Guernsey, IA Weather

: Updated for the 12z Aviation Discussion:

Key messages

- Shower and thunderstorm chances continue this morning, then gradually diminish later today and tonight.

- Next chance of rain returns Monday, with thunderstorms possible Monday afternoon/evening. Rain will linger through Tuesday.

- Highs in the 60s common, though rain and clouds could drop highs into the 50s in spots.

Short term

Issued at 115 AM CDT Sat Oct 31 2026

A broad, positively-tilted 500 MB trough is making its way gradually northeastward across the central U.S. at the current time and will cross Iowa later today into tonight. At the surface, a large high pressure area is situated far to our east over the eastern Great Lakes region, while broad low pressure sits along the western High Plains in the lee of the Rockies. This will keep Iowa within modest southeast to south breezes through the weekend. A weak and nebulous near-surface boundary is currently located from northwest to southeast across Iowa and is serving as a focus mechanism for convective development early this morning as it very slowly lifts north/northeastward. Away from this band isolated showers and storms are also developing elsewhere around the region, as broad but modest forcing for ascent associated with the approach of the 500 MB trough overlies increasing 850-925 MB winds within a moist airmass. This will be the rule for today as isolated to scattered convection continues, but trying to pin down details of location and timing for shower/storm development becomes rapidly more difficult more than a few hours in advance and have thus maintained broad mid-range (30-60%) POPs through about midday. Thereafter, with the aforementioned low-level boundary lifting north of our forecast area and the bulk of the forcing aloft also shifting northeastward as the 500 MB trough axis approaches, rain coverage and intensity will gradually decrease from the afternoon through the evening and into tonight with POPs more in the 10-20% range after dark.

On Sunday the first 500 MB trough will move away toward the Great Lakes and Ohio River valley, but a deeper and stronger trough will come ashore over the U.S. Pacific coast. Between these two systems, a brief period of mid-level ridging will provide a break and the forecast is dry during the day. This will also support some breaks in the clouds and at least periodic sunshine to return, but any resultant warming will be tempered by humid conditions and light southeasterly breezes. Highs will peak somewhere in the 60s in most areas.

Long term

Issued at 159 PM CDT Fri Oct 30 2026

A prolonged period of rain and some storms will arrive to start next week. The western U.S. trough will eventually eject into the plains, enhancing the low and midlevel jet in the warm sector. At this range, deterministic runs bring MUCAPE values around the 300 J/kg range into southern Iowa. The potential for surface- based severe weather is heavily challenged by morning rain and lingering cloud cover. Moderate wrap-around rain stays in the state for Tuesday and partially into Wednesday. NBM QMD guidance shows that much of the state has around a 50% chance of exceeding 2" of rain, which matches the early convective nature as well as the very high PWATs (1.5") by November standards. The progressive nature of convection and the long-duration of rain will reduce potential hydrologic impacts. Highs will cool into the 50s following the system's departure and the upstream pattern will remain active and amplified.

Aviation

Issued at 624 AM CDT Sat Oct 31 2026

Scattered SHRA are crossing the area this morning and have included TEMPO groups in the first few hours of the TAFs mentioning these. Most associated visibility restrictions will be MVFR. Low ceilings are also impacting most of the area with MVFR and occasionally IFR heights, IFR being more likely in the northwest at MCW/FOD. Coverage of showers should gradually diminish, and ceiling heights should gradually increase, as we move through late morning and into this afternoon.

Watches, warnings and advisories

None.