Prognostic Meteorological Discussion
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FXUS06 KWBC 281918
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Thu March 28 2024

6-10 DAY OUTLOOK FOR APR 03 - 07 2024

Dynamical model forecasts are in good agreement on the overall large-scale mean
500-hPa height pattern during the 6-10 day period. At the start of the period,
a strong ridge is centered near Greenland, with all ensemble means showing a
closed mid-level high with 500-hPa heights of around 555 dm. To the south, a
strong trough is centered over the North Atlantic with an elongated stretch of
subnormal 500-hPa heights extending westward into the eastern Contiguous U.S.
(CONUS) to a second strong mid-level trough with an axis along the Eastern
Seaboard. The Canadian ensemble mean is considerably weaker than the other two
ensemble means. The deeper solution is preferred since a majority of the tools,
including the operational GFS and European models, show deeper troughs along
the Eastern Seaboard and in the North Atlantic. Subnormal 500-hPa heights
extend southwestward from the eastern CONUS trough to a secondary height
minimum in northern Mexico. This feature remains weak relative to the negative
500-hPa height anomalies in the eastern CONUS, as was the case yesterday. The
Canadian ensemble mean is again an outlier, showing a stronger secondary height
minimum farther west, in northwestern Mexico. This results in a stronger
southern stream system. Again, the Canadian ensemble mean is not preferred
since the preponderance of evidence points toward a weaker southern stream
system. The amplified 500-hPa height anomaly over the Davis Strait, in
conjunction with the subnormal heights from the North Atlantic into the eastern
CONUS, are indicative of a strong negative phase of the North Atlantic
Oscillation (NAO). The magnitude of the negative NAO weakens with time, but it
is expected to remain negative until late week-2. In April, a negative NAO
generally correlates with below-normal temperatures across much of the CONUS,
especially west of the Mississippi River, and with above-normal precipitation
in parts of the Far West, the central Great Plains, and the Southeast.
Historically, however, there has been considerable variability, so the
correlations aren’t hard-and-fast rules. Today’s forecast is closer to these
historic correlations than yesterday, but some significant differences remain.

Meanwhile, a mid-level ridge is expected to be centered in the North Pacific at
the beginning of the period, with above-normal heights extending northward. The
European ensemble mean extends the above-normal 500-hPa heights into most of
Mainland Alaska as was the case yesterday, but the other two ensemble means are
significantly different, showing subnormal mid-level heights over most of
Alaska tied to an anomalous mid-level trough farther northwest. The subnormal
500-hPa heights over most of the state represent a significant change from
yesterday, when all ensemble means resembled today’s European ensemble mean,
with above-normal 500-hPa heights over most of the state. Despite the
preponderance of the guidance showing generally subnormal 500-hPa heights
across the state, this solution is not preferred due to the sharp change it
represents from yesterday, in addition to teleconnections on the Davis Strait
ridge favoring increased heights over Mainland Alaska.

Moving forward, the evolution shown by the dynamical models looks progressive
overall, but for the second consecutive day, models have slowed down the
eastward movement of large-scale features, with some features lingering in
place for a time before progressing eastward. For example, all model ensemble
means show a weak mid-level trough in southwestern Canada dropping into the
western CONUS and amplifying. This feature remains centered over the western
CONUS for several days before starting to lift eastward as the period ends.
Likewise, relatively higher heights build downstream in the eastern CONUS after
the initial mid-level trough shifts quickly eastward. Once a mid-level ridge is
established across the region, the feature remains in place as the axis extends
northward to the strong positive height anomaly over the Davis Strait. So there
is a period where features stagnate for a time after some progression early in
the period and, to a lesser extent, at the very end of the 6- to 10-day window.

There is still considerable inconsistency in the raw and calibrated outputs
from the ensembles, but differences are not as contradictory as they were
yesterday. The bias corrections still produce warmer results in most areas than
the raw output, and the reforecast tools tend to warm the solution even
further, but without sharply flipping the sign of the anomalies in some cases.
E.g., in the Far West, yesterday’s raw output from the GEFS favored
significantly colder than normal weather while the reforecast showed enhanced
odds for above-normal temperatures. Today, there is a notable reduction in the
cold signal from the reforecast compared to the raw output, but both solutions
still favor anomalously cold weather to some degree. Current disparities still
lower forecast confidence somewhat, but not to the degree noted yesterday.

Considering all these factors, the 6- to 10-day outlook is considerably
different than yesterday. With raw and derived temperature tools coming into
better agreement, the forecast roughly follows a blend of the tools, which puts
colder than normal mean conditions over much of the West, and enhanced chances
for above-normal temperatures over much of the Great Plains and Upper Midwest.
This dipole is flipped in comparison to yesterday, when the forecasts favored
warmth in the West and near- to below-normal temperatures in part of the
Nation’s midsection, albeit only slightly. Farther east, tools favor slightly
enhanced chances for subnormal mean temperatures in the Southeast and
mid-Atlantic region, with warmer than normal weather anticipated in northern
Maine and southern Florida. Chances for anomalous warmth exceed 50 percent in
part of the central Great Plains, and over 40 percent in a large part of the
Great Plains and Upper Midwest. Meanwhile, the enhanced chances for subnormal
temperatures exceed 40 percent over most areas from the western Rockies to the
Pacific Coast. This is a much larger part of the CONUS than saw odds topping 40
percent for either temperature extreme yesterday, due to the better consensus
in the tools.

Surplus precipitation is anticipated in Florida and Maine primarily from the
deep mid-level trough and associated surface storm and frontal complex quickly
moving eastward away from the CONUS. Elsewhere, surplus precipitation is
expected in most of the northern Great Plains and western CONUS due to the
mid-level trough expected to linger in the region through much of the period.
Above-normal rainfall is also anticipated along the Gulf Coast due to unusually
strong moisture influx from the Gulf of Mexico which may interact with a weak
frontal boundary. In contrast, drier than normal weather is favored in the
Middle Mississippi Valley, Ohio Valley, Great Lakes region, central
Appalachians, and mid-Atlantic region as a mid-level ridge builds in behind the
storm departing the East Coast early in the period.

There is increased uncertainty relative to yesterday in the 500-hPa height
field across Alaska, with some of today’s models showing much lower 500-hPa
heights than yesterday. However, all solutions show an anomalously sharp
gradient in 500-hPa heights from south to north across the state. This should
result in somewhat more storminess than normal, along with slightly enhanced
odds for below-normal temperatures which are not expected to reach extreme
values.

A mid-level trough and below-normal 500-hPa heights near Hawaii favor cooler
and wetter than normal conditions there, although the odds for both are
slightly lower than yesterday.

The official 6-10 day 500-hPa height blend consists of 55% of Today`s 6z GFS
Ensemble Mean centered on Day 8, 10% of Today`s GFS Superensemble Mean centered
on Day 8, 20% of Today`s 0z European Ensemble Mean centered on Day 8, and 15%
of Today`s 0z Canadian Ensemble Mean centered on Day 8


FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Near average, 3 out of 5, due to
fair agreement on the predicted circulation pattern and reduced disparity in
the raw and derived temperature and precipitation output from the dynamical
models.

8-14 DAY OUTLOOK FOR APR 05 - 11 2024

The week-2 500-hPa height forecast is expected to remain slowly progressive
overall, with some features stagnating for a few days before moving downstream
and weakening. The 500-hPa ridge in the eastern CONUS looks to remain in place
until late week-2, when it begins to drift eastward and weaken. The mid-level
trough initially settled into the interior West is also expected to remain
approximately in place before starting to shift eastward and weaken near the
end of week-2. At higher latitudes, anomalous ridging near the Davis Strait is
forecast to slowly drift southward and weaken through the period. Farther
upstream, the disparities in dynamical model forecasts of 500-hPa heights
across Alaska seem resolved by the end of week-2, when the ensemble means all
forecast mid-level heights to be above normal in western parts of the Mainland,
and near normal farther east.

The reduced uncertainty resulting from better agreement among the raw and
derived temperature and precipitation tools in the 6- to 10-day period carries
over into week-2, and in fact week-2 guidance is in better agreement than for
the 6- to 10-day period. A mean mid-level ridge in the eastern CONUS favors
above-normal temperatures across a large area from the eastern Great Plains to
the Atlantic Coast. Chances for above-normal temperatures are considerably
higher than yesterday due to the better agreement in the tools, exceeding 60
percent in most of the Great Lakes region and adjacent areas to the south and
west. Meanwhile, the mean mid-level trough in the West implies cooler than
normal weather from the Rockies westward. Enhanced chances for subnormal
temperatures exceed 50 percent over the Rockies and most of the Far West.

Near and upstream from the mean mid-level trough in the West, somewhat enhanced
chances for above-normal precipitation cover a large area from the western and
central CONUS eastward to the Appalachains and southeastward through the Gulf
Coast and Florida. Farther east, near the mid-level ridge axis, drier than
normal conditions are favored in the mid-Atlantic region and the Northeast,
particularly across eastern New England.

The unusually strong west-to-east mid-level jet across Alaska weakens with
time, but its effects are expected to drive conditions across the state for the
bulk of week-2. Thus there are enhanced odds for above-normal precipitation
through most of the state, along with increased chances for near- to
below-normal temperatures. However, the circulation pattern should generally
preclude intrusions of unusually cold or warm air from other parts of the globe.

500-hPa heights slowly increase over and near Hawaii during week-2 as the weak
mid-level trough continues to dissipate. In the mean, cooler and wetter than
normal conditions are again expected for week-2 across Hawaii, but late-week
changes in the mid-level circulation pattern reduced the odds for both compared
to yesterday.

The official 8-14 day 500-hPa height blend consists of: 20% of Today`s 6z GFS
Ensemble Mean centered on Day 11, 40% of Today`s GFS Superensemble Mean
centered on Day 11, 20% of Today`s 0z European Ensemble Mean centered on Day
11, and 20% of Today`s 0z Canadian Ensemble Mean centered on Day 11


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Near average, 3 out of 5, with the
temperature and precipitation tools coming into better agreement, and fair
agreement among model forecasts of the week-2 mean 500-hPa height 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
April 18.


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:
19570314 - 19530322 - 20060310 - 19530405 - 19510330


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:
19530321 - 19570314 - 19900314 - 19530405 - 20080408


6-10 DAY OUTLOOK TABLE
Outlook for Apr 03 - 07 2024

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



8-14 DAY OUTLOOK TABLE
Outlook for Apr 05 - 11 2024

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   B    A     E MONTANA   B    A     WYOMING     B    A
UTAH        B    A     ARIZONA     B    A     COLORADO    B    A
NEW MEXICO  B    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    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    B     W VIRGINIA  A    N
MARYLAND    A    B     DELAWARE    A    B     VIRGINIA    A    B
N CAROLINA  A    N     S CAROLINA  A    N     GEORGIA     A    A
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  N    A
AK ALEUTIAN B    A     AK WESTERN  B    A     AK INT BSN  B    A
AK S INT    B    A     AK SO COAST B    A     AK PNHDL    B    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.

$$



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