Extended Forecast Discussion NWS Weather Prediction Center College Park MD 316 PM EDT Sun Oct 6 2024 Valid 12Z Wed Oct 09 2024 - 12Z Sun Oct 13 2024 ...Hurricane Milton could bring life-threatening impacts across parts of Florida through Wednesday... ...Overview... Hurricane Milton is currently located in the western Gulf of Mexico and is forecast to continue to track generally east- northeastward across the Gulf while strengthening to possibly a major hurricane. Milton should be approaching the west coast of the Florida Peninsula by early Wednesday with significant rainfall/flooding, high wind, and storm surge threats. Elsewhere, an upper trough (anchored by an upper low that may track over or near New England) will move through the East midweek while an upstream upper ridge tracks from the West to Central U.S. bringing a period of climatologically warm weather. By later this week, a Pacific trough may push inland over the West with some generally light precipitation to accompany. ...Guidance/Predictability Assessment... Model guidance continues to suggest Milton will strengthen into a possibly major hurricane as it tracks east across the Gulf. There remain some north-south wobbles and uncertainty in the timing, with plenty of run to run variability. The CMC remains the slowest of the deterministic models as it has for multiple days. UKMET runs are on the southern side, while the 12Z GFS came in a bit north with the track and QPF axis. The 00Z and 12Z ECMWF runs are good middle ground solutions and are closest to the official track from the NHC. Timing variability also evident in the latest runs of the AI/ML models as well. Milton may transition to extratropical quite quickly Thursday after it crosses the Florida Peninsula. Farther north with the main jet stream, models are reasonably agreeable with the pattern early in the period. The 00/06Z and now newer 12Z guidance has become more agreeable in showing an upper trough in south-central Canada Friday and moving into the Great Lakes Saturday that could serve to shunt the northern extent of the upper ridge southward, along with pushing a cold front southeastward compared to continuity. Then across the West, the timing of a trough approaching from the eastern Pacific gets quite uncertain late week into the weekend without much model or run-to- run agreement at all. Recent models are generally shallower with the trough compared to older runs, leading to less support for moderate to heavy QPF in the Interior West. As of the 00Z/06Z cycle, the CMC appeared to be a fast outlier compared to the GFS/EC. Guidance has generally slowed in the 12Z cycle, so the 12Z CMC's timing of the trough/possible embedded upper low progression is now pretty similar to the 00/06Z runs of the GFS and EC, while the 12Z GFS/EC have slowed even further. Expect changes to this aspect of the forecast since models are waffling so much at this time. The WPC forecast was based on a blend of the deterministic 00Z ECMWF, 06Z GFS, and some 00Z UKMET early in the period, with increasing proportions of the ensemble means to half by Day 6 and over half Day 7 given the uncertainty particularly in the West. ...Weather/Hazards Highlights... Milton is forecast to be a major hurricane as it approaches the west coast of Florida by the start of the medium range period Wednesday. There is an increasing risk of life-threatening storm surge and wind impacts for portions of the west coast of the Florida Peninsula beginning potentially even Tuesday night. Residents in these areas should follow any advice given by local officials, and check back for updates to the forecast. 5 to 10 inches of rainfall with local amounts to 15 inches is possible for parts of the Florida Peninsula, but the exact axis is still uncertain and dependent on on the track Milton takes across Florida. The highest amounts are likely to be along Milton's track and north closer to the surface front and upper support. Regardless of the uncertainty, the ERO for Day 4/Wednesday continues to show a Moderate Risk across north-central portions of the Peninsula, including the metro areas of Tampa Bay and Orlando and just south of Jacksonville, with minimal changes to the previous issuance. By Thursday, the heaviest rainfall associated with Milton should be offshore of Florida, though continue to depict a Marginal Risk for northeast FL to account for possibly slower speed. Elsewhere, the upper low over/near New England should allow for some lake-enhanced rain within westerly flow across the Great Lakes/Interior Northeast on Wednesday. A front passing through the Pacific Northwest by midweek should produce some light rain and nonzero chances of snow in the highest elevations. Then another round of precipitation is likely to come into the West with upper troughing on Friday, for moderate amounts of rain and some higher elevation snow in the Pacific Northwest. Precipitation amounts into the Interior West late week-weekend are more uncertain related to the evolution of the trough. The strong and persistent western-central U.S. upper ridge will promote an extended period of well above normal temperatures over that part of the country. The highest anomalies are likely for the northern Plains by Wednesday-Thursday, and some locations should reach 20-30F above normal as highs in the 80s may extend to the Canadian border. Northern stream troughing and a cold front could push the greatest warm anomalies southeast into the central Plains and Mid/Upper Mississippi Valley Friday-Saturday. Meanwhile height falls slowly pushing in over the West Coast will support a trend toward near normal temperatures by Wednesday or Thursday. However, temperatures around 10 degrees above normal in the Southwest could set additional daily records though the temperatures have moderated compared to recent days and the short range. Meanwhile, cooler than average temperatures are forecast across most of the East as upper troughing sets up near the East Coast, with some potential frost/freeze concerns across portions of the Great Lakes region into the Appalachians and interior Northeast. Expect temperatures to moderate next weekend as the upper low scoots out of the region. Tate/Santorelli 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