Area Forecast Discussion
Issued by NWS Riverton, WY

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FXUS65 KRIW 201556 AAA

Area Forecast Discussion...UPDATED
National Weather Service Riverton WY
956 AM MDT Fri Apr 20 2018

.SHORT TERM...Today through Sunday night
Issued at 245 AM MDT Fri Apr 20 2018

The closed low is passing just north of the four corners region
today. Precip type has been difficult to forecast with this system
as models have been back and forth on how close the low would be.
For the last few nights 700mb temps have had a warming trend with
the current models landing between 0 and -3. So, I am going with
mostly rain with some rain/snow mix below 7000ft and snow above.
Precip should begin to dissipate from northwest to southeast around
06Z becoming more snow in south Fremont and east Sweetwater
Counties before exiting the area tomorrow morning. Upper level
ridging will reestablish itself Saturday through Sunday so expect
warmer temps and dry weather. Sunday night could see some shower
activity in the northwestern mountains due to an approaching system.

.LONG TERM...Monday through Friday
Issued at 245 AM MDT Fri Apr 20 2018

Interesting weather system for Monday into Monday night. Models
are in good agreement with how it tracks across the region. Rain
and snow chances look best over the north half of WY with less
activity in the south. Some snow may linger into Tuesday morning
east of the continental divide, but should end by late morning.
Cooler day Monday with highs in the 40s and 50s at the lower
elevations. Otherwise Tuesday will be dry with decreasing clouds.
High temps in the 40s and 50s once again. On Wednesday, it will be
dry for most locations. The GFS model indicates that isolated
showers could occur over and near the mountains Wed afternoon and
evening. The ECMWF model is dry. Have left the isolated mountain
showers in the forecast for now. Warmer on Wed with highs in the
50s and 60s. Dry Thursday with highs in the 50s and 60s. Next
Friday looks mostly dry east of the divide. Isolated showers or
thunderstorms west of the divide next Friday. High temps in the
60s to lower 70s at the lower elevations.


.AVIATION...For the 12Z TAFS through 12Z Saturday morning
Issued at 245 AM MDT Fri Apr 20 2018

An upper level low pressure system will move across southern
Colorado through this evening. Widespread MVFR conditions, local
IFR conditions in rain and snow will develop vicinity and south
and east of a KRKS-KLND-KRIW-KBYG line by 20z this afternoon with
snow levels around 6000 feet. Higher terrain above 8000 feet will
also become mostly obscured in this area; ceilings will likely
lower mostly into category after 00z Saturday. Precipitation will
decrease NW- SE 03z- 09z Saturday but areas of MVFR-IFR ceilings
and patchy fog are likely to linger through 12z.

Further north and west, VFR conditions will prevail through the
period with scattered MVFR shrasn pushing north to vicinity KBPI-
KWRL line by 20z this afternoon, followed by clearing 00z- 06z


Issued AT 245 AM MDT Fri Apr 20 2018

A large low pressure system will move just north of the 4-corners
area on today and then move east across Colorado tonight. Widespread
precipitation is expected across the Red Desert with a little snow
accumulation along with gusty northeast wind. Some rain or rain and
snow mixture and gusty northeast to east wind will extend as far
north as Fremont and Natrona Counties today into tonight with a
brief period up into Johnson County. The northern zones will be dry
with a period of gusty north wind as the storm moves by.





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