Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 412 PM EDT Thu Aug 18 2022 Day 3 Valid 12Z Sat Aug 20 2022 - 12Z Sun Aug 21 2022 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS SOUTHEAST ARIZONA INTO SOUTHWEST AND SOUTH-CENTRAL NEW MEXICO... ...2030z Update... Only minimal adjustments were necessary for this update based on the new 12z guidance, with the most significant change being a modest expansion of the Marginal Risk area over portions of the Midwest. This expansion was mainly towards the southwest (to include a large portion of MO), as global guidance is often too far north and east with weakly forced, warm season convection.. but some eastward expansion into IN/OH/MI was also necessary. This MRGL expansion is supported by the available (relatively) high resolution guidance, including the RGEM and downscaled versions of the GFS and ECMWF (which indicate localized 1-2"+ totals across the newly outlined region). Churchill ...Previous Discussion... ...Southwest and Four Corners into Central-Southern Rockies and Southern High Plains... Elongated shortwave energy will begin to move more swiftly eastward on day 3, especially by Sat night. Given the model trends with the heaviest QPF a bit farther downstream, have nudged the eastern portions of the Moderate, Slight, and Marginal Risk areas farther east across NM into West TX and the Panhandle compared to yesterday's Day 4 ERO. However, a key consideration for continuing the Moderate across southeast AZ, per collaboration with TWC/PSR/FGZ, is the expectation of heavy rainfall over these areas during day 2 (Fri-Fri night) and thus fairly wet antecedent conditions. Supporting both the Moderate and expanded Slight Risk areas is the first-guess fields form the Day 3 PQPF, along with 24hr average recurrence intervals or ARIs of 1-2 years based on the deterministic QPF on Day 3 (widespread areas of 1-2"). ...Parts of the Midwest... Similar to southwest WI into eastern IA and northern MO on Day 2, the slow-moving, compact mid-upper level trough will maintain a Marginal excessive rainfall risk on Day 3 across much of IL into southern WI and western IN. Activity will again be most prolific during the peak diurnal heating hours Sat afternoon, though again deep-layer instability may be modest at best (depending on pre-frontal cloud cover), while PW anomalies are rather unexceptional. Hurley Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt