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Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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089 FXUS63 KDMX 142344 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 644 PM CDT Sun Jul 14 2024 ...Updated for the 00z Aviation Discussion... .KEY MESSAGES... - Enhanced Severe Storm Risk Monday with potential of significant damaging wind gusts over 70 mph - Heat Advisory in place to this Evening and Monday South - Cooler and Mainly Dry Tuesday through Sunday && .DISCUSSION... Issued at 252 PM CDT Sun Jul 14 2024 .Short Term /Tonight through Monday Night/... Confidence Short Term: Low to Medium Several competing factors in the short term forecast again this period with regard to precip chances. Heat remains the constant for now, though debris clouds from leftover convection will modulate highs a bit again today in some areas. Weak synoptic surface features remain over the region. Aloft at H700, the leading edge of the cap of 10C was over eastern Iowa at 12z. This did allow the two MCS to increase in strength around sunrise as they reached the eastern extent of the H700 cap. The approaching wave/MCS from South Dakota has now entered the region of warmer air aloft and correspondingly diminished over northern Iowa as anticipated. By this afternoon, some increase in storm coverage is expected as the H700 wave over the Northern Plains tracks east into Iowa this evening and crosses the state overnight. The synoptic models (EC/GFS) are holding the H700 cap over Iowa through the overnight. CAMS, particularly the HRRR and ARW cores are showing some weakness in the cap again over eastern Iowa by 21-23z this afternoon. Though no solution is heavily favored over the other, we will keep some thunder chances this afternoon over the northeast along the US20 to US30 corridors. Tonight the main areas of convection should hold north of Iowa until late in the period when some storms may cross into northern Iowa prior to sunrise as a stronger MCS moves through southern Minnesota and Wisconsin. Lows tonight will fall to the upper 60s to lower 70s in the north while the central to south will remain in the mid 70s. Tomorrow lingering debris clouds north and the sagging surface boundary will hold temperatures in the 80s north while the south again will be in the 90s with heat indices in the 100s. Tomorrow will be similar to today with regard to timing out convection. We will still be battling the H700 cap for a portion of the day into the afternoon hours. The main difference tomorrow is the added surface moisture convergence along the boundary moving through the region, plus increasing shear during the day and afternoon. CAMS are now showing some earlier initiation with late morning into early/mid afternoon firing of convection along the sagging boundary into central Iowa. Upper level wind fields are looking more favorable for a potential severe bowing system with more significant damaging thunderstorm winds into the afternoon hours. Still a fair amount of uncertainty with initiation and placement, but a corridor between US20/I80 and around or slightly east of I35 is more favored at this time. SPC is upgrading SWODY2 to enhanced over central to eastern Iowa with this potential in mind. Will need to monitor trends overnight into early Monday morning with regard to outflow, approaching upper level system and model convective trends. After the main area of early afternoon convection exits the region, we will still see trailing convection along the boundary in the evening into overnight hours south as the front sags into northern Missouri. With upper level return flow over the boundary, more storms will be possible through Tuesday 12z in this area. Lows Monday night will fall to the lower 60s north to the lower 70s in the south. .Long Term /Tuesday through Sunday/... Confidence: Medium to High After tomorrow`s potential significant convection, we will get a welcomed break from storms, heat and humidity through the end of the period. Still looking on track for highs to cool to the 70s to lower 80s with lows in the 50s to lower 60s for much of next week. There is some uncertainty late in the period with regard to return moisture, but some showers may advance back into western section around next Sunday. && .AVIATION /00Z TAFS THROUGH 00Z TUESDAY/... Issued at 644 PM CDT Sun Jul 14 2024 A cluster of thunderstorms this evening is impacting KALO. While precipitation will pass near to just south of the terminal, lighting will be a threat for the next hour. Activity this evening should remain clear of other TAF sites. Confidence decreases on Monday morning as there is the potential for convection across northern and eastern terminals. Timing and location have been difficult to pin down and will depend greatly on how the current storms in Iowa and overnight convection across the midwest play out. Therefore have kept to VCTS mentions and will need to update later as confidence increases in the details. && .DMX WATCHES/WARNINGS/ADVISORIES... Heat Advisory until 8 PM CDT this evening for IAZ004-015-023- 024-033>035-044>048-057>062-070>075-081>086-092>097. Heat Advisory from 1 PM to 8 PM CDT Monday for IAZ057>062- 070>075-081>086-092>097. && $$ DISCUSSION...REV AVIATION...Hagenhoff