Sunrise 5:56 AM   Sunset 7:58 PM Moonrise 2:45 AM   Moonset 2:02 PM

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FXUS65 KGJT 031047 AFDGJT

Area Forecast Discussion National Weather Service Grand Junction CO 447 AM MDT Fri May 3 2024

KEY MESSAGES

- A system will brush the northern tier of eastern Utah and western Colorado today, bringing a few valley rain and mountain snow showers. Minor accumulations are expected with little to no impacts.

- Scattered showers are possible late Saturday mainly in the mountains. Elsewhere expect warmer and dry conditions.

- A strong system is expected on Sunday and Monday. It will bring widespread precipitation and strong winds.

SHORT TERM /THROUGH SATURDAY/
Issued at 115 AM MDT Fri May 3 2024

A shortwave trough will pass just north of the CWA later today. It will bring a cold front and enough moisture for scattered valley rain and mountain snow showers. The best chances for showers is along and north of the highway 40 corridor, but a few could reach as far as I-70 with little to no accumulation there. The northern mountains look to receive a bulk of the precipitation as well as the upper Yampa valley. Snow levels will range from 7-8 kft, but given most of this falls during the day snow should cause to limited impacts. Showers enter the area from Wyoming later this morning and continue pushing eastward this afternoon before exiting this evening. The prefrontal jet is quite strong with this system so daytime mixing and virga showers will allow these winds to reach the surface. This afternoon most locations see gusts over 25 mph, but they could be as high was 40-50 mph in spots. Right now that appears to be along and just north of I-70 from Rifle to Vail. Temperatures will be rather seasonable across the southern half of the area. Up north clouds and precip will keeps things cooler than normal.

Conditions dry out tonight due to a lack of lift, but the moisture never really leaves the region. A weak shortwave sneaks up from the southwest tomorrow during the day. It along with the moisture will support convection later in the day. The best chances for showers will be the southern and central mountains. The QPF is on the low side so impacts should be minimal. Temperatures recover and warm in this southwest flow aloft.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
Issued at 115 AM MDT Fri May 3 2024

Any lingering showers from Saturday afternoon along the Continental Divide mountains should diminish during the overnight hours Saturday night. After a warm day, nighttime temperatures will be quite mild with lows roughly 10 degrees above seasonal norms. For Sunday, attention quickly turns to a large and deep mid-level closed low pressure system that will be tracking across the Great Basin to round out the weekend. Ahead of this system, a tightening pressure gradient... along with a pronounced southwesterly mid and upper level jet with wind speeds of 40 to 50 kts at 700mb and over 100 kts at 250mb... will punch into eastern Utah and western Colorado Sunday afternoon. Strong diabatic heating will support deep boundary layer mixing, resulting in the efficient transport of very strong winds aloft down to the surface. Frequent surface wind gusts of 45 to 55 mph are likely to be common, with max gusts up to 60 mph in the valleys and 80 mph in the high elevations not ruled out. These are the types of setups that often produce our high end wind events here, so wind highlights are almost certainly going to be needed at some point. For now, keep an eye to the forecast and be prepared for a very windy day on Sunday.

Sunday night into Monday, models are highlighting a strong shortwave and vort max rounding the base of the closed low now over the northern Rockies, taking on a negative tilt, and swinging across eastern Utah and western Colorado. This potent and dynamic feature will also be accompanied by a strong cold front as it blasts through Sunday night into Monday. Ahead of and along the front, fairly widespread showers are expected to break out as moisture, surface convergence, and large scale forcing for ascent increases and becomes maximized. Right now, guidance is pointing towards the heaviest precipitation being confined to the central and northern Colorado mountains where QPF amounts of 0.50" to 1.00" are progged... with lesser amounts of 0.25" or less elsewhere. The air mass will initially be very warm, as evidenced by snow levels well above 9000 to 10000 feet, but will quickly cool to between 5000 and 6000 feet by early Monday morning in the wake of the front. No doubt the mountains way up high will see some snow from this system, but how much entirely depends on how much precip is left once the colder air moves in. Since this will be a fast moving system, and most of the significant precipitation will be over with by Monday afternoon, there's likely just not enough time when the highest QPF amounts and the colder air overlap. However, if there's one place where snow accumulations may be fairly decent, it's in the highest elevations of the Park Range as cold, upslope, orographic, northwesterly flow and another wave on Tuesday may allow snow to pile up in excess of 6 and possibly 12 inches.

Beyond Tuesday, the rest of the long term period likely remains unsettled with deterministic models and ensembles highlighting continued troughing across the Intermountain West. Showers in the high country will probably be a daily occurrence, particularly across the northern Colorado mountains. Elsewhere, the big story will be the cooler than normal temperatures with highs largely in the 50s and 60s down low, and 30s and 40s up high. Overall, the synoptics driving the pattern next week are chaotic and likely to be influenced by mesoscale processes and convection. As a result, expect to see some changes in the forecast and for the finer details to remain unclear until we get closer.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
Issued at 500 AM MDT Fri May 3 2024

VFR conditions should hold over the next 24 hours though cigs will be lowering up north in the afternoon as the next system works through. KHDN should see a passing shower with an outside chance of MVFR conditions by mid afternoon. Gusty afternoon winds of 25 to 40 mph are expected again at most sites. ILS cigs are possible at KEGE and KRIL late afternoon.

GJT WATCHES/WARNINGS/ADVISORIES

CO...None.
UT...None.

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