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Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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936 FXUS65 KGJT 191130 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 530 AM MDT Fri Jul 19 2024 .KEY MESSAGES... - Temperatures are expected to remain a few degrees above normal with daily thunderstorm chances through the remainder of the week with a slight drying trend late in the weekend. - Threats from thunderstorms will mainly be from gusty outflow winds though a few storms will be capable of producing small hail and moderate to heavy rainfall rates. Overall flooding threats remain low. - The combination of high based storms, gusty outflow winds and lightning will also keep a threat of new wildfire starts in the picture. && .SHORT TERM /THROUGH SATURDAY/... Issued at 418 AM MDT Fri Jul 19 2024 Satellite imagery shows the high pressure is slower to move out of southern Arizona than the models predict, but with a shortwave descending south out of Canada along the front range through the day to nudge it a bit this afternoon, it should still slide northwest towards the Great Basin through the short term period. That the high remains farther to the south is keeping light nocturnal showers going across southeastern Utah and southwestern Colorado at this time. These showers should diminish going into the morning hours. Though the dynamics associated with the descending shortwave are weak, it will be enough to enhance the normal diurnal showers and thunderstorms we`ve been having. Look for more widespread coverage today over the high country with some storms moving down off the mountains into the valleys through the afternoon. With the inverted- V soundings, these storms will produce strong outflow winds gusting 40-50 mph, especially in the lower valleys. With weak flow aloft, these storms may be slower moving, and in areas of training, can produce localized flash flooding. Always be aware of your surrounding when you`re out in the hills and note what weather is going on around you. As the shortwave pass south of the region late this afternoon, showers and thunderstorms will decrease northwest to southeast across the region with lingering showers mostly along the Divide through the evening. Drier air moves into the region Saturday with pwats dropping below 0.6 inches across the northern areas. Expect another round of diurnal driven afternoon showers and thunderstorms across eastern Utah and Western Colorado with the lingering moisture, but they will be isolated north of the I-70 corridor and more scattered to the south. These storms will last into the evening hours before tapering off. Temperatures will remain near normal to five degrees above normal through the short term period. && .LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/... Issued at 418 AM MDT Fri Jul 19 2024 The ridge of high pressure remains to our west over the Great Basin with a cut off low spinning over the Midwest to our east, leaving our CWA in a fairly stagnant pattern with northerly flow over the area this weekend through at least mid next week. The placement of the high pressure far enough west will keep the deeper moisture over Nevada, while the northerly flow advects drier air into the region by early next week with PWAT anomalies reducing to around 60 to 80 percent of normal across the northern and central portions of the area. Largely, the models are showing an overall decrease in storm activity although feel that persistence is usually a good bet as this is the same pattern that we`ve been under for some time. Anticipate there will be enough moisture trapped under this ridge to allow for daily afternoon convection, although best storm chances may be more relegated to the western Colorado divide and Four Corners regions where the better moisture resides due to the dry northerly flow. Moisture may slowly erode, but still be enough for a few storms to produce locally heavy rain at times although gusty outflow winds and small hail may be the more likely outcomes. Storms are likely to favor the higher terrain with some southward drift into lower elevations, especially down south, but the precipitation output for lower elevations is fairly meager at best. By mid to late next week though, the cut off low over the Midwest looks to get absorbed in Upper Midwest/Great Lakes trough. A Pacific low is projected to move inland over the PacNW and help nudge the high pressure ridge over the Great Basin further east, which may allow this moisture trapped underneath to begin advecting eastward into eastern Utah and western Colorado by next Thursday and beyond. This is still a ways out and a lot of factors will influence the forecast one way or the other, but it does provide a bit of hope for better moisture. Temperatures will be largely unchanged with no real advection either way, so again, persistence is your friend. Look for highs to be near to around 5 degrees above normal during the coming week with warm, above normal lows as well. && .AVIATION /12Z TAFS THROUGH 12Z SATURDAY/... Issued at 516 AM MDT Fri Jul 19 2024 Currently light showers are moving through the southwestern areas of the region. Clouds are building over most of the mountains and will develop into showers through the morning, becoming thunderstorms by about 18Z impacting the mountain TAF sites through the afternoon with lightning, gusty outflow winds and periods of moderate to heavy rain. convective activity will taper off northwest to southeast through the late afternoon and evening. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...MDA LONG TERM...DB AVIATION...DB