Extended Forecast Discussion NWS Weather Prediction Center College Park MD 256 AM EDT Wed Oct 23 2019 Valid 12Z Sat Oct 26 2019 - 12Z Wed Oct 30 2019 ...Overview and Guidance/Uncertainty Assessment... It remains the case that an amplified upper flow pattern will continue into next week, but forecast spread is more than normal. The majority of the ensemble/deterministic guidance continue to forecast a splitting of the flow just east of the Rockies which will likely result in a slowly moving closed low over New Mexico/Texas late this week that gets picked back up into the flow ahead of another incoming and amplifying trough through the Northwest/West. The GFS and to a lesser extent the GEFS have been the quickest show the least flow separation for days. The ECMWF/Canadian/UKMET and ECMWF ensembles remain the least progressive and show the most southern stream separation. Upstream flow amplitude, wavelength spacing, guidance trends and WPC continuity favor a solution most in line with this latter group of guidance. The WPC medium range product suite was primarily derived from a blend of the ECMWF/ECMWF ensemble mean into this weekend. By next Sun-Wed, amplification downstream of a strong Alaskan storm should favor another trough digging just east of southward through the Pac NW and Great Basin. This seems to again favoredECMWF ensembles given the lead-in pattern and its typically better handling of amplified flow over the GEFS at longer time frames. ...Weather Highlights/Threats... A favored slower evolution over the Southern Plains/Lower MS Valley allows for a longer and continued lead fetch of deep/tropical moisture out of the Gulf. Several inches of rain are possible from the Gulf Coast states to the OH Valley with the main supporting/ejecting system trending more northeastward than earlier guidance. This occurs a weak wave of low pressure slows the front through the mid-South. The boundary should slowly push northeastward through the Ohio Valley this weekend and weaken as it encounters ridging to its east and as a stronger front to its west largely absorbs/overtakes it. In the West, incoming cold front late this week into the weekend will be mostly cut off from the moisture supply but will still manage to spread moderate precipitation including mountain snows, especially over the n-central Rockies as enhanced by upslope fetch. Rain/snow potential may also spread northeastward next week across the n-central U.S. with slow system progression and emergence into the Plains. Temperatures will trend much colder than average in the West behind the lead cold front this weekend, with max temperatures 10-25 deg F below average Sunday into next Tuesday along/east of the Divide from western Montana to eastern Colorado as the front whooshes southward. Above average temperatures will be confined to the Southeast to the south and east of the front. Florida will continue to see high temperatures well into the 80s with some record highs possible this weekend. Fracasso/Schichtel Additional 3-7 Day Hazards information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, winter weather outlook probabilities and heat indices 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/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml