Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 222003

Area Forecast Discussion
National Weather Service Pocatello ID
203 PM MDT Tue Aug 22 2017

.DISCUSSION...Moisture draped across NV/UT slowly working north
per satellite imagery this afternoon. Have seen a few Cu develop
just north of UT border, but nothing yet in the way of developed
convection. Could see activity increase through the evening as
stronger convection shifts closer to the state line and outflows
help to induce development, but confidence low. Wednesday and
Thursday continue to look most likely for thunderstorms across the
region, but coverage still spotty with main dynamics over OR/WA,
shifting into MT by Thursday. Have kept coverage isolated, but
additional development could lead to fire concerns. See discussion
below. Latest indications are that convective activity could
linger into Friday as well with secondary shortwave shifting east
across northern CA/NV. Have increased PoPs slightly during the
afternoon/evening. Otherwise, upper ridge resurges Saturday into
early next week with upper high centered over Great Basin. Expect
return to dry/warm conditions Saturday through Monday. By Tuesday,
there is some hint that moisture could rotate around the high
with potential for next round of convection by mid week. Models
not consistent yet with the idea, so nudged precip chances up
slightly Tue without hitting mention. DMH


.AVIATION...Upper ridging is expected to shift eastward this evening
and will usher in some monsoonal moisture from the south. We should
begin to see some high VFR ceilings push in south to north through
the period with showers just beginning to develop late tomorrow
morning. Included VCTS for the afternoon hours tomorrow at KSUN as
airmass begins to destabilize over the Central Mountains.


.FIRE WEATHER...Dry and stable conditions are coming to an end this
afternoon as upper ridging shifts to the east. We will see an
increase in monsoon moisture overnight and into tomorrow which will
trigger showers and isolated to widely scattered afternoon/evening
thunderstorms. We may see cloud cover keep us from reaching
scattered coverage of storms, even as a shortwave lifts up from the
Great Basin across southern Idaho tomorrow afternoon. Showers and
isolated thunderstorms may linger over the Central Mountains
tomorrow night heading into Thursday. Winds will gradually increase
on Thursday afternoon in response to stronger mid-level flow with
700mb winds reaching 20 to 25 mph mainly across the Snake Plain.
Winds again on Friday may approach 20 to 25 mph, but surface RH is
expected to increase tomorrow and Thursday which will mitigate
critical fire threats. Drier conditions are expected on Friday, and
may present some fire weather concerns as winds may see some gusts.
We will be monitoring the forecast trends over the next couple days
to gain more certainty in the fire weather conditions for Friday.
Hot and dry conditions return to Idaho this weekend through much of
next week. Hinsberger



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