020
FXUS06 KWBC 281902
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Thu August 28 2025

6-10 DAY OUTLOOK FOR SEP 03 - 07 2025

The ECMWF, GEFS and Canadian ensemble models agree on the 500-hPa height
pattern forecast over North America and surrounding regions during the 6-10 day
period, with only small variations in the pattern. Model ensemble means predict
an amplified ridge and an associated positive 500-hPa height anomaly over the
Gulf of Alaska in the 6-10 day period, with one anomaly center over western
Canada and another anomaly center to the south of the Alaska Peninsula in both
the ECMWF and GEFS ensemble means. Daily ECMWF ensemble mean forecasts show the
center of positive 500-hPa height anomalies retrograding westward across the
Gulf of Alaska early in the period. Positive 500-hPa height anomalies extend
southward into the western contiguous United States (CONUS) in the ensemble
model forecasts, with ECMWF mid-level height anomalies more amplified than the
GEFS and Canadian model forecasts. The ECMWF, GEFS and Canadian ensembles
predict a trough and associated negative 500-hPa height anomalies to amplify
over the northern central CONUS, early in the period. Later in the period, this
trough begins to rapidly deamplify, as negative 500-hPa height anomalies
retract northward into Canada. The ECMWF ensemble predicts a greater magnitude
negative 500-hPa height anomaly centered over the Great Lakes region during the
6-10 day period. The manual 500-hPa height blend is based on the most recent
ensemble means of the ECMWF, GEFS and Canadian models, weighing the ECMWF model
greater due to recent model anomaly correlation skill.

Above normal temperatures are favored for the eastern Aleutians, Mainland
Alaska, and Southeast Alaska, under the predicted amplified ridge. Above normal
temperatures are very likely for much of the western CONUS, due to predicted
positive 500-hPa height anomalies over the region. Under a predicted trough and
negative 500-hPa height anomalies, below normal temperatures are favored over
most of the central and eastern CONUS, with probabilities exceeding 70 percent
for parts of the northern central CONUS. Near normal temperatures are favored
for most of the Gulf Coast with above normal temperatures favored for the
Florida Peninsula, to the south of a predicted stationary front. Near normal
temperatures are slightly favored for most of Maine, consistent with the
consolidation of calibrated ECMWF and GEFS model forecasts. Above normal
temperatures are favored for most of Hawaii, excluding southeastern areas of
the Big Island, influenced by above average sea surface temperatures in the
region.

Enhanced probabilities of above normal precipitation are predicted for parts of
the Aleutians, and across northern Mainland Alaska, consistent with the
precipitation consolidation. Below normal precipitation is favored for
Southeast Alaska, ahead of the amplified ridge, with probabilities exceeding 50
percent in the southern Alaska Panhandle. Below normal precipitation is
slightly favored for western Washington state, under positive 500-hPa height
anomalies, and for parts of the Northern Plains under anomalous northerly
mid-level flow. Near-to-above normal precipitation is favored over the
remainder of the CONUS for the 6-10 day period, consistent with most model
tools. Enhanced probabilities for above normal precipitation exceeding 40
percent are predicted for the Southwest, consistent with calibrated ECMWF and
GEFS ensemble forecasts. Enhanced probabilities for above normal precipitation
are predicted for the Northeast, ahead of the amplified trough. Near normal
precipitation is favored for most of Hawaii, where forecast tools are
inconsistent or indicate weak signals. Below normal precipitation is slightly
favored for the Big Island of Hawaii, consistent with the precipitation
consolidation.

The official 6-10 day 500-hPa height blend consists of 35% of Today`s 6z GFS
Ensemble Mean centered on Day 8, 40% of Today`s 0z European Ensemble Mean
centered on Day 8, and 25% of Today`s 0z Canadian Ensemble Mean centered on Day
8


FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Above average, 4 out of 5, due to
good agreement between ensemble model forecasts of an amplified mid-level
height pattern, offset by weak precipitation signals and some differences among
temperature and precipitation forecast tools for some areas.

8-14 DAY OUTLOOK FOR SEP 05 - 11 2025

Ensemble mean forecasts for the 500-hPa height pattern over North America
remain in general agreement during the 8-14 day period, while the overall
pattern deamplifies, and models predict weak 500-hPa height anomalies across
most of the domain. A ridge and positive 500-hPa height anomalies over the Gulf
of Alaska and Southwest Alaska deamplify in the week-2 period. Positive 500-hPa
height anomalies extend southward over the western CONUS in the week-2 manual
blend forecast and recent ensemble mean solutions. In the 8-14 day period
manual blend, a weak trough is predicted over the east-central CONUS, which has
deamplified significantly from the 6-10 day period. Where negative 500-hPa
height anomalies were predicted over most of the eastern CONUS in the 6-10 day
period, near-zero mid-level height anomalies are predicted in the week-2
period.

Above normal temperatures continue to be favored for most of Alaska, excluding
the North Slope, under continued positive 500-hPa height anomalies. Above
normal temperatures are likely for most of the western CONUS in the week-2
period, under positive 500-hPa height anomalies. Probabilities for below normal
temperatures are enhanced from the Southern Plains across most of the
Mississippi Valley to the Mid-Atlantic and southern New England, under a weak
trough and consistent with most model tools. Probabilities for above normal
temperatures are enhanced for the Gulf Coast in the week-2 period, to the south
of a stationary front. Positive sea surface temperatures in the region of
Hawaii favor above normal temperatures for all of the Hawaiian Islands, with
greater probabilities for the northwestern islands.

Under a less amplified circulation pattern in the week-2 period, above normal
precipitation is slightly favored for northern Mainland Alaska, supported by
calibrated model precipitation forecasts. Probabilities of below normal
precipitation are slightly enhanced for Southeast Alaska, ahead of the
deamplifying ridge. Near normal precipitation is slightly favored for Hawaii,
with uncertainty in model forecast tools. With a more zonal onshore flow
pattern forecast for the week-2 period, above normal precipitation is slightly
favored across most of the western CONUS. Above normal precipitation is also
slightly favored for the Gulf and southern Atlantic Coasts, as well as much of
the Northeast, consistent with the precipitation consolidation. Near-to-below
normal precipitation is favored over remaining areas of the northern central
and eastern CONUS under weak mid-level height anomalies.

The official 8-14 day 500-hPa height blend consists of: 35% of Today`s 6z GFS
Ensemble Mean centered on Day 11, 40% of Today`s 0z European Ensemble Mean
centered on Day 11, and 25% of Today`s 0z Canadian Ensemble Mean centered on
Day 11


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Near average, 3 out of 5, due to
good overall agreement on the mid-level height forecast, offset by a
low-amplitude pattern and weak signals in the precipitation tools for most
areas.

FORECASTER: D Collins

Notes:


The notation for the categorical forecast indicated on the maps is the same as
that in the tables: A-above   N-near normal   B-below


The temperature map shows regions with > 33% chance of being warmer (orange,
"A"), colder (blue, "B"), or close to (unshaded, "N"). Historical average
values for the calendar period of the forecast (dashes, "f").  Labels on the
shaded lines give the probability (> 33%) of the more likely category (B or A).
 Probability of N is always < 40%.


The precipitation map shows regions with > 33% chance of being wetter (green,
"A"), drier (tan, "B"), or close to (unshaded, "n"). Historical median values
for the calendar period of the forecast (dashes, "inches").  Labels on the
shaded lines give the probability (> 33%) of the more likely category (B or A).
 Probability of N is always < 40%.


In the southwest and other climatologically dry regions - there will be a
greater than 33.3% chance of no precipitation and occasionally even a normal
(i.e. Median) value of zero - especially during the dry seasons.  In such cases
a forecast of near normal is effectively a forecast of little or no
precipitation.


The climate prediction center uses 1991-2020 base period means as reference in
the climate outlooks.

The next set of long-lead monthly and seasonal outlooks will be released on
September 18.


Analogs to the 5 day mean observed pattern centered 3 days ago (D-3)
for the region from 20N to 70N latitude and 175E to 60W longitude
include the 5 day periods centered on the following dates:
19660824 - 19630828 - 19510902 - 19770818 - 19600808


Analogs to the 7 day mean observed pattern centered 4 days ago (D-4)
for the region from 20N to 70N latitude and 175E to 60W longitude
include the 7 day periods centered on the following dates:
19660823 - 19510903 - 19630827 - 19600808 - 19630822


6-10 DAY OUTLOOK TABLE
Outlook for Sep 03 - 07 2025

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    N     OREGON      A    N     NRN CALIF   A    A
SRN CALIF   A    A     IDAHO       A    A     NEVADA      A    A
W MONTANA   A    N     E MONTANA   A    N     WYOMING     A    A
UTAH        A    A     ARIZONA     N    A     COLORADO    B    A
NEW MEXICO  B    A     N DAKOTA    B    B     S DAKOTA    B    B
NEBRASKA    B    N     KANSAS      B    A     OKLAHOMA    B    A
N TEXAS     B    A     S TEXAS     B    A     W TEXAS     B    A
MINNESOTA   B    B     IOWA        B    N     MISSOURI    B    N
ARKANSAS    B    N     LOUISIANA   B    N     WISCONSIN   B    N
ILLINOIS    B    N     MISSISSIPPI B    N     MICHIGAN    B    A
INDIANA     B    A     OHIO        B    A     KENTUCKY    B    A
TENNESSEE   B    A     ALABAMA     B    N     NEW YORK    B    A
VERMONT     B    A     NEW HAMP    B    A     MAINE       N    A
MASS        B    A     CONN        B    A     RHODE IS    B    A
PENN        B    A     NEW JERSEY  B    A     W VIRGINIA  B    A
MARYLAND    B    A     DELAWARE    B    A     VIRGINIA    B    A
N CAROLINA  B    A     S CAROLINA  B    A     GEORGIA     B    A
FL PNHDL    N    N     FL PENIN    A    A     AK N SLOPE  A    A
AK ALEUTIAN A    A     AK WESTERN  A    N     AK INT BSN  A    A
AK S INT    A    N     AK SO COAST A    B     AK PNHDL    A    B



8-14 DAY OUTLOOK TABLE
Outlook for Sep 05 - 11 2025

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    A     OREGON      A    A     NRN CALIF   A    A
SRN CALIF   A    A     IDAHO       A    A     NEVADA      A    A
W MONTANA   A    A     E MONTANA   A    A     WYOMING     A    A
UTAH        A    A     ARIZONA     A    A     COLORADO    N    A
NEW MEXICO  B    A     N DAKOTA    A    N     S DAKOTA    N    N
NEBRASKA    N    A     KANSAS      B    A     OKLAHOMA    B    A
N TEXAS     B    A     S TEXAS     B    A     W TEXAS     B    A
MINNESOTA   N    N     IOWA        B    N     MISSOURI    B    N
ARKANSAS    B    N     LOUISIANA   B    A     WISCONSIN   B    N
ILLINOIS    B    B     MISSISSIPPI B    N     MICHIGAN    B    N
INDIANA     B    B     OHIO        B    N     KENTUCKY    B    B
TENNESSEE   B    N     ALABAMA     B    N     NEW YORK    B    A
VERMONT     B    A     NEW HAMP    B    A     MAINE       N    A
MASS        B    A     CONN        B    A     RHODE IS    B    A
PENN        B    N     NEW JERSEY  B    N     W VIRGINIA  B    N
MARYLAND    B    N     DELAWARE    B    N     VIRGINIA    B    N
N CAROLINA  B    A     S CAROLINA  N    A     GEORGIA     N    A
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  N    A
AK ALEUTIAN A    N     AK WESTERN  A    N     AK INT BSN  A    A
AK S INT    A    N     AK SO COAST A    N     AK PNHDL    A    B

                           LEGEND
TEMPS WITH RESPECT TO NORMAL     PCPN WITH RESPECT TO MEDIAN
A - ABOVE   N  - NEAR NORMAL     A - ABOVE   N - NEAR MEDIAN
B - BELOW                        B - BELOW

THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL
VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE
AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE.

FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 KWBC - ON AWIPS AS
PMDMRD.

$$