254
FXUS06 KWBC 251902
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 25 2024

6-10 DAY OUTLOOK FOR OCT 01 - 05 2024

The 6-10 day mean mid-level height pattern from the GEFS, ECENS, and Canadian
ensemble continue to forecast positive mid-level height anomalies over eastern
Canada and the northeastern contiguous U.S. (CONUS) with a mid-level ridge over
the western CONUS. Near-normal heights remain forecast across the southeastern
CONUS with a shortwave trough progressing through the region before moving off
the East Coast by the end of the period. In Alaska, a mid-level trough is
forecast across much of the state with the strongest negative anomalies focused
across the Gulf of Alaska. Negative 500-hPa height anomalies are stronger today
relative to yesterday with a more stationary pattern developing relative to
prior forecasts. In Hawaii, near to above-normal 500-hPa height anomalies are
forecast.

Above-normal temperatures are favored across much of the CONUS during the 6-10
day period with one exception across the Southern Appalachians and Mid-Atlantic
where near-normal temperatures are favored associated with a shortwave trough
moving across the southeastern CONUS. Near-normal temperatures are consistent
with reforecast and short-term bias-corrected tools from the GEFS and ECENS.
Otherwise, the strong positive height anomalies favored in the West and eastern
Canada bring strong chances for above-normal temperatures in the interior West
and the Northern Plains, Great Lakes, and Northeast. A trough approaching the
Pacific Northwest reduces probabilities for above-normal temperatures. In
Alaska, near- to below-normal temperatures are favored for southern Alaska with
troughing favored across much of the state. An area of above-normal
temperatures is favored in the northern Mainland displaced from the mid-level
trough. Near to above-normal temperatures are favored for Hawaii consistent
with the autoblend and consolidation tools.

The 6-10 day precipitation forecast favors above-normal precipitation for
portions of the Florida peninsula associated with a frontal boundary draped
across the state. Above-normal is also favored across portions of the Northeast
associated with a surface low-pressure system exiting the region. Another
small, slight tilt towards above-normal precipitation is in the Pacific
Northwest where the slightly deeper trough across the Gulf of Alaska may bring
enhanced precipitation to the region. However, most of the CONUS is forecast to
have below-normal precipitation beneath a mid-level ridge during the 6-10 day
period. In Alaska, above-normal precipitation is favored across the southern
half of the state associated with one or more extra-tropical cyclones that are
forecast to move through the region within the broader mid-level trough. In
Hawaii, above-normal precipitation is favored excluding the Big Island
consistent with the available tools.

The official 6-10 day 500-hPa height blend consists of 35% of Today`s 6z GFS
Ensemble Mean centered on Day 8, 40% of Today`s 0z European Ensemble Mean
centered on Day 8, and 25% 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. Good
agreement among the dynamical tools is offset by uncertainty regarding the
evolution of the height pattern in the Southeast.

8-14 DAY OUTLOOK FOR OCT 03 - 09 2024

The week-2 height forecast is similar to the 6-10 day period, with continued
good agreement among the models for above-normal 500-hPa heights across the
western and central CONUS. Meanwhile, near-normal heights remain forecast in
the southeastern CONUS with some uncertainty regarding the potential for
another tropical wave to move into the region. Ensembles from the GEFS and
ECENS show the potential of another tropical disturbance developing in the
Caribbean or Gulf of Mexico during the week-2 period. This area should be
watched carefully for potential development of a tropical system in light of
Hurricane Helene in this area during week-1. In Alaska, troughing continues
with below-normal 500-hPa heights, the strongest negative anomalies are found
in the Gulf of Alaska, a bit further south relative to the 6-10 day period. In
Hawaii, near-normal 500-hPa heights are forecast.

During week-2, above-normal temperatures remain favored across much of the
CONUS, excluding portions of the Mid-Atlantic and Pacific Northwest. In the
Mid-Atlantic a shortwave trough will be exiting the CONUS by the beginning of
week-2 and warming temperatures are favored behind this system. However, there
is a lot of uncertainty in the pattern across this region and so much of the
Southeast is only slightly favored to see above-normal temperatures. In the
Pacific Northwest, a trough along the West Coast is likely to bring slightly
enhanced onshore flow into the area and near-normal temperatures are favored.
Elsewhere in the CONUS, continued mid-level ridging and positive mid-level
height anomalies bring strong chances for above-normal temperatures to much of
the Interior West, Plains, and Mississippi Valley. In Alaska, above-normal
temperatures remain forecast in the northeastern Mainland with near to
below-normal temperatures favored along the western and southern coastal
regions of the State. In Hawaii, near-normal temperatures are favored for much
of the state, however, above-normal temperatures are slightly favored across
some of the western islands.

During the week-2 period, above-normal precipitation is favored across parts of
Florida, Southern Georgia and southeast South Carolina. In the Pacific
Northwest, a slight tilt towards above-normal precipitation is forecast with a
mid-level trough moving southeast along the British Columbia coast. Elsewhere,
below-normal precipitation is favored for much of the Mississippi Valley,
Plains and Interior West beneath a forecast mid-level ridge. In Alaska,
above-normal precipitation is favored beneath a mid-level trough that is
forecast to maintain unsettled weather in the region. In Hawaii, near-normal
precipitation is forecast consistent with the majority of available 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, Fair
agreement among the tools offset by a less amplified and progressive height
pattern.

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
October 17.


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:
19870912 - 19870917 - 19680924 - 20071009 - 19551006


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:
19870915 - 19870910 - 19680908 - 19680925 - 19680914


6-10 DAY OUTLOOK TABLE
Outlook for Oct 01 - 05 2024

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



8-14 DAY OUTLOOK TABLE
Outlook for Oct 03 - 09 2024

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

$$