Weather Service Report

FXUS65 KRIW 291802 AAA

Area Forecast Discussion...Update
National Weather Service Riverton WY
1204 PM MDT Sat Apr 29 2017

.SHORT TERM...(Today through Monday night)
Issued at 157 AM MDT Sat Apr 29 2017

Imagery shows longwave trof across the CONUS with closed low in base 
of trof centered over the 4 corners. Strong 120 to 160 kt jet 
associated with the LW trof stretches from the west coast down 
through the Desert SW...across the srn Rockies then out through the 
cntrl Plains/Great Lakes/New England. Wind speeds are minimal at jet 
level over WY. SFC has a cold front well south of the region across 
the srn Rockies/srn Plains with high P building into/across the nrn 
tier of states including WY. Weal inverted trofs extending from swrn 
CO into scntrl/cntrl WY and another through UT and into sern ID. 
Current decreasing (mainly) snow rotating from e to w across the srn 
half of the FA.

Upper closed low continues to slip s/se along with the cold front, 
moisture return and associated precipitation. A few lingering 
terrain/ll boundary forced snow possible this morning over s/cntrl WY
...with a couple terrain induced showers this afternoon will be 
about all in the way of precipitation chances as shortwave ridging 
aloft begins to overtake the FA from the southwest. These general 
conditions will last well into Sunday before an upstream sw trof 
rides through the nw flow aloft and into wrn WY with late 
afternoon/evening showers breaking out west of the Divide...with an 
associated cold front and some precipitation moving east of the 
Divide before sun-up Monday morning. Light non-highlight snow 
amounts expected with this system into early Monday afternoon.  

The next and somewhat more significant Wx system will then follow on 
the heals of Monday's system...sparked by the approach of yet 
another sw trof (with jet and associated cold front to follow just 
beyond this fcst period) entering the FA from the NW later Monday 
night. Precip chances will increase accordingly west of the 
Divide...especially over nwrn WY...with light snow expected to begin 
around midnight Monday, spreading to the south and east through the 
end of the fcst period. 

.LONG TERM...(Tuesday through Saturday)
Issued at 157 AM MDT Sat Apr 29 2017

A quick moving shortwave trough in the northwest flow will push
across the Cowboy State Tuesday with scattered to locally numerous
mountain snow, valley rain and snow showers. The main energy looks
to slide along the Divide with the best chances of precipitation
occurring along and east of the Divide, as well as far western
Wyoming. Looks like snow levels will vary from 5000 to 6500 feet.
Overall precipitation amounts look to be on the light side with 
some convection giving pockets with heavier amounts. Could even 
see a few thunderstorms Tuesday afternoon, but not enough
confidence to include in forecast at this time.

Upper level ridging builds into the area Wednesday and Thursday
with mainly dry conditions and a warming trend. Global models show
the ridging flattening, or at least the ridge axis shifting east 
into the Plains ahead of a potential trough pushing/digging into 
the Western U.S. Either way looks like the area will remain in 
the warm sector with perhaps enough moisture and instability to at
least mention convection over the west on Friday and then across 
the entire area Saturday.

Temperatures will be below average Tuesday with a warming trend to
above average temperatures by Thursday and lasting through


.AVIATION...(For the 18Z TAFS through 18Z Sunday morning) Issued 
at 157 AM MDT Sat Apr 29 2017


Scattered clouds between 2500 and 3500 feet will elevate early 
this afternoon with VFR conditions prevailing through the period. 


Issued AT 157 AM MDT Sat Apr 29 2017

Fire danger low across the forecast area through the next week. All 
fuels currently in green-up. Periods of isolated to widely scattered 
light rain and/or snow showers will occur Sunday afternoon into 
Monday afternoon...and again late Monday night through Tuesday 
night...with heaviest and most widespread precipitation occurring 
Tuesday afternoon and evening. Winds will be relatively light for 
the most part for the next several days...with brief gusty periods 
near any frontal passage (along with a wind shift). Smoke dispersion 
fair to very good this afternoon...good to excellent Sunday and 
Monday afternoons. 





LONG TERM...Murrell

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