597
FXUS06 KWBC 231908
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 23 2025

6-10 DAY OUTLOOK FOR AUG 29 - SEP 02, 2025

Toward the end of August, the Pacific-North American (PNA) pattern is forecast
to enter a positive phase, with an amplified ridge and associated positive
height anomaly center developing over western Canada. Troughing initially
situated to the south of Alaska is forecast to shift southeastward,
undercutting the ridge across Canada. The 0z and 6z GEFS depict a more
amplified trough reaching the west coast of the CONUS by the end of the
forecast period compared to the 0z ECENS and CMCE, resulting in more
uncertainty in the mid-level height evolution over the West. Additional
troughing is also predicted across the Bering Sea and the eastern U.S. Todays
manual 500-hPa height blend for the 6-10 day period depicts positive height
anomalies over western Canada extending into parts of the northwestern and
north-central CONUS, and over much of Mainland and Southeast Alaska. Negative
height anomalies are depicted from the Central Plains eastward to the Atlantic
Coast. Negative height anomalies are also favored over the Aleutians,
increasing in magnitude farther west. A weak mid-level flow pattern is
predicted in the vicinity of Hawaii, with near- to above-normal heights favored.

Troughing across the East favors increased probabilities of below-normal
temperatures for most of the CONUS east of the Rockies, with the highest
chances (greater than 70 percent) across parts of the Carolinas. Temperature
anomalies of -5 to -10 deg F will likely bring an early taste of Fall in time
of the Labor Day Holiday weekend. Conversely across the West, enhanced chances
for above-normal temperatures are favored, with the highest chances along the
Canadian Border across Montana and Idaho closer to the predicted positive
height anomaly center. There is more uncertainty across the Southwest, where a
stronger trough as depicted in the GEFS favors a cooling trend near the West
Coast and also shifts anomalous warmth downstream over the Rockies and Four
Corners. However, the weaker trough in the ECENS keeps coastal areas underneath
above-normal temperatures with below-normal temperatures forecast over the
Interior in the corresponding reforecast tool. Given that the analogs lean warm
over the West, above-normal temperature probabilities remain elevated near the
West Coast, but near-normal temperatures are favored further inland over the
Southwest. Above-normal temperature chances are increased over portions of
south Texas and the Florida Peninsula to the south of a stationary frontal
boundary. Near-to above-normal temperature chances are increased over Mainland
and Southeast Alaska consistent with the GEFS and ECENS reforecast tools and
above-normal mid-level heights. Weakly enhanced probabilities of below-normal
temperatures are forecast over parts of the Aleutians. Above-normal
temperatures are favored for nearly all of Hawaii, excluding southern parts of
the Big Island where near-normal temperatures are favored, supported by the
consolidated forecast tool.

Troughing over the East favors a stationary front set-up across the
south-central and southeastern CONUS serving as a focus for enhanced
precipitation throughout the period, with above-normal precipitation
probabilities increased over these areas. On the northern side of the boundary,
drier air and increased northerly mid-level flow favors enhanced chances of
below-normal precipitation over much of the Upper Midwest into the Ohio Valley,
also supported by analogs and teleconnections from the negative height anomaly
center over the East. Troughing approaching the West Coast, regardless of its
strength, leads to increasing onshore flow and moisture advection over much of
the West. This supports increasing probabilities of above-normal precipitation,
further aided by lower precipitation climatologies, particularly over coastal
California. Near-normal precipitation is favored over portions of southern
California and the Southwest farther displaced from the stronger onshore flow
likely to the north. Troughing over the Bering Sea favors increased chances of
above-normal precipitation over much of Mainland Alaska and the Aleutians, with
a slight tilt toward elevated below-normal precipitation odds over Southeast
Alaska due to more influence from the ridging over western Canada. A variable
precipitation pattern is forecast over Hawaii, with weak chances for
above-normal precipitation over the western-most islands, and conversely, weak
chances for below-normal precipitation over the Big Island.

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


FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Average, 3 out of 5, due to good
model agreement regarding the mid-level height pattern early in the period,
offset by increasing uncertainty, particularly over the western U.S.

8-14 DAY OUTLOOK FOR AUG 31 - SEP 06, 2025

During week-2, the 500-hPa pattern over North America is predicted to become
more zonal as logwave features from the 6-10 day period begin to weaken.
Overall, the manual height blend depicts positive height anomalies across
Canada extending slightly south into the northwestern and north-central CONUS
and west into portions of eastern Alaska. Closer to normal heights are
indicated over most of the CONUS, with weakly negative anomalies (-30 meters)
persisting over the Central Appalachians and Mid-Atlantic. Negative height
anomalies continue to be forecast over the Bering Sea and the Aleutians, with
evidence of a weakness in the height field extending southeastward to the West
Coast of the CONUS. Near-to above-normal heights are forecast to persist across
Hawaii.

Given the decreasing amplification in the mid-level height pattern, the
resultant temperature forecast is much more uncertain over the CONUS. Enhanced
probabilities for below-normal temperatures are forecast from the Central
Plains to the Eastern Seaboard, but probabilities are significantly reduced
compared to the 6-10 day period. Warmer air may also begin to migrate eastward,
favoring increasing chances for near- to above-normal temperatures over much of
the Northern Tier. Above-normal temperature probabilities remain elevated along
most of the Gulf Coast and over the Florida Peninsula to the south of a
stationary frontal boundary. Forecast tools are largely inconsistent over the
West, showing many of the same disparities highlighted in the 6-10 day period,
resulting in a slight tilt toward near-normal temperatures. High probabilities
of above-normal temperatures are highlighted over most of Mainland and
Southeast Alaska, with elevated chances of near- to below-normal temperatures
favored across the Aleutians. Above-normal temperatures remain favored over
Hawaii.

A more zonal flow pattern favors enhanced above-normal precipitation
probabilities across much of the western CONUS, with near-normal precipitation
remaining favored across portions of southern California and the Southwest. The
highest above-normal precipitation probabilities (50 percent) are posted across
the Pacific Northwest tied to enhanced onshore flow and a strong signal in the
GEFS and ECENS reforecast tools. A stationary front continues to support
slightly increased chances of above-normal precipitation across the
southeastern quadrant of the CONUS. The 0z GEFS indicates a more northward push
of moisture later in the period as the troughing in the East lifts out and the
mid-level flow becomes more southerly, although the ECENS still supports a
relatively drier pattern over the Great Lakes and Northeast where near- to
below-normal precipitation is forecast. Odds for near-to above-normal
precipitation continue to be elevated over much of Mainland Alaska and the
Aleutians associated with troughing over the Bering Sea early in the period.
Larger positive height anomalies downstream support increased chances for
below-normal precipitation over Southeast Alaska. Similar to the 6-10 day
period, slightly increased chances for above (below)-normal precipitation are
forecast over western Hawaii (the Big Island) during week-2.

The official 8-14 day 500-hPa height blend consists of: 25% of Today`s 6z GFS
Ensemble Mean centered on Day 11, 40% of Today`s 0z European Ensemble Mean
centered on Day 11, and 35% 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
decreasing amplification of the 500-hPa pattern and continued differences in
the temperature guidance over the western U.S.

FORECASTER: Thomas Collow

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:
19950820 - 19530820 - 19540829 - 19560808 - 19970902


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:
19980802 - 19950820 - 19560807 - 19530819 - 19970901


6-10 DAY OUTLOOK TABLE
Outlook for Aug 29 - Sep 02, 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      N    A
W MONTANA   A    A     E MONTANA   A    A     WYOMING     N    A
UTAH        N    A     ARIZONA     N    A     COLORADO    B    A
NEW MEXICO  B    A     N DAKOTA    A    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   A    B     IOWA        B    B     MISSOURI    B    A
ARKANSAS    B    A     LOUISIANA   B    A     WISCONSIN   B    B
ILLINOIS    B    B     MISSISSIPPI B    A     MICHIGAN    B    B
INDIANA     B    B     OHIO        B    B     KENTUCKY    B    N
TENNESSEE   B    A     ALABAMA     B    A     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    B
MARYLAND    B    N     DELAWARE    B    N     VIRGINIA    B    N
N CAROLINA  B    N     S CAROLINA  B    A     GEORGIA     B    A
FL PNHDL    B    A     FL PENIN    A    A     AK N SLOPE  A    A
AK ALEUTIAN N    A     AK WESTERN  N    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 Aug 31 - Sep 06, 2025

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

$$