604
FXUS06 KWBC 301901
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Sat August 30 2025

6-10 DAY OUTLOOK FOR SEP 05 - 09 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 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. Ridging and 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. Subtropical ridging to the south of a mean frontal boundary
favors above normal temperatures for most of the Florida Peninsula, consistent
with most of the dynamic temperature forecast tools. Above normal temperatures
are favored for Hawaii due to predicted ridging and above normal sea surface
temperatures in the adjacent Pacific, particularly across the western islands.

Near to above normal precipitation is forecast over most of the western and
central CONUS (except for parts of western Washington, northeastern Montana,
and western North Dakota, where below normal precipitation is likely under
500-hPa ridging), 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. Precipitation chances are also
elevated along the Atlantic Coast ahead of the predicted mean trough axis.
Below normal precipitation is slightly favored across the adjacent areas of the
Ohio Valley and Tennessee Valley 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.
Slightly below normal precipitation is favored for Hawaii, associated with
predicted above normal 500-hPa heights across the state, supported by the
consolidation precipitation forecast tool.

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 07 - 13 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. There is even some evidence of a reversal of the pattern by
the end of week-2 with strong troughing over the East on day 8 being replaced
by modest ridging by day 14. Conversely, the predicted ridge over the Gulf of
Alaska is expected to be a more stable feature with above normal heights
forecast across most of Alaska 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 CONUS, the
Northern Plains and parts of the Upper Mississippi Valley 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. Above normal temperatures are more likely for the Gulf Coast states, to
the south of a predicted frontal boundary and consistent with above normal SSTs
in the adjacent Atlantic and Gulf waters. Slightly below normal temperatures
are favored over parts of the Central and Southern Plains, supported by most of
the temperature forecast tools. 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 lower 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 weak troughing forecast over the Bering Sea. A dry pattern is more
likely across Southeast Alaska due to persistent ridging. Near normal
precipitation is favored across the Hawaiian islands, due to weak or
conflicting guidance.

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:
19630828 - 19510902 - 19660823 - 20090830 - 19880903


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 - 19510903 - 19630822 - 19660822 - 19870904


6-10 DAY OUTLOOK TABLE
Outlook for Sep 05 - 09 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    N     WYOMING     A    A
UTAH        A    A     ARIZONA     A    A     COLORADO    A    A
NEW MEXICO  N    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   B    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     B    N     NEW YORK    B    A
VERMONT     B    A     NEW HAMP    B    A     MAINE       B    A
MASS        B    A     CONN        B    A     RHODE IS    B    A
PENN        B    N     NEW JERSEY  B    A     W VIRGINIA  B    N
MARYLAND    B    N     DELAWARE    B    A     VIRGINIA    B    N
N CAROLINA  B    A     S CAROLINA  B    A     GEORGIA     B    N
FL PNHDL    B    N     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 07 - 13 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    A    A     S DAKOTA    A    A
NEBRASKA    A    A     KANSAS      N    A     OKLAHOMA    N    A
N TEXAS     N    A     S TEXAS     A    A     W TEXAS     N    A
MINNESOTA   A    A     IOWA        N    A     MISSOURI    N    N
ARKANSAS    N    N     LOUISIANA   A    A     WISCONSIN   N    N
ILLINOIS    N    N     MISSISSIPPI A    N     MICHIGAN    N    N
INDIANA     N    N     OHIO        N    N     KENTUCKY    N    N
TENNESSEE   N    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.

$$