951
FXUS06 KWBC 211902
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 21 2025

6-10 DAY OUTLOOK FOR AUG 27 - 31 2025

Today`s ensemble mean solutions generally depict a high amplitude 500-hPa
pattern across much of North America and surrounding areas. The most dominant
features include a strong ridge centered over northwestern Canada, a strong
mid-level low to its north over the Arctic Ocean, and a broad anomalous trough
over the eastern Contiguous U.S (CONUS). A complex pattern is forecast over the
eastern Pacific into the southwestern CONUS as a pair of negative height
anomaly centers are predicted. The first is predicted well south of the Gulf of
Alaska, undercutting the ridge to its north. A second, weaker trough is
predicted further to the southeast, along the West Coast of the CONUS.
Downstream of North America, anomalous ridging is predicted over the North
Atlantic extending northward to just off the coast of Atlantic Canada. Farther
to the south, subtropical ridging is forecast along much of the southern tier
of the CONUS, centered from the Rio Grande Valley to the western Gulf Coast
region.

A strong ridge forecast over northwestern Canada favors above-normal
temperatures for the southern and central Mainland, Southeast Alaska, and
southward to the northwestern CONUS. Probabilities of above-normal temperatures
exceed 80 percent for northeastern Washington State. Below-normal temperatures
are favored for the Alaska North Slope near a predicted anomalous mid-level low
over the adjacent Arctic Ocean. Farther to the south, below-normal temperatures
are slightly favored across interior southern California into the Southwest and
Great Basin associated with weak troughing forecast just off the coast and due
to the potential for increased cloudiness with enhanced monsoon moisture
forecast in the region during the period. Stronger chances of below-normal
temperatures are likely from most of the Eastern Seaboard westward to much of
the Plains due to anomalous troughing centered over the Great Lakes. Chances of
below-normal temperatures exceed 70 percent for the Ohio Valley, Mid-Atlantic,
southern Great Lakes, Middle Mississippi Valley, and adjacent areas of the
Central Plains and Northeast. Above-normal temperatures are more likely farther
to the south for the Florida Peninsula and the Rio Grande Valley and South
Texas due to predicted subtropical ridging. Increased probabilities of
above-normal temperatures are indicated for Hawaii (with the greatest
confidence over western and central portions of the state) driven mostly by
observed positive sea surface temperatures anomalies in the adjacent Pacific.

Above-normal precipitation is favored for a broad area of the Interior West
ahead of a trough predicted off the West Coast and associated with potential
influxes of monsoonal moisture. Increased chances of above-normal precipitation
extends eastward to much of the Central and Southern Plains, associated with a
predicted stationary frontal boundary. Below-normal precipitation is more
likely across the Upper Mississippi Valley, the Great Lakes, much of the Ohio
Valley, and into the Northeast associated with a predicted surface high
pressure and associated stable Canadian airmass. Above-normal precipitation is
slightly favored along the Southeast Atlantic Coast associated with a frontal
boundary. Near to below-normal precipitation is favored for Southeast Alaska
due to predicted positive 500-hPa height anomalies over the region. An active
pattern is more likely for the remainder of Alaska ahead of a mean trough
predicted near the Chukchi Peninsula, however, probabilities are reduced
relative to prior forecasts. Near-normal precipitation is more likely for most
of Hawaii associated with predicted anomalous ridging centered to the east of
the island chain.

The official 6-10 day 500-hPa height blend consists of 20% of Today`s 0z GFS
Ensemble Mean centered on Day 8, 20% of Today`s 6z GFS Ensemble Mean centered
on Day 8, 40% of Today`s 0z European Ensemble Mean centered on Day 8, and 20%
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 AUG 29 - SEP 04, 2025

Similarly to yesterday, the week-2 period features a marked reduction in
amplitude of most of the main features described in the 6-10 day discussion.
The mid-level ridge across northern North America has progressed east. However
there is little change in the location of the mid-level trough features between
the two outlook periods. The anomalous ridge is forecast to weaken and push
further inland over the Northwestern Territory and extends southward to the
Northern Rockies and Plains. A mid-level low to the north of Alaska is forecast
to significantly weaken. Farther to the south, persistent but shallow troughing
is predicted off the West Coast of the CONUS. A trough is forecast to persist
over the eastern Great Lakes well into week-2 but slowly weaken. Subtropical
ridging of typical strength for this time of year is forecast across much of
the southern tier of the CONUS. Generally near to above-normal 500-hPa heights
are forecast for Hawaii due to predicted anomalous ridging to the east of the
state early in the period followed by the potential development of another
ridge northwest of the state later in week-2.

Persistent ridging over western Canada favors above-normal temperatures across
much of southern and central Alaska and the northwestern CONUS. Above-normal
temperature probabilities exceed 50 percent along the U.S.-Canadian border of
the Northern Rockies and Plains. Near-normal temperatures are most likely for
northern Mainland Alaska. Below-normal temperatures are more likely across much
of the central and eastern CONUS due to a predicted anomalous trough centered
near the Great Lakes. However, there is more uncertainty in the longevity of
the below-normal temperatures relative to yesterday and probabilities are
correspondingly reduced. Probabilities of below-normal temperatures exceed 50
percent for parts of the Mid-Atlantic, Central and Southern Appalachians,
Southeast, Tennessee Valley and parts of the Middle and Lower Mississippi
Valley, and Central and Southern Plains. Above-normal temperatures are more
likely to the south of this trough, for the Florida Peninsula, most of the Gulf
Coast, the southern half of Texas, and southeastern portions of the Southwest,
associated with subtropical ridging. Above-normal temperatures are favored for
Hawaii due mostly to positive SST anomalies in the adjacent Pacific Ocean.

A wet pattern continues to be likely for much of the interior West, consistent
with analog guidance based on the 500-hPa height pattern. Model guidance is
bringing enhanced chances of above-normal precipitation to much of the Pacific
Northwest coastal areas in addition to interior portions of the region.
Precipitation amounts across the parts of the Southwest and Great Basin may be
enhanced due to the advection of monsoonal moisture into the region. The area
of increased above-normal precipitation chances extends to parts of the
Southern and Central Plains due to the potential of a mean frontal boundary in
the vicinity. Drier than normal conditions are more likely well to the north
and east of this boundary, across the Great Lakes as surface high pressure
associated with a Canadian airmass remains in place. Above-normal precipitation
is favored along the East Coast with the potential for an area of low pressure
to develop along the frontal boundary offshore. This could potentially bring
increased precipitation into portions of the Eastern Seaboard. As mid-level
ridging progresses inland, an increase in moisture is possible across parts of
Southeast Alaska, near-normal precipitation is favored in this area today. An
active pattern is more likely for much of the remainder of the state ahead of a
trough forecast over the Bering Sea. Drier conditions are becoming favored in
some tools across northwestern Alaska but some guidance remains wetter,
near-normal precipitation is favored across this region. Near-normal
precipitation is favored for Hawaii consistent with the blend of model tools
except for Kauai where there is better agreement among the tools.

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: Average, 3 out of 5, due to good
model agreement on the 500-hPa pattern early in the period, offset by increased
uncertainty and decreased pattern amplification later in week-2.


FORECASTER: Ryan Bolt

Notes:


Automated forecasts are issued on Saturday and Sunday. Occasionally manual
intervention is necessary to address quality control and consistency issues. In
these cases, forecasts are manually drawn but a full discussion is not issued.


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:
20010805 - 19950820 - 19530820 - 19910829 - 19960815


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:
20010805 - 19950820 - 19530819 - 19830801 - 19960816


6-10 DAY OUTLOOK TABLE
Outlook for Aug 27 - 31 2025

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    A     OREGON      A    A     NRN CALIF   A    A
SRN CALIF   B    A     IDAHO       A    A     NEVADA      B    A
W MONTANA   A    A     E MONTANA   A    A     WYOMING     N    A
UTAH        B    A     ARIZONA     B    A     COLORADO    B    A
NEW MEXICO  B    A     N DAKOTA    N    B     S DAKOTA    N    N
NEBRASKA    B    A     KANSAS      B    A     OKLAHOMA    B    A
N TEXAS     B    A     S TEXAS     A    A     W TEXAS     B    A
MINNESOTA   N    B     IOWA        B    N     MISSOURI    B    A
ARKANSAS    B    A     LOUISIANA   N    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    B
VERMONT     B    B     NEW HAMP    B    B     MAINE       B    B
MASS        B    N     CONN        B    N     RHODE IS    B    N
PENN        B    B     NEW JERSEY  B    N     W VIRGINIA  B    B
MARYLAND    B    B     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  N    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    N



8-14 DAY OUTLOOK TABLE
Outlook for Aug 29 - Sep 04, 2025

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

$$