HAMweather.com Area Forecast Discussion for County Warning Area GJT

Thu, 16 Feb 2012 07:28:20 GMT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND JUNCTION CO
957 PM MST WED FEB 15 2012

.SHORT TERM...(THIS EVENING THROUGH THURSDAY) ISSUED AT 157 PM
MST WED FEB 15 2012

WATER VAPOR IMAGERY SHOWING FAIRLY WELL DEFINED DEFORMATION ZONE
EXTENDING ACROSS CENTRAL UTAH INTO SOUTHWEST WYOMING THIS
AFTERNOON. THIS AREA OF WEAK ASCENT IS ALSO CORRELATED WITH
MOISTURE CONVERGING FROM SOUTHERLY FLOW AROUND THE LOW DRIFTING
SOUTHWARD ALONG THE CALIFORNIA AND NEVADA BORDER...AND ANOTHER
LINK TO MOISTURE PUSHING AHEAD OF A NORTHERN ROCKIES SHORTWAVE.
PWATS OVER WESTERN COLORADO INTO THE NORTHERN GREAT BASIN AND
NORTHERN ROCKIES ARE RUNNING NEAR A THIRD OF AN INCH...WHICH IS
CLOSE TO 150 PERCENT OF NORMAL. 

THE BULK OF THE SHOWERS HAVE BEEN CONCENTRATED MAINLY ACROSS THE
NORTHERN CWA WHERE WEAK UPGLIDE WAS COMBINING WITH THE ASCENT AND
MOISTURE CLOSER TO THE ABOVE MENTIONED DEFORMATION ZONE. HOWEVER
AS SEEN THE PAST FEW DAYS THE COOLER AIR ALOFT IS ADDING MORE OF A
CONVECTIVE ELEMENT THE PRECIPITATION THROUGH THE AFTERNOON HOURS.
EXPECT THE CONVECTION TO WANE NEAR SUNSET WITH THE BEST CHANCES OF
LINGERING SHOWERS REMAINING FOCUSED OVER THE NORTHERN MOUNTAINS
AND HIGH VALLEYS THROUGH MIDNIGHT UNDER THE DEFORMATION ZONE
WHICH WILL CONTINUE TO BE STRETCHED AND WEAKEN THROUGH THE NIGHT.
WILL RUN WITH PERSISTENCE ASSOCIATED WITH THE NEW SNOW COVER
ACROSS THE NORTH AND PUT IN PATCHY FOG OVER THE NORTHERN
VALLEYS...WHICH IS HINTED AT SOMEWHAT BY THE SREF PROBABILITIES.

A TRAILING SHORT WAVE ASSOCIATED WITH A PLAINS TROF WILL BE
SWINGING TOWARD THE NORTHERN COLORADO BORDER AS IT SHEARS APART ON
THURSDAY. WITH MOISTURE DECREASING AS WELL...FEEL ONLY ISOLATED TO
WIDELY SCATTERED SNOW SHOWERS WILL BE POSSIBLE OVER THE
MOUNTAINS...MAINLY DUE TO AFTERNOON INSTABILITY. HOWEVER WITH
FAVORABLE WESTERLY FLOW AND RESIDUAL MOISTURE...WILL FAVOR THE
HIGHER END OF THE POPS ACROSS THE NORTHERN AND CENTRAL MOUNTAINS. 

.LONG TERM...(THURSDAY NIGHT THROUGH WEDNESDAY) ISSUED AT 157 PM MST
WED FEB 15 2012

AN UPPER CLOSED LOW PRESSURE SYSTEM WILL BE LOCATED NEAR NRN BAJA 
PENINSULA THURSDAY EVENING. THIS STORM WILL SHIFT EASTWARD ACROSS 
NRN MEXICO LATE THURSDAY NIGHT AND FRIDAY WITH MINIMAL IMPACT ON OUR 
CWA. MEANWHILE WE WILL BE UNDER A WEAK DEFORMATION ZONE THURSDAY 
NIGHT AND TRANSITION TO A NWRLY FLOW FRIDAY AFTERNOON. SOME 
INSTABILITY WILL BE PRESENT FRIDAY AFTERNOON AS COLD ADVECTION 
STEEPENS LAPSE RATES ALLOWING FOR ISOLATED SHOWERS ACROSS THE NRN 
MTNS. HEIGHTS WILL RISE FRIDAY NIGHT AND SATURDAY AS A TRANSIENT 
RIDGE OF HIGH PRESSURE BUILDS AHEAD OF A DEEP CLOSED LOW THAT MOVES 
INTO THE PACIFIC NW STATES. THE FLOW ALOFT OVER OUR REGION WILL 
BEGIN TO BACK TO THE SOUTHWEST SAT AFTERNOON AS THE LOW PRESSURE 
SYSTEM MOVES EWRD TOWARD THE GRT BASIN. THIS WILL ALSO BRINGING 
WARMING ALOFT AND AT THE SURFACE AS WELL AS GENERALLY DRY 
CONDITIONS. 

THE ABOVE MENTIONED CLOSED LOW OPENS TO A LONG WAVE TROF AND MOVES 
EASTWARD INTO THE GRT BASIN SATURDAY NIGHT AND SUNDAY. MEANWHILE 
CLOUD COVER WILL INCREASE AND THICKEN WITH PRECIP SPREADING EASTWARD 
INTO THE CWA SUNDAY. AT THIS TIME MED RANGE MDLS IN VERY GOOD 
AGREEMENT AND IT APPEARS TO BE A FAIRLY POTENT STORM SYSTEM WITH THE 
POTENTIAL FOR WIDESPREAD PRECIP. WOULDNT BE SURPRISED IF HIGHLIGHTS 
BECOME NECESSARY. THE EC PUSHES THIS TROF EASTWARD SUNDAY NIGHT 
WHILE THE GFS HOLDS THE TROF OVER THE INTERMTN WEST. BLENDED POPS 
FAVOR THE EC AND THIS APPEARS TO BE A GOOD CHOICE AS FREQUENTLY THE 
GFS COMES AROUND TO THE EC SOLUTION. 

A NORTHWESTERLY FLOW WILL BE OVER THE REGION TUE/WED WITH LONG WAVE 
TROF TO OUR EAST. EMBEDDED SHRT WVS IN THE FLOW PROMISES A CHANCE OF 
SHOWERS...MOSTLY CONFINED TO THE MTNS ACROSS THE NORTH. 

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 954 PM MST WED FEB 15 2012

VFR CONDITIONS ARE EXPECTED AT ALL TAF SITE TONIGHT THROUGH
THURSDAY. ISOLATED SNOW SHOWERS OR FLURRIES WILL STILL BE POSSIBLE
NORTHWEST OF KVEL FOR LOCAL CIGS BKN025...BUT THESE FLURRIES WILL
DISSIPATE OVERNIGHT AND CIGS WILL LIFT AND BECOME SCATTERED.

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...NONE.
UT...NONE.