762
FXUS06 KWBC 031901
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Wed September 03 2025

6-10 DAY OUTLOOK FOR SEP 09 - 13 2025

The GEFS, ECENS, and CMCE are in good agreement that the highly amplified
longwave pattern becomes more zonal by mid-September. This pattern transition
is likely to eventually bring a warming trend to the central and then eastern
contiguous U.S. (CONUS) after a prolonged stretch of below-normal temperatures.
However, multi-model ensemble mean solutions depict below-normal temperatures
persisting through day 7 east of the Mississippi Valley and the 6-10 day
temperature outlook leans on the cooler side for most of the eastern CONUS.
Above-normal temperature probabilities increase farther to the west across the
Northern to Central Great Plains as the transition from below to above occurs
sooner. Model solutions continue to depict a shortwave trough reaching the West
Coast as early as day 6, which would enhance onshore flow and elevate the
chance of below-normal temperatures across much of California and the Great
Basin.

The highest forecast confidence in the 6-10 day precipitation outlook is across
the Pacific Northwest, northern California, and Northern Intermountain West
where the shortwave trough along with enhanced onshore flow support relatively
large above-normal precipitation probabilities (greater than 60 percent). These
large probabilities are also related to a drier climatology at this time of
year. Downstream of this shortwave trough, above-normal precipitation is
favored for the Northern to Central Rockies along with much of the Great
Plains, except along and south of the Red River. As of 11am MST on September 3,
the National Hurricane Center forecasts Hurricane Lorena in the East Pacific to
turn north-northeast towards the Baja Peninsula later this week. Enhanced low
to mid-level moisture, associated with the remnants of this tropical cyclone,
may interact with a stationary front located across the southern third of the
CONUS. Any heavier precipitation, associated with this enhanced moisture, is
expected to shift to the Southeast by day 6. A surface trough favors
above-normal precipitation for the Coastal Plain of the Southeast and
Mid-Atlantic, but it is less likely that significant precipitation shifts as
far west as the foothills of the Appalachians. After a slight uptick in
predicted precipitation for the Ohio Valley and Northeast during the past two
days, model guidance has trended back towards a drier solution due to a
persistent surface high anchored over southeastern Canada and the northeastern
CONUS.

The GEFS, ECENS, and CMCE have lower 500-hPa heights today across northwestern
Alaska in response to a strong 500-hPa closed low north of Alaska. Therefore,
below-normal temperatures are slightly favored for northwestern Alaska with
above-normal temperatures more likely across southern and eastern parts of the
state. From day 6 to 8, the ensemble means depict enhanced onshore flow
affecting much of Alaska and the outlook leans towards above-normal
precipitation for much of the state.

Based on the GEFS and ECENS, above-normal temperatures and above-normal
precipitation are favored for Hawaii.

The official 6-10 day 500-hPa height blend consists of 35% of Today`s 0z GFS
Ensemble Mean centered on Day 8, 35% 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: Average, 3 out of 5, due to a
transition to more zonal flow.

8-14 DAY OUTLOOK FOR SEP 11 - 17 2025

Multi-model ensemble means (GEFS, ECENS, and CMCE) are in good agreement with a
pair of 500-hPa troughs centered over the Southeast and just inland from the
West Coast. Due to the less amplified longwave pattern, 500-hPa height
anomalies are forecast to be small (within 30 meters averaged out during this
7-day period). The manual 500-hPa height blend depicts the largest anomaly
(+120 meters) over Hudson Bay and a teleconnection upon this prominent feature
was used as guidance in the week-2 temperature and precipitation outlooks.
Consistent with the positive 500-hPa height anomalies across the northern tier
of the CONUS and westerly mid-level flow, above-normal temperatures are favored
for a majority of the lower 48 states. This predicted switch to above-normal
temperatures across the Midwest would be a significant pattern change following
the extended period of below-normal temperatures from late August through early
September. Due to a relatively cool start to week-2, the outlook leans towards
below-normal temperatures for much of the East Coast. The amplified trough,
early in week-2, favors below-normal temperatures across parts of the Great
Basin, southern California, and the Desert Southwest.

Along and downstream of the 500-hPa trough entering the West, above-normal
precipitation is favored from the Pacific Northwest and northern California
east to the Northern to Central Great Plains and Upper Mississippi Valley. A
large-scale surface high, with its axis oriented from the Northeast
southwestward to the Ohio Valley, favors below-normal precipitation across much
of the Northeast, Mid-Atlantic, Great Lakes, and Ohio Valley. Based on a
teleconnection upon the positive 500-hPa height anomaly center over Hudson Bay,
probabilities for below-normal precipitation exceed 40 percent across parts of
the Great Lakes, Northeast, and Upper Ohio Valley. A lean towards below-normal
precipitation also includes the Tennessee Valley, Lower Mississippi Valley, and
parts of Texas as there is no apparent forcing for significant precipitation
across these areas. A mid-level trough and stationary surface front elevate the
chance of above-normal precipitation across eastern North Carolina and Florida
Peninsula. Overall the precipitation tools have trended drier across the
eastern CONUS. The deterministic ECMWF model and some its ensemble members have
surface low development near the East Coast later in week-2, but this seems to
be a lower probability outcome at this time. Westerly flow, associated with the
trough entering the West, would tend to suppress any late season monsoon
precipitation across the Desert Southwest.

As of 2pm EDT on September 3, the NHC is monitoring a tropical wave currently
over the eastern Atlantic and state that there is a 80 percent chance of
tropical cyclone (TC) development across the Main Development Region of the
Atlantic during the next week. Its future modeled track will be closely
monitored in the days ahead.

The ensemble means all depict a southward extension of a weak 500-hPa trough
over Mainland Alaska. With lower 500-hPa heights compared to yesterday, the
coverage of an increased chance for above-normal temperatures is reduced today.
A two-category change (above to below) was justified for northwestern Alaska
considering the more recent skill of the ECMWF reforecast. The GEFS and ECENS
reforecast tools are in good agreement with an elevated chance of below
(above)-normal precipitation forecast across western (southeastern) Alaska.

Based on the GEFS and ECENS, above-normal temperatures and above-normal
precipitation are favored for Hawaii. Positive sea surface temperature
anomalies also support above-normal temperatures, especially across the
northwestern islands.

The official 8-14 day 500-hPa height blend consists of: 35% of Today`s 0z GFS
Ensemble Mean centered on Day 11, 35% 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: Average, 3 out of 5, due to good
model agreement and continuity on the temperature outlook offset by a
transition to zonal flow and uncertainty with the future track of a tropical
cyclone emerging from the Main Development Region of the Atlantic.

FORECASTER: Brad Pugh

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:
19610819 - 19790821 - 19940818 - 19540831 - 19860904


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:
19610818 - 19790821 - 19860903 - 19890909 - 19510822


6-10 DAY OUTLOOK TABLE
Outlook for Sep 09 - 13 2025

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



8-14 DAY OUTLOOK TABLE
Outlook for Sep 11 - 17 2025

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

                           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.

$$