Tornado and Hail in Colorado, May 7, 2003

NORTHEAST AND NORTH CENTRAL COLORADO AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER CO
315 AM MDT WED MAY 7 2003

SHORT TERM DISCUSSION...AN INCREASE IN THUNDERSTORM COVERAGE CAN BE
EXPECTED ACROSS THE CWA DURING THE NEXT 24 HOURS. SEVERAL FACTORS
COMING TOGETHER FOR EVEN ISOLD SEVERE STORMS ACROSS NERN CO LATER
TDY AND THIS EVENING. BROAD UPPER LEVEL TROF ACROSS CENTRAL PORTIONS
OF CA AND NEVADA AND ASSOCD 110KT JET CORE WILL LIFT TO THE NE
ACROSS NERN CO THIS AFTN AND TNT PROVIDING FOR SOME SUPPORT ALOFT
FOR STORMS LATER TDY. IN ADDITION...INCREASING S-SE LOW LVL FLOW
WILL ADVECT SURFACE DEWPOINTS INTO THE LOWER AND MID 40S BY MIDDAY.
WITH THE SRLY FLOW...A DEN CYCLONE IS LIKLEY TO DEVELOP THIS MORNING
WITH A CONVERGENT BOUNDARY LIKELY TO SET UP JUST EAST OF THE DENVER
AREA. SHEAR PROFILE IN THE LOW LVLS STRENGTHENS DURING THE DAY WITH
STORM REL HELICITY VALUES OF 100-200 M2/S2. HOWEVER...ONLY MODERATE
INSTABILITY WILL TRY AND FACTOR AGAINST A MAJOR SEVERE WX DAY.
INTERACTIVE SOUNDINGS INDICATE CAPE VALUES ONLY BETWEEN 500-1000J/KG
AND POSSIBLY UP TO 1200J/KG OVER FAR NERN CO BY LATE IN THE DAY WITH
EVEN SOME SLIGHT WARMING ALOFT.

MAIN THREATS WILL BE LARGE HAIL AND A FEW WEAK TORNADOES FORMING
ALONG THE DEN COVERGENCE ZONE AND FURTHER EAST WITH THE STRONG SHEAR
PROFILE IN THE LOW LVLS. SPC HAS ALREADY TARGETED ERN CO FOR ISOLD
SEVERE AND THIS LOOKS FINE. CURRENTS FCSTS SEEM IN GOOD SHAPE AND
ALREADY HAVE SEVERE MENTIONED ACROSS FAR NERN CO. WILL PROBABLY ADD
A FEW MORE ZONES FOR SEVERE AND ADJUST TIMING/POPS.

NOT MUCH IN THE WAY OF STRATUS/FOG ATTM...EXCEPT ACROSS PTNS OF
SERN CO. LOW T/TD SPREADS ACROSS MUCH OF NERN CO SO WILL AT LEAST
KEEP SOME PATCHY FOG THIS AM. PROBABLY A LITTLE MORE HEATING THEN
PREVIOUSLY EXPECTED WITH LACK OF EARLY AM CLOUD COVER AND WILL BUMB
TEMPS UP SLIGHTLY. ENTREKIN

LONG TERM DISCUSSION...UNSETTLED PATTERN CONTINUES WITH SEVERAL WEAK
RIPPLES IN THE JET PASSING OVER OR JUST SOUTH OF US.  MAIN TROUGH
PASSES ABOUT SATURDAY.  LOTS OF QUESTIONS ABOUT THE DETAILS BUT WITH
GENERALLY SUBTLE FEATURES IT MAY NOT MAKE A LOT OF DIFFERENCE.
SLIGHT DRYING IN STORE THURSDAY AFTERNOON AND NIGHT.  FRIDAY SEEMS
TO BE THE MAIN QUESTION AS THE UPSTREAM SYSTEM MAY BEGIN TO SPREAD
SOME LIFT AND COOLING ALOFT AND ALSO PRODUCE UPSLOPE WINDS.  MODEL
CONSENSUS IS A SLOW ENOUGH TO HOLD THIS OFF UNTIL FRI NIGHT...WHICH
COULD PRODUCE A DAY WITH ONLY SHALLOW CONVECTION.  GIVEN THAT THERE
IS SOME UNCERTAINTY AND THERE WOULD LIKELY STILL BE A FEW
SHOWERS...I WILL LEAVE THIS FOR THE TIME BEING.  FOR SAT AND
BEYOND...GFS SEEMS IN THE MINORITY IN RUSHING A STRONG WAVE PAST US
AND KEEPING WESTERLY FLOW INTO THE EARLY PART OF THE WEEK.  OTHER
MODELS HAVE THE TROUGH GOING BY IN A COUPLE OF PIECES OVER THE
WEEKEND...THEN HAVING A BETTER DEFINED RIDGE AFTER THAT.  OUR
FORECAST IS MORE IN LINE WITH THIS CONSENSUS SO I WILL NOT MESS WITH
IT OTHER THAN TO TRIM HIGHS A BIT ON SAT.     GIMMESTAD

.DEN...NONE

COZ030>051-081200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE DENVER CO
1100 AM MDT WED MAY 7 2003

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

.DAY ONE...TODAY AND TONIGHT

SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER THE MOUNTAINS
AND EASTERN SLOPES AND SPREAD TO THE EAST ACROSS THE URBAN CORRIDOR
AND NORTHEASTERN PLAINS DURING THIS AFTERNOON AND EVENING.  A FEW
OF THESE STORMS MAY BECOME SEVERE WITH LARGE HAIL AND DAMAGING WINDS
ALONG WITH A POSSIBLE TORNADO.

AN UPPER LEVEL TROUGH MOVING ACROSS THE CENTRAL ROCKY MOUNTAINS
THIS AFTERNOON AND NIGHT WILL PROVIDE ADEQUATE INSTABILITY FOR
MODERATE TO STRONG THUNDERSTORM DEVELOPMENT.  WITH A LOW FREEZING
LEVEL LARGE HAIL WILL BE THE MOST LIKELY THREAT...BUT ADEQUATE
WIND SHEAR WILL BE PRESENT FOR SUPERCELL DEVELOPMENT AND POSSIBLE
TORNADO FORMATION.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

UNSETTLED WEATHER WILL CONTINUE THROUGH THE PERIOD AS A SERIES OF
WEATHER DISTURBANCES MOVE ACROSS THE STATE.  THERE WILL BE A CHANCE
OF SHOWERS AND THUNDERSTORMS EACH DAY...WITH SNOW SHOWERS POSSIBLE
IN THE HIGHER MOUNTAINS.  THE CHANCE OF SHOWERS APPEARS TO BE
GREATEST FRIDAY NIGHT AND SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATER THIS AFTERNOON AND EVENING.

GARD/COOPER