVER CO
114 PM MDT THU MAY 03 2007

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-
114 PM MDT THU MAY 03 2007

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATER THIS AFTERNOON
AND THIS EVENING

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

.DAY ONE...TODAY AND TONIGHT

A STRONG PACIFIC COLD FRONT IS ENTERING NORTHWEST COLORADO AT THIS
TIME ASSOCIATED WITH A FAST-MOVING UPPER LEVEL WAVE.  THE COLD FRONT
WILL BE PUSHING ACROSS THE MOUNTAINS THIS AFTERNOON WITH AN
INCREASING THREAT OF THUNDERSTORMS...SOME OF WHICH COULD PRODUCE
SMALL HAIL AND GUSTY WINDS.  THE MAIN SEVERE THREAT WILL OCCUR AS
THE FRONT EMERGES ONTO THE PLAINS LATE THIS AFTERNOON AND THEN
TRACKS ACROSS NORTHEAST COLORADO THIS EVENING.  VERTICAL WIND SHEAR
WILL BE INCREASING AS THE UPPER LEVEL TROUGH APPROACHES AND WILL BE
SUFFICIENT TO SUPPORT ORGANIZED STORMS AND POTENTIALLY A FEW
SUPERCELLS ON THE NORTHEAST PLAINS.  THE LIMITING FACTOR AT THE
MOMENT IS THE AMOUNT OF LOW LEVEL MOISTURE WITH DEWPOINTS IN THE MID
40S.  HOWEVER...WITH INCREASING SOUTH TO SOUTHEAST FLOW ON THE
PLAINS LOW LEVEL MOISTURE IS EXPECTED TO INCREASE.  ANOTHER LIMITING
FACTOR IS THE PRESENCE OF COOLER AIR EAST OF LIMON AS A RESULT OF A
COMBINATION OF CLOUDINESS AND COOL LOW LEVEL AIR FROM A SLOW-MOVING
COMPLEX IN OKLAHOMA.  THIS SYSTEM SHOULD SHIFT EASTWARD ENOUGH TO
ALLOW MORE WARMING BY THE TIME THE FRONT REACHES MORE EASTERN
SECTIONS AFTER 6 PM.

AT THIS TIME ENOUGH FACTORS FAVOR A POTENTIAL FOR SEVERE STORMS WITH
THE MOST LIKELY SEVERE WEATHER LARGE HAIL AND STRONG WINDS.
ISOLATED TORNADOES ARE POSSIBLE IF STORMS BECOME SUFFICIENTLY
ORGANIZED OVER THE NORTHEAST PLAINS.  CURRENTLY THERE IS A DENVER
CONVERGENCE ZONE IN PLACE BUT THIS IS LIKELY TO WASH OUT AS THE
SOUTHEAST FLOW INCREASES AND AT THIS POINT IS NOT EXPECTED TO BE A
MAJOR PLAYER IN SEVERE WEATHER TODAY BUT WILL HAVE TO BE MONITORED.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

A BROAD TROUGH OF LOW PRESSURE WILL SIT OVER THE WEST SLOPE
THROUGHOUT THE WEEKEND INTO THE FIRST PART OF NEXT WEEK.  THIS WILL
LEAD TO COOL AND UNSETTLED WEATHER FOR SEVERAL DAYS. AT THIS
TIME...IT APPEARS THE MOUNTAINS MAY RECEIVE SEVERAL INCHES OF SNOW
SATURDAY AND SUNDAY...MAINLY WEST OF THE DIVIDE.  FOR THE REMAINDER
OF THE DISTRICT...SOME SHOWERS ARE EXPECTED...MAINLY SATURDAY.
TEMPERATURES WILL BE VERY COOL WITH MAX TEMPERATURES ONLY IN THE 40S
AND 50S ACROSS THE PLAINS THIS WEEKEND.  THE SYSTEM IS EXPECTED TO
SLOWLY PULL OUT THE AREA WITH WARMER AND DRIER WEATHER RETURNING BY
WEDNESDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE REQUIRED AFTER 3 PM AND STORMS FARTHER
EAST COULD CONTINUE WELL AFTER DARK.

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