FOUS30 KWBC 120750 QPFERD Excessive Rainfall Discussion NWS Weather Prediction Center College Park MD 250 AM EST Thu Nov 12 2026 Day 1 Valid 12Z Thu Nov 12 2026 - 12Z Fri Nov 13 2026 Complex upper level evolution over the Northeast CONUS will lead to a small window of opportunity for locally heavy rain within the confines of northeastern NJ into portions of the NYC metro. Current assessment leans towards a short window in the afternoon and early evening hours for a band of shallow convection to materialize within the northern fringe of a developing low pressure off the northern NJ coast. Minor theta_E advection regime within the eastern flank of a developing trowal on the northern periphery of cyclogenesis will aid in a period of enhanced rainfall rates within the corridor containing the northeastern NJ counties south of NYC, into the lower NYC burroughs with emphasis on Staten Island into Brooklyn and perhaps lower Manhattan. This has been a theme the past few days from the CAMs, but there is a wavering in placement and longevity of any heavier echoes that transpire. Latest HRRR even places the heaviest QPF distribution off the coast which would negate any potential for flash flooding while the RRFS is the most aggressive in its interpretation. This has allowed for a some low-end FFG exceedance probs in the 00z REFS output in the aforementioned area, but certainly nothing overly concerning in the stance of the widespread, or even scattered flash flood prospects. After some coordination with the local NYC WFO, opted to maintain a nil risk for the threat, but did want to make mentioned locally 1-2" of rainfall in a 6-hr window is possible in that small area referenced above. Some ponding and heavy downpours are likely in this setup, but limited MUCAPE and longevity skew this more towards a non-zero threat, but still less than 5% overall. Thus, the probability of rainfall exceeding flash flood guidance is less than 5 percent. Kleebauer 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. Kleebauer 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... 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... ...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 $$