Red Flag Warning 20, NWS Pocatello, ID

Area Forecast Discussion
National Weather Service Pocatello ID
224 PM MDT Thu Aug 22 2019

.DISCUSSION...A cold front is marching through the region this
afternoon. This is producing a few showers and thunderstorms,
mainly closer to the divide. Much of this activity will quickly
diminish this evening. Dry weather will return to the region for
Friday and beyond. We'll see cooler temps behind the front for the
next several days as the flow gradually turns northwesterly. With
the northwesterly flow, we'll see the winds pick up as well,
especially over the weekend. Lake wind advisories for the American
Falls Reservoir certainly possible at points over the weekend.

Valle

&&

.AVIATION...Strong W to SW winds will continue through sunset
this eve post-cold front at KPIH/KIDA/KBYI, and may be a bit on
the slow side to drop off (between 8 PM and 11 PM). No major
runway crosswind issues are foreseen. Winds should remain lighter
at KDIJ (generally under 12 knots). We do maintain a low
confidence VCTS here through 10 PM, but overall the best chance of
post-frontal showers/storms will remain to the north. KSUN is
gusty out of the S, and we are expecting winds to shift to SW over
the course of the afternoon at 12G18 knots, so slight crosswind
conditions are possible here. Everything settles down tonight with
high confidence in VFR conditions overnight and throughout the
day on Fri into Fri night, with lighter winds as well. An
increasingly strong W-SW flow is expected Sat/Sun, so while
conditions will remain dry and VFR, expect a return to strong
afternoon and eve winds, especially at KPIH/KIDA. - KSmith/Valle

&&

.FIRE WEATHER...The cold front is east of the area, with widespread clouds, much
cooler temps, and much higher RH values now observed across SE
Idaho, and continued strong W/SW winds especially in the Snake
Plain. Many of the post-frontal echoes observed so far on radar are
not reaching the ground, but we do expect isolated showers/t-storms
this afternoon across Zones 422/475/476/411/northern 410. Any
rainfall amounts will be very light and non-impactful. Fairly steady
temp and RH values are expected Fri, with much lighter winds.

Next, all eyes are on a much stronger W/SW flow developing Sat and
Sun, with afternoon wind values expected to approach or reach
critical thresholds both days across at least portions of nearly
every zone. RH values will trend drier, but will be the limiting
factor for Red Flag conditions. Coverage of 15% RH values did
increase a bit with this afternoon's forecast update across western
Zone 410 and eastern Zone 425, and with at least 50% of both zones
now critical for both winds and RH, have issued a Fire Weather
Watch. RH values should generally remain above critical across the
rest of our zones. Winds and RHs look even slightly more critical
Sunday, but with plenty of lead time to play with and decent RH
recovery Sat night (so the 2 periods of concern are split anyway),
will hold with our initiation of messaging for Sat at this time. No
additional major wx systems are on the horizon at this time through
at least Wed next week. - KSmith/Valle

&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Saturday afternoon through Saturday
evening for IDZ410-425.

&&