Issued by NWS Grand Junction, CO
000 FXUS65 KGJT 070924 AFDGJT AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE GRAND JUNCTION CO 324 AM MDT THU MAY 7 2009 .SHORT TERM...TODAY THROUGH FRIDAY NIGHT... A SHORTWAVE TROUGH WILL MOVE THROUGH THE NORTHERN ROCKIES TODAY... COMPRESSING THE PRESSURE GRADIENT ENOUGH TO CAUSED INCREASED SURFACE WINDS THIS AFTERNOON. THE TAIL END OF THE SURFACE FRONT ASSOCIATED WITH THIS FEATURE WILL DRAG THROUGH THE FORECAST AREA FRIDAY. THERE IS VERY LITTLE MOISTURE ASSOCIATED WITH IT...SO ONLY ISOLATED THUNDERSTORMS ARE POSSIBLE OVER THE NORTHERN MOUNTAINS THIS AFTERNOON...SPREADING TO THE CENTRAL COLORADO MOUNTAINS FRIDAY AFTERNOON. THESE SHOULD BE DRY WITH GUSTY WINDS...ESPECIALLY FRIDAY AFTERNOON. MAX TEMPERATURES WILL REMAIN WARMER THAN NORMAL TODAY. ON FRIDAY THE SURFACE WINDS SHOULD INCREASE A BIT MORE AS THE WEAK FRONTAL FEATURE MOVES THROUGH THE AREA. MORE CLOUD COVER AND A BIT OF COLD ADVECTION WILL COOL OFF MAX TEMPS A FEW DEGREES AS WELL. .LONG TERM...SATURDAY THROUGH THURSDAY... MADE FEW CHANGES TO THE FORECAST AS ZONAL PATTERN PERSISTS. A DRY WEST FLOW WILL CONTINUE THROUGH THE LONG TERM PERIOD. A SERIES OF WAVES WILL MOVES ACROSS THE TOP OF A BROAD FLAT RIDGE THAT EXTENDS FROM WELL OFF THE SOUTHERN COAST OF CA ACROSS THE DESERT SOUTHWEST AND NORTHERN MEXICO. THESE IMPULSES WILL RIDE OVER THE TOP OF THE RIDGE. BUT WILL HAVE LITTLE EFFECT ON OUR PRACTICAL WEATHER...EXCEPT FOR AN INCREASE IN CLOUDS...WINDS AND A SLIGHT CHANCE OF MOUNTAIN SHOWERS OVER THE NORTH. THE FIRST IMPULSE DURING THIS PERIOD WILL PASS NORTH OF THE AREA SAT NIGHT. ISOLATED SHOWERS ARE POSSIBLE OVER THE HIGHER TERRAIN...BUT THE 00Z GFS PUTS THE BEST TIMING OVERNIGHT SO IT WILL GET NO DIURNAL HELP. SUNDAY SHOULD BE A LITTLE COOLER AS A RESULT. THEN AS THE PERIOD PROGRESSES...MODEL TIMING AND HANDLING GETS MORE PROBLEMATIC WITH EACH WEAK SHORTWAVE. THE GFS TREND HAS BEEN TO INTRODUCE A DEEPER WAVE ALONG THE COAST OR INTO THE GREAT BASIN TOWARDS THE END OF THE PERIOD OR BEYOND. AND THEN SUBSEQUENT RUNS FLATTEN THE FLOW AND TAKE MOST THE ENERGY ALONG THE U.S./CANADIAN BORDER. THE ECMWF HAS CONSISTENTLY KEPT A LESS AMPLIFIED SOLUTION. SO WILL MAKE FEW CHANGES TO THE DRY AND PERSISTENT FORECAST WITH ABOVE NORMAL TEMPS AND BREEZY AFTERNOONS. && .AVIATION... VFR CONDITIONS EXPECTED THROUGH FRIDAY. AREAS OF TURBULENCE OVER THE MOUNTAINS CAN BE EXPECTED DUE TO MODERATE WEST-NORTHWEST WINDS ALOFT. && .HYDROLOGY... WARM TEMPERATURES THIS WEEK WILL CONTINUE TO PROMOTE SNOWMELT IN THE MOUNTAINS OF WESTERN COLORADO AND EASTERN UTAH. FLOWS TODAY AND FRIDAY ALONG THE YAMPA RIVER...WHITE RIVER...LITTLE SNAKE RIVER AND ELK RIVER...WILL GENERALLY REMAIN STEADY WITH ONLY SMALL FLUCTUATIONS DUE TO DIURNAL TEMPERATURE CHANGE AND ITS EFFECT ON SNOWMELT RATES. WITH WARMER THAN NORMAL TEMPERATURES FOCUSED OVER CENTRAL COLORADO... SOUTHERN COLORADO AND SOUTHEASTERN UTAH...RIVERS IN THESE AREAS WILL SEE FLOW INCREASES THROUGH SATURDAY AS SNOWMELT INCREASES. THE ROARING FORK RIVER...FRYING PAN RIVER...CRYSTAL RIVER...EAGLE RIVER...PLATEAU CREEK...AND COLORADO RIVER WILL SEE STAGE INCREASES OF 1 TO 2 FEET BY THIS WEEKEND. ACROSS SOUTHWESTERN COLORADO THE GUNNISON RIVER...SAN MIGUEL RIVER...DOLORES RIVER...ANIMAS RIVER... AND SAN JUAN RIVERS WILL SEE STAGE INCREASES OF UP TO 1 FOOT. CAUTION SHOULD BE EXERCISED NEAR THE BANKS OF STREAMS AND RIVERS EXPERIENCING HIGHER FLOWS. HIGH FLOWS CAN ERODE AND WEAKEN RIVER BANKS MAKING THEM SUSCEPTIBLE TO COLLAPSING. && .GJT WATCHES/WARNINGS/ADVISORIES... .CO...NONE. .UT...NONE. $$ SHORT TERM.....CJC LONG TERM......JOE+ELH AVIATION.......JDC/CJC HYDROLOGY......BAL/CJC
