632
FXUS06 KWBC 271912
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Wed August 27 2025

6-10 DAY OUTLOOK FOR SEP 02 - 06 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
continue to predict an amplified ridge and an associated large positive 500-hPA
height anomaly centered over the Gulf of Alaska and Southeast Alaska, with some
deamplification over time. Positive 500-hPa height anomalies extend southward
into the western contiguous United States (CONUS). The ECMWF ensemble mean
predicts larger magnitude positive 500-Pa height anomalies centered slightly to
the east of the GEFS and Canadian ensemble means. The ECMWF, GEFS and Canadian
ensembles predict a trough and associated negative 500-hPa height anomalies to
amplify and retrograde westward over the 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 western Great Lakes
region during the 6-10 day period. The manual 500-hPa height blend is based on
the most recent 0Z 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 also 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 60 percent
for parts of the central CONUS. Above normal temperatures are favored for the
western Gulf Coast and Florida Peninsula, to the south of a predicted
stationary front. Near-to-above normal temperatures are slightly favored for
parts of northern New York and northern New England, consistent with calibrated
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 western and northern Mainland Alaska, under enhanced
southwesterly onshore flow. Below normal precipitation is likely for Southeast
Alaska, ahead of the amplified ridge, with probabilities exceeding 60 percent
in the southern Alaska Panhandle. Below normal precipitation is favored for
western Washington state, under positive 500-hPa height anomalies.
Near-to-above normal precipitation is favored over most of the CONUS for the
6-10 day period, consistent with most model tools. Enhanced probabilities for
above normal precipitation exceed 50 percent for parts of the Southwest,
consistent with calibrated ECMWF and GEFS ensemble forecasts. Near normal
precipitation is favored for Hawaii, where forecast tools are inconsistent or
indicate weak signals.

The official 6-10 day 500-hPa height blend consists of 35% of Today`s 0z 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 some differences among temperature and precipitation
forecast tools for some areas.

8-14 DAY OUTLOOK FOR SEP 04 - 10 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. A ridge and positive 500-hPa height anomalies deamplify
and retrograde over the Gulf of Alaska into the week-2 period. Positive 500-hPa
height anomalies extend southward over the western CONUS in the week-2 manual
blend forecast, with the ECMWF ensemble mean predicting more extensive positive
500-hPa height anomalies over the West than the GEFS ensemble mean. 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 East Coast in
the 6-10 day period, slightly positive mid-level height anomalies are predicted
in the week-2 period.

Above normal temperatures continue to be likely for most of Alaska, excluding
northern Mainland Alaska, under continued positive 500-hPa height anomalies.
Above normal temperatures are also likely for much of the West in the week-2
period, under positive 500-hPa height anomalies. Probabilities for below normal
temperatures are enhanced from the Great Plains across the Mississippi Valley
to the Appalachians, 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. Near normal temperatures
are slightly favored for most of the East Coast under rising mid-level heights.
Positive sea surface temperatures in the region favor above normal temperatures
for Hawaii, with greater probabilities for the northwestern islands.

Under a less amplified circulation pattern, near normal precipitation is
favored across most of Alaska in the week-2 period. Above normal precipitation
is slightly favored for parts of northern Mainland Alaska, supported by
calibrated model precipitation forecasts. Probabilities of below normal
precipitation are enhanced for Southeast Alaska, ahead of the deamplifying
ridge. Near normal precipitation is slightly favored for Hawaii, with
uncertainty in model forecast tools. Near-to-above normal precipitation is
slightly favored across the entire CONUS in the week-2 period, consistent with
most dynamical model forecast tools. Enhanced probabilities exceeding 40
percent for above normal precipitation are forecast for parts of the Southern
Plains in the week-2 period, supported primarily by calibrated ECMWF ensemble
precipitation forecasts. Enhanced probabilities for above normal precipitation
are also forecast for much of the Pacific Northwest with a more zonal onshore
flow pattern later in the week.

The official 8-14 day 500-hPa height blend consists of: 35% of Today`s 0z 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:
20040811 - 19600808 - 19940816 - 20090830 - 19630816


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:
20040811 - 19870903 - 19630815 - 19600808 - 19860905


6-10 DAY OUTLOOK TABLE
Outlook for Sep 02 - 06 2025

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



8-14 DAY OUTLOOK TABLE
Outlook for Sep 04 - 10 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    B    A
NEW MEXICO  B    A     N DAKOTA    B    N     S DAKOTA    B    N
NEBRASKA    B    A     KANSAS      B    A     OKLAHOMA    B    A
N TEXAS     B    A     S TEXAS     B    A     W TEXAS     B    A
MINNESOTA   B    N     IOWA        B    N     MISSOURI    B    N
ARKANSAS    B    N     LOUISIANA   N    N     WISCONSIN   B    N
ILLINOIS    B    N     MISSISSIPPI B    N     MICHIGAN    B    N
INDIANA     B    N     OHIO        B    N     KENTUCKY    B    N
TENNESSEE   B    N     ALABAMA     N    N     NEW YORK    B    A
VERMONT     N    N     NEW HAMP    N    N     MAINE       N    N
MASS        N    A     CONN        N    A     RHODE IS    N    A
PENN        B    A     NEW JERSEY  N    A     W VIRGINIA  B    A
MARYLAND    N    A     DELAWARE    N    A     VIRGINIA    N    A
N CAROLINA  N    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.

$$