210
FXUS06 KWBC 161901
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Fri May 16 2025

6-10 DAY OUTLOOK FOR MAY 22 - 26 2025

Today`s model solutions are in good agreement, with a fairly amplified 500-hPa
pattern expected across North America and surrounding regions. The manual
500-hPa height blend is based primarily on the operational ECMWF and ensemble
means from the GEFS, ECMWF and Canadian models, with the operational ECMWF
included to add more amplitude to the pattern which may be getting erroneously
flattened by outlier members in the ensembles. The resultant manual blend
features mid-level ridging and above-normal 500-hPa heights over the western
Contiguous United States (CONUS) and central Canada while a mid-level trough
and below-normal 500-hPa heights are forecast farther south and east over most
of the eastern CONUS. Weak troughing is also forecast to stretch across the
Bering Sea and through Mainland Alaska while an amplified ridge and
above-normal 500-hPa heights dominate areas farther south and west over the
Aleutians and adjacent North Pacific Ocean. Slightly below-normal 500-hPa
heights are predicted across Hawaii by most tools.

Mean surface low pressure should be centered somewhere over the western North
Atlantic or southernmost New England for the period, with higher pressures
farther to the west. This should usher below-normal temperatures into most of
the central and eastern CONUS outside Florida and parts of the Southern Plains,
where above-normal temperatures are favored. Probabilities of below-normal
temperatures exceed 70% from the Ohio Valley through the upper mid-Atlantic
Region and across southern New England. In contrast, near- to above-normal
temperatures are favored over most of the western CONUS under ridging and
positive 500-hPa height anomalies. Enhanced chances for cooler-than-normal
weather in the West are limited to portions of northwestern Washington, where
mid-level heights are lower. Chances of above-normal temperatures exceed 70%
over portions of the Four Corners Region. Beneath predicted negative 500-hPa
height anomalies, below-normal temperatures are favored over Northern and
Southeastern Alaska, while anticipated southerly surface wind flow favors
temperatures close to normal in much of the southern and western Mainland.
Above-normal temperatures are likely for Hawaii, with positive sea surface
temperature anomalies surrounding the Islands.

East of the mid-level trough, a surface low pressure center is forecast to move
along or near the East Coast and slowly weaken as it heads into eastern Canada.
This favors above-normal precipitation for much of the northeastern CONUS. Odds
for a wetter-than-normal period top 50 percent across southern New England.
Below-normal precipitation is favored farther southwest over portions of the
South Atlantic Region into the Lower Mississippi Valley and adjacent Southern
Plains under mean surface high pressure. Chances for subnormal precipitation
exceed 40 percent in portions of the Southern Atlantic Region southwestward
into the Central Gulf Coast. Abnormally dry conditions are also favored across
central and southern portions of the western CONUS in conjunction with the
amplified ridging predicted there. Above-normal precipitation is favored for
most of Alaska in association with the predicted trough over the State.
Increased odds for wet weather extend southeastward from Alaska into portions
of western Washington, in conjunction with relatively low heights there
compared to farther southeast. Precipitation consolidation tool forecasts favor
above-normal precipitation for Hawaii.

The official 6-10 day 500-hPa height blend consists of 17% of Today`s 0z GFS
Ensemble Mean centered on Day 8, 25% of Today`s 0z European Ensemble Mean
centered on Day 8, 40% of Today`s operational 0z ECMWF centered on Day 8, and
18% 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. Good
agreement on the height pattern among the ensemble means is offset slightly by
some areas of inconsistency among the dynamical and statistical temperature and
precipitation tools, and by slowly diverging model solutions toward the end of
the period, when slow deamplification is expected to begin.

8-14 DAY OUTLOOK FOR MAY 24 - 30 2025

Ensemble mean solutions for the 8-14 day period depict a slowly progressive and
deamplifying 500-hPa circulation pattern. Mean 500-hPa anomalies are generally
expected to be slightly east of their location relative to the 6- to 10-day
period and with lesser amplitude. Alaska is a bit of an exception. The
mid-level trough over the state weakens and drifts eastward while another
trough initially in eastern Siberia encroaches on Alaska from the west,
effectively retrograding the position of the mean mid-level trough over
northwestern North America. These changes result from a slow deamplification of
the pattern with time that resolves into a relatively flat, amorphous pattern
over the western Northern Hemisphere by the end of week-2, with near- to
above-normal heights broadly established at that time. Still, ensemble mean
solutions predict mid-level ridging and somewhat above-normal 500-hPa heights
over the western and central CONUS while a weak mean mid-level trough and
below-normal 500-hPa heights are expected over the Northeast. Weak troughing
slowly fills over Mainland Alaska and Southeast Alaska, with relatively lower
heights infringing on the far western CONUS by the end of the period.
Meanwhile, slightly below-normal 500-hPa heights are forecast to persist across
Hawaii, well to the south of a mean ridge forecast to cover the eastern North
Pacific.

Above-normal temperatures continue to be favored across most of western North
America, parts of the Southern Plains, and the Florida Peninsula in the week-2
period under ridging and positive mean 500-hPa height anomalies. Portions of
the Pacific Northwest are an exception, with lower heights drifting in from the
northwest slightly favoring cooler-than-normal conditions for the week.
Probabilities of above-normal temperatures exceed 50% for portions of the
southern Great Plains, near where positive height anomalies are greatest.
Below-normal temperatures are again favored for most of the eastern CONUS under
the slowly deamplifying trough, with reduced chances relative to the 6- to
10-day period. Still, odds for cooler-than-normal weather exceed 50 percent
across the Upper Ohio Valley and adjacent locations. Much of Florida and
adjacent Georgia should be exceptions. Along the East Coast, these locations
will be farthest removed from the slowly retreating, deamplifying mid-level
trough near the Northeast. Odds for anomalous warmth top 50 percent over
southern reaches of the Florida Peninsula. Above-normal temperatures are
favored for much of Mainland Alaska under slowly rebounding 500-hPa heights and
southerly surface flow, while temperatures closer to normal are favored along
the northern coastline and in Southeast Alaska. Above-normal temperatures are
also favored to persist across Hawaii during week-2 by dynamical models, likely
fueled by continued above-normal sea surface temperatures..

With deamplifying mid-level height anomalies, the precipitation anomaly pattern
is uncertain over much of North America. At this time, above-normal
precipitation is slightly favored for much of the continent under slightly
above-normal heights and areas of moist, southerly or easterly surface flow.
But in the CONUS, only portions of the southeastern Great Plains and adjacent
Lower Mississippi Valley have odds exceeding 40 percent for unusual wetness.
The exceptions, where near-normal precipitation is favored, are the central
Gulf Coast and part of the South Atlantic Region, the Great Lakes and adjacent
Upper Mississippi Valley, and most of the Intermountain West and Southwest.
Above-normal precipitation is favored slightly across most of Alaska south of
the Brooks Range under southerly mean surface wind flow. Above-normal
precipitation is also favored for Hawaii, consistent with the preponderance of
tools under persistently below-normal 500-hPa heights.

The official 8-14 day 500-hPa height blend consists of: 33% of Today`s 0z GFS
Ensemble Mean centered on Day 11, 34% of Today`s 0z European Ensemble Mean
centered on Day 11, and 33% 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. Good
agreement on the mean pattern continues, but is offset by the inherent
uncertainty in an evolving low-amplitude pattern.

FORECASTER: Rich Tinker

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
June 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:
19550522 - 19510517 - 19620516 - 19770521 - 19550530


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:
19570425 - 19510517 - 20070528 - 19590506 - 19820525


6-10 DAY OUTLOOK TABLE
Outlook for May 22 - 26 2025

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



8-14 DAY OUTLOOK TABLE
Outlook for May 24 - 30 2025

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

$$