Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 191708

Area Forecast Discussion
National Weather Service Riverton WY
1108 AM MDT Thu Apr 19 2018

.SHORT TERM...Today through Saturday night
Issued at 1257 AM MDT Thu Apr 19 2018

A low pressure system moves into the Pacific Northwest and digs
southeastward into the four corners region today. Clouds and
moisture will fill into the region ahead of this low. Shower
activity should increase over the mountains on late this afternoon.
Despite the cloud cover some warming should continue due to the
southerly flow. As the low moves into Southern Utah/Colorado Friday
there should be enough wrap around moisture to bring rain showers,
and a few snow showers, to the southeastern half of the FA. Any snow
totals will be low. Lincoln, Sublet, and Western Sweetwater Counties
will gusty out of the northeast Friday afternoon as the gradient
tightens with the low. The showers will fade from northwest to
southeast over Friday night as an upper level ridge returns. A
shortwave trough overriding the ridge may bring showers in the far
north mountains Saturday evening, but and precip would be quick hit
ting and result in very little accumulation.

.LONG TERM...Sunday through Thursday
Issued at 1257 AM MDT Thu Apr 19 2018

A low-amplitude trough is progged to push across the Northern
Rockies late Sunday night thru Monday evening. The associated cold
front is expected to sweep south, east of the Divide, Monday then
southwest across the rest of the area Monday evening. The best
chance of precipitation will be across the northwest and northern
parts of the area with chances spreading south during the day, but
not as high. 700 mb temperatures suggest mountain snow with rain
in the lower elevations possibly changing to snow before the
precip exits the area Monday evening. Windy to very windy
conditions are expected ahead, and behind this strong cold front.

Dry conditions are expected Tuesday in wake of this system.

Global models and their ensemble members have a large spread for
a potential storm system mid-late next week. The 00Z GFS is trying
to develop a longwave trough across the Rockies with cool and
inclement weather Thursday into the weekend. The ECMWF is much
flatter with a cut off, upper low off the California Coast early
in the week pushing into California/Desert Southwest by
Thursday/Friday, while the northern stream energy stays along the
Canadian/U.S. border. For now have gone with a blend of these
solutions with some low end PoPs.


.AVIATION...For the 18Z TAFS through 18Z Friday afternoon
Issued at 1046 AM MDT Thu Apr 19 2018

An upper level low pressure system is moving across the Great
Basin today and into the Four Corners area early Friday morning.
VFR conditions with mainly BKN-OVC mid and high clouds will
prevail over the area through much of the period. Surface NE
winds will increase to 20-35 knots from South Pass across the I-80
corridor after 03Z Friday. Isolated showers will be possible south
of a KCPR-KLND line between 06Z to 12Z Friday, with increasing
chances toward 12Z. Scattered to numerous showers will then
develop south and east of a KRIW-KLND-KEVW line, with MVFR
conditions after 12Z Friday and continue through the rest of the
TAF period. Temperatures for the four affected TAF sites (KRIW,
KLND, KRKS and KCPR) will be near the freezing mark. KRKS and KLND
will have the best chance for snow so far.


Issued AT 1257 AM MDT Thu Apr 19 2018

High pressure continues over the area today. Expect a warming and
drying trend in the lower elevations. RHs in areas 277, 278, and 279
do drop below 15 percent this afternoon and have somewhat gusty
winds but not strong enough at this time to cause a great concern.
Increasing cloud cover through the day should help keep
temperatures from climbing out of the 50s except for southern
Natrona County and eastern Sweetwater County. Rain/snow returns to
southern and central areas Friday.




LONG TERM...Murrell
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