Whitby Reservoir Idaho Weather Forecast Discussion

462
FXUS65 KBOI 150253
AFDBOI
Area Forecast Discussion
National Weather Service Boise ID
853 PM MDT Tue Oct 14 2025
.DISCUSSION...At 8 PM PDT satellite imagery showed upper
low over central California, and cloud tops rapidly cooling
in northern Nevada and shifting north. Models move pcpn into
southern ID overnight as the low moves eastward into NV,
then into UT Wednesday evening. Latest Hi-res NamNest model
brings pcpn only as far north (or northwest) as Stanley-Mountain
Home-Winnemucca Wednesday morning before shifting east again.
Several hours ago it brought pcpn all the way to Boise. Hi-res
HRRR model still brings light rain as far as Boise Wednesday
morning but less than before. These changes suggest less rain
west of Stanley-Mountain Home on Wednesday but we won`t update
just yet. We simply note these changes here. Current forecast
is on track otherwise.
&&
.AVIATION...Generally VFR this evening with a band of
light-moderate showers moving toward KTWF/KJER. IFR-VLIFR
in patchy valley fog Wednesday morning. Widespread
precipitation across SW ID tomorrow, periods of MVFR, and
IFR possible in rain showers and low ceilings. Snow levels
tonight starting at 7-8 kft MSL, lowering to 6-7.5 kft MSL
by mid-morning. Surface winds: variable 5-10kt. Winds aloft
at 10kft MSL: variable 5-15 kt.
KBOI...VFR overnight. Considered VCFG overnight, but confidence
not high enough at this time. MVFR likely/IFR possible from
early morning to mid-afternoon due to rain showers and low
ceilings. 60% chance of rain at the airport, maximized between
12z-18z. Surface winds: light and variable overnight, becoming
NW 5-10 kt Wed/20z.
&&
.PREV DISCUSSION...
SHORT TERM...Tonight through Thursday night...An upper low
centered along the central California coast will lift northeast
tonight into Wednesday. Showers will move north into southwest
Idaho and far southeast Oregon as the low approaches. Another
band of showers, similar to but slightly more developed than this
morning`s precipitation, is expected to develop across
southwest Idaho late tonight into Wednesday along a shortwave
rotating around the low. This band may bring moderate
precipitation totals up to 0.25 to 0.50 inch, with slightly
higher totals possible in the mountains. The band is most likely
to develop between Twin Falls and Boise, but some hi-res models
bring it as far west as the Boise metro Wednesday morning.
Precipitation will become more showery in the afternoon and
focused in the Magic Valley and central Idaho mountains, with a
10-20% chance of thunderstorms also developing. Snow levels will
remain high through the event, generally 6500 to 8000 feet MSL,
limiting accumulating snow to the highest peaks. It will remain
cool and breezy as the low moves through.
Precipitation will end from west to east Wednesday night. A cool
air mass in place will allow low temperatures to dip into the
30s in the lower valleys, resulting in potential for frost.
However, steady northwest winds overnight will limit this
potential except in more sheltered areas. Cool and dry
northwest flow on Thursday will bring mostly sunny skies, breezy
afternoon winds (locally gusts to around 30 mph southeast of
Boise), and slightly below normal temperatures.
LONG TERM...Friday through Tuesday...High pressure building in the
North Pacific keeps general northwesterly flow across the region
through early Sunday. This will keep temperatures seasonal, skies
partly cloudy, and a slight chance of precip mostly north of our
forecast area Friday evening. Models continue to be uncertain about
a potential deep trough on Sunday, with not much change from the
midnight shift`s forecast. The GFS/EC deterministic and roughly half
of ensemble members show a deep wet trough dig into the region
Sunday evening. This would drop temps to 10 degrees below normal
Monday and Tuesday and bring 40-60% chance of precip to most of the
area. It would also drop snow levels to 4-5 kft MSL with a few
inches of snow possible in Central Idaho ridges. However, the other
half of GFS/EC ensemble members and the deterministic Canadian keep
the trough very flat, which would still bring some moisture, but
limit the precip amounts and potential temp drop off. The
disagreement among models is still significant, but given the
deterministic GFS and EC agreement I slightly favored the cooler
and wetter forecast in this afternoon`s package.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.
&&
$$
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DISCUSSION...LC
AVIATION.....CH
SHORT TERM...ST
LONG TERM....JM

NWS BOI Office Area Forecast Discussion