325
FXUS02 KWBC 141845
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
245 PM EDT Tue Oct 14 2025

Valid 12Z Fri Oct 17 2025 - 12Z Tue Oct 21 2025


...Guidance/Predictability Assessment...

Model guidance remains in relatively good agreement during the
medium range period, handling the evolution of several large scale
trough/ridge features across the CONUS reasonably well despite a
highly amplified 500mb flow pattern. Only minor differences were
noted for Days 3 and 4, so a composite blend of the 00Z EC, 00Z
UKMET, 00Z CMC and 06Z GFS deterministic runs sufficed to begin the
period. However, larger discrepancies started cropping up by Day
5, most notably with the evolution of a potent Pacific trough that
is progged to push inland over British Columbia and the Pacific
Northwest late in the weekend into early next week. While the
EC/GFS/UKMET all had similar solutions depicting the trough digging
deeper along the West Coast, the CMC shows the trough becoming
completely sheared apart as it moves across the Pacific Northwest.
As a result of being much faster and flatter than consensus, the
00Z CMC was removed from the blend starting on Day 5 and was not
considered for the remainder of the forecast. To compensate, more
weighting was placed on the EPS and GEFS ensemble means, which
ultimately made up slightly more than 50% of the blend for Day 6
and 7. The greater weighting of the ensemble means resulted in a
more stable forecast that preserved continuity while reducing some
of the timing and positional differences that are typical for the
latter half of the medium range forecast period.

...Weather/Hazards Highlights...

Lingering upper troughing in Atlantic Canada (tied to the current
coastal storm) still supports continued unsettled and borderline
windy conditions over New England through late week with cooler
than normal temperatures that will slowly moderate with time.

The troughing and associated surface frontal boundary in the West
will promote cool and showery weather (with some snow at higher
elevations) over the northern/central Rockies to start, with
broader light rain in advance of the surface low that is poised to
track from the northern Plains into southern Canada. As the
attendant cold front passes through the Plains, moisture will
increase in advance of it through the Mid-MS Valley where rainfall
could increase by Saturday. The WPC Day 5/Saturday Excessive
Rainfall Outlook (ERO) maintains a Marginal Risk area centered over
the Mid-South given favorable upper support, moisture and
instability. Given the somewhat progressive nature of the upper-
level and surface features, this rainfall will continue to spread
eastward into the Northeast later Sunday into early next week,
particularly near and along the track of a deepening/consolidating
low pressure system (and into the Southeast ahead of the cold
front). Temperatures will be mild ahead of the cold front with
highs well into the 70s/80s Friday from the Corn Belt to the Ozarks
with 90s across South Texas.

By late next weekend into early next week, another deepened system
will enter the Pacific Northwest/West Coast with another round of
valley rain and higher mountain snow that will then dig and spread
across the West and downstream to the Rockies. The Day 5/Saturday
ERO maintains a coastal Washington Marginal Risk area given a
favorable guidance signal.

Miller/Schichtel


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 (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:

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






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