The best forecast information available is the NWS area forecast discussion:
(Western central mountains, ID)
SHORT TERM...TODAY THROUGH THURSDAY...FORECAST CHALLENGES CONTINUE
TO BE MAX TEMPERATURES AND PROBABILITIES AND COVERAGE OF AFTERNOON
AND EVENING THUNDERSTORMS BOTH TODAY AND THURSDAY. TODAY OUR AREA
WILL BE UNDER A RELATIVELY DRY SOUTHWEST FLOW ALOFT AHEAD OF A WEAK
SPLITTING UPPER LEVEL TROUGH WHICH WILL BE MOVING ONSHORE THIS
AFTERNOON. BOTH GFS AND ECMWF WANT TO CENTER THE SURFACE THERMAL
TROUGH IN NORTHWEST NEVADA THIS AFTERNOON. COMPARED TO THE
ECMWF...THE GFS CONFIGURES THE PRESSURE GRADIENT TO GIVE THE BEST
DOWN VALLEY FLOW ON THE IDAHO SIDE...WHICH MIGHT HELP EXPLAIN THE
SLIGHTLY WARMER GFS MOS TEMPERATURES FOR THE TREASURE VALLEY. WE
BLENDED ANALOG AND BC OUTPUT FROM ALL AVAILABLE MODELS AND CAME UP
WITH HIGHS FOR TODAY VERY CLOSE TO PREVIOUS FORECASTS. THE ACTUAL
READINGS WILL DEPEND ON LOCATION OF THE THERMAL AXIS...STRENGTH OF
DOWN VALLEY FLOW...AND HIGH CLOUD COVER. OVERNIGHT LOWS WILL BE 5-10
DEGREES ABOVE NORMAL OWING TO CLOUD COVER. ON THURSDAY A WEAK COLD
FRONT CROSSES THE AREA LOWERING MAX TEMPERATURES ABOUT 8 DEGREES.
TODAY MOISTURE IS MAINLY AT HIGH LEVELS. HOWEVER MODEL SOUNDINGS
INDICATE ENOUGH MOISTURE AND INSTABILITY OVER OUR NORTHERN ZONES FOR
ISOLATED LATE AFTERNOON AND EVENING HIGH BASED DRY THUNDERSTORMS...
AIDED BY VERY WARM TEMPERATURES. ON THURSDAY MOISTURE CONVERGENCE
JUST AHEAD OF AND ALONG THE COLD FRONT...PLUS LIFT ALONG THE FRONT
AND OVER THE MOUNTAINS...WILL SUPPORT MORE WIDESPREAD CONVECTION...
PARTICULARLY NORTH OF BURNS AND ACROSS BAKER COUNTY INTO THE WEST
CENTRAL IDAHO AND BOISE MOUNTAINS.