ZCZC SPCFWDDY1 ALL
FNUS21 KWNS 171634
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1134 AM CDT Thu Jun 17 2021
Valid 171700Z - 181200Z
...CRITICAL FIRE WEATHER AREA FOR SOUTH CENTRAL WYOMING...
Some refinements were made to the isolated dry thunderstorm area
across portions of central/southern Nevada and southwest Utah. The
latest high-resolution CAMs and SREF guidance depict a lower
likelihood of dry thunderstorms in this region as compared to
previous runs. Otherwise, the balance of the previous forecast
remains on track. See the discussion below for more details.
.PREV DISCUSSION... /ISSUED 1250 AM CDT Thu Jun 17 2021/
An upper-level high will remain over the Four Corners region today,
allowing for strong diurnal heating and the deepening of a thermal
trough over the Four Corners/Great Basin region. To the north,
pressure gradient winds will increase through the day as surface
high pressure builds over the Pacific Northwest with a lingering low
over the Plains. This will support elevated to critical fire weather
conditions across the northern Great Basin and into the northern
...Central to Northern Rockies and Great Basin...
Dry conditions will persist for much of the northern Great Basin and
into the northern Rockies, and active fires within the region over
the past few days are indicative of receptive fuels. Afternoon RH
values in the single digits are expected across NV/UT, increasing to
the teens and low 20s with northward extent into northern MT and
western ND. The synoptic pressure gradient over the northern Great
Basin and central/northern Rockies will be augmented by early
afternoon as boundary-layer mixing transports stronger mid-level
flow to the surface. Sustained winds between 15-20 mph (gusting to
25-35 mph) will support areas of elevated conditions. Critical
conditions remain likely across south-central WY where terrain
influences will regionally strengthen winds to 20-25 mph (with gusts
up to 40-45 mph possible) along the I-80 corridor.
Evening soundings from across the Four Corners region show mid-level
moisture atop of deep, well-mixed boundary layers with 100-500 J/kg
MUCAPE. This environment supported isolated to scattered
thunderstorms Wednesday afternoon, and despite some convective
overturning, mean easterly winds into NM/AZ will continue to supply
mid-level moisture and maintain favorable thermodynamic profiles for
thunderstorms this afternoon. Strong heating coupled with orographic
ascent will favor isolated, to perhaps scattered, thunderstorms
across the broader Southwest/Four Corners region. PWAT values
between 0.5 to 0.75 inches suggest a mix of wet and dry storms.
...Southern Arizona/New Mexico Border...
Elevated fire weather conditions are expected this afternoon along
the southern AZ/NM border. Southeasterly winds are forecast to
increase to near 15 mph (with occasional gusts upwards of 25 mph) in
response to the deepening thermal low to the west. Single digit to
low teen RH values are expected, and fuels remain receptive per
recent fire activity.
A dry continental air mass has moved into the central Great Lakes
region on the eastern periphery of a surface high. The approach of a
surface low/trough to the northwest through the day will increase
southwesterly winds to 10-15 mph as RH values fall to near 20%.
10-hour fuel moisture values in the 5-6% range are noted, as well as
high ERC values per recent fuel analyses. Although winds should
generally remain below elevated thresholds, pockets of elevated fire
weather conditions are possible.