Area Forecast Discussion
Issued by NWS Boise, ID
FXUS65 KBOI 260255
Area Forecast Discussion
National Weather Service Boise ID
855 PM MDT THU AUG 25 2016
.DISCUSSION...Upper trough in Montana is oriented to the
southwest across Idaho and Oregon. Bulk of the moisture with the
trough remains too far to the northeast for showers, but there is
just enough moisture/instability for cloud buildups over the far
northern mountains. The clouds will decrease overnight resulting
in clear skies. The trough will push east by late Friday. Dry
weather with mostly clear skies are expected on Friday.
Temperatures will be slightly warmer, with highs within a few
degrees of normal. Winds will be light. Forecast is on track.
.AVIATION...VFR with MVFR-IFR visibilities from wildfire smoke in
valleys. Surface winds: Generally northwest 10 kts or less. Winds
aloft at 10KFT MSL: north 5-10 kts, becoming west around 09Z.
SHORT TERM...Tonight through Saturday...Axis of a weak upper
level trough continues to sink south over the forecast area. Some
cumulus developing over the higher terrain of the West Central
and Boise Mountains this afternoon, but no precipitation has been
reported. Have decreased pops along the eastern border of the
forecast area, so there will be no mention of precipitation for
tonight. Friday will see a dry northerly flow over the region as
the upper level trough continues to sink to the south. Saturday
flow aloft will shift to the northwest as another upper level
trough drops south over British Columbia. Conditions will remain
dry through the short term with temperatures warming to near
normal by Saturday.
LONG TERM...Saturday night through Thursday...Dry and warm westerly
flow aloft on Sunday will shift into the southwest on Monday, with
little change through Tuesday. Uncertainty increases starting
Tuesday night as a deepening upper level trough off the northwest
coast ejects a shortwave across northern California and the
intermountain area. The main problems are timing and chances of
measurable precipitation. Latest model solutions bring the
disturbance across our area as early as Tuesday night or as late as
Wednesday evening. Model precipitation forecasts also differ
considerably, but the system is expected to weaken as it moves
inland, and any monsoon moisture should track over eastern Idaho and
Wyoming, similar to the ECMWF. For now our forecast confines
mentionable precipitation to the central Idaho mountains.
Temperatures will be around 5 degrees above normal.
PREV SHORT TERM...JA
PREV LONG TERM....JT/WH