911
FXUS06 KWBC 211901
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Mon April 21 2025

6-10 DAY OUTLOOK FOR APR 27 - MAY 01, 2025

Today`s numerical models generally depict a high amplitude 500-hPa pattern
across much of the country. The period begins with a strong ridge over the
eastern Contiguous U.S. (CONUS) and an upstream trough over the interior West.
Ridging is forecast off the West Coast of the CONUS and a trough is forecast
over the Bering Sea. The ridge in the East is forecast to slowly decrease in
magnitude and progress from the Great Lakes region toward the East Coast by Day
10. In its wake the trough over the interior West is forecast to persist
(particularly over the Southwest). The ECMWF and GEFS ensemble means show a
separate shortwave trough ejecting from the West into the Northern Plains and
Great Lakes by the middle and end of the period. This 500-hPa setup supports
the development of a potent surface low on the lee side of the Rockies and a
favorable setup for a potentially very active pattern across much of the Plains
and Mississippi Valley. Farther to the north, the trough over the Bering Sea is
forecast to persist throughout the period. A separate mid-level low is forecast
to strengthen over the Gulf of Alaska by the end of the period, setting up a
potentially active pattern for Southeastern Alaska by day 10. Mean troughing is
also forecast across much of Hawaii, with below normal heights generally
predicted across the state.

Above normal temperatures are favored  for most of the CONUS east of the
Rockies. Probabilities of above normal temperatures exceeds 80 percent across
much of the Lower and Middle Mississippi Valley where southerly flow is likely
to be persistent throughout most of the period. Conversely, a tilt toward below
normal temperatures is indicated for parts of the Southwest, due to persistent
troughing. Near to above normal temperatures are favored for much of the south
coast of Alaska associated with predicted southerly or southwesterly onshore
flow and above normal sea surface temperatures (SSTs) in adjacent waters. Below
normal temperatures are more likely for northern and western Alaska due to
persistent troughing and associated below normal heights. Above normal
temperatures are likely for Hawaii, adjacent to above normal SSTs.

An active period is anticipated across much of the center of the CONUS.
Persistent southerly flow ahead of a predicted trough over the west should
transport ample Gulf moisture northward. At the same time, surface low pressure
is forecast to develop in the lee of the Rockies and move northeastward to the
northern Plains and Great Lakes. This surface low combined with available
moisture from the Gulf leads to increased chances of above normal precipitation
for most of the central CONUS. Probabilities of increased precipitation amounts
relative to normal exceed 60 percent for much of the Plains and parts of the
Upper Mississippi Valley associated with the predicted surface low. Conversely,
a slight tilt toward below normal precipitation is indicated along most of the
Eastern Seaboard and eastern Gulf Coast due to predicted anomalous ridging and
associated surface high pressure. An active pattern is likely for southeastern
Alaska as a surface low is forecast to strengthen over the Gulf of Alaska later
in the period. Above normal precipitation probabilities exceed 50 percent for
Southeast Alaska and adjacent areas of the Mainland. A tilt toward above normal
precipitation is also indicated for Hawaii as a mean 500-hPa trough and below
normal heights are forecast across the area.

The official 6-10 day 500-hPa height blend consists of 20% of Today`s 6z GFS
Ensemble Mean centered on Day 8, 50% 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
a predicted amplified 500-hPa flow pattern.

8-14 DAY OUTLOOK FOR APR 29 - MAY 05, 2025

The week-2 period begins with an amplified pattern featuring anomalous ridging
over the Eastern Seaboard and troughs over the Southwest and Northern Plains.
As time progresses the flow pattern becomes much more zonal across the CONUS
with near to above normal 500-hPa heights predicted for almost all of the Lower
48 by the end of the period. Conversely, the flow pattern remains amplified
across Alaska as anomalous troughing is forecast to persist over the Eastern
Bering Sea, southwestern Mainland Alaska, and the Gulf of Alaska. This combined
troughing leads to predicted near to below normal heights across most of the
state with the strongest negative height anomalies forecast for southwestern
Alaska. Near to below normal heights are forecast to persist across Hawaii due
to predicted troughing in the vicinity.

With the flow pattern expected to become more zonal across the CONUS, a
moderating trend is likely across most areas of the Lower 48. Above normal
temperatures are favored across the vast majority of the CONUS. The lone
exception is for parts of the southwestern CONUS where weak troughing may
persist well into the week-2 period. Enhanced probabilities of near normal
temperatures are indicated for this area. Near to above normal temperatures are
favored for much of southern Alaska underneath predicted southerly flow
combined with above normal SSTs adjacent to the South Coast. Below normal
temperatures are more likely for northern and western Alaska associated with
predicted mean troughing and northeasterly low-level flow. Above normal
temperatures remain likely for Hawaii associated with above normal SSTs in
nearby waters.

An active pattern is anticipated to continue into week-2 for much of the
Plains, Mississippi Valley, and Great Lakes, particularly early in the period.
Enhanced southerly flow should continue to transport ample Gulf moisture
northward into the Southern Plains and Lower Mississippi Valley early in week-2
while surface low pressure increases precipitation chances northeastward to the
Great Lakes. Chances of above normal precipitation exceeds 50 percent from the
Arklatex to the Ozarks where Gulf moisture advection is likely to be most
pronounced. Conversely, as troughing weakens and progresses eastward, offshore
northeasterly low-level flow is predicted to develop across much of California,
leading to a slight tilt toward below normal precipitation. Conversely,
enhanced moisture flow ahead of a predicted surface low over the Gulf of Alaska
favors above normal precipitation for southern and eastern Alaska southward to
parts of the Pacific Northwest. Above normal precipitation probabilities exceed
50 percent for Southeast Alaska where onshore flow is likely to be most
pronounced. A slight tilt toward above normal precipitation persists for Hawaii
near a predicted trough.

The official 8-14 day 500-hPa height blend consists of: 20% of Today`s 6z GFS
Ensemble Mean centered on Day 11, 50% 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: Below Average, 2 out of 5, due to
a predicted transition to a lower amplitude pattern across much of the country.

FORECASTER: Scott H

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:
20020421 - 20000402 - 20080417 - 20020504 - 19730422


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:
20020420 - 20000403 - 19730421 - 19810407 - 20080416


6-10 DAY OUTLOOK TABLE
Outlook for Apr 27 - May 01, 2025

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



8-14 DAY OUTLOOK TABLE
Outlook for Apr 29 - May 05, 2025

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    N     OREGON      A    N     NRN CALIF   A    B
SRN CALIF   A    N     IDAHO       A    N     NEVADA      A    N
W MONTANA   A    N     E MONTANA   A    N     WYOMING     A    N
UTAH        A    N     ARIZONA     N    N     COLORADO    A    A
NEW MEXICO  N    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     N    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    A     NEW YORK    A    A
VERMONT     A    A     NEW HAMP    A    A     MAINE       A    A
MASS        A    A     CONN        A    N     RHODE IS    A    N
PENN        A    A     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 B    N     AK WESTERN  B    N     AK INT BSN  B    A
AK S INT    N    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.

$$