Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 280827
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
227 AM MDT WED SEP 28 2016

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT

TEMPERATURE DEW POINT SPREADS APPEAR TO BE GREATER ATTM THAN THIS
TIME YESTERDAY MORNING. WILL THEREFORE LEAVE FOG OUT OF THE
FORECAST FOR NOW FOR THIS MORNING IN THE VALLEYS AND BASINS. THE
RIDGE OF HIGH PRESSURE IS OVERHEAD ATTM. WE CAN EXPECT ANOTHER
ULTRA FALL LIKE DAY WITH SLIGHTLY WARMING TEMPERATURES TODAY.
TONIGHT, A 1030MB SFC HIGH WILL SLIDE SOUTHEAST FROM CANADA INTO
THE NORTHERN PLAINS AND Minnesota. THIS WILL CAUSE WINDS TO BLOW
FROM A GENERALLY SOUTHEAST DIRECTION TONIGHT, AND THEN VEER TO A
SOUTH SOUTHWEST DIRECTION BY THURSDAY WITH THESE WINDS DRAWING IN
MOISTURE IN FROM THE SOUTH. WITH A MID AND UPPER LEVEL TROUGH
TRACKING EAST ACROSS THE REGION ON THE BACKSIDE OF THE RIDGE
THURSDAY, ALONG WITH CORRESPONDING INCREASING CAPES IN NORTHWEST
WY THURSDAY AFTERNOON, NEGATIVE LIFTED INDICES, AS WELL AS
INCREASING DIFLUENT SSW FLOW, HAVE INCREASED POPS IN WESTERN WY
THURSDAY FOR WESTERN WY WHICH WILL INITIATE A GOOD CHANCE OF
SHOWERS AND ISOLATED THUNDERSTORMS. INCREASED POPS OVER 50 IN THE
WESTERN MTNS., THESE SHOWERS WILL DISSIPATE AFTER MIDNIGHT
THURSDAY NIGHT. ON FRIDAY AFTER THE TROUGH PASSES, WE CAN EXPECT
MORE ISOLATED SHOWER ACTIVITY FRIDAY AFTERNOON WITH LINGERING
INSTABILITY AND MOISTURE. TEMPERATURES WILL REMAIN MILD THROUGH
THE PERIOD WITH H7 TEMPS EXPECTED TO BE UP AROUND 10C.

.LONG TERM...SATURDAY THROUGH WEDNESDAY

Medium range guidance is coming into much better agreement tonight
as to general timing and location (although the new Euro is a
little slower and further south with time as a stronger shortwave
drops down the back side of the trough and redevelops the lower
further south than the GFS and GEM) of our significant weather
maker early next week. Generally all the guidance is digging the
system into the PacNW Sunday and then into Great Basin Sunday
night and across Wyoming on Monday into Monday night. There`s
still variation on location as it tracks across us Monday into
Tuesday but with the mean trough just to our west and with a
slight negative tilt, it should have a good chance of tracking
across the south half of our area similar to the last one. Will
need to increase pops quite a bit tonight as the procedure pops
are always woefully underdone in these situations. Nice day to
start the period Saturday with 60s west and 70s east (with 50s and
some 60s mountains). On Sunday, it still looks like a lead
shortwave will swing into the west and then weaken with a decent
chance of showers/isold storms in mainly the west. Some deeper low
level moisture may hold on in the far ern zones for a few stronger
storms late Sunday. Main trough dynamics/jet support start working
in later Sunday night into Monday with impressive dynamics across
much of the area. Significant lower elevation rain and mountain
snow will be possible Monday/Monday night with some wraparound
potential on Tuesday. Temperatures will be sharply cooler/colder
Monday into Tuesday after a have way decent day Sunday.

&&

.AVIATION.../12Z ISSUANCE/

VFR conditions with unlimited ceilings will continue to prevail
through 12z Thursday.  Surface high pressure sliding southeast
across the High Plains will result in a prevailing east to southeast
wind around 10 knots east of the Continental Divide Wednesday
afternoon.  An upper level disturbance drifting north across the
Great Basin will spread isolated to widely scattered showers north
to a vicinity KJAC-KLND-KRWL line by 12z Thursday.
&&

.FIRE WEATHER...

Quiet fire weather conditions expected through Thursday as high
pressure remains anchored over the area today with light winds and
a trough of low pressure approaches Wyoming Wednesday evening,
introducing shower activity to southwestern Wyoming by the evening
hours. Temperatures will cool only slightly under the influence
of this approaching system through the remainder of the week. A
better chance of showers and thunderstorms is slated for Thursday,
especially in western Wyoming as the trough moves through. Fire
weather concerns will generally remain low over the following few
days.

&&

.RIW Watches/Warnings/Advisories...None.

&&

$$

SHORT TERM...Lipson
LONG TERM...PS
AVIATION...AEM
FIRE WEATHER...Lipson



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