Extended Forecast Discussion NWS Weather Prediction Center College Park MD 158 AM EST Wed Nov 6 2024 Valid 12Z Sat Nov 09 2024 - 12Z Wed Nov 13 2024 ...Watching Hurricane Rafael as it tracks into the Gulf of Mexico toward the Central Gulf Coast... ...Overview... An upper high will remain anchored over or just north of the Bahamas through the period, with ridges extending out from this high into the Gulf of Mexico and eastern U.S. at times. The National Hurricane Center continues to issue advisories for Hurricane Rafael which should weaken in a few days as it tracks closer to the central Gulf Coast. The combination of Rafael's moisture and a frontal system supported by an upper low ejecting northeast from the Plains may produce some areas of locally heavy rainfall from the Gulf Coast northward. Meanwhile, a series of Pacific systems will increase coverage of rain and higher elevation snow over the West from the weekend into early next week. Much of the East should see above normal temperatures through the period while the southern Rockies will start the weekend on the chilly side and cooler temperatures will spread across the West next week. ...Guidance/Predictability Assessment... For Hurricane Rafael, there is still considerable guidance spread (as the 00Z UKMET switched to a western/southwestern Gulf track versus bringing it to the central Gulf Coast) but overall the majority of dynamical/machine learning (ML) guidance is gradually narrowing the solution spread with a track approaching the central Gulf Coast. The system should also weaken as it reaches the northern Gulf, with latest guidance unsure of whether it will get lifted northward/northeastward or continue meandering over the Gulf. Continue to monitor latest NHC products for additional information on Rafael. A model average has provided a fairly consistent forecast of the upper low ejecting from the Plains, but guidance has been more erratic with details of a shortwave that enters western North America during the weekend and may have some influence on the remaining upper low energy by the start of next week (with some debate over which energy may be more pronounced at that time). This leads to uncertainty for some details of the frontal system reaching the Northeast. There are continued timing and amplitude differences for the larger scale trough moving into/through the West early next week, with GFS runs leaning slower and ECMWF faster. Latest ML models show a similar spread, arguing for a blend/compromise approach. This also mitigates issues for how energy may be distributed within the upper trough by the middle of next week, with individual solutions ranging between greater dynamics in the northern part of the trough, or farther south, to an evenly phased trough. A compromise also looks best for the next system that may come into the picture over the northeastern Pacific by next Wednesday. Overall a blend of the 12Z/18Z GFS, 12Z ECMWF, and the 18Z GEFS/12Z ECens means provided the most agreeable starting point for the forecast overall, with more operational model weight early nearly even model/mean weight by next Tuesday-Wednesday. ...Weather/Hazards Highlights... The combination of the Plains system pushing into the Mississippi Valley and moisture from Rafael, which is forecast to be south of the central Gulf Coast by the weekend, will lead to the potential for some areas of heavy rainfall between the central Gulf Coast and Lower Ohio Valley. While there is still spread in the guidance for where the moisture axis will be, clustering is significantly improved from just 24 hours ago. The Day 4 Excessive Rainfall Outlook valid Saturday-Saturday night maintains a Marginal Risk area across this region. It will take additional time to see if guidance resolves details sharply enough to merit an embedded Slight Risk. By Sunday, guidance signals become more diffuse along the front in the east-central U.S., leaving just the central Gulf Coast region with somewhat elevated potential for heavy rainfall due to the continued proximity of Rafael and meriting a Marginal Risk area in the Day 5 ERO. Some rainfall may linger beyond Sunday but most of the East should trend drier by Monday-Tuesday. Also of note, a wave tracking from the southern Bahamas into the eastern Gulf may increase rainfall over Florida around Sunday-Monday. The West will see a wetter regime with high elevation snow, starting in the Pacific Northwest and then spreading farther south into parts of California and east into the Rockies. Highest totals should be in the Sunday-Monday time frame with a vigorous upper trough and frontal system approaching/reaching the area. While there is still a fair amount of spread for QPF magnitudes, first-guess guidance is showing enough of a signal to introduce a Marginal Risk area in the Day 5 ERO over parts of the Pacific Northwest where initial soil conditions are neutral to damp. Another system may bring additional focused precipitation to the Pacific Northwest next Wednesday. Depending on western upper trough progression, some rainfall may develop over the central U.S. by the middle of next week. Except for the Great Lakes into New England during the weekend, the eastern half of the country will likely see above normal temperatures through the period. Warmest anomalies should be for morning lows, reaching 20-25F above normal on one or more days over the South and extending a little farther northeastward at times. Coverage of plus 10-15F anomalies for highs should increase going from the weekend into the first half of next week. Corresponding to these relative anomalies, there will be better potential for some record warm lows versus more isolated records for daytime highs. The northern Plains will also be well above normal until a cooling trend Tuesday-Wednesday, while the southern Plains will be warmest early next week. Chilly temperatures over the southern Rockies/High Plains will gradually moderate much of the West will be near normal during the weekend. The upper trough pushing into the West next week will expand the coverage of below normal temperatures from west to east. Rausch 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