163 FXUS65 KBOU 170946 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 346 AM MDT Tue May 17 2022 .SHORT TERM...(Today and tonight) Issued at 342 AM MDT Tue May 17 2022 Broad zonal flow should remain in place today, with a subtle shortwave tracking across the CO/WY border later this afternoon. This should provide enough lift for widely scattered thunderstorms later this afternoon, which will be the main concern over the next 24 hours. At the surface, a fairly impressive moisture gradient has setup across the forecast area. Dew points across the high country and the foothills are in the teens to mid 20s, with Td's in the upper 40s across the far northeast corner of the state. We should see gradual moistening, especially after noon, with a push of northeasterly surface flow. As temperatures warm into the 80s across the plains, this should lead to MLCAPE increasing to 500-1500 J/kg - generally east of I-25/north of I-70 - with sufficient (25-40kt) deep layer shear. The biggest remaining question for today is the overall convective coverage. CAM guidance consensus is for convection to initiate near the Cheyenne Ridge just after noon, and propagate towards the east/southeast. HREF paintball plots and the past few HRRR cycles suggest that storms will gradually grow upscale. Damaging winds will be the main hazard today... especially with steep low level lapse rates and >1000 J/kg DCAPE, but can't rule out some large hail as well. The forecast for the Denver metro is also relatively uncertain and will be dependent on how much moisture can advect into the area. Can't rule out a storm or two, even on the dry side of the boundary. Any storm that does manage to develop in the drier airmass would generally produce little rain but gusty outflow winds, as a result of a fairly classic looking inverted V sounding. A few storms will also possible over the higher terrain, though with limited instability, these storms aren't expected to be particularly intense. There is a very low threat of burn area flash flooding given PWAT values less than a half inch. By the evening hours, thunderstorms should diminish as instability wanes and the more organized convective activity pushes eastward into Kansas/Nebraska. Overnight lows will drop back to the upper 40s/low 50s for the plains with cooler temperatures across the higher elevations. .LONG TERM...(Wednesday through Monday) Issued at 342 AM MDT Tue May 17 2022 On Wednesday, most of the U.S. will be under the influence of a zonal flow aloft with a weak to moderate west-northwesterly flow over Colorado. Some post frontal cooling will result in max temperatures on the plains being some 5 degrees cooler than Tuesday's readings. In addition, models are showing some increase in low level moisture across the plains and Palmer Divide, mainly south of I-70. This increase in moisture combined with daytime heating and a passing upper level disturbance should result in a better chance for afternoon showers and storms mainly to the south and southeast of Denver. There is quite a bit of discrepancy between the models on the amount of instability. The majority of the models show meager CAPE which would result in mainly weak storms with gusty winds and light rainfall. However, a few of the models such as the NAM do show CAPE's around 1000 J/KG along with some shear to suggest the slight potential for one or two of the storms to become marginally severe during the afternoon or early evening. On Thursday, the upper flow strengthens over Northern Colorado as a broad upper trough begins to sag into the Upper Great Basin. This pattern will allow a much drier airmass to move into North Central and Northeastern CO. along with increasing westerly winds. A mountain wave along the lee of the Rockies could lead to windy conditions across the higher foothills with gusts to 55 mph possible. East of the mountains, downsloping flow will result in gusty winds, dry conditions and much above normal temperatures with max temperatures in the mid 80s to lower 90s. Much colder temperatures along with much needed precipitation is expected across the forecast area Thursday night into Saturday as the upper trough deepens and settles over Colorado. A strong cold front associated with the trough is progged to push across the Northeastern plains Thursday evening with temperatures expected to plummet from near 80 degrees in the early evening to the upper 40s around midnight. Precipitation is expected to increase from north to south overnight and become likely across much of the CWA by Friday afternoon as upslope flow deepens and QG ascent increases. At this time, it looks like Thursday night's and Friday's precipitation should be all rain on the plains with snow in the higher elevations. The highest potential for accumulating snow appears to be over the eastern slopes of the Front Range Mountains and the foothills above 7000 feet. Friday night into Saturday morning, the rain may mix and change over to snow on the plains. The current thinking is that most of the snow should melt as it falls due to warm ground temperatures with only light accumulations expected. The Palmer Divide could see a little more accumulation due to colder temperatures. In addition, it's looking like many plains locations could see a freeze Saturday morning as temperatures are forecasted to fall below 32 degrees. For Sunday into early next week, we should see a warming trend with decreasing chances of showers. && .AVIATION...(For the 06Z TAFS through 06Z Tuesday night) Issued at 1126 PM MDT Mon May 16 2022 VFR conditions will continue overnight into Tuesday. A very weak surface boundary briefly shifted winds at DEN to the ENE but winds at the terminals should remain below 8kt through most of the night. A front will shift winds to the north or northeast late tomorrow morning. Scattered showers and perhaps a thunderstorm or two will develop after 19-20z, but most of this activity should remain northeast of DEN. Can't rule out a brief period of variable or gusty winds with outflow tomorrow afternoon, but confidence is low at this point. Northerly winds will continue into the evening before gradually shifting back to drainage winds after 06z Tuesday night. && .FIRE WEATHER... Issued at 342 AM MDT Tue May 17 2022 Dry conditions are likely across the southern portions of the forecast area on Tuesday, especially over South Park, the southern Foothills, and Palmer Divide. Winds are forecast to remain below criteria through the day, limiting the overall fire danger. Isolated to scattered thunderstorms are expected to develop in the afternoon, which will bring wetting rain chances to the area, but also variable/gusty winds and lightning. Thursday will be dry, warm, and breezy with a good chance of Red Flag conditions in the afternoon for the plains and lower foothills. A cold front in the late afternoon or early evening will bring a shift to strong north winds. Colder temperatures and a good chance of precipitation is expected Friday. Warm and breezy conditions are possible again on Monday. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Hiris LONG TERM...jk AVIATION...Hiris FIRE WEATHER...Hiris/jk