709
FXUS06 KWBC 241902
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Tue September 24 2024

6-10 DAY OUTLOOK FOR SEP 30 - OCT 04, 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), a building mid-level ridge
over the western CONUS. Near to below-normal heights across the southeastern
CONUS, the result of lingering mid-level low pressure associated with remnants
of Tropical Storm Helene that is forecast to develop into a tropical cyclone in
the Gulf of Mexico. This may disrupt the relatively stable pattern that much of
the CONUS has seen over the past couple of weeks and will need to be watched
this week. In Alaska, a mid-level trough is forecast across much of the state
with the strongest negative anomalies focused across the Gulf of Alaska. 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 main exception in the Central and Lower Mississippi River
Valley where near-normal temperatures are favored associated with a shortwave
trough moving across the eastern CONUS resulting from some remnant energy of
Tropical Storm Helene that is forecast to linger across the region late into
week-1. 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
northeastern 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 Southeast and Mid-Atlantic associated with the remnants of
Tropical Storm Helene. The energy associated with this tropical cyclone is
likely to bring unsettled weather to these areas. However, across most areas
west of the Mississippi, below-normal precipitation is favored beneath a
mid-level ridge across. In Alaska, above-normal precipitation is favored across
western and southern Alaska associated with one or more extra-tropical cyclones
that are forecast to move through the region within the broader mid-level
trough. In Hawaii, near-normal precipitation is favored 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, 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: 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 02 - 08 2024

The week-2 height forecast is very similar to the 6-10 day period, with
continued good agreement among the models for above-normal 500-hPa heights
across the western CONUS and eastern Canada. Meanwhile, near to slightly
below-normal heights remain forecast in the southeastern CONUS with uncertainty
regarding the evolution of the pattern following Tropical Storm Helene. 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 Tennessee River Valley and Southern
Appalachians. In these areas near-normal temperatures are forecast with
continued weak shortwave troughing in the region. Surrounding this area are
slightly reduced chances for above-normal temperatures relative to much of the
rest of the country with some short-term bias-corrected tools indicating near
to below-normal temperatures, but with reforecast tools showing above-normal,
weak chances for above-normal temperatures are favored. Elsewhere, continued
mid-level ridging and positive mid-level height anomalies bring strong chances
for above-normal temperatures to much of the interior West and Northern Tier of
the CONUS. 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. This is consistent
among most forecast tools and is the result of a baroclinic zone forming ahead
of weak shortwave troughing across the Tennessee Valley. A slight tilt towards
above is also forecast for parts of the Northeast where a weak area of
low-pressure may traverse the region. Elsewhere, below-normal precipitation is
favored for much of the Mississippi Valley, Plains and Interior West beneath a
forecast mid-level ridge. 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. 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, 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, 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:
19870915 - 19680924 - 19870910 - 20081007 - 20030918


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:
19870914 - 19680925 - 20030921 - 20081006 - 19870909


6-10 DAY OUTLOOK TABLE
Outlook for Sep 30 - Oct 04, 2024

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    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    N    B     LOUISIANA   A    B     WISCONSIN   A    B
ILLINOIS    A    N     MISSISSIPPI N    N     MICHIGAN    A    N
INDIANA     A    N     OHIO        A    N     KENTUCKY    A    N
TENNESSEE   A    N     ALABAMA     A    A     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    N     NEW JERSEY  A    N     W VIRGINIA  A    N
MARYLAND    A    A     DELAWARE    A    A     VIRGINIA    A    A
N CAROLINA  A    A     S CAROLINA  A    A     GEORGIA     A    A
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  A    A
AK ALEUTIAN B    N     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 02 - 08 2024

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    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    N     KENTUCKY    A    B
TENNESSEE   N    B     ALABAMA     A    N     NEW YORK    A    N
VERMONT     A    A     NEW HAMP    A    A     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    A    N     DELAWARE    N    N     VIRGINIA    A    N
N CAROLINA  A    N     S CAROLINA  A    N     GEORGIA     A    N
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  A    A
AK ALEUTIAN B    A     AK WESTERN  N    A     AK INT BSN  A    A
AK S INT    N    A     AK SO COAST N    A     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.

$$