245 FXUS65 KBOU 301035 AFDBOU Area Forecast Discussion National Weather Service Denver/Boulder CO 435 AM MDT Mon Apr 30 2018 .SHORT TERM...(Today and tonight) Issued at 430 AM MDT Mon Apr 30 2018 Forecast area remains under a broad swly diffluent flow aloft in advance of a deepening mid-level trough slowly migrating eastward over the Intermountain Region. 06z Model run has the 500mb trough axis passing over the Salt lake City area around 18z today and convective precip forming over the northwest corner of Colorado about that time. Through the day should see the flow aloft strengthen and so will swly surface winds on the plains with pressure falls on the plains. Strongest sfc winds on the plains roughly southeast of a Parker to Sterling line and centered around Limon in Lincoln County by mid-afternoon. Prevailing speeds across this portion of the CWA expected to be in the 15-25 mph range by midday, with peak gusts in the 25-40 mph range across ern Elbert, Lincoln, eastern portions of Adams and Arapahoe and southern Washington Counties this afternoon. The strong gusty winds and RH values in the 7 to 12 percent range will likely result in patchy to areas of blowing dust in this same area. Therefore, will add this to today's forecast. This same area is presently under a RED FLAG WARNING starting at 10 AM MDT this morning and ending at 7 PM MDT this evening. It's possible the waning could be extended another hour or hour for Lincoln County should the gusty swly winds continue, but will hold off for now. Otherwise, as the upper trough and cold pool aloft moves closer to the forecast area, should see an increase in clouds initially over the high country and later today out over the plains. Should also see the formation of isolated to scattered showers/t-storms in the northern mtns by around midday as moisture increases and mid- level temperatures cool. By late afternoon, shower/t-storm coverage should expand southward over remaining mtn areas with passage of a weak shortwave disturbance. For the plains, HiRes models indicate a narrow band of convection, i.e., t-storms forming along a sw-nw convergence zone lying across Morgan and Logan Counties around 00z/Tue. And as the shortwave passes should see convection initiation. Gusty winds and lightning probably main product of these short-lived storm cells. See this convection going away before midnight as it shifts up in to Sedgwick and Phillips Counties. otherwise it should remain dry elsewhere on the plains under late tonight with a weak push of cooling, more humid slips down from sern WY and wrn NE. With a shift to n-nely bndry layer winds, could see low and mid-level clouds form along the Front range as well as a few sprinkles. Do not see as fog at this time, but wouldn't rule it out around dawn. .LONG TERM...(Tuesday through Sunday) Issued at 430 AM MDT Mon Apr 30 2018 The middle of the week will be trending cooler and wetter across much of Northern Colorado as upper low over the southern Great Basin impacts the region. On Tuesday, Northeast Colorado will be in a post frontal regime with shallow upslope flow and gradual moistening of the airmass. PW values are forecast to increase to .50-.75" over the plains by later Tuesday afternoon. Only marginal instability will result, given the cool low levels of the atmosphere, so mainly rains showers and possibly an embedded, yet non- severe thunderstorms. The closed low circulation will begin to lift out and move northeast across Colorado in the Wednesday through early Thursday time frame. This will increase widespread ascent aloft coupled with 100+kt jet streak streaming across Colorado. Given the track of the low across the central and northern portions of the state, the best chance of precipitation will be over Northern Colorado, mainly north of the Interstate 70 corridor and lesser chances further south. Expect decreasing showers by Thursday night as the low moves out onto the central plains with drying and subsident airmass taking over across Colorado. Model forecast qpf is fairly substantial from the GFS/European with a broad 1-2 inches of water from Denver northward to the northern border areas with lesser amounts further south. The NAM amounts have the heaviest qpf further north towards our border areas with Wyoming. This system will be fairly warm with all rain at lower elevations and snow levels ranging from 8000-9500 feet on Wednesday before lowering a bit more on Thursday. The best chance of accumulating snow in the mountains would be on Wednesday night and Thursday as flow turns northwest along with cold air advection. High pressure ridge aloft will build over the region on Friday and Saturday with warmer temperatures and only a slight chance of showers over the mountains. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 430 AM MDT Mon Apr 30 2018 VFR conditions today with s-swly winds light early this morning, then increasing to 10-20kts by midday. Stronger winds expected at KAPA and KDEN this afternoon with possible gusts to 30kts. May even some blowing dust for a time with the gusty winds and low relative humidity. Tonight, winds will diminish as remain southerly until a shift to the north-northeast around 09z with the passage of a weak cold front. Could see scattered to broken clouds flow around dawn with ceilings possibly as low as 6000 ft agl. Not expecting any precip with this surge, although foothills areas could see sprinkles or drizzle. && .FIRE WEATHER... Issued at 430 AM MDT Mon Apr 30 2018 Expect another windy and warm day today with wind speeds of 15 to 25 mph with gusts in the 30 to 40 mph range across eastern portions of Adams and Arapahoe Counties, and eastern Elbert, Lincoln and Washington Counties this afternoon. It appears the southern foothills in Jefferson and Douglas Counties will also blow today, and with low humidities, this area will also be included in the Red Flag Warning in effect for the counties mentioned above. Expect minimum relative humidities in the 7-15 percent range, even though temperatures will be slightly cooler today. The RED FLAG WARNING will run from 10 AM to 7 PM MDT today. && .BOU WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from 10 AM this morning to 7 PM MDT this evening for COZ216-245>247-249. && $$ SHORT TERM...Baker LONG TERM...Entrekin AVIATION...Baker FIRE WEATHER...Baker