Area Forecast Discussion
Issued by NWS Riverton, WY

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972
FXUS65 KRIW 190520
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1120 PM MDT Sun Aug 18 2019

.SHORT TERM...This afternoon through Monday

Dry, warm and breezy conditions will be the norm for much of the
week this week. Winds are not expected to be as strong this
afternoon, compared to what occurred the last couple of days. This
trend will continue into Monday, with gusts of 25 to 30 mph
confined to the mountains and the Wind Corridor, from southern
Lincoln to Natrona County. Hot temperatures will return Monday,
with readings in the lower to middle 90s occurring east of the
Divide.

Critically low relative humidity values and clear skies will
continue the threat for fires this week. It cannot be overstated
the fire danger that is in place and that will continue into the
foreseeable future. Do NOT attempt any burning of any kind during
this time.

.LONG TERM...Monday night through Sunday

Ridging will continue across the area through the period, so there
is little change to the forecast. Above normal temperatures are
expected with a decrease in the wind speeds Tuesday as the pressure
gradient weakens. This should improve the fire conditions
somewhat. However, with the very dry atmosphere in place, relative
humidity will remain in the teens for many locations and in some
areas fall into the single digits at times.

High temperatures for the week will be in the 90s in the lower
elevations with 70s to low 80s higher up. The chance of
precipitation looks limited at best, staying in the slight category
for Tuesday and Wednesday. The latest NBM run continues to run the
PoPs to high, so we blended with EC/GFS to bring them down to more
reasonable levels. The models are still hinting a pattern for next
weekend very similar to this weekend. This could mean a repeat of
dry and windy conditions and a return of fire weather concerns.

&&

.AVIATION...For the 06Z TAFS through 06Z Tuesday
Issued at 1120 PM MDT Sun Aug 18 2019

Conditions will be VFR at all terminals. Westerly surface wind
speeds will be less on Monday afternoon than what has been observed
the past few days. KRKS and KCPR will still see 15G25kts by 18Z/Mon,
while several other terminals can expect 10G18kts to develop between
19Z-22Z/Mon. Speeds will diminish quickly after 00Z/Tue with all
terminals 10kts or less by 03Z/Tue.

&&

.FIRE WEATHER...

...Red Flag Warnings continue over much of Central and Southwest
Wyoming through Monday evening...

Critical fire weather conditions are still expected today across
much of central and southern Wyoming. Confidence remains high for
humidity falling to 10 to 15 percent and winds 15 to 20 mph, with
frequent gusts approaching 35 mph. With the drier air returning
northeastward, the southern Big Horn range will also begin to see
critical conditions this afternoon. Warnings now include zone
285. Will issue a Rangeland Fire Danger Statement for Monday, for
those zones that do not have critical fuels.

Monday looks to be another critical day across Wyoming. Humidity
values will be even lower across the forecast area, as a drier
airmass shifts in from the southwest. RH values will be in the
single digits across much of central and southern zones, with
lower to middle teens occurring in all but the highest elevations.
winds will be slightly lower once again, with southwest wind gusts
up to 30 mph occurring from southern Lincoln County to Natrona
County, as well as over the mountains. Winds will be light in the
central basins. Hot temperatures will return Monday, with the
drier airmass. Readings in the 90s will be widespread east of the
Divide. To add an additional hazard, the Haines Index will be up
to 6 over much of the forecast area as well. Thus, have extended
the current warnings and issued new warnings for Monday to account
for all these hazards. Similar conditions are expected Tuesday,
although, winds will be lighter. However, a Haines Index of 6
will remain in place across areas west of the Divide. Zones 283,
288 and 289 are included in these areas.


&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 9 PM MDT Monday for WYZ277>280-283-285-
288-289-300-414-416.

Red Flag Warning from noon to 9 PM MDT Monday for WYZ275-281-282-
415.

&&

$$

SHORT TERM...LaVoie
LONG TERM...Swanson
AVIATION...CNJ
FIRE WEATHER...LaVoie



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