Wildfire in Idaho, July 25 to 30, 2017

Area Forecast Discussion
National Weather Service Pocatello ID
919 PM MDT Tue Jul 25 2017

.UPDATE...

Minor update to ensure that there is at least a slight chance in
all areas through Wednesday. Thunderstorm chances tonight look
mainly focused across the central Idaho mountains and also across
the southern highlands. Convection this evening across south
central Idaho and Nevada will likely move into northern Utah and
the south Idaho highlands as it slowly dissipates overnight.
Expect convective debris Wednesday morning, rather similar to
Tuesday morning.

Valle

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.PREV DISCUSSION... /issued 212 PM MDT Tue Jul 25 2017/

DISCUSSION...Isolated to widely scattered thunderstorms expected
over the mountains this evening, then much of the activity will
die off late this evening. Attention turns to the disturbance over
northern California and thunderstorms developing in western
Nevada. Part of that disturbance will enter Cassia County area
near Wednesday morning and advance along the South Central and
Caribou Highlands through the day. A few storms may produce .10 to
20 precipitation. The middle level winds over the Central
Mountains on Wednesday are variable at times, and models are
struggling with placement of showers and thunderstorms. We may get
a mixed bag tomorrow. Precipitable water values are over an inch
and with slow mid level winds, will have to watch for isolated
cells with heavy rain. That changes Thursday with the disturbance
over California ejecting northeast. Thursday should be a pretty
active thunderstorm day for the Central Mountains and South
Central/Caribou Highlands, some with strong outflow winds.
Friday, a little more dry air from the west moves in, but that is
short lived. The monsoon moisture begins to circulate back into
the Great Basin, including Idaho over the weekend and probably
into Monday or Tuesday. A very unsettled pattern. RS

AVIATION...Radar and a perusal of model guidance paints a fairly
wet picture for SE Idaho compared to the past 3 weeks as
monsoonal moisture streams into the region. Each model places the
most persistent shower/t-storm activity in slightly different
areas this afternoon, possibly affecting airports not seeing
showers now. This doesn't leave me with much confidence to back
off from -SHRA VCTS at any given terminal, and low confidence in
placement/timing. Activity will be sct, but some areas may see
multi-hour dry periods, while others may see more persistent
showers/storms. Even with heavy downpours and gusty winds near TS,
confidence is moderate to high in VFR conditions. Activity
settles down but may not end completely overnight, with VFRs
expected. Sct showers/t-storms should increase again by midday Wed
with at least similar coverage to today. Storms will be quite wet
compared to what we have seen so far this summer, so can't rule
out brief MVFRs if a TS moves directly over a terminal, but
largely VFR conditions again expected. Winds outside of TS will be
12 kts or less both days. - KSmith/Keyes

FIRE WEATHER...Cloud cover has kept thunderstorms a minimum today
although where clouds have thinned or cleared, we've seen a few try
to pop up this afternoon. With limited instability, the risk of
anything over isolated/widely scattered is pretty low. Monsoon
moisture continues to remain over the area through Thursday. With
deeper moisture in place, locally heavy rain is possible along with
gusty winds over 30 mph. The rain could easily become an issue on
burn scars or for crews out in fields that would flood or become mud
pits. Coverage on Wednesday COULD end up being scattered due to less
cloud cover early on, but confidence is pretty low as we have been
basically nowcasting under this pattern. More instability would mean
more coverage, and higher risk of heavy rain and gusty winds. One
thing to remember in this pattern is that risk overnight rain and
isolated storms is definitely there until Friday. The models are all
over the place by late week and the weekend as they can't decide
what to do with the building ridge and any systems working around
the center of it. The current forecast remains warmer and drier with
more isolated showers and storms.  That will likely change between
now and then.  Keyes

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&