Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
359 AM EDT Tue Oct 27 2026
Valid 12Z Fri Oct 30 2026 - 12Z Tue Nov 03 2026
...Broadening precipitation coverage is forecast across much of
the lower 48...
...Overview...
Late this week, an upper low near the Pacific Northwest will
anchor a trough across the West, while a shortwave moves through
the central U.S. north and west of warm mean ridging in the
Southeast. The central U.S. shortwave combined with Pacific and
Gulf moisture will spread rain and thunderstorms across the Plains
Friday and shifting across the Mississippi Valley and East over the
weekend, with moderate to heavy rain totals possible in the
southern tier. Meanwhile, southern and northern stream energies
interacting within the trough in the West will swing the southern
side of the trough east and bring additional precipitation to the
West this weekend. Forecast models indicate the upper trough should
make its way across the Intermountain West and likely become a
closed low when it reaches the central U.S. by next Tuesday. This
is forecast to carry a surface low/frontal system and bring
widespread rain to the central U.S. again early next week.
...Guidance/Predictability Assessment...
Model guidance is generally agreeable with the large scale pattern
described above, though with typical differences in the details
that will affect sensible weather. A blend of the dynamical and AI
guidance worked well to depict the pattern through Friday-Saturday
since model variations were relatively small.
More model differences start to arise by Sunday. The primary
concern is how much energy drops south from the northern stream of
the trough in the West, and how/when it interacts with the southern
stream energy moving east through the Pacific. Some models phase
in quickly, like the AIFS, and bring a deeper trough to southern
California. The southern stream energy will be carrying an an
unusually far south (~25N latitude) non-tropical surface low
eastward through the Pacific into southern California/northern
Mexico that brings an atmospheric river with it. With its phasing
aloft, the AIFS continues to be among the fastest solutions with
bringing that surface low east reaching the coast.
Then some occasional models split the flow even into early next
week, holding back an upper low over California while the northern
stream tracks more quickly east. The 00Z AIGFS is still showing
this pattern, but overall this seems to be more of an outlier now,
as the new 00Z CMC switched to a more phased pattern like the other
guidance after its older 12Z run had split flow. So preferred the
GFS/ECMWF/AIFS solutions that had a phased trough pattern that
steadily tracks east through the weekend into Monday, which then
develops into a closed upper low over the central U.S. by next
Tuesday. A deepening surface low pressure system looks to accompany
this upper low. The best model clustering appears to be around the
ECMWF, AIFS, and CMC with this upper and surface low. The 00Z GFS
looks much farther south of consensus. On the whole, favored those
but also increased the proportion of ensemble means as the period
progressed, with means reaching half the model blend by Day 7 to
mitigate the individual model differences.
...Weather/Hazards Highlights...
Rain and thunderstorms are forecast to continue across the
southern Plains into Friday with a shortwave aloft and lingering
tropical moisture. This rainy and stormy pattern will move east
across the southeastern U.S. into the weekend, and locally heavy
rain is possible. Farther north, rounds of rain are also forecast
across the north-central U.S., with generally modest amounts.
Florida could also see diurnally driven scattered showers and
thunderstorms.
One round of precipitation is forecast across the Intermountain
West/Southwest on Friday ahead of the upper trough axis. Heavy rain
is possible in the Southwest with ample moisture. Then over the
weekend, Pacific moisture will increase across the West and bring
broadening precipitation chances to California and across the
Intermountain West. Precipitation placement, type (including snow
levels), and amounts are all somewhat uncertain given the upper-
level and surface flow model differences, so continue to monitor
future forecasts as the details could change. Some rain should
overspread much of the central U.S. on Sunday and could increase on
Monday as the low strengthens. Some northern/central High Plains
snow or rain/snow mix cannot be ruled out on the backside of the
low. Additionally, gusty winds may be possible in the Plains behind
the reasonably strong surface low.
Well above average temperatures are expected for much of the
central and eastern U.S. under mean upper ridging (albeit with
occasional shortwaves) through the period. Highs in the 70s are
forecast as far north as the Ohio Valley at times, as broad areas
reach around 10-20 degrees above normal. Temperatures should be
somewhat below average in the western U.S. underneath the upper
trough, especially for highs. By early next week, the Plains should
moderate to near normal temperatures as the upper trough/low moves
eastward.
Tate
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 forecast, excessive rainfall outlook,
winter weather outlook probabilities, heat indices and Key Messages
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
https://www.wpc.ncep.noaa.gov/#page=ovw
