Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS65 KRIW 142012

Area Forecast Discussion
National Weather Service Riverton WY
212 PM MDT Mon Oct 14 2019

.SHORT TERM...(This evening through Tuesday)
Issued at 158 PM MDT Mon Oct 14 2019

Front is progressing through northern WY ATTM, with north winds
from COD to THP to KYC. Moisture remains very limited with this
passage, with difficulty even creating lower clouds, so
precipitation will be minimal to none through this evening. Breezy
conditions will continue across south WY this afternoon, and
northerly winds behind the front for the Big Horn and Wind River
Basins, along with Johnson County late this afternoon. As the
associated shortwave sweeps across ND and ridging builds back in,
lighter southerly and westerly flow will resume overnight and 
continue during the day Tuesday. 

.LONG TERM...(Tuesday night through Monday)
Issued at 158 PM MDT Mon Oct 14 2019

The flattening ridge axis will be approaching from the west 
Tuesday night. By Wednesday, an approaching shortwave ejecting off
a long wave trough off the Pacific Coast will begin to head in 
our direction. This will tightening the gradient within the 
flattening ridge. The ridge will also bring in warmer temperatures
as 700mb increase to 8C, a good increase of 14C over what is 
projected for earlier this week across northeast Wyoming. This 
will lead to an increased risk of critical fire weather with warm,
breezy and dry conditions expected. The most critical fire 
weather areas of concern Wednesday appear to be across Sweetwater 
County where dew points are projected to be as low as 8F according
to the MOS MEX. This is where critical fuels still exist. 
Wednesday will be the warmest day in many places but Thursday will
be almost as warm. West southwest winds draw in the milder air 
will out ahead of the aforementioned shortwave. A few showers will
break out across Northwest Wyoming as weak QG forcing shows up in
western Wyoming, the jet streak shifts to our south, and the 
environment becomes slightly unstable. Then on Friday, expect 
cooler weather when the shortwave tracks across the area along 
with weak instability over the north. This along with a westerly 
upslope flow would keep showers in the northwest that will turn to
snow after the frontal passage associated with the shortwave. 

As for next weekend, the models are showing better agreement as 
to where to close off the upper low with the approaching long wave
trough, namely over Colorado by Sunday. The snowfall in western 
Wyoming will likely increase Saturday as the long wave trough 
approaches from the Great Basin along with weak instability and 
increasing westerly difluent upslope flow. Then on Sunday, with 
the long wave trough overhead, precip will propagate to areas 
east of the Divide as the trough closes off the upper low over 
Colorado. Because of this, there is the potential for an upslope 
event with snow levels potentially reaching the basin floors east 
of the Divide by Sunday. Snow would likely continue in the west. 
After the low scoots off to the east across the Plains, northwest 
upslope flow behind the low will continue in northwest Wyoming 
with snow showers expected there then.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 158 PM MDT Mon Oct 14 2019

VFR conditions expected through the next 24 hours, with mostly
clear skies. FEW to SCT conditions may build across COD/WRL/CPR
through the rest of today as a weak front moves through, but no
restrictions expected. Areas south of the divide will continue
with gusty southwest winds today, with some gusts near 30 knots
expected. Areas north and east of the divide will see winds shift
from the north as the front comes to rest along the divide. These
north winds will briefly reach 20 knots this afternoon before
relaxing at sunset. Winds will be lighter tomorrow area wide with
relaxed pressure gradient across the state. Skies will again be
mostly clear, with only SCT high clouds expected.


Issued AT 158 PM MDT Mon Oct 14 2019

A combination of a gusty wind and low humidity will bring 
critical fire weather to southern Wyoming for the rest of this 
afternoon. Elsewhere, a gusty wind will occur as a dry backdoor 
cold front moves across the area. Relative humidity could fall 
under 15 percent for portions of central Wyoming as well. Mixing 
and smoke dispersal will range from fair in northern Wyoming to 
excellent in the south. Tuesday will feature cooler weather east 
of the Divide behind the front, with temperatures west of the 
Divide unchanged. Wednesday will be warmer, breezy, and dry, and 
will be the warmest day of the week, along with another potential 
for critical fire weather, especially in Sweetwater County. 
Thursday will be rather warm as well but not quite as dry. Some 
showers could occur in Northwest Wyoming Thursday. Next Friday 
through next weekend will feature a trend toward cooler and more 
unsettled weather.


Red Flag Warning until 7 PM MDT this evening for WYZ277>279.



National Weather Service Glossary of Abbreviations