165 FOUS30 KWBC 131942 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 342 PM EDT Mon Apr 13 2026 Day 1 Valid 16Z Mon Apr 13 2026 - 12Z Tue Apr 14 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF NORTH-CENTRAL TO NORTHEAST WISCONSIN AND NORTHWEST L.P. OF MICHIGAN... 16z update... 12z CAMs remain on track for an active thunderstorm environment with potential training cells capable of 1.75"+/hr rates and localized 2-3" totals. There remains continued latitudinal variance in the overall solution suite with another slight southward shift in the axis of heavy rainfall. The shortwave exiting the northern High Plains and expanding right entrance jet outflow dynamics will allow for strengthening of the low level jet; that initial WAA elevated cells should develop along a favorable west to east orientated line generally parallel to the mean steering flow to allow for training cells. However, the slightly stronger LLJ inflow and southward proximity to more unstable/moist air will allow for initially severe probably rotating updrafts in S MN to expand, grow up-scale to broader clusters and remain capable to intersect with rainfall of those initial WAA cells. However, stronger inflow and rotation of updrafts could allow for increased southward propagation as well,this may reduce some of that overlap maintaining situational uncertainty, though given the highly saturated ground condition and coordination with local forecast offices, have introduced a Slight Risk of Excessive rainfall across north-central WI to northeast WI. Downstream into the L.P. of Michigan, the overall convective complex will roll through the areas saturated by heavy rainfall yesterday, overall intensity should be reducing along with increasing forward speeds to limit rainfall totals. However, (near) record wet early spring, including spots of 2-4" yesterday, grounds are near or fully saturated that any rainfall will be converted to runoff and possible flash flooding. As such, the Slight Risk extends across Lake Michigan to encompass those areas most affected. Further south toward Chicagoland and across N IND, the 12z HRRR is bullish for convection breaking the cap across N IL later this evening with stronger convective cores expanding through interaction with the LLJ allowing for a favorable environment for 2-3" rainfall due to training. While recently dry over the last few days/week, the area also remains well above average in upper soil saturation values, AoA 60%, combined with larger urban centers prone to flash flooding including: Chicago, Gary, South Bend/Elkhart and Toledo, have expanded the Marginal Risk to account for this potential scenario. Gallina ~~~Prior Discussion~~~ A Marginal Risk for excessive rainfall was maintained for this period from eastern Minnesota to Lower Michigan. Although there was a modest decrease in the neighborhood probabilities for >1" totals, there still 20 to 40% across eastern Wisconsin and western Michigan as a formidable LLJ and increasing convergence within a progressing warm front could very well maximize the potential for heavier precip. Some rivers and streams across the region have ongoing minor flooding and any additional rainfall could speed up snow melt. Campbell/Kleebauer Day 2 Valid 12Z Tue Apr 14 2026 - 12Z Wed Apr 15 2026 ...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL ACROSS THE CENTRAL L.P. OF MICHIGAN... 21z update... ...Great Lakes Region... With the introduction of a Slight Risk across portions of WI, MI for the current Day 1 period, the affects of today's rainfall activity will likely result in changes and adjustments to this forecast. The synoptic environment did not change much with another leading shortwave/vorticity center lifting out over the mean ridge in the Great Lakes region. This will drive stronger confluence of the LLJ across Iowa to break out another round of strong/severe thunderstorms Tuesday evening. Overall deep layer steering flow and fairly orthogonal ascent over boundary reinforced by day 1 thunderstorm activity should help to focus a similar west to east (WNW to ENE) oriented axis of training thunderstorms. Upper-level dual jet couplet will further enhance up-scale growth to a broader complex to maintain through the overnight period, likely tracking through areas along or just south of the Day 1 activity. Still, most of the area remains at near or above record spring rainfall and soils are fairly saturated, so with cells capable of 1.5-2"/hr rates and localized totals of 2-3+" suggest the placement of a Slight Risk of Excessive Rainfall across portions of eastern WI and central MI (along and north of I-94). ...Pecos River Valley through Southern Plains into Ozark Plateau... Little change in expected evolution, storm mode across this area with the new 12z suite of guidance. Isolated cells along the dry line will be initially slow moving eventually locally expanding into smaller clusters after sunset. High moisture, slow cell motions may result in locally heavy rainfall 3-4", but will be isolated to widely scattered in nature. As such overall coverage suggests the Marginal Risk in place will suffice. The Marginal Risk area is connected to the area of concern over the Great Lakes and while there was some consideration of splitting the Marginal areas north of the Ozark Plateau to the Iowa border, but the threat remains non-zero and confidence is not that high on precise areas to remove; just note the coverage will decrease northward along the dry-line with best probability near the Lower Pecos and south- central OK based on current guidance suite. Gallina Day 3 Valid 12Z Wed Apr 15 2026 - 12Z Thu Apr 16 2026 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM TEXAS TO THE UPPER MIDWEST/GREAT LAKES REGION... 21z update... The surface to mid-level environment remains very similar to the prior 3 days, with a stark dry line extending from the Pecos River Valley across the Southern Plains into the Upper Mississippi Valley. The longer wave mid-level trough is starting to finally ejecting northeast into the central Plains though weakening as it progresses northward. The deep layer moisture axis and instability shift slightly eastward. As such clusters of thunderstorm activity with ample 1.5" Total PWats should result in rates up to 2"/hr and localized totals over 3" resulting in widely scattered clusters along/ahead of the main front, maintaining the need for the axis of Marginal Risk from northeast TX across the Ozark Plateau. Across the Great Lakes, overall moisture and instability will be reducing compared to prior days with warm front (mid-level confluence axis) continuing to drift further south across the Great Lakes. This moves further from the hydrologically sensitive/saturated areas of the northern Great Lakes region, but multiple days of stronger activity (current D1 and D2 periods) are likely to result in areas that will have saturated ground conditions by Day 3. Currently, the best overlap and probabilities for the most active convection on day 3 to be across NE IL across N IND into S MI and a Slight Risk may be required; however, without soil conditions becoming saturated yet, will hold off on delineating a categorical Slight Risk at this time. Gallina Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt