524
FXUS06 KWBC 262032
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EST Tue November 26 2024

6-10 DAY OUTLOOK FOR DEC 02 - 06 2024

Todays model solutions from the GEFS, ECMWF, and Canadian ensemble means for
500-hPa heights and anomalies are very similar to yesterday and all depict a
low frequency wave train pattern over North America during the 6-10 day period
average, with ridging forecast over the West Coast and troughing over the
eastern Contiguous U.S. (CONUS). Consistency in model solutions from run to run
is notable, increasing forecast confidence.

A strong cold front and an associated cold airmass are favored to move over the
CONUS east of the Rockies during the week-1 period, resulting in a strong tilt
towards below-normal temperatures, especially east of the Mississippi River
where probabilities greater than at least 50% are almost universal and
exceeding 80% for the much of the Tennessee and Ohio Valleys, Mid-Atlantic and
Southeast U.S. Meanwhile, amplified ridging over the West Coast favors
above-normal temperatures roughly from the Rockies westward particularly along
the West Coast and the Desert Southwest where probabilities exceed 50%.
Probabilities are lower over the northern Great Basin which is prone to cold
nighttime surface inversions, pushing down the average temperature anomaly over
the forecast period. Widespread positive height anomalies over eastern Siberia
and the Bering Sea favor below-normal temperatures for the western coast of
Alaska, while strong onshore flow off the Gulf of Alaska favors above-normal
temperatures for southeastern Alaska, particularly the Panhandle where
probabilities exceed 60%. Above-normal temperatures are also favored for
Hawaii, consistent with model guidance.

Model solutions of the ridge over the West Coast depict a very high amplitude
feature with positive height anomalies extending well north of the U.S.-Canada
border, limiting Pacific moisture fluxes into the continent and favoring
below-normal precipitation for much of the Lower 48. Odds are highest for
Northern California and extending to the western slope of the Rockies where
probabilities exceed 50%. Easterly return flow is depicted over the Gulf of
Mexico, tilting the odds toward above-normal precipitation for portions of the
Southern Plains. Although a strong ridge is favored over the West Coast, the
potential for an Alberta-type clipper system slightly favors above-normal
precipitation for portions of the Northern Plains into the northern Great
Lakes. Strong onshore flow into southeastern Alaska increasingly favors
above-normal precipitation for much of the state, while the western and
northern portions remain at near- to below-normal precipitation under positive
500-hPa height anomalies. Model guidance indicates increasing suppressed
convection south of Hawaii, tilting the odds towards below-normal precipitation
for Molokai and islands to the south, while near-normal precipitation remains
favored for Oahu and Kauai.

The official 6-10 day 500-hPa height blend consists of 33% of Today`s 0z GFS
Ensemble Mean centered on Day 8, 34% of Today`s 0z European Ensemble Mean
centered on Day 8, and 33% of Today`s 0z Canadian Ensemble Mean centered on Day
8


FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Very high, 5 out of 5, with strong
agreement among forecast models across variables.

8-14 DAY OUTLOOK FOR DEC 04 - 10 2024

Model ensembles favor a persistence of the synoptic pattern from the 6-10 day
period. Like the early period, the week-2 500-hPa manual height blend features
amplified ridging over the West Coast and a broad trough over the eastern CONUS
and North Atlantic. The week-2 temperature and precipitation outlooks are also
very similar to the 6-10 period, once again with high forecast confidence due
to both the persistent pattern as well as good model agreement.

Continued positive 500-hPa height anomalies over western North America continue
to favor above-normal temperatures for the western half of the CONUS. Chances
of above-normal temperatures are increased from the earlier forecast period,
with at least 60% chances favored west of the Rockies except for the northern
Great Basin where nighttime cold inversions erode period-average positive
temperature anomalies. The trough depicted over the eastern CONUS during the
6-10 day period is favored to weaken somewhat, slightly reducing chances of
below-normal temperatures for the eastern half of the country. Probabilities
remain above 70% for portions of the Mid-Atlantic where cold air is favored to
linger throughout the period. With continued onshore flow off the Gulf of
Alaska, elevated chances of above-normal temperatures are favored to spread
over most of the state. Northwestern Alaska continues to tilt towards near- to
below-normal temperatures under the continued influence of ridging over eastern
Siberia. Persistence is also the preferred solution for the Hawaiian Islands,
with the whole state favored for above-normal temperatures.

Continued amplified ridging over the western CONUS favors below-normal
precipitation to persist for much of the Lower 48 through week-2. Chances are
slightly reduced over the Central Plains and into the Ohio Valley and
Mid-Atlantic but remain above 50% for portions of Northern California and
western Nevada. Continued return flow off the Gulf of Mexico keeps portions of
the Southern Plains tilting towards above-normal precipitation, while Alberta
clippers remain a possibility along the U.S.-Canada border, tilting the odds
slightly toward above-normal precipitation for portions of the Northern Plains
through the Upper Great Lakes . As onshore flow continues off the Gulf of
Alaska, the tilt towards above-normal precipitation is favored to spread
further into the Mainland covering most of the state, except along the western
coast where near-normal precipitation is indicated. Across Hawaii, below-normal
precipitation is favored for the Big Island, while near-normal precipitation is
favored for the remainder of the islands.

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: Above average, 4 out of 5, with
good agreement among forecast models across variables, offset by differences in
depicted amplitude of synoptic features and weaker anomalies during the
forecast period.

FORECASTER: Daniel Barandiaran

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
December 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:
19631113 - 19611126 - 19801203 - 19731111 - 19661202


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:
19801202 - 19631114 - 19731110 - 20051130 - 19611126


6-10 DAY OUTLOOK TABLE
Outlook for Dec 02 - 06 2024

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



8-14 DAY OUTLOOK TABLE
Outlook for Dec 04 - 10 2024

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

$$