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6-10 Day outlooks are issued daily between 3pm & 4pm Eastern Time. All forecasts issued on weekends are completely automated while all weekday outlooks are modified by the forecaster.
Please refer to the U.S. Prognostic Discussion for an explanation of terms and symbols used on these maps.
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Prognostic Discussions
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Valid: Oct 01 - 05, 2023 (6-10 Day Outlook)
Valid: Oct 03 - 09, 2023 (8-14 Day Outlook)
Issued: Sep 25, 2023 |
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Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Mon September 25 2023
6-10 DAY OUTLOOK FOR OCT 01 - 05 2023
The GEFS, Canadian, and ECMWF ensemble means are in good agreement predicting
an amplified 500-hPa ridge over southwestern Alaska and the Bering Sea. A
trough is predicted over the western contiguous U.S. (CONUS) in the GEFS, ECMWF
and Canadian ensemble means that de-amplifies during the period. Ensemble mean
solutions are in good agreement predicting a persistent amplified ridge over
the eastern CONUS.
Below normal temperatures are favored over most of Alaska, excluding western
and northern Alaska, under anomalous northerly flow to the east of the
predicted amplified ridge. Below normal temperatures are favored for most of
the western CONUS, under a mean trough and weak negative 500-hPa height
anomalies. Above normal temperatures are likely for the central and eastern
CONUS under an amplified ridge. Prevailing southerly surface flow along with a
ridge aloft results in large probabilities of more than 80 percent for above
normal temperatures across the Upper Mississippi Valley.
Above normal precipitation is favored for northern Mainland Alaska, while below
normal precipitation is favored for southern Mainland Alaska, under anomalous
northerly flow ahead of the predicted ridge. Above normal precipitation is
favored for the northern half of the West, ahead of a predicted trough, and
over much of the Great Plains region in the central CONUS, with predicted
surface southerly flow. Below normal precipitation is likely for most of the
eastern CONUS, under the predicted ridge. Above normal precipitation is
slightly favored for the Florida Peninsula, with a storm system potentially
passing just east of this region.
The official 6-10 day 500-hPa height blend consists of 30% of Today's 0z 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 on an amplified mid-level height pattern over North America and
fairly good agreement among the tools.
8-14 DAY OUTLOOK FOR OCT 03 - 09 2023
Model forecasts continue to predict a ridge over southwest Alaska in week-2.
The GEFS and Canadian ensemble means show somewhat less amplified positive
500-hPa height anomalies over the region than the ECMWF ensemble mean. The
ECMWF ensemble mean forecast was favored in today’s manual blend of 500-hPa
height forecasts, due to recent greater anomaly correlation">anomaly correlation to observations
than the GEFS and Canadian ensemble means. The GEFS, ECMWF, and Canadian
ensemble means agree in predicting a more zonal flow pattern over the CONUS, at
the start of the week-2 period, with the development of a trough along the
western CONUS later in the period. The manual blend of model 500-hPa height
forecasts predicts a trough axis slightly further west in the 8-14 day period
than in the 6-10 day period. A ridge and positive 500-hPa height anomalies
persist over the eastern CONUS during week-2.
Below normal temperatures continue to be favored over interior and southeastern
Alaska during week-2, under anomalous northerly flow, while above normal
temperatures are favored for western Mainland Alaska and the Aleutians, under
the positive 500-hPa height anomaly center. Below normal temperatures are
favored over most of the western third of the CONUS under a predicted trough.
Above normal temperatures continue to be likely for the eastern two-thirds of
the CONUS under an amplified ridge.
Above normal precipitation is favored for central and northern areas of Alaska,
under anomalous northwesterly flow, while near to below normal precipitation is
favored for southern areas of the state. Above normal precipitation is favored
for most of the western CONUS, outside climatologically dry areas of the
Southwest, ahead of a predicted trough. Below normal precipitation is favored
from the Tennessee Valley to the Northeast, under the predicted ridge. There is
greater uncertainty for the precipitation forecast for the Southeast, where
near normal precipitation is favored.
The official 8-14 day 500-hPa height blend consists of: 30% of Today's 0z 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: Average, 3 out of 5, due to good
overall agreement on the 500-hPa height pattern in week-2, offset by increasing
uncertainty in temperature and precipitation tools.
FORECASTER: D Collins
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
October 19.
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:
20071009 - 20010927 - 19620930 - 20081006 - 19870918
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:
20010926 - 19620929 - 20071008 - 19621004 - 19870917
6-10 DAY OUTLOOK TABLE
Outlook for Oct 01 - 05 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON B A OREGON B A NRN CALIF B N
SRN CALIF B N IDAHO B A NEVADA B A
W MONTANA B A E MONTANA N A WYOMING B A
UTAH B A ARIZONA B N 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 B S TEXAS A N W TEXAS A A
MINNESOTA A A IOWA A A MISSOURI A B
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 A B
VERMONT A B NEW HAMP A B MAINE A B
MASS A B CONN A B RHODE IS A B
PENN A B NEW JERSEY A B W VIRGINIA A B
MARYLAND A B DELAWARE A B VIRGINIA A B
N CAROLINA A B S CAROLINA A B GEORGIA A B
FL PNHDL A N FL PENIN N N AK N SLOPE N A
AK ALEUTIAN N B AK WESTERN N N AK INT BSN B A
AK S INT B B AK SO COAST B B AK PNHDL B N
8-14 DAY OUTLOOK TABLE
Outlook for Oct 03 - 09 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON B A OREGON B A NRN CALIF B A
SRN CALIF B N IDAHO B A NEVADA B N
W MONTANA B A E MONTANA B A WYOMING B A
UTAH B A ARIZONA B N 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 A LOUISIANA A A WISCONSIN A A
ILLINOIS A A MISSISSIPPI A N MICHIGAN A N
INDIANA A N OHIO A B KENTUCKY A B
TENNESSEE A B ALABAMA A N NEW YORK A B
VERMONT A B NEW HAMP A B MAINE A B
MASS A B CONN A B RHODE IS A B
PENN A B NEW JERSEY A B W VIRGINIA A B
MARYLAND A B DELAWARE A N VIRGINIA A B
N CAROLINA A N S CAROLINA A N GEORGIA A N
FL PNHDL A N FL PENIN A N AK N SLOPE N A
AK ALEUTIAN A N AK WESTERN A A AK INT BSN B A
AK S INT B N AK SO COAST B N AK PNHDL B 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.
$$
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Surface Forecasts,
500mb Heights and Anomalies,
Time Series of Surface Forecast Skill,
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