487
FXUS06 KWBC 311907
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Sun August 31 2025

6-10 DAY OUTLOOK FOR SEP 06 - 10 2025

The ECMWF, GEFS and Canadian ensemble models broadly agree on the 500-hPa
height pattern over North America and surrounding regions during the 6-10 day
period, with only minor variations among the models in terms of amplitude and
phase of predicted wave features. The manual height blend is based on ensemble
means, weighing the ECMWF model greater due to recent model anomaly correlation
skill. The manual blend shows a strong ridge and above normal 500-hPa heights
over eastern Alaska, western Canada, and the western Contiguous U.S. (CONUS),
while a deep trough with below normal 500-hPa heights are predicted over the
eastern CONUS. Another trough is forecast over the Bering Sea. Near to slightly
above normal 500-hPa heights are predicted across Hawaii.

Above normal temperatures are favored for the Aleutians, the Alaska Panhandle,
most of Mainland Alaska, and western CONUS due to predicted broad anomalous
ridging and above normal 500-hPa heights over these areas. Conversely, the
highly amplified trough forecast across the eastern CONUS, especially early in
the period, strongly favors below normal temperatures over most of the eastern
and central CONUS, except for the Gulf Coast states where above normal
temperature are favored due to subtropical ridging to the south of a mean
frontal boundary, consistent with most of the dynamic temperature forecast
tools. Above normal temperatures are favored for Hawaii due to slightly above
normal 500-hPa heights and above normal sea surface temperatures in the
adjacent Pacific.

Near to above normal precipitation is forecast over most of the western and
central CONUS, consistent with the autoblend and consolidated precipitation
forecast tools. Influxes of monsoonal moisture across the Southwest combined
with a stationary frontal boundary across the southern High Plains are the main
drivers for this predicted active period. Conversely, near to below normal
precipitation is favored across most of the eastern CONUS (except for the
southern Atlantic Coast where above normal precipitation chances are elevated
ahead of the predicted mean trough axis) due to predicted surface high pressure
associated with a cool stable Canadian airmass. Below normal precipitation is
also favored for Southeast Alaska, associated with anomalous ridging forecast
over western Canada. Above normal precipitation is more likely across most of
the remainder of Alaska ahead of a trough predicted over the Bering Sea. Near
normal precipitation is favored for Hawaii, associated with predicted near
normal 500-hPa heights across the state.

The official 6-10 day 500-hPa height blend consists of 30% of Today`s 6z GFS
Ensemble Mean centered on Day 8, 40% of Today`s 0z European Ensemble Mean
centered on Day 8, and 30% 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 among todays ensemble means.

8-14 DAY OUTLOOK FOR SEP 08 - 14 2025

By week-2, a transition in the 500-hPa pattern is well underway across much of
the country. As time progresses, a much more zonal regime takes hold across
much of the CONUS. An anomalous trough is predicted over the Bering Sea and the
Aleutians, while a ridge and above normal 500-hPa heights are forecast over
Alaska, western Canada and western CONUS  throughout the period. The strong
anomalous ridge predicted over the western CONUS in the week-2 period is
expected to quickly weaken compared with the 6-10 day period and is replaced by
shallow cyclonic flow by the middle of the period. Generally near normal
heights are forecast for Hawaii throughout the period.

Near to above normal temperatures are likely for most of Alaska due to
persistent ridging and above normal heights. Enhanced probabilities of above
normal temperatures extend southward across much of the western and central
CONUS, due to predicted ridging early in the period. Conversely, below normal
temperatures are favored for the northeastern CONUS due to predicted anomalous
troughing early in the period, supported by most of the temperature forecast
tools. Above normal temperatures are more likely for the southeastern CONUS, to
the south of a predicted frontal boundary and consistent with above normal SSTs
in the adjacent Atlantic and Gulf waters. Above normal temperatures are likely
for Hawaii, due largely to observed above normal SSTs in the adjacent Pacific.

A wet pattern is favored for most of the western and central CONUS, due to a
combination of residual monsoonal moisture and a transition to a more zonal or
weakly cyclonic flow pattern toward the middle and end of the period. Above
normal precipitation chances are elevated along the Gulf and Southeast coasts
around the periphery of a predicted anomalous trough early in the period.
Modestly enhanced chances of below normal precipitation is forecast for parts
of Tennessee Valley, the Ohio Valley, the Great Lakes, and the Northeast due to
predicted surface high pressure early in the period. These enhanced below
normal precipitation chances were kept low due to the potential transition to a
wetter pattern toward the end of week-2. Above normal precipitation is favored
for most of Mainland Alaska and the Alaska Peninsula ahead of troughing
forecast over the Bering Sea and the Aleutians. Above normal precipitation is
favored across the Hawaiian islands, consistent with the consolidation
precipitation forecast tool.

The official 8-14 day 500-hPa height blend consists of: 30% of Today`s 6z GFS
Ensemble Mean centered on Day 11, 40% of Today`s 0z European Ensemble Mean
centered on Day 11, and 30% of Today`s 0z Canadian Ensemble Mean centered on
Day 11


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Below average, 2 out of 5, due to
uncertainties surrounding a predicted transitional 500-hPa flow pattern across
much of North America.

FORECASTER: Luke H

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:
19630827 - 19810825 - 19870903 - 19790820 - 19660823


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:
19630827 - 19870903 - 19510903 - 19630822 - 19810824


6-10 DAY OUTLOOK TABLE
Outlook for Sep 06 - 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    A    A
NEW MEXICO  A    A     N DAKOTA    N    N     S DAKOTA    B    A
NEBRASKA    B    A     KANSAS      B    A     OKLAHOMA    B    A
N TEXAS     B    A     S TEXAS     A    A     W TEXAS     N    A
MINNESOTA   B    N     IOWA        B    N     MISSOURI    B    A
ARKANSAS    B    N     LOUISIANA   A    N     WISCONSIN   B    B
ILLINOIS    B    B     MISSISSIPPI B    N     MICHIGAN    B    B
INDIANA     B    B     OHIO        B    B     KENTUCKY    B    B
TENNESSEE   B    B     ALABAMA     B    B     NEW YORK    B    N
VERMONT     B    N     NEW HAMP    B    N     MAINE       B    N
MASS        B    N     CONN        B    N     RHODE IS    B    N
PENN        B    B     NEW JERSEY  B    N     W VIRGINIA  B    B
MARYLAND    B    N     DELAWARE    B    N     VIRGINIA    B    N
N CAROLINA  B    A     S CAROLINA  B    A     GEORGIA     A    A
FL PNHDL    A    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    A     AK SO COAST A    A     AK PNHDL    A    B



8-14 DAY OUTLOOK TABLE
Outlook for Sep 08 - 14 2025

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

                           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.

$$