Prognostic Meteorological Discussion
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FXUS06 KWBC 021935
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Mon October 02 2023

6-10 DAY OUTLOOK FOR OCT 08 - 12 2023

There is considerably less uncertainty than at the end of last week regarding
the mid-level height pattern during the extended range period. Models are in
general agreement showing the 6-10 day period starting out fairly amplified,
with mid-level troughs over the eastern North Pacific and the eastern CONUS
while a strong anomalous ridge is centered south of Greenland. The GEFS is a
bit stronger and farther southeast with the North Pacific trough than the other
ensemble means. Meanwhile, a mid-level ridge is expected to be centered near
the Canadian Prairies with an axis extending southward just west of the Front
Range of the Rockies. Guidance is less consistent with this feature than with
others; the European ensemble mean is stronger than the GEFS and the Canadian
ensemble mean with this feature. There is also some discrepancy near Hudson
Bay, as the GEFS and European ensemble mean keep 500-hPa heights somewhat
higher than the Canadian ensemble mean, but none of the inconsistencies has
much of an effect on sensible weather across the CONUS.

This is likely a transient pattern, with some progression and de-amplification
taking place as the 6-10 period progresses. Teleconnections indicate that the
well above-normal 500-hPa heights south of Greenland are not consistent with a
strong mid-level trough over the north-central or northeastern North Pacific.
This is borne out in all the ensemble means, though there are some
discrepancies regarding the placement and strength of specific features,
especially at the end of the period. By day 9, most guidance shows a weaker
mid-level trough farther east in the North Pacific and a weakening trough that
has moved from the eastern CONUS into or near the western North Atlantic Ocean,
a positive 500-hPa height anomaly center near Hudson Bay, and a trough in the
northeastern North Pacific, with subnormal 500-hPa heights extending near or
into the Pacific Northwest. The Canadian ensemble means show lower heights near
Hudson Bay and a larger positive 500-hPa anomaly across part of the western
CONUS compared to the GEFS and European ensemble means. The preponderance of
the guidance favors the higher 500-hPa heights near Hudson Bay and mid-level
heights closer to normal in the western CONUS, so this is the favored solution
at this time.

By day 10 or shortly thereafter, another change in the mid-level pattern is
getting underway, showing some retrogression and re-amplification of features
across Canada, the northwestern CONUS, and the North Pacific, which will be
most notable during week-2. The European ensemble mean is slower to start this
retrogression than the other ensemble means, but all show it well underway by
the middle of week-2.

The favored 6-10 day pattern would lead to below-normal temperatures from the
eastern to the south-central CONUS near and behind the strong mid-level trough.
Cold weather may impact vulnerable crops during the last half of the period in
the middle Ohio Valley, central Appalachians, and adjacent areas. Meanwhile,
the Canadian ridge favors above-normal temperatures farther west from the upper
Mississippi Valley and Great Plains to the West Coast, with the best odds for
warmth in the northern halves of the High Plains and eastern Rockies, closest
to the mid-level ridge centered near the Canadian Prairies. Farther east,
downstream from the ridge and upstream from the trough, below-normal
precipitation is most likely, except for some potential moisture intrusion
along the Gulf Coast, and some storminess in part of New England just
downstream from the eastern CONUS trough.

The mid-level trough southeast of Alaska is expected to bring heavy
precipitation into the Pacific Northwest, with odds for above-normal
precipitation exceeding 60 percent from the Cascades westward. In addition,
this feature favors wet weather in eastern and particularly southeastern Alaska
near and east of the trough axis. The low 500-hPa heights also somewhat enhance
chances for below-normal temperatures over most of Mainland Alaska.

The official 6-10 day 500-hPa height blend consists of 15% of Today`s 6z GFS
Ensemble Mean centered on Day 8, 35% of Today`s GFS Superensemble Mean centered
on Day 8, 15% of Today`s operational 6z GFS centered on Day 8, 10% of Today`s
0z European Ensemble Mean centered on Day 8, 15% of Today`s operational 0z
ECMWF centered on Day 8, and 10% 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
general agreement among the tools on the broadscale pattern, with the noted
discrepancies not having a dramatic impact on sensible weather in the CONUS and
Alaska.

8-14 DAY OUTLOOK FOR OCT 10 - 16 2023

During week-2, retrogression of the de-amplified pattern is expected, along
with some re-amplification of certain features. By the end of the period, a
positive 500-hPa anomaly center is forecast west of Hudson Bay and north of the
Canadian Prairies while the strong mid-level trough near the western CONUS is
re-positioned westward and broadened, with the axis extending southward into
the North Pacific well west of the Pacific Northwest. There is a bit more
uncertainty in the East, but 500-hPa heights should generally be near to
slightly below normal, with a weak trough axis from near the New England coast
southeastward into the North Atlantic.

The re-building heights in Canada and the weakening of the mid-level trough in
the East should displace the cold air that settled into the eastern CONUS
during the 6-10 day period, with temperatures climbing above normal there by
the end of week-2. The speed of this transition is uncertain, as are the
temperature anomalies early in the period - good radiational cooling underneath
surface high pressure could allow nighttime temperatures to drop lower than
indicated by guidance during days 8 and 9. This uncertainty led to a forecast
favoring neither colder than normal nor warmer than normal temperatures in much
of the East. But odds favor above-normal temperatures over the rest of the
CONUS, with the most enhanced chances in the northern Plains closest to the
mid-level high pressure centered north of the Canadian Prairies. The
precipitation forecast pattern is similar to the 6-10 day period, with dry
weather slightly favored over much of the interior CONUS and parts of the East
Coast and wetter than normal weather in the Northwest and near the Gulf Coast.
With the mid-level ridge center established well north in Canada, some return
flow of Gulf moisture is possible late week-2, reducing the odds for subnormal
precipitation during week-2 as a whole across the interior CONUS.

The trough south of Alaska will continue to favor wetter-than-normal weather in
the eastern Mainland and southeastern Alaska and drier conditions farther west.
In addition, the below-normal 500-hPa heights slightly increase the odds for
below-normal temperatures over most of the Mainland and the Aleutians.

The official 8-14 day 500-hPa height blend consists of: 45% of Today`s 6z GFS
Ensemble Mean centered on Day 11, 15% of Today`s GFS Superensemble Mean
centered on Day 11, 30% of Today`s 0z European Ensemble Mean centered on Day
11, and 10% of Today`s 0z Canadian Ensemble Mean centered on Day 11


FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Near normal, 3 out of 5, for
general agreement in the evolution of the mid-level height pattern, tempered by
differences in the timing and magnitude of evolving features.

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
October 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:
19941015 - 19830930 - 20081011 - 19981015 - 19841013


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:
19941015 - 19830929 - 20081010 - 19520911 - 19841013


6-10 DAY OUTLOOK TABLE
Outlook for Oct 08 - 12 2023

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



8-14 DAY OUTLOOK TABLE
Outlook for Oct 10 - 16 2023

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

$$



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