Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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940 FXUS63 KDMX 161744 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1244 PM CDT Sun Jun 16 2024 ...Updated for the 18z Aviation Discussion... .KEY MESSAGES... - Storms ending this morning except possibly the far southeast. Additional storms possible far north late this afternoon and especially tonight. A few severe storms could occur. - Heat indicies of 95 to 100 possible today and again Monday. - Storm chances return Tuesday night and Wednesday. A few severe storms again will be possible. && .DISCUSSION... Issued at 411 AM CDT Sun Jun 16 2024 A complex of storm is currently lifting slowly lifting northeast across parts of central and northern Iowa with additional activity in far southwest Iowa and back into northeast Kansas. Gusty winds and brief heavy rain continue with the Iowa storms and should be out of the forecast area by around 7 am. The activity over southwest Iowa and into Kansas is a bit of a wild card as there is potential that an MCV will evolve from it and it could trigger convection as it spirals east/northeast and could bring some convection into southeast Iowa later this morning. Have added low pops to this area and will continue to monitor this activity and adjust pops as necessary. For today, surface low pressure over north central South Dakota will lift northeast into northern Minnesota while lee side cyclogenesis over eastern Colorado occurs leading to another area of low pressure, with a boundary linking the two. This will drag the boundary into north central and northwest Iowa today while the thermal ridge leans into the state ahead of this boundary. The instability axis will reside in vicinity of the surface boundary along with pooling dew points in the low 70s on the south side of the boundary. There are a lot of things to unpack here from storm chances to heat potential. Let`s tackle the heat first. As discussed previously, the NBM has been running quite warm with the upcoming highs for Sunday and Monday and this is being caused by the warm bias correction that is being ingested into the guidance from numerous sources and this drives the NBM itself to near the 75th percentile. While the thermal ridge will be moving over the state today, deeper moisture will be in place as well, which makes it more difficult to heat than drier air. Thermal profiles also do not support the current NBM forecast so will continue to adjust below that. Finally, highs under the thermal ridge upstream did not reach these warmer values and expect the same today through Monday. So it will be warm but expect the NBM temperatures to underperform. With the boundary and the instability axis in the area this afternoon, a few storms could develop in northern Iowa but it does appear the elevated mixed layer (EML) capping should hold most of the day in that region and it does not appear there will be enough large scale forcing to help punch through any convective inhibition. Have held low pops in northern Iowa but again better chances it stays dry. The main complex of storms is expected to the north in South Dakota and Minnesota overnight. There most likely will be outflow dropping south from these storms into northern Iowa later tonight and into Monday morning with convective bubbling occurring as the outflow proceeds south. It is possible the outflow is near severe early and there is enough CAPE and updraft acceleration potential for a few storms with large hail. Monday`s weather will be dependent on the aforementioned outflow boundary and how far south it can get and maintain. Guidance suggests it should erode or be pushed back to Minnesota. This is likely as a large subtropical high protrudes further north into the New England region while an upper level low moves east to near Idaho. This will steepen the southwest flow aloft which would promote driving any boundary quickly north by the afternoon as the capping EML spreads back over the area. The sub-tropical high is looking stronger and further north than previous projections. The surface boundary should move into Iowa Tuesday night and into Wednesday and will bring a return for thunderstorms chances, a few of which may be severe. The boundary though likely will stall over Iowa and should be pushed back to the north as the sub-tropical high ridging into mid-Mississippi River Valley increases. This will bring the above normal temperatures back to the forecast Thursday and Friday. && .AVIATION /18Z TAFS THROUGH 18Z MONDAY/... Issued at 1242 PM CDT Sun Jun 16 2024 VFR conditions with gusty southwest winds to prevail for the next 6 hours. 30kt gusts are possible before sunset. Low confidence rain and thunderstorms for KMCW remain for overnight tonight so have left VCSH. Clouds associated with rain will fill into MVFR in the far north in the morning, affecting at least KMCW. Have left out of KFOD and KALO due to lower confidence. Gusty southwest winds to resume tomorrow after 14z. && .DMX WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Donavon AVIATION...Jimenez