FOUS30 KWBC 131950 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 250 PM EST Sat Dec 13 2025 Day 1 Valid 16Z Sat Dec 13 2025 - 12Z Sun Dec 14 2025 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF SOUTHEASTERN FLORIDA... A weak mid-level wave over the eastern Gulf will aid in increasing mid-level flow/ascent across the Florida Peninsula and adjacent Gulf Stream during the overnight hours. Meanwhile, low-level moisture will increase across coastal areas as a weak surface boundary/inverted trough becomes established just inland across the Peninsula. PW values should increase into the 1.6-1.8 inch range amid 500+ J/kg SBCAPE. Meanwhile, point forecast soundings depict favorable kinematic profiles for relatively slow-moving cells that could impact urban areas of southeast Florida along the I-95 corridor. Local 1+ inch/hr rates are possible. Urban flash flooding is possible in the 03-12Z timeframe this evening/tonight. Cook Day 2 Valid 12Z Sun Dec 14 2025 - 12Z Mon Dec 15 2025 ..THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF WESTERN WASHINGTON STATE LATE SUNDAY NIGHT/EARLY MONDAY MORNING... 2100 UTC Update -- No changes made to the Marginal Risk outlook based on the new (12Z) guidance. 12Z HREF window runs through the entire D2 period, and of note is the uptick in 0.50"/hr probabilities after 06Z -- peaking over 80% across the Olympic Ranges toward 12Z Mon, and over 40% across portions of the Cascades in WA. Hurley Previous discussion... Maintained the Marginal Risk area over parts of the Olympic and northern Cascade Ranges in Washington as the next push of moisture approaches late Sunday night into the early morning hours of Monday. The models have shown some run to run differences with QPF but no real clear trend. One consistent signal is that the orientation of the moisture plume remained more southwest-northeast than the event that just ended a couple of days ago. That still points to the idea that rainfall may not increase in coverage or intensity until late in the Day 2 period. Based on the expected IVT plume increasing to over 600 at about the time that the flow reaches the coast and begins to take on more of an on- shore component...am inclined to follow the ensemble idea of 0.75 inches to locally 1.5 inches of precipitation focused in the terrain. The area is sensitive given the nearly week-long excessive rainfall event...so any additional rainfall is expected to bring renewed hydrologic concerns. Given a fairly tight window of opportunity for rainfall during the outlook period...and at least some questions about timing of the onset....still think a Marginal Risk is sufficient for now although later shifts can adjust if needed. Bann Day 3 Valid 12Z Mon Dec 15 2025 - 12Z Tue Dec 16 2025 ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF WASHINGTON AND OREGON... 2100 UTC Update -- Only minor (cosmetic) changes made to the previous D3 outlook, some of which was to pull the eastern edges of the Slight ever so slightly westward in WA based on the latest snowfall forecast (lowering snow levels). Hurley Previous discussion... Areal coverage of rainfall expands and rain rates increase on Monday as a well defined atmospheric river continues to direct abundant moisture into the Washington coastal ranges and Cascades that gradually makes its way southward into Oregon. Given antecedent conditions from the excessive rainfall event from earlier in the week plus whatever falls on Day 2...the concern is for renewed flooding potential in addition to worsening on-going flooding especially in the terrain with potential for additional landslides or mudslides. Saw little reason to modify the Slight risk area that propagated into the Day 3 period from yesterdays Day 4 outlook especially given the magnitude of the IVT and precipitable water values forecast by the global models. The focus of the heavy rainfall should gradually shift southward into an area that did not receive as much rainfall from the previous atmospheric river. Opted to extend a Marginal risk area along the coast as far south as northwestern California more in deference to uncertainty of timing as to the rainfall amounts. Bann 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