749
FXUS06 KWBC 131902
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Fri September 13 2019
6-10 DAY OUTLOOK FOR SEP 19 - 23 2019
Today's model solutions are in fair agreement in depicting a moderately
amplified 500-hPa height pattern across much of the forecast domain. A trough
is forecast over mainland Alaska. Downstream, a weak trough is predicted across
the northern Rockies while broad ridging is forecast to dominate much of the
central and eastern CONUS. Today's manual 500-hPa height blend favors the 0Z
ECMWF ensemble mean and features near to above normal heights across most of
the CONUS as well as over the Aleutians. Below normal heights are favored for
all of mainland Alaska and for most of Florida and southeastern Georgia.
Near to above normal temperatures are favored across the CONUS. The near normal
probabilities in the Rockies are due to the de-amplifying trough. Probabilities
of above normal temperatures exceed 70 percent over the Great Lakes underneath
predicted ridging and positive 500-hPa height anomalies. Above normal
temperatures are likely across southern Alaska, consistent with the
reforecast-calibrated GEFS and autoblend tools. Inland portions of mainland
Alaska favor slightly below normal temperatures in association with negative
500-hPa height anomalies.
There are above normal probabilities of precipitation in the Pacific Northwest
in association with mean low pressure in the Gulf of Alaska. Above normal
probabilities are favored over portions of the desert Southwest due to the
potential for influx of tropical moisture from the east Pacific. Enhanced
probabilities of above normal precipitation are also favored over the Great
Plains out ahead of the weak mean trough. Below normal probabilities are
favored in the northern Rockies and for the eastern third of the CONUS. This is
a stark contrast from yesterday's forecast. In the northern Rockies, drier air
is descending from Canada. For the Southeast, recent model guidance has
converged on a solution that shows a potential tropical system moving eastward
into the Atlantic away from the forecast domain for the valid period.
Conversely, a trough forecast over western portions of mainland Alaska favors
near normal precipitation along the coast near the Bering Strait and above
normal precipitation across the Aleutians, eastern mainland Alaska, and the
Alaska panhandle.
The official 6-10 day 500-hPa height blend consists of 10% of Today's 0z GFS
Ensemble Mean centered on Day 8, 35% of Today's 6z GFS Ensemble Mean centered
on Day 8, 5% of Today's operational 6z GFS centered on Day 8, 45% of Today's 0z
European Ensemble Mean centered on Day 8, and 5% of Today's operational 0z
ECMWF centered on Day 8
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Average, 3 out of 5, due to decent
model agreement across the domain, but with some disagreement in timing of the
pattern.
8-14 DAY OUTLOOK FOR SEP 21 - 27 2019
During the week-2 period, models generally depict a progression of the 500-hPa
height pattern across much of the forecast domain. A mean trough is forecast
near the Gulf of Alaska. Ridging is forecast over western Canada, resulting in
a trend toward higher 500-hPa heights in the western CONUS. Weak mean cyclonic
flow is favored across the Great Lakes region. The ensemble means predict that
subtropical ridging will dominate most of the southwestern and south-central
CONUS. However, there is much uncertainty across the Southeast and along the
eastern seaboard due to the potential for tropical activity later in the
period. The official manual 500-hPa height blend depicts positive height
anomalies across most of the western and north-central CONUS. Below normal
heights are favored across most of mainland Alaska, the southeastern CONUS, and
along coastal areas of the northeastern CONUS.
Above normal temperatures are favored for the CONUS. The highest
probabilities of above normal temperatures are indicated along the West Coast
and northern Rockies extending into the northern Great Plains underneath
predicted above normal heights. Near to above normal temperatures are favored
for Alaska, consistent with the reforecast-calibrated GEFS and autoblend tools.
Above normal probabilities of precipitation are favored in the Pacific
Northwest in association with a large area of mean low pressure near the Gulf
of Alaska. Below normal precipitation probabilities are forecast for the
northern Rockies eastward into the northern Great Plains, Midwest, and Great
Lakes underneath predicted ridging. Elevated chances of above normal
precipitation in the Southwest are associated with the potential influx of
tropical moisture from the eastern Pacific. Above normal precipitation is
slightly favored for the Southeast and mid-Atlantic coastlines due to the
potential for tropical cyclone development later in the period. There is still
great uncertainty across the Southeast due to uncertainty in the tropical
Atlantic. There are increased chances of near to above normal precipitation
across eastern mainland Alaska, the Aleutians, and the Alaska panhandle due to
persistent surface low pressure systems forecast near the Alaska peninsula.
Below normal probabilities are favored over western mainland Alaska, consistent
with the reforecast and autoblend tools.
The official 8-14 day 500-hPa height blend consists of: 10% of Today's 0z GFS
Ensemble Mean centered on Day 11, 30% of Today's 6z GFS Ensemble Mean centered
on Day 11, 5% of Today's operational 6z GFS centered on Day 11, 50% of Today's
0z European Ensemble Mean centered on Day 11, and 5% 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
generally good agreement between models on the predicted 500-hPa height
pattern, but offset somewhat by differences among the temperature and
precipitation forecast tools and uncertainty in the tropics.
FORECASTER: Adam Hartman
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 1981-2010 base period means for
temperature...precipitation...and 500-hpa heights as reference in the climate
outlooks.
The next set of long-lead monthly and seasonal outlooks will be released on
September 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:
19950927 - 20090913 - 19790925 - 19890828 - 19850912
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:
20090913 - 19620924 - 19790925 - 19950926 - 20010924
6-10 DAY OUTLOOK TABLE
Outlook for Sep 19 - 23 2019
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A N OREGON A N NRN CALIF A N
SRN CALIF A N IDAHO A B NEVADA A N
W MONTANA A B E MONTANA A B WYOMING A B
UTAH A N ARIZONA A A COLORADO A A
NEW MEXICO A 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 A A
MINNESOTA A A IOWA A A MISSOURI A A
ARKANSAS A A LOUISIANA A A WISCONSIN A A
ILLINOIS A A MISSISSIPPI A N MICHIGAN A B
INDIANA A N OHIO A B KENTUCKY A B
TENNESSEE A B ALABAMA A B 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 B
MARYLAND A B DELAWARE A B VIRGINIA A B
N CAROLINA A B S CAROLINA A B GEORGIA A B
FL PNHDL A B FL PENIN A B AK N SLOPE N A
AK ALEUTIAN A A AK WESTERN N N AK INT BSN N A
AK S INT N A AK SO COAST A A AK PNHDL A A
8-14 DAY OUTLOOK TABLE
Outlook for Sep 21 - 27 2019
STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN
WASHINGTON A A OREGON A N NRN CALIF A N
SRN CALIF A N IDAHO A N NEVADA A N
W MONTANA A B E MONTANA A B WYOMING A B
UTAH A N ARIZONA A A COLORADO A A
NEW MEXICO A A N DAKOTA A B S DAKOTA A B
NEBRASKA A B KANSAS A B OKLAHOMA A N
N TEXAS A N S TEXAS A N W TEXAS A A
MINNESOTA A B IOWA A B MISSOURI A B
ARKANSAS A N LOUISIANA A N WISCONSIN A B
ILLINOIS A B MISSISSIPPI A N MICHIGAN A B
INDIANA A B OHIO A N KENTUCKY A N
TENNESSEE A N ALABAMA A N NEW YORK A N
VERMONT A N NEW HAMP A N MAINE A N
MASS A N CONN A N RHODE IS A N
PENN A N NEW JERSEY A N W VIRGINIA A N
MARYLAND A N DELAWARE A N VIRGINIA A N
N CAROLINA A A S CAROLINA A A GEORGIA A N
FL PNHDL A A FL PENIN A A AK N SLOPE N N
AK ALEUTIAN A A AK WESTERN A B AK INT BSN N A
AK S INT A A AK SO COAST A A AK PNHDL A 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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