Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
140 AM EST Sat Nov 09 2019
Valid 12Z Tue Nov 12 2019 - 12Z Sat Nov 16 2019
...Record cold next week for much of the central/eastern states...
...Pattern Overview and Guidance/Predictability Assessment...
Punctuated upper ridging will meander off the coast of California,
favoring troughing east of the Rockies. Over Mexico, a slow-moving
closed low will eventually rejoin the southern edge of the
westerlies after Wednesday and track across the northern Gulf of
Mexico. The models/ensembles were in good agreement overall but
with varying degrees of speed/track/evolution differences in a
fairly perturbed pattern. The 12Z GFS/ECMWF and 00Z ECMWF formed
much of the base for the forecast with the 12Z NAEFS/ECMWF
ensemble mean as a needed smoother. Largest differences were in
the Southeast as the Mexican upper low and a northern stream
shortwave merge/phase/interact which may induce cyclogenesis and
increase precipitation over the region. 12Z ECMWF appeared too
aggressive but the 12Z GFS too quick (both their biases). 12Z
ECMWF ensemble mean and NAEFS mean were weaker but perhaps better
placed, along with the 00Z/08 ECMWF (just offshore). Secondarily,
troughing in the eastern Pacific may approach California in some
fashion as a shortwave may crest the upper ridge along 140W.
Ensembles have trended more bullish but will need to wait to see
if any precipitation can be realized south of NorCal.
...Weather Highlights/Threats...
Cold Canadian high pressure will move out of the central/southern
Plains Tuesday and into the Ohio Valley by Wednesday, bringing in
well below average temperatures that will likely break daily
records across a sizable area of the eastern half of the CONUS
Tue-Wed. This equates to high temperatures in the 40s from Texas
into the lower MS Valley, 30s in the TN Valley, 20s in the
Midwest, and teens in the northern Great Lakes, which is more
typical of mid-winter in some locations. For some, this could be
the earliest in the season such cold will be observed in the
period of record. Temperatures will moderate for later in the week
as the high moves offshore and weakens, but highs will remain
about 10-15 degrees below average along and east of the
Mississippi into next Friday. West of the Rockies (but including
parts of the Front Range), temperatures will stay above average by
about 5-10 degrees.
Low pressure will move out of New England Tuesday with a swath of
snow to the northwest of the track and lake-effect snows for the
Great Lakes with very cold temperatures aloft over still warm
water. By the end of the week, the upper low once over Mexico will
reach the Gulf and its interaction with a frontal boundary could
spread increasingly heavier precipitation over the Southeast as
low pressure develops near Florida. This may lift northeastward
into next Saturday along the coast with some high elevation snow
possible for the southern Appalachians per the current evolution
in the lingering cold air mass.
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
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