Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
1159 AM EDT Mon Oct 28 2019
Valid 12Z Thu Oct 31 2019 - 12Z Mon Nov 04 2019
...Much below normal temperatures over the Rockies/Plains will
moderate by this weekend...
...Developing storm affects the eastern U.S. Thu-Fri...
...Overview and Guidance/Uncertainty Assessment...
Models and ensemble means agree that a persistent eastern Pacific
ridge will promote broad cyclonic flow downstream, with a mean
trough axis tending to align over the east-central states.
Guidance consensus and continuity provide fairly high confidence
in the large scale pattern but individual embedded features have
lower predictability. By early next week there are also some
aspects to the forecast that become more uncertain near the West
Coast and the northern Plains.
The most notable weather feature in the medium range is the upper
trough over the central U.S. as of early Thu that ejects
north-northeastward thereafter, supporting development of surface
low pressure that tracks from the central Ohio Valley into Quebec
through Friday. The CMC continues to be an outlier with a more
phased/open system aloft leading a faster and less wound-up wave,
so the CMC was not included in the blend beyond Day 3. The
forecast blend through Day 4 is a blend of 00Z ECMWF/UKMET and 06Z
GFS.
Behind the eastern system the aforementioned model blend
represented consensus well for the upstream trough aloft
amplifying into the lower 48 along with the associated cold front
which progresses through the central part of the U.S. Sat. There
is decent agreement and consistency with the next frontal system
expected to reach the northern tier/Great Lakes by days
6-7/Sun-Mon. There is some uncertainty with low pressure off CA by
Sunday with the GFS stronger, but by Monday the system is in
pretty close agreement with 06Z GFS/GEFS and 00Z ECWMF/ECENS. An
increasing usage of the 06Z GEFS/00Z ECENS is used in the blend
with good agreement across the CONUS.
...Weather Highlights/Threats...
Widespread precipitation shield across the northeastern U.S. is
expected into this weekend with some snow possible in the
northwestern periphery of the system (Midwest to Upper Great
Lakes) and areas of heavy rainfall along with pockets of strong
convection in the warm sector. Expect highest rainfall totals from
early Thu onward to extend from along and just west of the
Appalachians into the Northeast. A brief period of strong winds
will occur over parts of the Great Lakes/Northeast. Behind this
system expect periods of lake effect rain/snow with periodic light
precipitation over other parts of the northern tier in association
with a couple fronts dropping south from Canada. The front
trailing from the late week eastern storm will settle over the
Florida Peninsula and could provide a focus for light rain into
early next week.
The Rockies and Plains will remain quite chilly for the rest of
the work week with a fairly broad area seeing temperatures 10-30F
below normal. These areas should trend much closer to average by
Sun-Mon while locations closer to the West Coast should see highs
up to 5-10F above normal from the weekend onward as the Pacific
ridge aloft extends its influence a little farther eastward.
Meanwhile frontal passage over the East will replace initial
warmth (plus 10-20F anomalies for morning lows and moderately warm
highs on Thu) with cooler readings generally 5-15F below normal.
Jackson
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