Area Forecast Discussion
Issued by NWS Riverton, WY

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229
FXUS65 KRIW 180544
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1144 PM MDT Sat Jun 17 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 210 PM MDT Sat Jun 17 2017

Cold drying north northwest flow will be over the area tonight.
High pressure from the great basin will build north on Sunday with
decreasing northwest flow.  Conditions will remain dry and stable
with warming.  Monday will be warmer again as high pressure dominates
the weather pattern.  Some moisture will move in on Tuesday with
continued warming combining for instability and the development
of isolated showers and thunderstorms, mainly over the mountains
in the afternoon.

.LONG TERM...(Tuesday night through Saturday)
Issued at 210 PM MDT Sat Jun 17 2017

Beginning of fcst, weak nearly zonal ridging expected across the
western CONUS with a ridge topping SW trof racing across the nrn
states, including WY. This will allow for some thunder/shower
activity over the FA...particularly east of the Divide as an upper
level induced front moves through. By Wednesday, drier flat ridging
aloft resumes with post frontal nrly flow at the SFC east of the
Divide and wrly/swrly flow across the west...inducing lee side low
pressure over cntrl WY. Gusty afternoon winds will be probable
across srn WY. Additionally, The models currently show another weak
racing SW trof to zip across the FA Wednesday night, which could
extend a period mainly terrain induced afternoon/early evening
showers/storms to last a bit longer overnight...with a couple of
stronger storms over Johnson county (the usual).

Thursday, zonal to slight nwrly flow aloft continues with somewhat
lower heights...causing temps to fall off a bit. Otherwise, mostly
precipitation free other than a few orographically initiated
showers/storms in the afternoon/evening period. Gusty west to
northwest winds across srn WY once again...north behind another weak
front east of the Divide. Friday, more zonal flow aloft, drier and
perhaps slightly cooler as heights fall off a bit (again). Only very
slim chances for precip over the far nrn zones...with the mountains
of the far north seeing the best chance.

Saturday, the blend mdls are not taking much credence in the
possibility of a rather strong trof passage across the nrn tier of
states (yet)...which could cause a period of strong frontogenesis
over the nrn High Plains and eventually come roaring through the ern
FA. this would lower temps a fair amount east of the
Divide...provide at least a few more clouds and increasing forcing
for some high based Thunder (if the timing is right)...some severe
wind blowers. For now, will just keep a watch for further potential
come next Saturday and adjust accordingly. If this scenario was to
come true...the next day (Sunday) could be quite interesting severe-
wise.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1143 PM MDT Sat Jun 17 2017

VFR conditions will prevail through 12z Monday.  Surface N-NW winds
10-20kts will prevail across the area Sunday afternoon, with these
winds diminishing around sunset.  SCT-BKN FL120-140 will be found
across the northern and eastern Wyoming through Sunday afternoon
with clearing Sunday evening.

&&

.FIRE WEATHER...
Issued AT 210 PM MDT Sat Jun 17 2017

Cold drying north northwest flow will be over the area tonight.
High pressure from the great basin will build north on Sunday with
decreasing northwest flow.  Conditions will remain dry and stable
with warming.  Monday will be warmer again as high pressure dominates
the weather pattern.  Some moisture will move in on Tuesday with
continued warming combining for instability and the development
of isolated showers and thunderstorms, mainly over the mountains
in the afternoon.  Mixing heights and transport winds should combine
for good to excellent smoke dispersal in the afternoons through
Tuesday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Baker
LONG TERM...Braun
AVIATION...Meunier
FIRE WEATHER...Baker



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