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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Wednesday
• 
• High: 75 °
• Low: 41 °
• T-Storms

• Thursday
• 
• High: 66 °
• Low: 37 °
• T-Storms

• Friday
• 
• High: 61 °
• Low: 43 °
• Chance of Rain

• Saturday
• 
• High: 91 °
• Low: 50 °
• Partly Cloudy

• Sunday
• 
• High: 79 °
• Low: 43 °
• Partly Cloudy

Area forecast discussion 
National Weather Service Cheyenne Wyoming 
722 PM MDT Tuesday may 22 2012 


Update... 
falling temperatures and improving relative humidities have 
combined with decreasing winds to bring an end to critical fire 
weather conditions across the area. So...let the red flag warning 
expire at 7 PM. 


&& 


Previous discussion... /issued 520 PM MDT Tuesday may 22 2012/ 


Aviation...00z taf issuance... 


Mainly high clouds will continue to move over the terminals tonight 
into Wednesday then ceilings will lower to near MVFR levels during the 
day Wednesday along with scattered showers. Surface cold front will pass across 
all terminals by late this evening. -Re- 


Previous discussion.../issued at 303 PM MDT Tuesday may 22 2012/... 


Short term...tonight through Thursday... 


The very warm...dry and windy weather will continue over the County Warning Area 
through the early evening hours. Many locations broke their daily 
high temperature records for today...with some places setting their 
all time may readings. 


A large change in weather is still on tap for the region the next 
few days and beyond. Heights aloft will lower through Thursday over 
The Rockies with a broad trough carved out over the western United 
States at least through Wednesday night. The 300 mb jet will be 
likewise progress across the County Warning Area from north to south. At the 
surface...the cold front is currently located from southwest South 
Dakota to southwest Wyoming. That front will move through the County Warning Area 
tonight. A surface low will develop along the front over eastern 
Colorado on Wednesday. The combination of the surface forcing and 
jet dynamics along with the increased moisture will produce 
widespread showers and some storms over the County Warning Area Wednesday afternoon 
and into Thursday morning. The surface forcing then weakens and the 
300 mb jet moves back slowly north Thursday afternoon...decreasing 
the shower coverage. The temperatures should be cold enough for snow 
above 8000 feet Wednesday night and Thursday morning with small 
accumulations likely. Temperatures will be much cooler as well with 
highs in the 50s and 60s over the lower elevations Wednesday and 
Thursday. 


Long term...Thursday night through Tuesday... 


The models continue to show a potentially unsettled period setting 
up for Friday and Sat. On Thursday night a midlevel trough digs into the 
Great Basin and then closes off over Nevada by Friday. In response to this 
trough...strong south-to-southwest midlevel flow will spread over 
increasing southeast low level flow. Low level moisture will really increase by Friday 
afternoon...with low to middle 40s dewpoints spreading westward to the 
Laramie range. Lowered maximum temperatures on Friday as moisture and upslope 
combine to produce a stratus deck over the plains...especially up 
against the Laramie range. Thunderstorm chances on Friday afternoon look minimal 
over the plains with the GFS showing negative Li only along the 
Laramie range. There will likely be some drizzle and light rain Friday 
night through Sat morning due to the deepening low level saturation. 


The closed midlevel low begins to progress northeastward by Sat with 
a threat of severe weather developing during the afternoon. The models 
all show a surface low forming during the afternoon over the plains...however 
they differ with the location from northeast Colorado to southeast Wyoming. 
The best chances of severe storms would be to the north of the surface 
low...where moist low level easterly winds produce the highest 
instability and shear. The 12z GFS shows Li values approaching -6c 
over the northern half of the Panhandle with 70kts of deep layer 
shear. Will continue to monitor the severe weather threat on Sat 
with future model runs. 


The trough continues northeastward into the northern plains on sun 
with a cold frontal passage on Sun morning over the County Warning Area. Much drier 
air will filter into the area with the westerly boundary layer 
winds...effectively ending the shower and thunderstorm threat. Looks like a 
nice Memorial Day with a shortwave ridge over Montana-Wyoming and seasonal 
temperatures. 


&& 


Fire weather... 


Cooler temperatures and widespread showers will then push into 
the area for Wednesday with the passage of a cold front tonight. 
The wetter and cooler conditions will persist over the County Warning Area through 
Saturday and will minimize fire weather concerns. Warmer and drier 
conditions will return to the region Sunday and into early next 
week. 


&& 


Cys watches/warnings/advisories... 
Wyoming...none. 
NE...none. 


&& 


$$ 




Short term/fire weather...Weiland 
long term...Finch