805
FXUS06 KWBC 131916
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Tue August 13 2019
6-10 DAY OUTLOOK FOR AUG 19 - 23 2019
Model solutions are in good agreement in predicting an upper-level amplified
trough over the western Aleutians. Downstream, model solutions continue to
indicate a weak 500-hPa ridge over the west-central CONUS, and a weak trough
over the eastern CONUS. The resultant of manual blend indicates negative
500-hPa height anomalies over much of Alaska, while positive 500-hPa height
anomalies are predicted over most of the CONUS.
A broad subtropical ridge favors enhanced probabilities of near to above normal
temperatures throughout much of the CONUS, except for parts of the Northern
Rockies and the Northern Plains in association with cold air advection from
northwestern Canada. Above normal temperatures are likely across the southwest
coast of mainland Alaska, the Aleutians, and parts of the Alaska Panhandle due
to anomalous southerly surface flow during the period and above normal SSTs in
soundings. Below normal temperatures are favored over east-central mainland
Alaska underneath below normal 500-hPa heights over the region.
A prolonged break in the monsoon is likely during mid to late August. Near to
below normal precipitation is likely across parts of the Southwest, Great Basin
eastward to the Central and Southern Plains as a 500-hPa ridge becomes centered
well south of the Four Corners region and northwesterly flow prevails. The
ridge aloft is likely to suppress convection across most of Texas. Potential
frontal activity forecast to enhance convection, which favors above normal
precipitation over the parts of the Northern Plain, and the Mississippi Valley.
Predicted mean southerly flow and associated moisture advection increase
chances for above normal precipitation across the Gulf Coast to much of the
eastern CONUS. Near to below normal precipitation is favored for much of
mainland Alaska, consistent with the forecast consolidation tool. Above normal
precipitation probabilities are increased over parts of the south coast of
mainland Alaska, the Aleutians and the Alaska Panhandle underneath near to
below normal 500-hPa heights.
The official 6-10 day 500-hPa height blend consists of 20% of Today's 0z GFS
Ensemble Mean centered on Day 8, 20% of Today's 6z GFS Ensemble Mean centered
on Day 8, 20% of Today's GFS Superensemble Mean centered on Day 8, 20% of
Today's 0z European Ensemble Mean centered on Day 8, and 20% of Yesterday's 12z
European Ensemble Mean centered on Day 7
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Above average, 4 out of 5, due to
good model consistency and a well established longwave pattern.
8-14 DAY OUTLOOK FOR AUG 21 - 27 2019
During Week-2, the predicted 500-hPa circulation pattern is similar to the
pattern for the 6-10 day period. The ensemble means remain in good agreement
today and feature an amplified 500-hPa pattern at the higher latitudes of the
Northern Hemisphere. An upper-level trough is likely to persist across the
Aleutians, while mostly zonal flow is forecast across much of mainland Alaska.
Weak 500-hPa height anomalies are predicted over most of the CONUS except for
the Northeast and parts of the northern CONUS where above normal heights are
favored.
Below normal temperatures are likely to persist over the northern Rockies due
to the forecast trough over northwestern Canada. The subtropical ridge is
likely to expand north and east during Week-2, increasing the probabilities for
near to above normal temperatures across the western to the central and eastern
CONUS. The highest probabilities of above normal temperatures continue to be
forecast for the southern High Plains, Southern Rockies, the Southwest, and the
Northeast based on the anomalous subtropic ridge aloft and underneath predicted
above normal 500-hPa heights over the Northeast. Below normal temperatures are
likely across parts of eastern mainland Alaska underneath below normal 500-hPa
heights, while above normal temperatures are likely to persist for the
remainder of the state, consistent with consolidation forecast tool and above
normal SSTs in surrounding areas.
The suppressed monsoon is likely to persist for much of Week-2 with the 500-hPa
ridge axis extending from the Desert Southwest eastward to parts of the
southern Great Plains. The predicted 500-hPa height pattern and influx of
anomalous moisture result in increased chances of above normal precipitation
from the Pacific Northwest extending east into parts of the northern Plains,
the upper-Mississippi Valley, and parts of the Great Lakes. The enhanced odds
for above normal precipitation forecast across parts of the Lower Mississippi
Valley and Southeast are related to a weakening front at the beginning of
Week-2. Below normal precipitation is favored for the far Northeast, consistent
with the consolidation forecast tool. Near to above normal precipitation is
favored for Alaska in association with storm systems forecast near southern
Alaska.
The official 8-14 day 500-hPa height blend consists of: 20% of Today's 0z GFS
Ensemble Mean centered on Day 11, 20% of Today's 6z GFS Ensemble Mean centered
on Day 11, 20% 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 Yesterday's
12z European Ensemble Mean centered on Day 10
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Average, 3 out of 5, due to good
agreement among the ensemble means on the longwave pattern but offset by weak
signals in the precipitation tools.
FORECASTER: Qin Z
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
August 15.
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:
19620726 - 19870821 - 19560728 - 19930806 - 19780825
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:
19620726 - 19560727 - 19780825 - 19870821 - 19670726
6-10 DAY OUTLOOK TABLE
Outlook for Aug 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 N N E MONTANA N N WYOMING A B
UTAH A B ARIZONA A B COLORADO A B
NEW MEXICO A B N DAKOTA N 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 N MISSOURI A A
ARKANSAS A A LOUISIANA A A WISCONSIN A N
ILLINOIS A A MISSISSIPPI A A MICHIGAN A N
INDIANA A A OHIO A A KENTUCKY A A
TENNESSEE A A ALABAMA A A NEW YORK A A
VERMONT A N NEW HAMP A N MAINE A N
MASS A N CONN A A RHODE IS A N
PENN A A NEW JERSEY A A W VIRGINIA A A
MARYLAND A A DELAWARE A A VIRGINIA A A
N CAROLINA A A S CAROLINA A A GEORGIA A A
FL PNHDL A A FL PENIN A A AK N SLOPE B B
AK ALEUTIAN A A AK WESTERN A B AK INT BSN B B
AK S INT B N AK SO COAST A N AK PNHDL N A
8-14 DAY OUTLOOK TABLE
Outlook for Aug 21 - 27 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 B A E MONTANA B A WYOMING A N
UTAH A B ARIZONA A B COLORADO A B
NEW MEXICO A B N DAKOTA A A S DAKOTA A A
NEBRASKA A N KANSAS A N OKLAHOMA A A
N TEXAS A A S TEXAS A N W TEXAS A B
MINNESOTA A A IOWA A N MISSOURI N A
ARKANSAS N A LOUISIANA N A WISCONSIN A N
ILLINOIS A N MISSISSIPPI N A MICHIGAN A A
INDIANA A A OHIO A A KENTUCKY A A
TENNESSEE A A ALABAMA N A NEW YORK A N
VERMONT A B NEW HAMP A B MAINE A B
MASS A N CONN A N RHODE IS A N
PENN A A NEW JERSEY A A W VIRGINIA A A
MARYLAND A A DELAWARE A A VIRGINIA A A
N CAROLINA A A S CAROLINA A A GEORGIA A A
FL PNHDL A A FL PENIN A A AK N SLOPE N N
AK ALEUTIAN A A AK WESTERN A N AK INT BSN N N
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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