Williamsburg, IA Weather

Key Messages

- Above normal temperatures and dry conditions to continue through the weekend.

Short Term

Issued at 151 AM CDT Wed Oct 21 2026

Water vapor imagery this morning shows a weak shortwave embedded in the midlevel flow over northeastern Kansas and northwest Missouri. This is generating an area of showers over eastern Kansas and Nebraska and is expected to move east-northeastward into northern Missouri and southern Iowa. However, dry air and weak forcing will lead to the majority of the showers dissipating prior to reaching northeast Missouri and southeast Iowa around 10 AM. Any showers that do reach the area would not have measurable rainfall; instead, evaporation would result in virga.

Following this shortwave's journey along the midlevel ridge, a stream of moisture will begin filtering into parts of Iowa, which remains under the influence of high pressure over the northeast US. However, dewpoints will still remain in the mid to upper 40s due to mixing within the boundary layer. Combined with highs in the low 70s to mid 70s and isolated clouds south of Highway 30, today looks to be yet another beautiful fall day.

Thursday, as a trough comes ashore along the California coast, the ridge axis and a high pressure across southern Canada will shift eastward. This high pressure will merge with the eastern high pressure, causing it to retrograde over the Great Lakes. This will lead to the warmest day so far, with temperatures a few degrees higher in the mid 70s.

Long Term

Issued at 151 AM CDT Wed Oct 21 2026

Above normal temperatures are expected to continue through the next week. As the ridge axis begins to shift eastward on Friday and Saturday, a tightening surface pressure gradient will lead to breezy conditions. Fire weather concerns are low despite the prevailing dry conditions due to moisture advection earlier in the week. However, any dry advection could lead to an increase in the fire weather risk Friday or Saturday.

Behind the ridge, a trough will lift out of the Rockies and into the northern Plains. While the axis of moisture advection will stay to our west in eastern Nebraska and western Iowa, increased cloud cover is likely through the weekend with the broad synoptic lift. Associated with the trough will be a surface cold front, which will slowly sag through the Upper Midwest. Forcing along the front will lead to a low chance (10-30%) for showers Monday, which will be our first chance for measurable rainfall since October 16. As this front moves across the CWA, it is expected to stall out, providing a further focus for precipitation next week.

Aviation

Issued at 530 AM CDT Wed Oct 21 2026

VFR conditions to prevail through the period. A weak shortwave to bring an increase in mid and high level clouds this morning primarily across southern IA and northern MO. Otherwise, quiet conditions to continue with winds switching out of the southwest mid morning remaining under 10kts through the evening. After midnight, some model guidance has a low chance (<10%) of some MVFR fog developing in a weak convergent flow regime. Decided to leave out mention at this time due to low confidence in timing and location.