Area Forecast Discussion
Issued by NWS Riverton, WY
Issued by NWS Riverton, WY
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436 FXUS65 KRIW 211703 AFDRIW Area Forecast Discussion National Weather Service Riverton WY 1103 AM MDT Sat Sep 21 2024 .KEY MESSAGES... - A cold front is passing through early this morning, with increased northerly wind behind the front through Friday evening east of the Continental Divide down into Sweetwater County. - It will be cooler today behind the cold front and remain cool through Tuesday as another weather system brings a cold front through on Monday. - A dirty ridge will bring back above normal temperatures by the middle part of next week. - Very little precipitation is on the horizon for WY, which will exacerbate drought conditions across the state. && .DISCUSSION... Issued at 1256 AM MDT Sat Sep 21 2024 A loosely coupled upper-low currently located over central CA and a trough in western MT will continue to slide eastward today. The shortwave trough has already passed north of WY this morning and the upper-low will pass to the south tonight, which means most of the area will miss out on any precip chances as the weather systems split the state. Some rain drops may fall across far southeastern Sweetwater/Natrona County tonight as the upper-low passes to the south. A strong cold front is sweeping through the area this morning and will bring much cooler temperatures today into tonight. This cold front is also bringing strong wind to northern portions of the area east of the Continental Divide. A peak wind gust of 62 mph was measured at Buffalo - Johnson County Airport around 11 PM. Windy conditions will push south through this morning with the cold front, but gusts that high are not expected. Gusts of 30 to 50 mph will occur early this morning as this cold front shifts south. Overnight lows tonight will be chilly in the mid to upper 30s for lower elevations east of the Continental Divide. Wouldn`t be surprised if there was frost in low spots Sunday morning. For those who still have a garden it doesn`t look like this will be a freeze event, so impacts should be minimal to vegetation. A brief ridge moves overhead on Sunday in between weather systems, which will allow for temperatures to rebound a bit, back to about seasonal averages for this time of year. Another trough surges down from the northwest very quickly on Monday. Very light precip accumulations are possible (30%) with this weather system as it really won`t have enough time to drop more than a few hundredths of liquid for any location. Model guidance has come into better agreement on the weather pattern for the middle part of the week. Model guidance now shows a substantial ridge developing by Wednesday and remaining in place until, at least, next weekend. This will result in temperatures that are well above normal and no precipitation. With no meaningful precipitation in sight drought conditions will worsen. Also, fire weather season looks like it is trying to hold on a bit longer. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1102 AM MDT Sat Sep 21 2024 With a cold front having passed from north to south east of the continental divide this morning, and a cutoff low over Arizona moving NE to the Four Corners area, the surface pressure gradient over much of WY will increase NE winds from northeast to central to south-central WY this afternoon. KRKS and eastern Sweetwater County could see gusts over 30 kts, with gusts 15-20 kts in the Bighorn Basin, Johnson County, and Wind River Basin. Partly cloudy skies over northern WY will decrease through the day, with clouds increasing over southern WY due to the cutoff low. VFR conditions are expected at all TAF sites through the next 24-30 hours. A couple of high resolution models are indicating some weak convection over SE Sweetwater County as well as the southern parts of the Wyoming Range late this afternoon and early evening, but chances are quite low. Primary impact from the low pressure system over UT/CO the next 36 hours will be the gusty NE winds and increased clouds over southern WY through early Sunday afternoon. Skies then become mostly clear Sunday afternoon from the west to east. Clouds will increase over northern WY Sunday night into Monday morning due to a weak system moving through MT. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .RIW WATCHES/WARNINGS/ADVISORIES...None. && $$ DISCUSSION...Rowe AVIATION...McDonald