677
FXUS06 KWBC 011902
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Tue October 01 2024

6-10 DAY OUTLOOK FOR OCT 07 - 11 2024

During early to mid-October, the GEFS, ECENS, and CMCE are in good agreement
that an expansive and anomalous 500-hPa ridge develops and persists over the
western and central contiguous U.S. (CONUS). This ridge begins to become
established just prior to the 6-10 day period and the ridge axis is forecast to
be centered across the Rockies. The ensemble mean solutions depict positive
500-hPa height departures for the western two-thirds of the CONUS. The
anomalous mid-level ridging supports increased above-normal temperature
probabilities from the West Coast eastward to the Mississippi Valley. The
largest probabilities (more than 80 percent) are forecast across the interior
West and Northern to Central Great Plains where 5-day temperatures are likely
to average near or more than 15 degrees F above-normal. For the eastern CONUS,
an amplified 500-hPa trough is expected to result in cooler-than-normal
temperatures across the Mid-Atlantic on days 6 and 7. Given the relatively
strong cold signal in the uncalibrated model guidance and a negative phase of
the North Atlantic Oscillation, a slight lean towards below-normal temperatures
is forecast for parts of the Northeast, Mid-Atlantic, and Central to Southern
Appalachians. Closer to the Gulf Coast and across Florida, above-normal
temperatures are more likely based on the reforecast tools.

In addition to the unseasonably warm temperatures, the anomalous 500-hPa ridge
is likely to result in a very dry pattern with little to no precipitation for a
majority of the CONUS. Along and to east of the predicted ridge axis,
below-normal precipitation is favored across most of the western and central
CONUS. An amplified trough offshore of the West Coast slightly favors
above-normal precipitation for parts of the Pacific Northwest. According to the
National Hurricane Center at 2pm EDT on October 1, there is a 40 percent chance
of tropical cyclone (TC) development over the northwestern Caribbean Sea and
southern Gulf of Mexico during the next 7 days. Until this potential TC forms,
model guidance will vary on its strength and track. Many GEFS and ECMWF
ensemble members depict a TC tracking slowly east from the Gulf of Mexico to
Florida or as far north as southern Georgia next week. Despite the uncertainty
on the eventual strength and track of this potential TC, precipitation tools
are in good agreement with increased above-normal precipitation probabilities
for parts of the Southeast. The model solutions have a sharp cutoff in the
precipitation amounts farther to the north with below-normal precipitation
favored for the Southern Appalachians and Tennessee Valley. The GEFS and ECENS
favor low pressure development near New England by day 7, tilting the 6-10 day
outlook towards the wet side for that region.

The GEFS, ECENS, and CMCE agree with an amplified trough over Alaska which
leads to increased above-normal precipitation probabilities for southeastern
parts of the state. Downslope surface flow results in elevated below-normal
precipitation probabilities across northern Mainland Alaska. Onshore flow
favors above-normal temperatures across eastern Mainland Alaska. The elevated
below-normal temperature probabilities forecast for coastal western Alaska and
the Aleutians are related to below-normal sea surface temperatures.

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

The official 6-10 day 500-hPa height blend consists of 40% 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: Forecast confidence: Above
average, 4 out of 5, due to good model agreement on anomalous ridging and its
effects on temperature and precipitation for the central and western CONUS.

8-14 DAY OUTLOOK FOR OCT 09 - 15 2024

The GEFS, ECENS, and CMCE maintain a stable longwave pattern with the anomalous
500-hPa ridge anchored over the west-central CONUS. The ECENS has this
mid-level ridge strengthening late in week-2 with daily 500-hPa height
departures peaking to more than 180 meters above normal across North Dakota and
Montana. Strongly enhanced above-normal temperature probabilities are forecast
throughout the western and central CONUS. Probabilities exceed 80 percent
across the Northern Great Plains given the excellent model agreement on a
stable longwave pattern and the highly amplified ridge. Temperatures are
favored to be near normal for much of the eastern CONUS due to a trough just
offshore of the East Coast.

Due to the broad and amplified 500-hPa ridge, a dry pattern is likely to
persist for a majority of the CONUS through mid-October. Any TC that forms in
the Gulf of Mexico by early next week is expected to move slowly which elevates
above-normal precipitation probabilities for parts of the Southeast. A low
pressure system is forecast to move away from New England on days 8 and 9.
Therefore, the 8-14 day outlook is drier for this region compared to the 6-10
day outlook. The GEFS favors a TC in the East Pacific tracking northwest
towards the Baja Peninsula and Gulf of California by the beginning of week-2.
This could lead to enhanced low to mid-level moisture spreading north to the
Desert Southwest. Although the GEFS reforecast tool depicts slightly elevated
above-normal precipitation probabilities for the Southwest and Great Basin, the
8-14 day outlook preferred the drier ECENS reforecast and uncalibrated model
solutions at this time.

An amplified 500-hPa trough and enhanced onshore flow favor above-normal
precipitation across southeastern Alaska. Downslope surface flow leads to
elevated below-normal precipitation probabilities across the northern third of
Mainland Alaska. Model guidance remains consistent and in good agreement with
increased above (below)-normal temperature probabilities for eastern Mainland
Alaska (coastal western Alaska and the Aleutians).

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

The official 8-14 day 500-hPa height blend consists of: 40% of Today`s 6z GFS
Ensemble Mean centered on Day 11, 40% of Today`s 0z European Ensemble Mean
centered on Day 11, and 20% of Today`s 0z Canadian Ensemble Mean centered on
Day 11


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Above average, 4 out of 5, due to
a stable longwave pattern and excellent agreement among the temperature tools
with the highest uncertainty in the precipitation outlook for the Southwest.

FORECASTER: Brad Pugh

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:
20051014 - 19640920 - 19841012 - 20051009 - 20090919


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:
20051013 - 19841011 - 20030910 - 19640920 - 20041009


6-10 DAY OUTLOOK TABLE
Outlook for Oct 07 - 11 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    A    B     LOUISIANA   A    B     WISCONSIN   A    B
ILLINOIS    A    B     MISSISSIPPI N    B     MICHIGAN    A    B
INDIANA     N    B     OHIO        N    B     KENTUCKY    N    B
TENNESSEE   N    B     ALABAMA     N    N     NEW YORK    N    B
VERMONT     N    A     NEW HAMP    N    A     MAINE       A    A
MASS        N    A     CONN        B    A     RHODE IS    B    A
PENN        N    B     NEW JERSEY  B    B     W VIRGINIA  B    B
MARYLAND    B    B     DELAWARE    B    B     VIRGINIA    B    B
N CAROLINA  B    N     S CAROLINA  N    A     GEORGIA     N    A
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  N    B
AK ALEUTIAN B    N     AK WESTERN  N    N     AK INT BSN  A    B
AK S INT    N    N     AK SO COAST N    A     AK PNHDL    N    A



8-14 DAY OUTLOOK TABLE
Outlook for Oct 09 - 15 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    A    B     LOUISIANA   A    B     WISCONSIN   A    B
ILLINOIS    A    B     MISSISSIPPI A    B     MICHIGAN    A    B
INDIANA     A    B     OHIO        A    B     KENTUCKY    N    B
TENNESSEE   N    B     ALABAMA     N    B     NEW YORK    N    B
VERMONT     N    B     NEW HAMP    N    B     MAINE       A    N
MASS        N    B     CONN        N    B     RHODE IS    N    B
PENN        N    B     NEW JERSEY  N    B     W VIRGINIA  N    B
MARYLAND    N    B     DELAWARE    N    B     VIRGINIA    N    B
N CAROLINA  N    B     S CAROLINA  N    N     GEORGIA     N    A
FL PNHDL    N    A     FL PENIN    A    A     AK N SLOPE  A    B
AK ALEUTIAN B    N     AK WESTERN  N    N     AK INT BSN  A    N
AK S INT    A    A     AK SO COAST N    A     AK PNHDL    N    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.

$$