Severe Thunderstorm Warning 57, NWS Denver/Boulder, CO

NORTHEAST AND NORTH CENTRAL COLORADO AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
245 PM MDT MON MAY 26 2003

SHORT TERM DISCUSSION: SCTD TSTORMS FIRING OVER AND ALONG THE FRONT
RANGE STILL ON THE 35-50 DBZ REFLECTIVITY RANGE ATTM. ALTHOUGH
SHOULD SEE CELLS INTENSIFYING AS THEY MOVE SLOWLY SEWRD OVR THE I-25
URBAN CORRIDOR...PARK AND WELD COUNTIES IN NEXT 1-2 HRS. 12Z/MM5
INDICATED MLCAPE VALUES IN THE 900-1250 J/KG RANGE THIS AFTN ALONG
THE FRONT RANGE...WHILE THE 20KM ETA GIVES MLCAPE VALUES FOR THE
SAME AREA IN THE 1600-2150 J/KG RANGE FOR SAME PD. UNFORTUNATELY
MUCH OF THIS ENERGY MIGHT REMAIN UNTAPPED SHOULD EXPANDING OVERCAST
PREVENT ANY ADDITIONAL HEATING. EVEN SO BLV STORMS FIRING OVR THE
FOOTHILLS AND CHEYENNE RIDGE WILL GENERATE OUTFLOW BNDYS STG ENOUGH
TO PRODUCE A FEW STG/SVR T-STORMS ON THE ADJACENT HIGH PLAINS. HAIL
AND DAMAGING TSTORM WINDS OUR MAIN CONCERN. WITH DERIVED
PRECIPITABLE WATER VALUES IN THE 0.70-0.80 INCH RANGE AND SFC DEW
POINTS IN THE LWR/MID 50S...COULD ALSO SEE 1-HR RAINFALL RATES APCHG
AN INCH...WITH EVEN GREATER RATES FM SLOW MOVG STORMS FORMING ERLY
THIS EVE OVR SRN FTHLS AND ON THE MONUMENT RIDGE ALONG A NEARLY
STATIONARY WIND CNVGNC BNDRY.  MM5 SHOWS THIS BNDRY STRETCHING NEWRD
ACRS XTRM SRN DOUGLAS...SERN ERN ELBERT AND NRN LINCOLN CTYS THRU
MID-EVE. 0-3KM SHEAR/HELICITY MAY BE ENOUGH IN THIS REGION TO ALSO
PRODUCE A FEW LANDSPOUTS FROM NON-SUPERCELL TSTORMS. OVRNIGHT SKIES
GO MOCLEAR XCPT ON THE NERN PLAINS WHERE WE COULD SEE LOW CLOUDS AND
PATCHY FOG FORMING WITH SELY LOW-LVL FLOW AFTER MIDNIGHT. TUESDAY
ATMOSPHERE NOT LOOKING AS WET NOR AS UNSTABLE...ALTHOUGH MODELS
HINTING AT PASSAGE OF WEAK MID-LVL WAVE EMBEDDED WITHIN MODERATE
NWLY FLOW ALOFT BTWN 18Z-21Z.  AT SAME TIME BNDRY LYR WINDS ON THE
PLAINS GO NELY. ISOLATED AFTN/EVE T-STORM COVERAGE IN CURRENT FCST
PCKG LOOKS GOOD FOR TOMORROW...ALTHOUGH THE CHANCE FOR MEASURABLE
RAINFALL AND LIGHTNING LOOKS SLIGHTLY BETTER IN THE FRONT RANGE
FTHLS.  BAKER

LONG TERM DISCUSSION: MAIN QUESTION IS DETAILS ABOUT THE STRENGTH OF
THE RIDGE TOWARD THE END OF THE PERIOD.  ECMWF IS WEAKER WITH THE
SHORTWAVES COMING OVER THE TOP OF THE RIDGE.  THIS IMPLIES LESS
COOLING IN THE FRI/SAT TIME FRAME AND KEEPS MOISTURE SUPPRESSED MORE
THAN GFS.  IT THEN HAS MORE WESTERLY FLOW UNDERCUTTING THE RIDGE
OVER THE WEEKEND WHICH COULD BRING SOME MOISTURE UP FROM THE SW.
GFS MEANWHILE HAS A DECENT SHOT OF COOL AIR ON THE PLAINS FRI...THEN
REBUILDS THE RIDGE MORE STRONGLY OVER THE WEEKEND...WHICH COULD BE
TRENDING US BACK TOWARD A STRONGER CAP AND MORE HEAT.  DROPPED
TEMPERATURES A BIT WED...THEN RAISED THEM THU IN ACCORDANCE WITH
MODEL TRENDS.  BROADBRUSH FORECAST AFTER THAT...NOT SHOWING AS MUCH
COOLING AS THE GFS WOULD IMPLY STILL THINKING THAT THE WAVE PASSING
NORTH OF US MAY BE WEAKER OR FARTHER NORTH.  I SUSPECT THE LOW LEVEL
COOLING WILL BE MORE THAN ALOFT AND WILL OFFSET ANY MOISTURE
INCREASE...BUT ENOUGH UNCERTAINTY FOR THE SLIGHT CHANCE OVER THE
WEEKEND.     GIMMESTAD

.DEN...NONE.

COZ030>051-271200-

HAZARDOUS WEATHER OUTLOOK...CORRECTED TYPOS AND FORMAT
NATIONAL WEATHER SERVICE DENVER CO
1120 AM MDT MON MAY 26 2003

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

.DAY ONE...TODAY AND TONIGHT

SHOWERS AND THUNDERSTORMS SHOULD BEGIN FORMING OVER THE FRONT RANGE
BY NOON...AND OVER THE CHEYENNE RIDGE NORTH OF FORT COLLINS BETWEEN
1 AND 2 PM. LIGHT WINDS ALOFT SHOULD THEN MOVE THESE STORMS
SOUTHEAST OVER THE INTERSTATE 25 CORRIDOR WHERE SURFACE DEW POINTS
IN THE LOWER TO MID 50S AND STEEP LAPSE RATES WILL AID IN PRODUCING
STRONG THUNDERSTORM UPDRAFTS. A FEW THUNDERSTORMS ALONG THE I-25
CORRIDOR TO AS FAR EAST AS GREELEY MAY BECOME SEVERE BETWEEN 3 AND 6
PM. HAIL UP TO 3/4 INCH IN DIAMETER AND WIND GUSTS TO 60 MPH ARE
POSSIBLE. THESE SLOW MOVING STORMS MAY ALSO PRODUCE RAINFALL RATES
UP TO AN INCH PER HOUR.

THIS EVENING THUNDERSTORM ACTIVITY IS EXPECTED TO SHIFT SOUTH OVER
THE MONUMENT RIDGE OF EASTERN DOUGLAS...ELBERT AND LINCOLN COUNTIES
WHERE A FEW STORMS MAY BECOME SEVERE. SLOW MOVING STORMS FORMING
ALONG A WIND CONVERGENCE BOUNDARY IN THIS AREA WILL ALSO BE CAPABLE
OF RAINFALL RATES OF 2 TO 2 1/2 INCHES PER HOUR. SOME FLOODING OF
LOW LYING AREAS IS THEREFORE POSSIBLE.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

THERE WILL STILL BE A SLIGHT CHANCE OF AFTERNOON AND EVENING
THUNDERSTORMS ON TUESDAY...MAINLY OVER THE FOOTHILLS AND THE I-25
CORRIDOR.  THE THREAT OF SEVERE WEATHER WITH THESE STORMS WILL BE
LOW.  AN UPPER LEVEL RIDGE WILL THEN MOVE OVER COLORADO...WITH A LOW
THREAT OF THUNDERSTORM ACTIVITY RETURNING FOR THE WEEKEND.

.SPOTTER INFORMATION STATEMENT...

STORM SPOTTER ACTIVATION MAY BE NECESSARY AFTER 3 PM TODAY. SHOULD
CONVECTION DEVELOP SOONER THAN EXPECTED IN THE NORTHERN FOOTHILLS
AND ALONG THE CHEYENNE RIDGE...SPOTTER ACTIVATION MAY BE NEEDED
SOONER.

BAKER/GIMMESTAD