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Area Forecast Discussion
Issued by NWS Des Moines, IA
Issued by NWS Des Moines, IA
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203 FXUS63 KDMX 180348 AFDDMX Area Forecast Discussion National Weather Service Des Moines IA 1048 PM CDT Sat Aug 17 2024 ...Updated for the 06z Aviation Discussion... .KEY MESSAGES... - Isolated diurnal driven showers in the north will diminish after sunset. - Mostly dry on Sunday, although a low chance (< 20%) of high based showers or sprinkles in the far west. - Mostly dry with seasonal conditions mid-late week. && .DISCUSSION... Issued at 226 PM CDT Sat Aug 17 2024 This evening through Sunday... Stacked low pressure system continues to sit and spin over the Great Lakes vicinity this afternoon. Broad cyclonic flow remains anchored over the upper Midwest along with a corresponding shield of pesky low clouds, once again pivoting through the region. Regional radars showing isolated to widely scattered showers moving s/sewd across the northern sections pf Iowa and expect these to continue through sunset, before dying with loss of heating. Any rainfall amounts will be minimal. Overnight, the sfc high will make a stronger push to build swd out of the northern Plains. Hence, expecting skies to gradually clear and winds becoming light/variable. The guidance continues to trend a bit more aggressive with fog formation overnight. The 12z HREF is showing a patchwork of higher probabilities (20-50%) of vsbys < 1/2 mile, with the MAV/MET guidance indicating a few of the more fog prone sites (e.g. KEST/KMCW) could crash to 1/4 mile. As we know, fog forecasting is fickle, but continued the trend of mentioning patchy/areas of fog in the north for now, and will have future shifts monitor trends this evening. On Sunday, any morning fog should dissipate fairly quickly with a mostly sunny start. However, diurnal cumulus will develop again as heating commences. In the upper levels, a weak shortwave is expected to dive sewd on the east flank of the developing upper ridge during the afternoon hours. The best upper lift and low level moisture convergence should remain west of our forecast area, generally along and west of the Missouri River. However, the various ensemble and CAM solutions have trended eastward with the precipitation axis for tomorrow afternoon. At this time, soundings/X-sections in this forecast area indicate that the low levels will remain quite dry, and not supportive for precipitation, although a few high based sprinkles are possible. However, have trended sky cover higher due to increasing confidence of mid/high level cloudiness. Highs on Sunday should still be in the low to mid 80s. Monday through late week... Early next week, the models remain in good agreement showing the upper ridge expanding eastward into the Corn Belt. This is expected to result in mostly dry conditions, with a slow warming trend. Highs will range from the upper 70s to mid 80s, with mid to upper 80s likely by weeks end. Lows will be seasonal in the 60s. Precip chances are relegated to low chance /20-30%/ PoPs on Tuesday night, and again late on Friday. && .AVIATION /00Z TAFS THROUGH 00Z MONDAY/... Issued at 1048 PM CDT Sat Aug 17 2024 Widespread VFR conditions are expected for much of the forecast period. The exception would be toward daybreak on Sunday morning when localized MVFR visibilities in fog develop, mainly across northern Iowa. Winds remain light from the north overnight and into Sunday. && .DMX WATCHES/WARNINGS/ADVISORIES...None. && $$ DISCUSSION...Fowle AVIATION...Cogil