Preliminary Forecasts
Issued by NWS
Issued by NWS
850 FXUS02 KWNH 080652 PREEPD Extended Forecast Discussion NWS Weather Prediction Center College Park MD 251 AM EDT Wed May 8 2024 Valid 12Z Sat May 11 2024 - 12Z Wed May 15 2024 ...Emerging Texas/Gulf Coast/Southeast Heavy Rainfall Threat... ...Pattern Overview and Guidance/Predictability Assessment... Overall, guidance reasonably agrees for mean troughing to linger over the eastern U.S. while a modest Rex block/split flow pattern will take its time to de-amplify over the western U.S. through much of a mainly benign medium-range weather pattern there. A number of shortwave troughs are forecast to rotate around the mean upper trough in the East, and they present some issues as to when and where the shortwaves may interact and/or amplify. This has implications to coastal cyclogenesis specifics for this weekend. WPC progs have consistently shown moderate low developments given uncertainties, but there have been some stronger all-things come together solutions. Most recently, the 12 UTC UKMET offered the most robust low far southward offshore the Southeast to then up/off the coast, but the 00 UTC UKMET has started to back-off. As for the Rex block in the West, models generally show a gradual pattern flattening with time, with emerging differences on whether a southern stream low-amplitude trough ejects to the southern Plains or remains slow-moving over the Southwest into early-mid next week. Despite timing differences and varied lead impulses to consider, there is a growing downstream response signal for rainfall fueling moisture/instability to increasingly return/spread over TX and the Gulf Coast region/Southeast Sunday-next Wednesday. Given uncertainties, the WPC medium range product suite was primarily derived from a composite blend of compatible guidance from the latest GEFS/ECMWF/Canadian ensemble means and the National Blend of Models to offer a solid pattern base and reasonable continuity. ...Weather/Hazards Highlights... Moderate rainfall will linger this weekend over the Northeast with wrapback moisture and upper trough support as downstream energy transference leads to coastal low genesis, but details remain uncharacteristically uncertain even as we enter short range time frames. Upstream northern stream systems will then periodically offer bouts of mainly lighter rains from the north-central U.S. to the Great Lakes/Northeast this weekend to next midweek, albeit also with uncertainty in focus/timing, but with limited impact. Meanwhile to the south, a cooling/slowing trailing front along with a reinforcing front and upper shortwaves are expected to periodically focus precipitation from the southern Rockies/Plains out through the Gulf of Mexico and Gulf Coast/Florida this weekend through early-mid next week. A growing but still not solidified guidance signal offers support for moisture to increase along the Gulf Coast and vicinity ahead of the returning warm front. Heavy rain may work inland over time as the front edges northward. The WPC Day 5/Sunday into Monday Excessive Rainfall Outlook introduced a Marginal Risk area from SE Texas to southern Louisiana/Mississippi. Drenched soils from recent heavy rains also prompted an embedded Slight Risk area around Houston/SE Texas and SW Louisiana. Heavy rain and a threat of runoff issues may also spread through the central Gulf Coast to the Southeast early-mid next week to monitor. Schichtel 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 (QPF), excessive rainfall outlook (ERO), winter weather outlook (WWO) probabilities, heat indices, and Key Messages can be accessed from: 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 $$