Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
216 AM EDT Sat Oct 13 2018

Valid 12Z Tue Oct 16 2018 - 12Z Sat Oct 20 2018

...Cooler than average temperatures for much of the lower 48 next
week...


...Pattern Overview...

An upper low near Baffin Island/Davis Strait will meander in place
as upper ridging in the Northeast Pacific pushes into western
Canada and flattens. This will favor positively tilted troughing
from the Four Corners region (where an upper low will wobble
around) to the Great Lakes/Northeast where a couple cold fronts
will swing through. Across Florida, subtropical ridging will hold
in place, maintaining warm weather but with a daily chance of
rain/storms as a front stalls over the peninsula.


...Guidance/Predictability Assessment...

A multi-model deterministic blend served as a reasonable starting
point for the forecast during days 3-5 (Tue-Thu). Trend has been
for ridging in the northeastern Pacific into western Canada to
hold on to some amplitude longer than was forecast 24 hrs ago,
thus helping to form a stronger front east of the Canadian Rockies
into the Great Lakes next Fri/Sat. Lots of deterministic spread
exists with this system but for now will only show a modest
surface low given the lack of consistency in both the GFS/ECMWF.
Stationary boundary will mostly remain across the northern Gulf
through the week with an inverted trough out of the NW Gulf into
SE Texas.


...Weather Highlights/Threats...

Well below average temperatures on Tuesday (likely breaking record
low minima and maxima over many stations from KS/CO southward to
TX/LA) will start to relent but still continue into Wednesday
across much of Texas where highs will struggle to reach the 60s
away from the coast. On the warm side, parts of Florida may
tie/break record highs south of the front where upper ridging will
be centered.

Precipitation may be heavy on Tuesday over northern Texas on the
cool side of the front but between the upper low to the west and
the upper ridge to the east. The rain axis will extend
northeastward to the Mid-Atlantic but in lessened amounts. The
rest of the lower 48 behind the front will be largely dry with
some rain/snow showers around the Lakes.


Fracasso


WPC medium range 500 mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indexes are found 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