Severe Thunderstorm Warning 19, NWS Grand Junction, CO

WESTERN COLORADO & EASTERN UTAH AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
230 PM MDT TUE AUG 14 2001

TROUGH AXIS SITUATED OVER NORTHWEST COLORADO WILL CONTINUE TO SHIFT
EASTWARD AND SHUNT DEEPER MONSOONAL MOISTURE AWAY.  NORTHWEST FLOW
BEHIND TROUGH WILL ADVECT DRIER AIR ACROSS THE FORECAST AREA.. MODEL
DATA INDICATE PRECIPITABLE WATER LOWERING TO AROUND 0.5 BY WEDNESDAY
AFTERNOON.  THIS TREND ACCEPTABLE AS WATER VAPOR IMAGERY SHOWS DRIER
AIR OVER NEVADA AND WESTERN UTAH.  SUBSIDENCE AND DRIER AIR WILL DO
BATTLE WITH STRONG SURFACE HEATING AND INSTABILITY WEDNESDAY
AFTERNOON.  ETA MODEL HINTS AT MINOR COLD ADVECTION TO WEAKEN ANY
CAPPING MID LEVEL INVERSION THAT FORMS BEHIND TROUGH AXIS.  WILL GO
ALONG WITH MOS GUIDANCE POPS NEXT TWO DAYS.. IE.. SCATTERED SHOWERS
IN THE MOUNTAINS WITH ISOLATED ACTIVITY IN THE LOWER VALLEYS.
WEATHER PATTERN APPEARS SIMILAR FOR THURSDAY AS LIGHT NORTHWEST FLOW
PERSISTS WITH EMBEDDED IMPULSES.  LOWER LEVEL MOISTURE WILL BE
SUFFICIENT TO KEEP SCATTERED THUNDER THREAT ONGOING INTO THURSDAY.
FRISBIE

EXTENDED:  MODELS FAIRLY CONSISTENT IN MOVING HIGH PRESSURE EAST...
WITH THE RIDGE AXIS REACHING CENTRAL CO BY MONDAY.  ONCE THE
AXIS IS EAST OF US...SOUTHERLY FLOW WILL CARRY SUBTROPICAL MOISTURE
OVER THE FORECAST AREA. UNTIL THEN NORTHWEST FLOW WILL TEND TO KEEP
AREA RELATIVELY DRY. HOWEVER WILL KEEP A SLIGHT CHANCE DOWN SOUTH
THROUGH THE WEEKEND JUST BECAUSE MOISTURE WILL REMAIN MORE ABUNDANT
THERE. DIURNAL HEATING WILL BE ENOUGH FOR AT LEAST A FEW
THUNDERSTORMS EACH AFTERNOON AND EVENING. THEN ON MONDAY...WILL BACK-
PEDAL A BIT IN INTRODUCING POPS OVER THE NORTH. FEEL IT WILL TAKE A
DAY OR SO FOR THE MONSOONAL MOISTURE TO MAKE ITS WAY UP TO THE
NORTHERN ZONES. BUT BY TUE...WILL PRETTY MUCH COVER FORECAST AREA
WITH SLIGHT CHANCE TO CHANCE.

.GJT...NONE.