Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
421 PM EDT Tue Oct 22 2019
Valid 12Z Fri Oct 25 2019 - 12Z Tue Oct 29 2019
...Overview and Guidance/Uncertainty Assessment...
Amplified pattern to continue into next week but with muted
confidence later this week. 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 would get picked back up
into the flow ahead of another incoming trough through the
Northwest. The GFS has remained the quickest model for several
cycles but even the GEFS ensembles have trended slower in the past
24 hrs. The ECMWF ensembles remain slower than the GEFS and the
Canadian ensembles were quite varied (some as slow as the slowest
ECMWF members but others as quick as just behind the GFS). With an
increased number of ECMWF members and the continued agreement of
the ECMWF/Canadian and UKMET (though the UKMET was in between the
ECMWF/GFS), opted to continue to favor the slower camp but not as
slow as the ECMWF/Canadian. By next Sun-Tue, amplification
downstream of a strong Alaskan storm should favor another trough
digging just east of southward through the Pac NW and Great Basin.
Ensembles were in much better agreement here with more typical
differences between the GEFS (a bit weaker/farther east) and the
ECMWF ensemble mean (a bit deeper and farther west). Again favored
the ECMWF ensembles given the lead-in pattern and its typically
better handling of amplified flow over the GEFS.
...Weather Highlights/Threats...
With a favored slower evolution over the Southern Plains/Lower MS
Valley, this allows for a longer and continued fetch of moisture
influx out of the Gulf and over the front. Several inches of rain
are possible from the NW Gulf northward through Louisiana/Arkansas
as 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 light to perhaps moderate
precipitation out of Montana through Wyoming.
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
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
Hazards:
- Heavy rain across portions of the Southeast, the Middle/Lower
Mississippi Valley, and the Tennessee Valley, Fri-Sun, Oct 25-Oct
27.
- Heavy rain across portions of the Southeast, the Southern
Mid-Atlantic, the Southern Appalachians, and the Tennessee Valley,
Tue, Oct 29.
- Flooding possible across portions of the Northern Plains.
- Flooding occurring or imminent across portions of the
Northern/Central Plains, the Upper/Middle Mississippi Valley, and
the Pacific Northwest.
- Much below normal temperatures across portions of the Central
Plains, the Central Great Basin, the Northern Plains, the Northern
Rockies, the Central Rockies, and the Northern Great Basin,
Sun-Tue, Oct 27-Oct 29.
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