FOUS30 KWBC 122019 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 319 PM EST Thu Nov 12 2026 Day 1 Valid 16Z Thu Nov 12 2026 - 12Z Fri Nov 13 2026 ...THERE IS A MARGINAL RISK FOR EXCESSIVE RAINFALL FROM EASTERN PENNSYLVANIA INTO LONG ISLAND... A Marginal Risk was introduced in this update based off of the 12Z HRRR and REFS guidance, which both show a narrow stripe of 1-3" somewhere between Philadelphia and New York. By 18Z this afternoon, convection is expected to focus along an east-west oriented warm front lifting into the I-95 corridor. Should storms become surface based and begin to rotate, forecast hodographs suggest the Bunkers motion will be favorably aligned with the boundary to support cell training over urbanized areas. Cell coverage remains in question, but given the signal in the 12Z guidance along the urban corridor, opted to upgrade to a Marginal Risk. Asherman Day 2 Valid 12Z Fri Nov 13 2026 - 12Z Sat Nov 14 2026 The probability of rainfall exceeding flash flood guidance is less than 5 percent. Asherman Day 3 Valid 12Z Sat Nov 14 2026 - 12Z Sun Nov 15 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS NORTHWEST WASHINGTON STATE IN THE AREA OF THE OLYMPIC PENINSULA... ...2030Z Update... Forecast is on track for the Marginal Risk emanating from a second atmospheric river Saturday night. Expect additional rainfall of 1-3" atop the Olympic Peninsula between 00Z-12Z Sunday before the cold front presses eastward, which could lead to isolated flooding issues as it overlaps with the rainfall from the previous day. Asherman ...Previous Discussion... Area of heavy rainfall in the form of a moderate, yet progressive atmospheric river will send another wave of enhanced precipitation into the vicinity of the Olympic Peninsula on Saturday leading to a low-end threat of flash and areal flooding for the weekend. Heavy precipitation in the periods prior have allowed for local streams and rivers, mainly the Skokomish in the valley areas around the Olympics, to swell enough to warrant some extra caution for flooding around the river itself. Latest USGS gauge data signals the river running high, into the 75th percentile to date, for streamflows with some of the gauges running just below action stage at this juncture. Rainfall forecasts of an additional 1-3", locally higher, are expected for the D3 time frame with much of the rain occurring in a 12-hr window before the passage of a cold front late in the forecast period (Sat night into Sun morning). This could send some of the river banks overflowing and cause some local flood concerns, some of which could be flashy given the nature of the heavier rainfall on top of the hydrologic function of the river. With the forecast remaining fairly steadfast in its presentation and with previous coordination with the local Seattle WFO already okay with the current risk area, felt there was no necessary changes needed with the latest forecast as everything remains on track from a synoptic and hydrologic standpoint. Kleebauer Day 4 and Day 5 Valid 12Z Sun Nov 15 2026 - 12Z Tue Nov 17 2026 ...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS OF EASTERN TEXAS AND WESTERN LOUISIANA SUNDAY... 20Z Update... With the 12Z guidance not presenting any strong reason to deviate from the previous forecast, made only minor adjustments to the Day 4 Marginal Risk over eastern Texas and western Louisiana. This included trimming some of the northern extent of the previous outlook. Consensus of the preferred guidance indicates the heaviest amounts are likely to center near the upper Texas and southwestern Louisiana coasts, with limited instability likely tempering rates to the north. Some models are showing amounts that would warrant an upgrade along the coast. However, due to uncertainty regarding whether the heaviest rainfall will develop offshore, held off from upgrading to a Slight Risk at this time. Pereira Previous Discussion... ...Eastern Texas/Western Louisiana... Uncertainty remains in the rainfall forecast from the Day 3 into the Day 4/Sunday period across the southern Plains to Gulf Coast as a complex split flow pattern evolves. For Sunday, northern stream energy should merge with/overtake a leading southern stream wave providing the necessary lift to support scattered to widespread storms. Southeasterly flow setting up on the southwestern side of post-frontal high pressure will lead to moist Gulf return flow this weekend and particularly into Sunday, helping to push a lingering frontal boundary over the Gulf back north as a warm front into Texas. The combination of moisture and modest instability as well as strong lift along the frontal boundary/coastal convergence should support the potential for some more robust thunderstorms producing locally heavy downpours. Despite the latest 00Z GFS/AIGFS remaining outliers on depicting heavier amounts, the rest of the deterministic guidance are well clustered on the potential for heavy rainfall across eastern Texas into western Louisiana, with locally heavy totals of 3-5" possible. This would be more than sufficient to support a threat for at least isolated flash flooding, and possibly a higher risk as confidence increases in the forecast. ...Gulf Coast... Guidance indicates the upper-energy will translate eastward Day 5/Monday possibly leading to some additional storms along the Gulf Coast. However, strengthening high pressure to the north and a reinforcement of colder, dry air along the backside of the wave look to help push the frontal boundary into the Gulf. This should keep greater moisture/instability and the focus for storms mostly offshore. Even if the boundary/storms were to set up a bit further north along the coast, FFGs are high and would require a much greater signal for widespread coverage/several inch rainfall totals to raise a concern for flash flooding. Therefore, the probability of rainfall exceeding flash flood guidance is less than 5 percent. Putnam 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 $$