393
FXUS06 KWBC 061929
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Tue May 06 2025

6-10 DAY OUTLOOK FOR MAY 12 - 16 2025

Today`s ensemble mean solutions are in very good agreement in depicting a high
amplitude 500-hPa pattern across much of North America. The period begins with
a decaying positive North Atlantic Oscillation (NAO) characterized by anomalous
troughing over the Davis Strait extending southward to Atlantic Canada. A
strong anomalous ridge is forecast across the Upper Mississippi Valley/western
Great Lakes and a trough or closed low is predicted to undercut this ridge over
the Lower Mississippi Valley. Across western North America and the Eastern
Pacific, three main features are forecast to dominate, the first two features
being a pair of troughs located over the Bering Sea and near the west coast of
the Contiguous United States (CONUS). Ridging is forecast in between these two
troughs well offshore of the Pacific Northwest. The pattern is forecast to be
slow-moving such that by the end of the period, the trough over the Bering Sea
is predicted to essentially remain in place. The downstream trough near the
West Coast is forecast to slowly move to the Interior West by day 10. The
anomalous ridge over the Upper Mississippi Valley is forecast to drift eastward
to the eastern Great Lakes toward the end of the period. Finally, the trough or
closed low over the Lower Mississippi Valley is predicted to slowly lift
northeastward to the Southeast by the middle of the period and then to the
southern Atlantic and mid-Atlantic coasts.

Above normal temperatures are likely for most of the northern two-thirds of the
CONUS east of the Rockies due to anomalous and persistent ridging. The highest
likelihood of unseasonable warmth is across the Upper Mississippi Valley and
adjacent areas of the Plains and western Great Lakes, near the center of the
predicted mean ridge. Enhanced probabilities of above normal temperatures are
relatively lower along coastal areas of the Northeast and northern Mid-Atlantic
as teleconnections from the trough offshore of northeastern Canada are
supportive of the potential of back-door cold fronts. Below normal temperatures
are likely along the west coast of the CONUS as a strengthening trough is
forecast to slowly move inland during the period. Probabilities of above normal
temperatures are enhanced across much of the southern High Plains, ahead of the
predicted West Coast trough. Near normal temperatures are favored for the Gulf
Coast region and adjacent areas of the Lower Mississippi Valley and Southeast,
as a slow moving low progresses from the central Gulf Coast to the Southeast. A
slight tilt toward above normal temperatures are indicated for southwestern
Alaska ahead of the Bering Sea trough. Above normal sea surface temperatures
(SSTs) in nearby waters may also contribute to increasing chances of above
normal temperatures for this region. Below normal temperatures are slightly
favored for parts of eastern Mainland Alaska consistent with predicted below
normal heights and for Southeast Alaska underneath anomalous northerly
mid-level flow. Near normal temperatures are favored for the remainder of the
state due to weak or conflicting guidance. A slight tilt toward above normal
temperatures is indicated for parts of the Aleutians consistent with the
majority of dynamical model guidance. Above normal temperatures are likely
across Hawaii consistent with anticipated above normal sea surface temperatures
(SSTs) in adjacent waters.

An active period is anticipated across much of the western CONUS as an
anomalous trough pushes inland from the Pacific during the period. Above normal
precipitation is favored for most areas of the CONUS from the Rockies westward.
Chances of precipitation are enhanced much farther to the south along the coast
of California than typical for this time of year due to the unusual strength of
the predicted trough. As the trough progresses eastward, above normal
precipitation probabilities increase across much of the Northern Plains. Above
normal precipitation is also likely for the Southeast as a slow moving low
pressure system is expected to promote ample moisture advection into this
region from the Gulf and Atlantic. In between these two active regions, near to
below normal precipitation is more likely across most of the Southern Plains,
Mississippi Valley, Great Lakes, and Northeast. Conversely, above normal
precipitation is favored across much of Alaska due to persistent anomalous
troughing predicted over the Bering Sea. Above normal precipitation is also
favored for Hawaii, consistent with skill weighted calibrated precipitation
amounts calculated from the GEFS and ECMWF ensembles.

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
good agreement among todays ensemble means.


8-14 DAY OUTLOOK FOR MAY 14 - 20 2025

The week-2 period begins with a highly amplified pattern featuring anomalous
ridging over the Great Lakes and troughs over the Southeast, the western CONUS,
and Bering Sea. As time progresses the pattern remains persistent in many
areas. The trough over the Bering Sea is generally forecast to remain in place
and gradually reduce in intensity. The trough over the West Coast is forecast
to slowly progress eastward, potentially leading to a more active pattern
across the Plains with time. Models then depict a retrogression of a trough
back toward the West Coast near the end of the period. The ridge over the Great
Lakes is generally forecast to remain in place while the trough over the
Southeast very slowly progresses northeastward toward the Mid-Atlantic coast
and eventually offshore. After this low departs, increased ridging is predicted
across the Southern Plains and eventually for parts of the Mississippi and
Tennessee valleys with time. Generally near normal 500-hPa heights are forecast
for Hawaii, well to the south of a mean ridge forecast across the eastern
Pacific.

Above normal temperatures are favored for most of the CONUS from the Plains
eastward. This is especially true for the Great Lakes due to persistent
ridging. However, relatively modestly enhanced probabilities of above normal
temperatures are indicated for the Northeast and Mid-Atlantic coast as
confidence is tempered by the potential for back-door cold fronts. Near normal
temperatures are favored farther to the south, across southern portions of the
Eastern Seaboard due to forecast troughing early in the period. Cooler than
normal temperatures are favored from the Rockies to the West Coast as a strong
trough slowly pushes eastward across the interior West and then potentially
retrogrades back to the West Coast near the end of the period. Near normal
temperatures are favored for most of Alaska due to weak or conflicting
guidance. However a slight tilt toward above normal temperatures are indicated
for extreme southwestern Mainland Alaska, the Alaska Peninsula, and parts of
the Aleutians due, in part, to anticipated above normal SSTs in nearby waters.
Slightly enhanced probabilities of below normal temperatures are indicated for
a small portion of northwestern Alaska underneath predicted below normal
mid-level heights. Above normal temperatures remain likely across Hawaii
associated with anticipated above normal SSTs in adjacent waters.

An active pattern is anticipated to continue into week-2 for much of the West
(with the exception of the immediate coast and climatologically dry areas of
the Southwest) due to a slow moving trough. As this trough slowly progresses
eastward, a more active pattern is favored for much of the Plains eastward to
the Upper Mississippi Valley as surface low pressure is forecast to develop. An
area of greater than 50 percent chance of above normal precipitation is
indicated from parts of the Great Basin northeastward to the northern High
Plains associated with this predicted surface low. Predicted anomalous
southerly flow ahead of the low leads to an increase in probabilities of above
normal precipitation southward across the central Plains and northern parts of
the Southern Plains. Above normal precipitation is also favored for parts of
the Southeast and Mid-Atlantic (particularly early in the period) as a trough
slowly exits the region. In its wake, a strengthening ridge favors below normal
precipitation across the Lower Mississippi Valley and the western and central
Gulf Coast region and adjacent areas of the Southern Plains. Similarly,
predicted ridging slightly favors below normal precipitation for much of the
Northeast and adjacent areas of the eastern Great Lakes. An active pattern and
increased above normal precipitation chances remain forecast for much of
southern and central Alaska due to persistent troughing over the Bering Sea.
Above normal precipitation is also favored for Hawaii, consistent with skill
weighted calibrated precipitation amounts calculated from the GEFS and ECMWF
ensembles.

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: Above average, 4 out of 5, due to
a predicted fairly persistent pattern.


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:
19510519 - 19570427 - 19880520 - 19800518 - 19930502


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:
19510517 - 19610515 - 19570425 - 19700502 - 20060428


6-10 DAY OUTLOOK TABLE
Outlook for May 12 - 16 2025

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  B    A     OREGON      B    A     NRN CALIF   B    A
SRN CALIF   B    A     IDAHO       B    A     NEVADA      B    A
W MONTANA   N    A     E MONTANA   A    A     WYOMING     A    A
UTAH        N    A     ARIZONA     N    N     COLORADO    A    N
NEW MEXICO  A    N     N DAKOTA    A    A     S DAKOTA    A    N
NEBRASKA    A    N     KANSAS      A    N     OKLAHOMA    A    N
N TEXAS     A    B     S TEXAS     N    B     W TEXAS     A    B
MINNESOTA   A    N     IOWA        A    N     MISSOURI    A    N
ARKANSAS    A    N     LOUISIANA   N    N     WISCONSIN   A    N
ILLINOIS    A    N     MISSISSIPPI N    N     MICHIGAN    A    B
INDIANA     A    N     OHIO        A    N     KENTUCKY    A    N
TENNESSEE   A    A     ALABAMA     N    A     NEW YORK    A    B
VERMONT     A    B     NEW HAMP    A    B     MAINE       A    B
MASS        A    B     CONN        A    B     RHODE IS    A    B
PENN        A    B     NEW JERSEY  A    N     W VIRGINIA  A    A
MARYLAND    A    A     DELAWARE    A    A     VIRGINIA    A    A
N CAROLINA  A    A     S CAROLINA  A    A     GEORGIA     N    A
FL PNHDL    N    A     FL PENIN    A    A     AK N SLOPE  N    N
AK ALEUTIAN A    A     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 May 14 - 20 2025

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

                           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.

$$