In Casper this morning, the weather was chilly, quite breezy and sunny. There are no clouds in the sky though there is some dust near the horizon because of the wind. The cold front moved through the area last night, and now things are much cooler.
The National Weather Service (NWS) in Riverton, WY, forecasts a sunny and windy day today, with a high temperature of 74 F and a west wind of 24-29 mph, gusting to 39 mph. This evening will be mostly clear and breezy, with a low temperature of 47 F, and west winds from 17-22 mph, decreasing to 7-12 mph this evening. There is a Special Weather Statement and a Hazardous Weather Outlook in place concerning the high wind and potential for fire danger, as well as some snow in the western mountains. The Storm Prediction Center (SPC) has issued a Critical Fire Risk for much of Wyoming today, as shown below.
The visible satellite imagery shows a blanket of clouds moving in from the northwest.
The enhanced infrared satellite imagery shows that these clouds are not very thick, and have low, warm tops.
The water vapor satellite imagery shows plenty of moisture return behind the cold front, most of which is surging from the Pacific Northwest.
The 12Z upper air sounding from Riverton, WY, shows a much drier atmosphere today as compared to yesterday. The dewpoint depressions were large throughout the column, and there was only 0.20 inches of precipitable water present. There was no Convective Available Potential Energy (CAPE) and only a slight thermal inversion near the surface. The 0-3 km average lapse rate was 6.7 C/km.
The deep-layer shear was 85 kts, and the low-level shear was 24 kts. Shear at all levels was due to a mix of speed and directional changes.
The surface observations (from the SPC Mesoscale Analysis Map) show the cool temperatures and low dewpoints throughout the state today.
The surface pressure map shows a tight pressure gradient running through the middle of the state. This explains our high winds this morning and afternoon. This gradient will weaken throughout the day, though the RAP shows few changes over the next six hours.
Synoptically speaking, the 300 mb NAM chart (from Unisys) shows a jetstreak passing through the southern part of the state today. The entire state is experiencing zonal flow at the 300 mb level.
The 500 mb NAM chart show nos significant vorticity advection across the state today. This chart has been excluded from today’s post.
The 700 mb NAM chart shows no rapidly-rising air over the state today. This chart has been excluded from today’s post.
The 850 mb NAM chart shows some lingering Cold Air Advection (CAA) behind the cold front. The gradient is not very sharp, but the winds blow directly across it from cold to warm.
Overall, I expect today to be cool, dry and windy. It is a relief from the heat that we’ve experienced over the last few days, and it is nice to cruise with the windows down on our return trip to New Mexico.
Thank you for reading my forecast.
The upper air soundings and mesoscale analysis plots are from the Storm Prediction Center website.
The forecasted upper air soundings are from TwisterData.com.
The surface observation and upper level charts are from Unisys Weather.
The satellite data is from NASA – MSFC