248 FXUS02 KWBC 270756 PMDEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 356 AM EDT Mon Apr 27 2026 Valid 12Z Thu Apr 30 2026 - 12Z Mon May 04 2026 ...Heavy rain and flooding threat increasing across the south- central U.S. late week into the weekend... ...Overview... An amplified upper flow pattern will lead to episodes of active weather across parts of the country beginning later this week and lasting through early next week. A strengthening low pressure system will bring much needed rain to the Northeast Thursday into Friday, with coastal low development leading to multi-day rains into northern New England through the weekend into early next week. Meanwhile, a southern stream Pacific low ejecting out of the Southwest will set the stage for heavy rain from the south- central to southern U.S. late week into the weekend. ...Guidance/Predictability Assessment... The latest guidance continues to have a decent handle on the increasingly amplified blocking pattern that is expected to mature later this week and persist into the first week of May. That being said, as is typically the case with blocking patterns, models can sometimes struggle with the smaller scale features and details. Case in point, the timing of the southern stream Pacific low advancing inland across southern California and the Southwest continues to trend slower, which is a trend that first started several days ago. Given the influence of this feature on the potential heavy rain event across Texas later this week, opted to derive the WPC forecast using a composite blend that initially leaned on the slower (and farther south) solutions of the ECMWF, EC-AIFS, and to a lesser extent, the GFS. By Day 6 and 7, the blend shifted higher weights towards the EC and GEFS ensemble means, which offered a compromise between stability and detail of features along with continuity. ...Weather/Hazards Highlights... A frontal system associated with a deepening trough over the Northeast will begin to spread much needed rainfall into the region on Thursday. The primary low pressure system will weaken as it tracks into southeast Canada, but secondary coastal development off the Mid-Atlantic will take control soon after as it approaches southern New England later Thursday into Friday. The newly formed low will then begin to draw a long fetch of anomalous Gulf/Atlantic moisture northward, supporting an axis of heavy rainfall totaling 1-3" across northern New England and especially the southern half of Maine. While the signal for heavy rain is noteworthy and could lead to runoff or localized poor drainage flooding, recent moderate to severe drought conditions will likely render most of the rain more beneficial than hazardous. As a result, no Day 4/Thursday ERO was highlighted for the time being. The coastal low stalls out later Friday into the weekend, allowing intensity to wane but keeping conditions cool, windy, and wet/unsettled through early next week. A little snow wrapping in on the back/colder side of the storm can't be ruled out either across the higher elevations of northern New England or the Interior Northeast. Meanwhile, a southern stream Pacific low will slowly track inland across southern California, the Southwest, and the Four Corners states Thursday into Friday, spreading light to moderate low elevation rain and higher elevation mountain snow into the region. As this feature ejects eastward into the southern Plains, it will begin to interact with a nearly stationary boundary draped roughly along I-20 in Texas. Anomalous Pacific and Gulf moisture overrunning this frontal boundary combined with impressive dynamics and forcing from a strong upper jet will lead to the increasing potential for significant rainfall across central and southern Texas. Despite questions with respect to the quality of instability (particularly north of I-20) and the ongoing drought conditions over parts of the region, the heavy rain signal is concerning. For the Day 4/Thursday ERO, the existing Marginal Risk was expanded southward in an effort to capture the current forecast QPF max while also accounting for the better instability south of I-20 (and especially along and south of I-10). An upgrade to a Slight Risk was considered, but opted to hold off for now given uncertainty with mesoscale details. After Thursday, waves along the frontal zone will expand the rainfall footprint eastward over the Mid-South and Southeast Friday into the weekend, with additional risks of heavy rain and potential flooding. As a result, a Day 5/Friday ERO was introduced for most of eastern Texas, southern Arkansas, the northern half of Louisiana, and southwestern Mississippi. Additional upgrades and expansions farther east are possible with future updates. Elsewhere, another Pacific closed low may approach northern California and the Great Basin later this weekend into early next week, bringing cooler and unsettled weather featuring low elevation rain and high country mountain snow. Miller Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation forecast, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml https://www.wpc.ncep.noaa.gov/#page=ovw $$