The Weather Prediction Center

College Park, MD


Extended Forecast Discussion




Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
441 PM EDT Thu Oct 06 2022

Valid 12Z Sun Oct 09 2022 - 12Z Thu Oct 13 2022

...Overview...

Next week looks to start out with an amplified pattern, with upper
troughing over the east-central U.S. and a Canadian surface high
creating a cool and dry airmass. Meanwhile an eastern Pacific
upper high will extend general ridging into the West, save for a
shortwave in the Northwest and another in northern
Mexico/southwestern U.S. that should cause continued showers
there. The overall pattern becomes more uncertain after energy
digs into the western U.S. Tuesday, with model guidance waffling
on the evolution of this energy into midweek and beyond. But the
current forecast shows troughing progressing into the
north-central U.S. with a reasonably strong cold front ahead of it
as well as rain chances, while a southern stream upper low may
spin into the Great Basin.


...Guidance Evaluation/Predictability Assessment...

Model guidance has been and continues to be persistent in showing
troughing with its axis across the eastern U.S. early next week.
The 00Z UKMET was perhaps a bit of an outlier with the timing of a
shortwave within this trough. Models also show good consensus with
the general ridge pattern centered in the eastern Pacific and
extending into the West Coast, along with better agreement for a
shortwave in the Northwest Sun and weak energy over northern
Mexico opening into a trough. Thus the early part of the medium
range period fronts/pressures forecast was based on a blend of the
00/06Z GFS and 00Z ECMWF and CMC along with a bit of continuity.

By Tuesday-Thursday, models have shown considerable changes over
the past couple of days with the eventual evolution of potent
energy coming into the West. This energy stems from Siberia into
the Bering Sea during the short range period, so considering this
tends to be an uncertain area for models, more forecast changes
may continue over the next few days. After yesterday's guidance
indicated a strong upper low was likely to form in the West as
most energy dove southward, for the most part the 00Z/06Z model
cycle and newer 12Z model cycle shows more of the energy remaining
in the northern stream and tracking a trough eastward. The CMC
runs have stuck with a closed low type solution, however. Some
ECMWF/GFS runs do show a weaker southern stream closed low forming
by Wed or Thu, with perhaps some energy tracking south but the
aforementioned Northwest shortwave also looks to play a role in
forming the low. Thus the WPC forecast trended weaker with the
upper low in the West, with a combination of the deterministic
models and ensemble means in the forecast blend, and continuing to
include some continuity in the forecast blend as well for
potential that models could change back. For QPF, this also led to
a drier solution than continuity across the Intermountain West per
model trends, but wetter and more broad than the 13Z NBM was, as a
middle ground.


...Weather/Hazards Highlights...

The combination of persistent monsoonal moisture and an upper low
evolving into a trough over northwest Mexico will continue to fuel
diurnal showers and thunderstorms over parts of the Desert
Southwest/southern Rockies through early next week, with the
greatest rainfall totals expected for central and southern New
Mexico based on latest model guidance. Moisture could stream into
the Southern Plains and produce some showers and thunderstorms
there as well. Then a strong cold front associated with the
western to central U.S. trough will produce rain and potentially
some high elevation snow for the northern Rockies around
Tuesday-Wednesday, and then moisture and thus rain chances spread
into the central U.S. to Midwest/Great Lakes. Elsewhere, light to
locally moderate rainfall should spread northward over the Florida
Peninsula as easterly low level flow strengthens behind a front.

Much of the northwestern U.S. should see above normal temperatures
at least through Monday with highs 10 to locally 20F above normal.
Recent forecasts show the Pacific Northwest may stay warmer than
normal through the week as well if troughing evolves by staying to
its east, but areas across the Great Basin/Rockies are likely to
cool down, followed by the central U.S. behind a cold front. Highs
look to be around 5-10F below normal for those areas, with lows
closer to normal. But these forecasts could change as the pattern
hopefully becomes clearer with time. The East is likely to start
next week with cooler than normal weather and moderate to near
normal as the week progresses.


Tate

Hazards:
- Much below normal temperatures across portions of the
Mid-Atlantic, the Lower Mississippi Valley, the Central
Appalachians, the Tennessee Valley, the Middle Mississippi Valley,
the Northeast, the Southern Appalachians, the Upper Mississippi
Valley, the Southeast, the Great Lakes, and the Ohio Valley, Sun,
Oct 9.

Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php

WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, experimental excessive rainfall
outlook, 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/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml

$$





Last Updated: 441 PM EDT THU OCT 06 2022