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Area Forecast Discussion
Issued by NWS Grand Junction, CO
Issued by NWS Grand Junction, CO
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931 FXUS65 KGJT 152339 AFDGJT Area Forecast Discussion National Weather Service Grand Junction CO 539 PM MDT Mon Jul 15 2024 .KEY MESSAGES... - Temperatures are expected to remain a few degrees above normal with daily thunderstorm chances through the remainder of the week and into the weekend as moisture is recycled under the area of high pressure over the region. - Threats from thunderstorms will mainly be from gusty outflow winds though a few storms will be capable of producing smaller hail and moderate to heavy rainfall rates. Overall flooding threats remain low. - The combination of high based storms...gusty outflow winds and lightning will keep also keep a threat of new wildfire starts in the picture. && .SHORT TERM /THROUGH TUESDAY NIGHT/... Issued at 252 PM MDT Mon Jul 15 2024 SubTropical High pressure was centered over the S.Rockies on this morning`s H500 hand analysis map. This high will be slowly nudged back to the West through midweek as another trough digs into the Upper MidWest. Staying under the main circulation of this high will basically bring a run...rinse and repeat pattern in place the next several days. There is a lack of a deeper monsoonal moisture tap and large scale forcing so there is nothing really to throw a dart at for the thunderstorm forecast. Instead mesoscale forcing is more likely to give a clue to where storm chances may be a bit more robust...as in the remnant circulation that was drifting northward through central Utah this morning and fired early storms off the Tavaputs. Another weakly defined wave in PVU fields across N.Utah has also given the storms over the Uintas a bit of punch. These won`t be handled well in the models and expect to makes adjustment on the fly the next few days. The pattern will support the typical terrain based storms forming by mid-day. The challenge will be watching how these storms evolve through the day with moisture profiles still suggestive of gusty outflow winds and boundary interactions driving storm the storm mode. Under the right scenario some of the storms will be capable of heavier rainfall rates and producing some hail but the flooding threat remains low at this time. The moisture profile and lingering energy supports nocturnal storm activity but again nothing is written in stone attm. Otherwise temperatures will continue to run above normal until further notice with residual convective cloud cover highly dictating overnight lows as well. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Issued at 252 PM MDT Mon Jul 15 2024 High pressure will be sitting directly overhead by Wednesday with a westward shift by Friday over the Great Basin and Desert Southwest. PWAT values hover around 130 percent of normal Wednesday and Thursday before inching up towards 160 percent of normal by Friday into the coming weekend. With high pressure directly overhead Wednesday and Thursday, moisture will get recycled under the high for daily afternoon storms forming over the high terrain with gusty outflow winds, lightning and small hail the primary threats. Cannot rule out locally heavy rain with stronger storms but excessive rainfall does not appear widespread as moisture is not as robust. The high will retrograde back to the west by Friday into the weekend as a few shortwaves track around the northern side of the ridge through the Northern Rockies and drop down across the Divide and Front Range, so this could be the reason for the slight bump up in moisture levels and could result in increased shower and thunderstorm coverage compared to Wednesday and Thursday. The lower elevations may see some storms late in the day, especially Friday into the weekend but overall should remain drier with gusty outflow winds the primary concern. Temperatures remain mostly unchanged during this stretch as high pressure keeps highs around 5 degrees above normal but could end up closer to normal by the weekend due to increased clouds and showers. This pattern though with the high pressure ridge to our west and northerly to northwest flow over western Colorado is not a particularly favorable for a monsoonal moisture return. Daily storms and convection seem more a product of recycled moisture left under this ridge and disturbances tracking down the Front Range into the Plains. Details are a bit unresolved so some uncertainty exists in the forecast this weekend and beyond. && .AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/... Issued at 534 PM MDT Mon Jul 15 2024 Showers and storms have fired again this afternoon bringing some brief, heavy rain and gusty outflow winds to TAF sites. This trend will continue through 02-03Z before convection dies down. Outflow boundaries will linger across the region keeping those variable and gusty winds in the forecast for the next several hours, however. Calm conditions expected overnight with another round of convection expected again tomorrow afternoon and evening with more gusty outflows and some brief, heavy rain. Despite the convection, widespread VFR is expected to continue for the next 24 hours. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...15 LONG TERM...MDA AVIATION...TGJT