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Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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151 FXUS65 KGJT 172107 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 307 PM MDT Sat Aug 17 2024 .KEY MESSAGES... - Deeper monsoonal moisture develops this evening and thunderstorm and shower coverage will increase Sunday. - Localized flash flooding remains a concern Sunday & Monday with some training thunderstorms possible. - While moisture values decrease Tuesday, remnant moisture will keep afternoon showers a threat on the terrain Tuesday and Wednesday. - PWAT values remain in excess of 130 percent of normal through week`s end, keeping showers and thunderstorms in the forecast. && .SHORT TERM /THROUGH SUNDAY NIGHT/... Issued at 300 PM MDT Sat Aug 17 2024 Monsoonal moisture has made an abrupt return to the region. Deep saturation has yet to enter the equation though. This morning`s Grand Junction sounding showed some weak moisture return to the mid levels with the dry boundary layer still holding solid. Dewpoints are still reflecting this around the area this afternoon, with many spots holding on to upper 30`s and low 40`s dewpoints. Around the Utah line things get a little wetter, but one has to cross west of the Wasatch to get into the deeper moisture. This deeper moisture should arrive on our doorstep early this evening along a shortwave trough that will work on some moisture and provide additional rounds of showers. Most of this activity will favor the terrain, with a few drifting over the valleys. Gusty outflows around 45 mph and some light rain are possible this evening. Showers wane steeply after midnight. Some activity could linger on the west side of the Divide, but will conclude before daybreak. Deeper convection returns Sunday with the atmosphere well saturated and PWAT values in excess of 150 percent of normal around the CWA. With the dry boundary layer conditions out of the way on Sunday, we can expect some productive showers around the area. Localized flash flooding becomes a concern under training storms Sunday afternoon and evening. Probabilistic forecasts hint at a swath of rainfall in excess of 1/2 an inch across the San Juans and northeastward into the Central Mountains. While this remains a target of concern, there will likely be other areas of productive rainfall. Showers will slowly decay into lighter stratiform precipitation Sunday night and taper by daybreak Monday. Afternoon temperatures will hover around climatology thanks to cloud cover from storms, while overnight lows will remain on the warm side in the higher dewpoint regime within the tropical influenced airmass. && .LONG TERM /MONDAY THROUGH SATURDAY/... Issued at 300 PM MDT Sat Aug 17 2024 On Monday not much changes in the pattern with a strong low pressure still located off the Pacific Northwest coast, and high pressure over the Southern Plains. These two features will keep the anamolous plume of moisture across our area so look for another day of scattered convection. A shortwave not associated with the low or high passes to our north and causes a slight drying on Tuesday. As that occurs the high pressure nudges closer to the area before the troughing eventually shoves to high way east. We will see a downturn in afternoon storms. Despite the drying moisture is replaced rather quickly so chances increase on Wednesday. It appears that the moisture will stay rather steady through the end of the week. These daily rounds of convection will lead to a continually saturating profile, with the potential for heavy rain outweighing odds for gusty winds with storms. As a result, flash flooding concerns will increase from midweek onwards so, similar to last week, be sure to stay tuned to the latest forecast before heading out or making plans to recreate. Temperatures through the period will be a bit of a rollercoaster. As the new work week begins daytime highs will be sitting a few degrees above normal before climbing to 4 to 8 degrees above normal for Tuesday. If the monsoon surge comes back as anticipated, Wednesday`s highs will moderate by a couple of degrees before dropping back to below normal from Thursday onwards. Overnight lows through the long term will be unseasonably warm for mid to late August. && .AVIATION /18Z TAFS THROUGH 18Z SUNDAY/... Issued at 1105 AM MDT Sat Aug 17 2024 Scattered storms are moving through eastern Utah now and that trend will continue through the evening. Additional develop over the high terrain is expected over portions of Colorado as well. These storms will be capable of strong winds and brief heavy rainfall. VFR conditions will prevail, but period of MVFR are possible. Showers linger tonight with minimal impacts. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...LTB LONG TERM...KJS AVIATION...TGJT