Area Forecast Discussion
Issued by NWS Riverton, WY

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
000
FXUS65 KRIW 190510
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1110 PM MDT Fri May 18 2018

.SHORT TERM...(This evening through Monday)
Issued at 113 PM MDT Fri May 18 2018

A large Pacific low pressure trough over the northern Rockies
and Great Basin spreading moisture and instability across
western, northern and central Wyoming will continue to produce
showers and thunderstorms with small hail, strong gusty winds and
local heavy rain tonight, then decreasing through Friday.
Temperatures will cool with increasing relative humidity. Showers
and isolated thunderstorms spreading east will linger into Saturday
then decrease as the trough moves east and high pressure moves in from
the west. Enough heating is expected to keep some showers over the
west and north on Sunday and Monday with warming.

.LONG TERM...(Monday night through Friday)
Issued at 113 PM MDT Fri May 18 2018

BY MONDAY NIGHT THE NEXT CLOSED LOW TO OUR WEST IS PROGGED TO DRIFT
SOUTHEAST TO SOUTHERN CALIFORNIA, THUS INCREASING THE SOUTHERLY
DIFLUENT FLOW OVER OUR CWA AHEAD OF THE LOW. THE MOST UNSTABLE
CONDITIONS APPEAR TO BE OVER JOHNSON COUNTY MONDAY EVENING. THE
HIGHEST SCATTERED POPS WILL BE OVER THE NORTH AND WEST. THIS
SOUTHERLY DIFLUENT FLOW WILL CONTINUE THROUGH TUESDAY AS THE CLOSED
LOW MIGRATES ACROSS THE GREAT BASIN SO ANOTHER DAY OF ACTIVE
AFTERNOON AND EVENING CONVECTION IS ANTICIPATED TUESDAY, ESPECIALLY
FOR CENTRAL AND EASTERN ZONES. JOHNSON COUNTY IS AGAIN PEGGED TO
RECEIVE THE MOST SIGNIFICANT CONVECTION AND RESULTANT RAINFALL
TUESDAY NIGHT. ON WEDNESDAY, THE MODELS BEGIN TO DIVERGE. THE EURO
PULLS THE H5 LOW TO NORTHWEST WYOMING WHERE AS THE CANADIAN AND THE
GFS KEEP IT SPINNING OVER THE GREAT BASIN. ANOTHER ROUND OF
CONVECTION IS SLATED, MAINLY FOR CENTRAL AND NORTHERN WYOMING FOR
WEDNESDAY AFTERNOON AND EVENING. FREMONT COUNTY IS SLATED TO HAVE -6
LIFTED INDICES SO FREMONT COUNTY COULD BE UNDER THE GUN WEDNESDAY.
THEN BY THURSDAY, THE THE CANADIAN AND EURO IS RELATIVELY QUICK TO
TRACK THE ASCT TROUGHPA ACROSS WYOMING WHERE AS THE GFS IS THE
SLOWEST, BRINGING IT THROUGH FRIDAY. IN ANY EVENT, CONVECTION
APPEARS MOST LIKELY NORTH AND WEST OF WHAT IS LEFT OF THE CLOSED LOW
WITHIN THE TROUGH ACROSS NORTHERN AND WESTERN WYOMING ON THOSE DAYS.
THE GFS IS ALREADY INDICATING -7 LIFTED INDICES FOR JOHNSON COUNTY
FOR THURSDAY. TEMPERATURES WILL GRADUALLY WARM THROUGH MID WEEK,
THEN LEVEL OFF, WITH THE FAR WEST COOLING OFF ON THE BACK SIDE OF
THE SLOW MOVING TROUGH LATER NEXT WEEK.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday)
Issued at 1110 PM MDT Fri May 18 2018

West of the Continental Divide...KJAC, KBPI, KPNA, and KRKS

MVFR conditions will set-up at KRKS early Saturday morning in the
wake of a west moving cold front. East-northeast surface wind 15-
25kts a good bet for much of Saturday at KRKS. Ceilings should rise
to VFR around midday Saturday with scattered afternoon showers
developing. Other terminals should largely remain VFR with surface
wind less than 12kts through the forecast period. Scattered
afternoon convection should wane across the area between 00Z-02Z/Sun
with VFR conditions remaining.

East of the Continental Divide...KCPR, KCOD, KRIW, KLND, and KWRL

Scattered light rain showers remain across central sections of the
region late Friday evening. Low-level upslope and plenty of boundary
layer moisture will lead to persistent IFR/MVFR ceilings at all but
KWRL through midday Saturday. It is likely to take until late
Saturday afternoon for some clearing to begin and for ceilings to
rise to VFR. Thunderstorms not expected today with cooler, more
stable airmass in place. North to northeast surface winds will
gradually diminish through the day Saturday.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued AT 113 PM MDT Fri May 18 2018

A large Pacific low pressure trough over the northern Rockies
and Great Basin spreading moisture and instability across
western, northern and central Wyoming will continue to produce
showers and thunderstorms with small hail, strong gusty winds and
local heavy rain tonight, then decreasing through Friday.
Temperatures will cool with increasing relative humidity. Showers
and isolated thunderstorms spreading east will linger into Saturday
then decrease as the trough moves east and high pressure moves in from
the west. Enough heating is expected to keep some showers over the
west and north on Sunday and Monday with warming. Mixing heights will
lower Saturday with general good smoke dispersal in the afternoon.
Areas with lower clouds and heavier precipitation will have poor
smoke dispersal.

&&

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

$$

SHORT TERM...Baker
LONG TERM...Lipson
AVIATION...CNJ
FIRE WEATHER...Baker



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.