Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EST Wed November 29 2023
6-10 DAY OUTLOOK FOR DEC 05 - 09 2023
The GEFS, Canadian, and ECMWF ensemble means are in good agreement that an
amplified 500-hPa trough shifts eastward from the northeastern Pacific to the
western contiguous U.S. (CONUS) from days 6 to 10. Ahead of this mid-level
trough, enhanced Pacific flow is likely to promote above-normal temperatures
throughout the western and central CONUS. Strong downsloping surface flow
results in above-normal temperature probabilities exceeding 80 percent across
the northern and central Great Plains. Forecast confidence in the temperature
outlook remains lower for the eastern CONUS due to uncertainty on the track of
a low pressure system near the East Coast and the strength of cold air
advection in its wake. Similar to yesterday, the 6-10 day outlook leans towards
the colder model guidance given the negative NAO and likelihood for at least a
brief period of cold air advection. The largest below-normal temperature
probabilities (more than 50 percent) are forecast across Florida where the
ensemble means depict the most anomalous cold.
Despite the continued uncertainty on where low pressure develops near the East
Coast and its subsequent track, any significant precipitation is likely to be
limited to the Northeast on day 6 (December 5). Therefore, near to above-normal
precipitation is favored for this region. Elsewhere across the eastern CONUS,
below-normal precipitation is likely due to mean northerly surface flow. The
increased below-normal precipitation probabilities extend eastward to the
middle and lower Mississippi Valley, central and southern Great Plains, and
Southwest due to a mean 500-hPa ridge. Precipitation tools favor a slight lean
towards above-normal precipitation for the lower Rio Grande Valley. Enhanced
onshore flow and a trough progressing slowly inland favor elevated above-normal
precipitation probabilities across the Pacific Northwest, northern California,
northern to central Rockies, and northern Great Plains.
Model solutions feature a strengthening ridge over the Aleutians which is
likely to result in below-normal temperatures across much of western Alaska.
Near to above-normal temperatures are favored for the remainder of Alaska with
modest onshore flow. The ridge over the Aleutians favors below-normal
precipitation for southwestern Alaska, while above-normal precipitation is more
likely across eastern Alaska due to an eastern Gulf of Alaska trough.
The 6-10 day temperature and precipitation outlooks for Hawaii are based on the
consolidation tool. Above-normal temperatures are favored for the entire
Hawaiian island chain. Near normal precipitation is favored for the Big Island,
while elevated above-normal precipitation probabilities are forecast across the
remainder of Hawaii.
The official 6-10 day 500-hPa height blend consists of 30% of Today's 6z GFS
Ensemble Mean centered on Day 8, 35% of Today's 0z European Ensemble Mean
centered on Day 8, and 35% 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
improved agreement among the temperature and precipitation tools.
8-14 DAY OUTLOOK FOR DEC 07 - 13 2023
The GEFS, ECMWF, and Canadian ensemble means have trended towards a building
ridge over the Aleutians during week-2, while the longwave pattern becomes more
progressive across the CONUS. The building ridge upstream over the Aleutians
could eventually lead to strengthening Arctic high pressure at the high
latitudes of western North America. This evolving pattern will have to be
closely monitored for a potential pattern change beyond the week-2 period. The
temperature outlook, valid for December 7 to 13, continues to favor
above-normal temperatures for nearly all of the CONUS based on the enhanced
Pacific flow leading into week-2. Any anomalous cold across the eastern CONUS
is expected to moderate by day 10 and the week-2 outlook generally favors
either near normal temperatures or slightly leans towards above for this
region.
Increased above-normal precipitation probabilities are forecast from the
Pacific Northwest and northern California eastward to the north-central CONUS
due to the 500-hPa trough shifting inland from the northeastern Pacific. The
ECMWF model is the most bullish with surface low development across the central
high Plains with a track northeastward to the upper Mississippi Valley.
Cyclonic flow slightly favors above-normal precipitation across the Great Lakes
and Northwest, while a predicted surface front results in slightly elevated
above-normal precipitation probabilities across the Florida Peninsula and
southern Texas. Due to weak and conflicting signals among the precipitation
tools, near normal precipitation is favored for the Mid-Atlantic, much of the
Southeast, lower Mississippi Valley, and parts of the southern Great Plains.
The week-2 outlook leans dry across southern California and the Southwest but
forecast confidence is low and could become wetter if the trough entering the
West is more amplified.
Downstream of the amplified ridge axis, below-normal precipitation is favored
for southwestern Alaska and the Alaska Peninsula. Based on the consolidation
tool, elevated above-normal precipitation probabilities are forecast across
parts of eastern Alaska. North to northeast surface flow supports increased
below-normal temperature probabilities across southwestern and central Alaska.
The week-2 temperature outlook for Hawaii is based on the consolidation tool
and favors warmer than normal conditions across the state. Increased
above-normal precipitation probabilities are forecast for much of Hawaii which
may be related to the MJO shifting east from the Indian Ocean to the
west-central Pacific during the next two weeks.
The official 8-14 day 500-hPa height blend consists of: 30% of Today's 6z GFS
Ensemble Mean centered on Day 11, 35% of Today's 0z European Ensemble Mean
centered on Day 11, and 35% of Today's 0z Canadian Ensemble Mean centered on
Day 11
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Average, 3 out of 5, due to
improved agreement among the ensemble means on the evolving longwave pattern
offset by a predicted transient pattern over the CONUS.
FORECASTER: Brad Pugh
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
December 21.
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:
19881213 - 20051211 - 20001119 - 20021129 - 19761130
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:
20001119 - 19891119 - 19881212 - 19791113 - 19571123
6-10 DAY OUTLOOK TABLE
Outlook for Dec 05 - 09 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A A NRN CALIF A A
SRN CALIF A B IDAHO A A NEVADA A A
W MONTANA A A E MONTANA A A WYOMING A A
UTAH A B ARIZONA A B COLORADO A N
NEW MEXICO A B N DAKOTA A A S DAKOTA A N
NEBRASKA A B KANSAS A B OKLAHOMA A B
N TEXAS A B S TEXAS A B W TEXAS A B
MINNESOTA A N IOWA A B MISSOURI A B
ARKANSAS A B LOUISIANA A B WISCONSIN A N
ILLINOIS A B MISSISSIPPI N B MICHIGAN A N
INDIANA A B OHIO N B KENTUCKY N B
TENNESSEE N B ALABAMA N B NEW YORK N N
VERMONT B N NEW HAMP B N MAINE N N
MASS B N CONN B N RHODE IS B N
PENN N N NEW JERSEY B N W VIRGINIA N B
MARYLAND N B DELAWARE B B VIRGINIA N B
N CAROLINA N B S CAROLINA B B GEORGIA B B
FL PNHDL B B FL PENIN B B AK N SLOPE N A
AK ALEUTIAN B N AK WESTERN B N AK INT BSN N N
AK S INT B N AK SO COAST B N AK PNHDL N A
8-14 DAY OUTLOOK TABLE
Outlook for Dec 07 - 13 2023
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON N A OREGON A A NRN CALIF A A
SRN CALIF A N IDAHO A A NEVADA A A
W MONTANA A A E MONTANA A A WYOMING A A
UTAH A A ARIZONA A B COLORADO A A
NEW MEXICO A N N DAKOTA A A S DAKOTA A A
NEBRASKA A A KANSAS A N OKLAHOMA A N
N TEXAS A N S TEXAS A N W TEXAS A N
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A N 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 A
VERMONT N A NEW HAMP N A MAINE N A
MASS N N CONN A N RHODE IS N N
PENN A A NEW JERSEY A N W VIRGINIA A N
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 N A AK N SLOPE N N
AK ALEUTIAN B B AK WESTERN B N AK INT BSN N N
AK S INT B N AK SO COAST B N 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.
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