901
FXUS06 KWBC 181902
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Fri April 18 2025

6-10 DAY OUTLOOK FOR APR 24 - 28 2025

Multi-model ensemble means (GEFS, ECENS, and CMCE) depict a persistent longwave
pattern over the Contiguous U.S. (CONUS) through late April. Another amplified
trough is forecast to progress eastward over the West while a broad anomalous
ridge remains centered over the east-central CONUS. The ECENS and CMCE are the
most amplified with the trough near the West Coast. Positive 500-hPa height
anomalies along with southerly surface flow favor above-normal temperatures
from the Great Plains to the East Coast. Large probabilities (exceeding 80
percent) are forecast for the Lower Mississippi Valley and parts of the
Southeast where 5-day temperatures are likely to average near 10 degrees F
above normal. Above-normal temperature probabilities are lower across the
Northeast due to close proximity of negative sea surface temperature anomalies
offshore and an increased chance of at least a brief period of northeasterly
flow. Since the manual 500-hPa height blend has larger negative anomalies,
associated with the West Coast trough, and the reforecast GEFS and ECENS
trended colder, more of the western CONUS is included in the enhanced
below-normal temperature probabilities compared to the previous day.

On day 6 (April 24), model solutions remain consistent and in good agreement
with a stationary front located from the Southern Great Plains east to the
Tennessee Valley. This stationary front is then forecast to shift northward
towards the Midwest before shifting back south as a cold front. This
oscillating front is likely to be the focus for heavier precipitation and
above-normal probabilities are slightly larger (greater than 40 percent) across
the Ohio Valley. To the east of the Appalachians, 5-day precipitation amounts
are forecast to be lower with the GEFS, ECENS, and CMCE generally depicting
less than one inch. Near normal precipitation or a slight lean towards
above-normal precipitation is forecast for much of the East Coast. As another
amplified 500-hPa trough reaches the West Coast on day 8 and then progresses
inland, surface low development is probable across the Central High Plains by
the end of this period. This evolving pattern aloft and at the surface favors
above-normal precipitation for a majority of the western and central CONUS.
Based on good model agreement and consistency along with support from the
analog tool, above-normal precipitation probabilities exceed 50 percent
throughout the Great Plains.

Although the ensemble means vary on its amplitude, they agree on the
development of anomalous 500-hPa troughing over the Bering Sea and Aleutians.
This trough and its associated southwesterly flow favor near to above-normal
temperatures and above-normal precipitation across the southern half of Alaska.
Nearby surface high pressure and northeasterly flow support increased
below-normal temperature probabilities for northern Alaska. It appears that the
Brooks Range will likely be the dividing line between colder- and
warmer-than-normal temperatures.

Based on the GEFS and ECENS, above-normal temperatures and above-normal
precipitation are favored for Hawaii. The model solutions remain consistent
that a slow-moving low pressure system, to the northwest of Hawaii, brings an
increased chance of heavier precipitation especially across the northwest
islands.

The official 6-10 day 500-hPa height blend consists of 30% of Today`s 6z 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 model agreement and a persistent longwave pattern.

8-14 DAY OUTLOOK FOR APR 26 - MAY 02, 2025

The GEFS, ECENS, and CMCE maintain a 500-hPa trough (ridge) over the western
(eastern) CONUS through the beginning of May. By the end of week-2, the ECENS
and CMCE are the most amplified with a trough extending from the Gulf of Alaska
southeastward to the West Coast. A broad area of positive 500-hPa height
anomalies coupled with a lack of any cold air advection, consistent among all
the ensemble means, support increased above-normal temperature probabilities
for a majority of the lower 48 states. A large area with above-normal
temperature probabilities in excess of 70 percent covers the Central Great
Plains, Middle to Lower Mississippi Valley, and portions of the Southeast. Due
to more anomalous 500-hPa troughing among the ensemble mean solutions today,
the area with favored below-normal temperatures was expanded to include nearly
all of California and parts of Arizona and Nevada.

Along and downstream of an amplified longwave trough axis, above-normal
precipitation is favored for much of the western and central CONUS. Based on
the likelihood for surface low development to the lee of the Rockies and
consistent with the analog tool, above-normal precipitation probabilities are
enhanced across the northern Rockies and Great Plains. Near normal
precipitation is favored for much of the East Coast where the dynamical model
output (wetter) differs from the analog tool (drier). Similar to yesterday, a
slight lean towards below-normal precipitation is forecast for parts of the
Southeast based on the uncalibrated ECENS and CMCE. Above-normal precipitation
is slightly favored across south Florida as model guidance features an easterly
wave crossing this area with ensemble means having near 0.75 inch of
precipitation.

A broad trough is forecast over the Bering Sea and Aleutians. Downstream of
this broad trough, above-normal precipitation is favored for the southern-two
thirds of Alaska. The enhanced onshore flow leads to increased chances of
above-normal temperatures for southern Alaska, while nearby surface high
pressure and easterly flow favor below-normal temperatures across northern
Alaska.

Based on the GEFS and ECENS, above-normal temperatures and above-normal
precipitation are favored for Hawaii. Positive sea surface temperature
anomalies also support above-normal temperatures throughout Hawaii.

The official 8-14 day 500-hPa height blend consists of: 30% of Today`s 6z 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, due to
good model agreement on a fairly stable longwave pattern for this time of year.

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 May
15.


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:
20000331 - 19990421 - 19750329 - 19710425 - 19610405


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:
20000330 - 19990420 - 19750329 - 20020330 - 19610407


6-10 DAY OUTLOOK TABLE
Outlook for Apr 24 - 28 2025

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  N    A     OREGON      N    A     NRN CALIF   B    A
SRN CALIF   B    N     IDAHO       A    A     NEVADA      N    A
W MONTANA   A    A     E MONTANA   A    A     WYOMING     A    A
UTAH        A    A     ARIZONA     A    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    A     MICHIGAN    A    A
INDIANA     A    A     OHIO        A    A     KENTUCKY    A    A
TENNESSEE   A    A     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    A     NEW JERSEY  A    A     W VIRGINIA  A    A
MARYLAND    A    A     DELAWARE    A    A     VIRGINIA    A    A
N CAROLINA  A    A     S CAROLINA  A    A     GEORGIA     A    A
FL PNHDL    A    N     FL PENIN    A    N     AK N SLOPE  B    N
AK ALEUTIAN A    A     AK WESTERN  A    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 Apr 26 - May 02, 2025

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    A     OREGON      A    A     NRN CALIF   B    A
SRN CALIF   B    A     IDAHO       A    A     NEVADA      N    A
W MONTANA   A    A     E MONTANA   A    A     WYOMING     A    A
UTAH        A    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    A
INDIANA     A    A     OHIO        A    A     KENTUCKY    A    A
TENNESSEE   A    N     ALABAMA     A    B     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    A
MARYLAND    A    N     DELAWARE    A    N     VIRGINIA    A    N
N CAROLINA  A    N     S CAROLINA  A    N     GEORGIA     A    N
FL PNHDL    A    N     FL PENIN    A    N     AK N SLOPE  B    N
AK ALEUTIAN N    N     AK WESTERN  N    A     AK INT BSN  B    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.

$$