Severe Thunderstorm Warning 155, NWS Denver/Boulder, CO

NORTHEAST AND NORTH CENTRAL COLORADO AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DENVER COLORADO
315 AM MDT MON SEP 17 2001

WATER VAPOR AND LIGHTNING PLOTS SHOW A PRETTY HEALTHY SHORT WAVE
MOVING OUR WAY TODAY.  SOME SHOWERS WERE ALREADY MOVING ACROSS THE
MOUNTAINS AT 09Z...AND THESE WILL BECOME MORE WIDESPREAD DURING THE
DAY AND THROUGH THE EVENING AS UPWARD Q-G FORCING WITH SHORT WAVE
ACTS EFFICIENTLY ON MOIST AND MODERATELY UNSTABLE AIRMASS.  IN
ADDITION...WEAK UPSLOPE COMPONENT WILL DEVELOP OVER THE PLAINS
AS HIGH PRESSURE SINKS THROUGH THE NORTHERN AND CENTRAL PLAINS AND
DIURNAL PRESSURE FALLS INCREASE OVER THE SAN LUIS VALLEY AND
NORTHERN NEW MEXICO.  WILL THEREFORE BUMP UP POPS IN/NEAR THE
MOUNTAINS TO LIKELY TODAY AND ACROSS MOST OF THE PLAINS TONIGHT AS
WAVE MOVES SLOWLY EASTWARD.  IN THE MOUNTAINS...SNOW LEVEL EXPECTED
TO DROP TO 10 THOUSAND FEET WITH 700 MB TEMPS DROPPING TO ABOUT 4C.
SNOW MODEL SUGGESTS A COUPLE INCHES AND SEE NO REASON TO ARGUE.

AREAS OF FOG OVER THE PLAINS ARE EXPECTED TO LIFT SLOWLY THIS
MORNING WITH ALL THE CLOUDS ON TOP.  THAT WILL ALSO KEEP TEMPS QUITE
COOL SO WILL SHAVE A DEGREE OR TWO OFF GUIDANCE.

NOT SURE HOW MUCH PRECIP WILL LINGER INTO TUESDAY BUT AT THIS TIME
APPEARS BEST POPS WILL BE CONFINED TO THE NORTHEAST CORNER AS SHORT
WAVE CONTINUES TO MOVE SLOWLY EASTWARD.  WITH SOME SUNSHINE AND LOW
LEVEL DESTABILIZATION BEHIND TROF AXIS WE MAY STILL BE ABLE TO POP A
FEW SHOWERS UP TO OR THROUGH THE SUBSIDENCE INVERSION.  DUE TO
AMOUNT OF SUBSIDENCE WILL LOWER POPS TO ISOLATED IN MOUNTAINS WITH
DIMINISHING WORDING ON THE PLAINS.

MRF ADVERTISES A WEAK SHORT WAVE APPROACHING LATE THURSDAY WITH SOME
INCREASE IN MOISTURE WHICH REMAINS IN PLACE THROUGH FRIDAY.  WILL
LET DAY SHIFT ADD THIS CHANCE TO THE EXTENDED IF OTHER MODELS
SUPPORT.

BARJENBRUCH

.DEN...NONE.

COZ030>051-172000-

HAZARDOUS WEATHER OUTLOOK FOR NORTHEAST AND NORTH CENTRAL COLORADO
NATIONAL WEATHER SERVICE DENVER CO
1100 AM MDT MON SEP 17 2001

THIS OUTLOOK PERTAINS TO THE FOLLOWING COLORADO COUNTIES

ADAMS     ARAPAHOE     BOULDER   CLEAR CREEK   DENVER       DOUGLAS
ELBERT    GILPIN       GRAND     JACKSON       JEFFERSON    LARIMER
LINCOLN   LOGAN        MORGAN    PARK          PHILLIPS     SEDGWICK
SUMMIT    WASHINGTON   WELD

SYNOPSIS...AN UPPER LEVEL TROUGH WILL MOVE ACROSS THE FORECAST AREA
THIS AFTERNOON AND TONIGHT.  AS SURFACE LOW PRESSURE DEEPENS OVER
NORTHEASTERN NEW MEXICO...LOW LEVEL UPSLOPE FLOW WILL STRENGTHEN
AND CONTINUE TO PUSH MOISTURE AGAINST THE EAST FACE OF THE MOUNTAINS.
THE INSTABILITY CREATED BY THE APPROACH OF THE UPPER TROUGH WILL ALLOW
SHOWERS AND THUNDERSTORMS TO FORM OVER THE MOUNTAINS AND OVERRIDE THE
COOLER AIR MASS IN PLACE OVER MOST OF THE NORTHEASTERN PLAINS.  WHILE
AMPLE SHEAR WILL BE PRESENT FOR ISOLATED SEVERE THUNDERSTORMS TO
FORM...CLOUDINESS OVER MUCH OF THE NORTHEASTERN PLAINS WILL PREVENT
MUCH OF THE NECESSARY HEATING TO OCCUR.  HOWEVER...SATELLITE IMAGERY
THIS MORNING SHOWS EROSION OF THE CLOUD DECK ESPECIALLY OVER THE PALMER
DIVIDE WHICH WILL ALLOW SUFFICIENT SURFACE HEATING THIS AFTERNOON FOR
POSSIBLE SEVERE THUNDERSTORM DEVELOPMENT THERE.

SCATTERED SHOWERS WITH EMBEDDED ISOLATED THUNDERSTORMS WILL CONTINUE TO
FORM OVER THE MOUNTAINS AND MOVE OFF THE FOOTHILLS OVER THE URBAN
CORRIDOR AND NORTHEASTERN PLAINS THROUGH THE AFTERNOON AND EVENING.
THE SHOWERS AND THUNDERSTORMS WILL INCREASE IN STRENGTH AND COVERAGE
LATER THIS AFTERNOON AND INTO THE EVENING.  ISOLATED SEVERE
THUNDERSTORMS WILL FORM OVER THE PALMER DIVIDE.  THESE STORMS MAY
PRODUCE LARGE HAIL...DAMAGING WINDS AND BRIEF HEAVY RAIN.
SPOTTER ACTIVATION WILL NOT BE REQUIRED.

ON TUESDAY...SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS DURING THE
MORNING WILL DECREASE BY AFTERNOON AND EVENING.

GARD...WFO BOULDER