Extended Forecast Discussion NWS Weather Prediction Center College Park MD 207 PM EST Thu Nov 7 2024 Valid 12Z Sun Nov 10 2024 - 12Z Thu Nov 14 2024 ...Watching Hurricane Rafael as it tracks into the Gulf of Mexico... ...Overview... The National Hurricane Center continues to issue advisories for Hurricane Rafael as it tracks across the Gulf this weekend into early next week while weakening as it interacts with a mean upper ridge stretching from the Bahamas. Models and the NHC forecast reflect recent trends toward keeping the system well south of the central Gulf Coast while it weakens. However 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 through Sunday before the front continues eastward with lighter rain. Farther west, a large scale system will bring an episode of rain and high elevation snow to the Pacific Northwest through the Rockies Sunday-Monday with this system continuing into the eastern half of the country by mid-late week. Another system should focus additional precipitation over the Northwest by midweek. Expect above normal temperatures over most of the East for a majority of the period while the upper trough crossing the West early next week will bring a couple days of cool temperatures to the region. ...Guidance/Predictability Assessment... Continue to monitor latest NHC products for additional information on Hurricane Rafael which should weaken as it tracks over the Gulf of Mexico. The most recent NHC forecast track shows a preference more like the ECMWF/UKMET with a southwestern dive toward or into Mexico (albeit with only a weak surface low remaining). GFS runs have been just lingering and weakening the remaining low over the central Gulf. CMC runs that bring Rafael onshore into the central Gulf Coast are considered outliers, but have been somewhat consistent from run to run. Meanwhile there is a contingent of some AI/ML models from 00Z that take a weak Rafael near the central/eastern Gulf Coast and across the northern Florida Peninsula. Despite the spread, at least it is pretty clear that the center of Rafael itself should not impact the U.S., aside from its tropical moisture spreading northward. Farther north, guidance remains fairly agreeable for the closed upper low forecast to depart from the Upper Midwest early Sunday onward. There is still a fair amount of spread for trailing shortwave energy reaching the West on Sunday and continuing eastward thereafter. Other guidance suggests that the 12Z CMC closing off an upper low in the southeastern U.S. on Tuesday or so is particularly suspect, though the older 00Z CMC that seemed like an outlier in forming a closed upper low off the East Coast by midweek ended up being somewhat supported by the newer 12Z EC/GFS. Regardless, a pattern close to the ensemble means seems best. There are some timing and amplitude differences for the large scale upper trough nearing the West Coast by early Monday and continuing into the East after midweek, as well as for the resulting surface evolution. A blend/compromise approach among recent GFS/ECMWF runs and their means appears most reasonable for resolving these. The 00Z CMC was notably faster but the 12Z CMC was in somewhat better agreement. Deterministic and AI/ML models generally agree with showing a surface low strengthening near the Great Lakes region by the end of the period. The next round of troughing coming into the eastern Pacific by Thursday shows some minor differences as well, with the new 12Z GFS perhaps being a slow outlier. The WPC forecast blend favored the 06Z GFS/00Z ECMWF with lesser proportions of other models and ensemble means early on. As the forecast progressed, increased the proportion of ensemble means to half Day 6 and more Day 7 as spread increased. ...Weather/Hazards Highlights... While confidence is gradually increasing that Hurricane Rafael should remain well south of the Gulf Coast as it weakens from the weekend into early next week, guidance continues to show an axis of anomalous moisture extending northward from the Gulf and interacting with a front progressing across the east-central U.S. (slower and more wavy over the South) along with some limited instability. Model/ensemble solutions still vary in the details but consistency with the overall pattern favors holding very close to continuity for the existing Marginal Risk area extending from the central Gulf Coast into the Ohio Valley/central Appalachians in the Day 4 (Sunday-Sunday night) Excessive Rainfall Outlook. Rainfall looks lighter by Monday though there may be a few embedded heavy showers across parts of the Southeast. Additionally, parts of Florida may see some increase in rainfall around Sunday-Monday with a weak wave brushing the southern part of the state. An upper trough with leading surface front focusing an atmospheric river will approach the Pacific Northwest and then move inland Sunday-Monday, bringing an episode of focused precipitation to the region. For the Day 4/Sunday ERO there is still some variance for rainfall amounts but first-guess guidance and neutral to damp soil conditions favor maintaining the Marginal Risk area over western Washington into northwestern Oregon. By Day 5/Monday the moisture axis should sink a little south before progressing inland, while the GFS in particular offers potential for modest instability. Monday's ERO thus covers areas into northern California. However, another round of precipitation may impact the Pacific Northwest by late in the Day 5 ERO period, so this issuance of the ERO extends farther north from the previous issuance to add the bulk of the Pacific Northwest. High elevation snow is likely from the Cascades into the Sierra Nevada, while eastward progress of moisture and dynamics will also spread snow into the northern- central Rockies during the first half of next week. There may or may not be a break in precipitation around Tuesday, but additional meaningful precipitation is likely over the Pacific Northwest by Wednesday-Thursday as another system approaches. The system affecting the West early in the week will progress eastward and bring some areas of precipitation to the eastern half of the country during at least parts of the Tuesday-Thursday period. Important lower-predictability details still have to be resolved before confidence can increase regarding specifics of where/when the greatest totals will occur. But the low track near the Great Lakes could spread to moderate to high winds especially over the waters but possibly for some land areas like Michigan's Upper Peninsula. While system progression will provide some day-to-day variability, much of the eastern half of the country should see well above normal temperatures from Sunday into early next Thursday. Expect the warmest anomalies to be for morning lows, including some readings at least 20F above normal over the South early Sunday. Broadest coverage of plus 10F or greater highs should be during Monday-Wednesday. The northern and southern thirds of the Plains will also see a period of warmth Sunday-Tuesday (and still southern Texas on Wednesday). Corresponding to these relative anomalies, there will be better potential for some record warm lows versus more isolated records for daytime highs. Parts of the Northeast may be near normal at times though. The southern Rockies/High Plains will remain chilly to the extent that snow cover lingers, while the upper trough crossing the West early next week will bring a brief period of moderately below normal temperatures. Tate/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