Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Tue Oct 08 2019
Valid 12Z Fri Oct 11 2019 - 12Z Tue Oct 15 2019
...Record cold to gradually relent in the Central Rockies to
Northern Plains/Upper Midwest...
...Pattern Overview and Guidance/Uncertainty Assessment...
An anonymously deep upper low will very slowly lift through the
Upper Midwest/western Great Lakes through the weekend. Near the
east coast, a potential subtropical system is forecast to track
close to southeastern New England (near the 40/70 benchmark). The
National Hurricane Center is monitoring this area for development.
Please reference their outlooks for more information.
The models and ensembles were in generally good/great agreement on
the synoptic pattern with typical timing differences in the
west/central CONUS--GFS generally quicker and ECMWF generally
slower with the UKMET/Canadian in between. A blended solution was
preferred given the deterministic-subset cluster well within the
multi-center ensemble cluster. Off the east coast, models were
still having trouble resolving the track/intensity and even
structure of the hybrid system through the period. Preferred the
slower/western solutions given the transient Rex block pattern and
separation from the upstream closed/cutoff low which should favor
a system west of 70W. Agreement among the 12Z ECMWF/UKMET/Canadian
with the 12Z ECMWF ensemble mean was convincingly strong.
Ultimately, as the whole pattern unwinds, the Atlantic system will
be pushed farther out to sea as the cold front reaches the east
coast around Sunday.
...Weather Highlights/Threats...
Amplified pattern will bring record cold to the west and central
states that will moderate after Friday. Still, temperatures 20-40
degrees below average on Friday should still be below average by
about 10-20 degrees by next Tuesday over the Dakotas. Milder than
average temperatures will precede the cold front across the
eastern states and the South and will stay near to above average
along the Gulf Coast.
Upper Midwest system will continue to bring wind/snow and
pre-frontal/lower-latitude rain to the region Friday.
Precipitation will wind down over the weekend but will continue to
wrap around the surface low as it moves into western Ontario. Over
New England and the coastal Mid-Atlantic, models show large spread
in rainfall amounts depending on the proximity and strength of the
ocean system. For now, took a modest approach given the
uncertainty with 1-1.50" from 12Z Fri onward over eastern MA
diminishing to near zero along/west of I-87.
In the Pacific Northwest, a cold front will push through the area
on Saturday with only light rain and mountain snow Fri/Sat west of
the Cascades that will spread into northern Idaho and northwestern
Montana next Sun/Mon. By then, Gulf moisture may begin to spread
northward as the tail-end of the stationary front may lift back
northward ahead of the western front moving through the Plains.
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