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Area Forecast Discussion
Issued by NWS Pueblo, CO
Issued by NWS Pueblo, CO
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940 FXUS65 KPUB 212049 AFDPUB Area Forecast Discussion National Weather Service Pueblo CO 249 PM MDT Fri Jun 21 2024 .KEY MESSAGES... - A Flash Flood Watch remains in effect until Midnight tonight for the San Juan Mountains. More localized flash flooding possible across the remainder of the mountains through midnight. - A few strong to severe thunderstorms possible over the mountains and valleys today with hail up to 1 inch and wind gusts up to 60 mph along with locally heavy rainfall. - Drier and warmer pattern expected through Tuesday with isolated mainly mountain thunderstorms and temperatures reaching 100-105 again across the southeast plains next week. - Another uptick in thunderstorms possible mid to late week. && .SHORT TERM /THROUGH SATURDAY NIGHT/... Issued at 239 PM MDT Fri Jun 21 2024 Anomalously high moisture over the region (PWATs 200-250%+ of normal) ahead of a shortwave trough will provide plenty of fuel for strong to severe thunderstorms across the mountains and valleys through this evening with heavy rainfall and flash flooding the primary concerns. Soils are most saturated over the Eastern San Juans were a little over an inch of rain fell yesterday afternoon through last night. A Flash Flood Watch remains in effect for this area until midnight. Cloud cover has hampered heating across this area today as well as across portions of the central mountains which has limited instability. But as cloud breaks and surface heating occurs, odds for severe thunderstorms will increase as the afternoon and evening continue. High res models develop a couple rounds of convection, one which is moving through the mountains now, and another which is associated with the stronger forcing with the upper trough axis this evening through tonight. This latter wave may be the one to bring the heavier rainfall to the eastern San Juan mountains. Mean QPF from HREF suggests another inch of rain could fall across the eastern San Juan mountains with up to 0.5 inches elsewhere across the remainder of the mountains and valleys. 90th percentile QPF shows up to 1.75 inches of rain across the Southwest mountains and west slopes of the southern Sangre De Cristo range which would be the higher side of possibilities. Stronger shear and CAPE today will lead to one or two strong to severe storms across the mountains as well. Storms have been and will continue to be relatively quick moving (around 25-30 mph) but storm intensities and antecedent soil moisture could result in flash flooding for the more susceptible areas elsewhere across the mountains such as burn scars, and the Chalk Cliffs. Rock slides will be possible across the steeper terrain as well. So far rises on the gaged smaller creeks in the eastern San Juans have remained within banks and below action stage with additional room for rainfall. So far it still appears that storm intensity and rainfall rates may be the primary driver for flash flooding for these areas. As storms move off the mountains into the adjacent plains late this afternoon and evening, storms will become more higher based as dew points have been mixing out into the 40s east of the mountains. Downdraft CAPE of 1000-1300 J/kg will lead to more of a high wind risk (gusts to around 60 mph) from the stronger cells along the I-25 corridor, however some small hail (up to an inch) could fall along the lower eastern slopes of the southeast mountains. Activity should diminish after midnight as the trough axis shifts eastward and drier air works in from the north. Clouds and showers will be latest to clear across the southern mountains. Saturday will be drier and warmer, but there will still be sufficient moisture for afternoon and evening showers and thunderstorms. These will be higher based and less conducive for producing heavy rainfall and flash flooding. However there may still be sufficient lingering low level moisture to yield CAPE up to 1000 J/kg and deep layer shears are progged to be around 30-40kts. So we may still have a strong storm or two over the mountains and valleys depending on how quickly this low level moisture mixes out. East of the mountains, thunderstorm chances fall off quickly and these will be high based with gusty winds and lightning the primary risks. Thunderstorms will diminish quickly with loss of heating Saturday evening. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Issued at 239 PM MDT Fri Jun 21 2024 The heat continues to build for Sunday through Tuesday as the upper ridge builds northward back over southern CO. H7 temperatures +18 to +21 C will result in max temps back in the mid 90s to 105 degree range over the southeast plains with 80s for the valleys and 60s and 70s for the higher mountains/mountain communities. Monday and Tuesday could see more Head Advisories for portions of the I-25 corridor and southeast plains depending on these details, and this risk will be monitored closely. Fortunately, winds look relatively light which should mitigate any critical fire weather potential even though relative humidity values will be quite low in the afternoons. There will still be enough mid/high level moisture present for isolated high based thunderstorms each day, mainly across the mountains. Gusty winds and lightning with little to no rainfall would be the primary risks. Upper high picks up some subtropical moisture Wednesday into the latter part of next week which will bring increasing moisture and better chances for thunderstorms to the region especially Thursday into Friday as moisture quality increases. This will take the edge off temperatures some, but temperatures will still remain hot with highs 5-10 degrees above normal. Models advertise another upper trough for next weekend which shunt the moisture plume to the east and south once again so any uptick in thunderstorms late week appears temporary. -KT && .AVIATION /00Z TAFS THROUGH 00Z SATURDAY/... Issued at 239 PM MDT Fri Jun 21 2024 KALS: Thunderstorms will continue into the evening with -SHRA lingering until midnight at KALS as a disturbance moves through CO. Cigs could drop into the MVFR to even high end IFR range with +RA should a strong thunderstorm directly impact the terminal. Gusty erratic winds up to 50 kts, and small hail would also be possible. Thunderstorm risk diminishes after 02z though VFR cigs may continue until early morning. If clearing takes place earlier than anticipated some patchy ground fog could occur, though confidence in this still looks low. VFR conditions with light winds and drier conditions can be expected for Saturday. KCOS and KPUB...Best chance for VCTS will be at the KCOS terminal this afternoon between 23 and 01z. Gusty erratic winds up to 40 kts will be the primary concern. KPUB will be less likely to see VCTS but winds will become driven by outflows from weakening showers and thunderstorms as they move off the mountains bringing a gusty westerly wind shift into the terminal around 00z. Winds will be light after 02z and predominantly northwest to westerly at speeds under 10 kts. Tomorrow will be VFR with drier conditions and diurnally driven winds. -KT && .PUB WATCHES/WARNINGS/ADVISORIES... Flood Watch until midnight MDT tonight for COZ068. && $$ SHORT TERM...KT LONG TERM...KT AVIATION...KT