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National Weather Service Forecast Discussion |
National Weather Service Forecast 48 Hour Graphical Forecast Today's Weather Story |
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000 FXUS65 KBOU 181427 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 827 AM MDT Wed May 18 2022 .UPDATE... Issued at 816 AM MDT Wed May 18 2022 Taking a look at current temperature observations across the region, the high country remains on the cooler side this morning. GOES-16 indicates mid-high level cloud cover over the mountains and valleys; NBM has a persistent cloud decks staying over this region through the afternoon thus this update includes lower afternoon high temperatures for areas west of I-25. Relative humidity remains on the higher side (35-50 percent) this morning which should lower to 20-30 percent this afternoon. This will lead to pockets of near critical fire weather conditions in northern Weld/Lamar counties through late afternoon. && .SHORT TERM...(Today and tonight) Issued at 437 AM MDT Wed May 18 2022 Today, temperatures will be a few degrees cooler, with highs in the low 80s on the plains and 50s and 60s in the high country. A weak disturbance in the flow aloft will force scattered afternoon convection concentrated in the southern part of the forecast area, generally Park County, the Palmer Divide and adjacent plains, where there should be a little more heating, moisture, and instability. There is a marginal risk of severe storms bringing lightning, gusty winds, hail, and light rainfall. Inverted-v forecast soundings suggest the primary threat will be the gusty outflow winds. By evening, most storms should have exited east. Tonight, there will be increasing northwesterly to westerly flow aloft a strong jet moves over the Pacific Northwest. .LONG TERM...(Thursday through Tuesday) Issued at 437 AM MDT Wed May 18 2022 On Thursday a broad upper trough will stretch from the Pacific Northwest eastward into the Northern Great Plains States. Colorado will lie on the southern side of this system under the influence of a moderate westerly flow aloft. This pattern will lead to dry, very warm and breezy conditions across North Central and Northeastern Colorado. Downsloping flow east of the mountains will result in much above normal temperatures on the plains with max temperatures ranging between the mid 80s and lower 90s. Drastically colder and wetter weather is expected Thursday night through Saturday as the upper trough deepens over the Southern Rockies. Snow should develop in the Northern Mountains around midnight as mid level moisture and QG lift increases. A Canadian Front associated with the trough is expected to move across Northeastern Colorado Thursday evening bringing a sharp drop in temperatures along with gusty north to northeasterly winds. There could be some timing issues in when the precipitation develops across the area. The consensus of the models is that initially the moisture behind the front may be too shallow to produce precipitation overnight across the Front Range Urban Corridor. The exception may be areas further north such as the Fort Collins area where there will be better QG lift associated with the upper jet. The showers should gradually shift southward into Metro Denver sometime during the morning hours as the upslope deepens and QG lift increases. Model cross sections are suggesting a ramping up of the precipitation Friday afternoon as the upslope deepens behind a secondary surge. Many of deterministic and ensemble members are showing the deep upslope flow continuing across the Northern/ Central Front Range mountains and foothills and adjacent Plains/Palmer Divide through noon Saturday. In addition, there looks to be plenty of QG ascent from a 100KT upper jet over Central Colorado. The combination of these factors should produce a good amount of much needed precipitation across most of the forecast area. Confidence is growing that heavy snow will fall across the Front Range Mountains and foothills above 7000 feet with 6 to 18 inches of accumulation possible, Therefore, have decided to issue a Winter Storm Watch from midnight Friday through Noon Saturday for these areas. The heaviest snow should be focused over the eastern slopes with lighter amounts expected west of the divide. Snowfall amounts for the lower elevations are a little more tricky. At this time, it appears that the rain over the Front Range Urban Corridor may mix and change over to snow Friday night and continue into Saturday morning. The current thinking is that most of the snow should melt as it falls due to warm ground temperatures with mainly light accumulations expected. The Palmer Divide could see a few inches of accumulation due to colder temperatures. In addition, many plains locations could see a freeze both Saturday and Sunday morning as temperatures are forecasted to dip below 32 degrees. For Sunday into early next week, we should see a warming trend. However, the cool and unsettled weather may continue as another upper level shortwave is progged to move across the region. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 437 AM MDT Wed May 18 2022 Expect VFR conditions through the TAF period. Moderate drainage wind should persist this morning until a weak northerly surge around noon. Tomorrow afternoon, storms will probably stay mostly south and east of the terminals. Outflow from those storms should turn winds southeasterly in the evening, then drainage winds are likely for the night. && .FIRE WEATHER... Issued at 437 AM MDT Wed May 18 2022 Today, much of our northern plains will have minimum humidity in the 15 to 20 percent range and a few areas may briefly fall below 15 percent. These areas may also see a few marginal gusts of 25 to 30 mph, but any critical fire weather conditions should be limited in coverage and duration and in areas that have recently received precipitation, so we have decided not to issue any fire highlights. Very warm, dry and breezy weather will result in near-critical to critical fire weather conditions across South Park, the Southern Foothills, Plains and Palmer Divide on Thursday. && .HYDROLOGY... Issued at 437 AM MDT Wed May 18 2022 Today, scattered showers and storms will be concentrated in the southern part of the forecast area, generally Park County, the Palmer Divide and adjacent plains. Few storms are expected near the burn areas, and storms should move quickly and bring light precipitation. && .BOU WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Thursday morning through Thursday evening for COZ214-216-238>251. Winter Storm Watch from late Thursday night through Saturday morning for COZ031-033-035. Winter Storm Watch from Friday afternoon through Saturday morning for COZ034-036. && $$ UPDATE...AD SHORT TERM...EJD LONG TERM...jk AVIATION...EJD FIRE WEATHER...EJD/jk HYDROLOGY...EJD NWS BOU Office Area Forecast Discussion
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