Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks 
NWS Climate Prediction Center College Park, MD 
300 PM EDT Fri August 23 2024 
 
6-10 DAY OUTLOOK FOR AUG 29 - SEP 02, 2024 
 
The GEFS, ECENS, and CMCE ensemble means are in good overall agreement on the  
mean 500-hPa circulation pattern over the forecast domain during the 6-10 day  
forecast period. Two anomalous ridges are predicted over the vicinity of North  
America; one centered near Vancouver Island, Canada, and the other over far  
eastern Canada. The manual height blend depicts maximum positive height  
anomalies for these two centers of >120 m and >90 m, respectively. With the  
exception of the northern Intermountain West and Pacific Northwest, forecasted  
positive height anomalies over the contiguous U.S. (CONUS) are small. Ensemble  
means also predict a mean mid-level trough over central Canada and the adjacent  
north-central CONUS. A moderate 500-hPa trough continues to be forecasted by  
the GEFS and ECENS across the eastern Bering Sea/western Alaska, while the CMCE  
features substantially smaller negative height anomalies. Above normal heights  
are depicted across Southeast Alaska, with near normal heights indicated over  
the remainder of the eastern mainland. Over the Hawaiian archipelago, mid-level  
heights are predicted to be near or slightly above normal. 
 
The 6-10 day temperature outlook favors below normal temperatures from the  
northern and central portions of the Plains eastward into the Upper Mississippi  
Valley, as depicted by the auto-blend temperature forecast. This forecast  
represents a reasonable compromise between the various models which differ on  
the spatial extent of the favored cooler-than-normal temperatures. The raw and  
bias-corrected temperature tools depict a somewhat broader coverage of favored  
below normal temperatures compared to the reforecast temperature tools. Below  
normal temperature chances are slightly enhanced over far southwestern  
California which is favored by nearly all the temperature tools. For most of  
the remainder of the CONUS, above normal temperatures are favored, supported by  
most temperature tools and consistent with a broad mid-level ridge and  
associated positive height anomalies. Maximum probabilities favoring above  
normal temperatures exceed 70% over the Pacific Northwest. For Alaska, most  
tools agree on favored below normal temperatures for southwestern and northward  
along the extreme western parts of the mainland, the Alaska Peninsula, and the  
Aleutians, consistent with the mid-level trough and associated negative height  
anomalies over that region. Above normal temperatures are favored over most of  
the remainder of the mainland. Above normal temperatures are indicated over the  
Hawaiian islands, based on the ERF-CON and automated temperature tools. 
 
The 6-10 day precipitation outlook favors above normal precipitation within a  
sideways “Y”-shaped pattern that includes the Northeast, Great Lakes, northern  
Ohio Valley, the upper half of the Mississippi Valley, the central Plains, Four  
Corner states, Nevada, northern and central California, southern Oregon,  
western and southern Texas, southern Louisiana and the Florida Peninsula. The  
northern portion of this area of favored above normal precipitation is related  
to the expected passage of a low pressure system. The Four Corners region  
precipitation is most likely associated with the summer monsoon, while the  
favored above normal precipitation in much of California may be related to a  
nearby trough and has the support of most of the objective precipitation tools.  
Below normal precipitation is favored from the Pacific Northwest eastward  
across the northern Rockies into the northern Plains, and is associated with  
the mid-level ridge that is expected to be centered over British Columbia.  
Elsewhere, which includes a large fraction of the Lower 48 states, near normal  
precipitation is favored. The below normal precipitation favored during the  
past few days across the interior Gulf Coast region is expected to give way to  
increasingly moist Gulf inflow and increased precipitation. In Alaska, there is  
excellent agreement among the precipitation tools for above normal  
precipitation across most of the state, associated with widespread onshore flow  
at low-levels and mid-levels along and ahead of the trough predicted over the  
eastern Bering Sea and western Alaska. For Hawaii, the ERF-CON and automated  
precipitation tools favor above normal precipitation during the 6-10 day  
period, associated with the potential for one or two tropical systems to move  
through the area. 
 
The official 6-10 day 500-hPa height blend consists of 35% of Today's 0z GFS  
Ensemble Mean centered on Day 8, 40% of Today's 0z European Ensemble Mean  
centered on Day 8, and 25% of Today's 0z Canadian Ensemble Mean centered on Day  
8  
  
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Above average, 4, on a scale of  
1-5, due to good agreement among the various height forecasts and surface  
temperature fields, offset somewhat by greater differences among the  
precipitation guidance. 
 
8-14 DAY OUTLOOK FOR AUG 31 - SEP 06, 2024  
 
During week-2, the ensemble means are in fairly good agreement on the mean  
circulation pattern across the forecast domain. In the full 500-hPa height  
fields, a weak trough is depicted near the West Coast of the CONUS and a  
low-amplitude ridge is indicated over the western interior CONUS. A  
low-amplitude trough is predicted over the East. As is the case with the 6-10  
day manual height blend, all areas of the lower 48 except for the northwestern  
CONUS are expected to be under small positive height anomalies. The two largest  
positive height anomaly centers are depicted farther east during week-2, with  
the western center now well into British Columbia and the eastern center just  
south of Greenland. In Alaska, a weakening trough is predicted over the eastern  
Bering Sea and western Alaska with maximum predicted height departures on the  
manual height blend about 60 meters below normal just south of the Aleutians.  
This blend also depicts positive height anomalies and associated mid-level  
ridging across most of the remainder of the state. Well to the south, heights  
are forecast to be near or slightly above normal in the vicinity of the  
Hawaiian islands. 
 
The 8-14 day temperature outlook favors below normal temperature chances over  
much of the eastern Great Plains, the Upper and Middle Mississippi Valley, the  
Great Lakes region, and the Ohio Valley. This represents a significant increase  
in coverage of favored below normal temperatures compared to yesterday’s week-2  
temperature outlook. This is based on the predicted passage of a mid-level  
trough and accompanying cold front. A tiny area of below normal temperature  
chances is possible along the far southern California coast. Most of the  
remainder of the CONUS is favored to have above normal temperatures, and is  
supported by the consolidation and automated temperature tools, and reforecast  
temperatures from the GEFS and ECENS. Maximum probabilities favoring above  
normal temperatures exceed 70% over the Pacific Northwest and adjacent parts of  
the northern Intermountain region. In Alaska, coverage of favored below normal  
temperatures is restricted to far western parts of the state. Above normal  
temperatures are favored for most of the remainder of Alaska, excluding the  
southern mainland coast and Southeast Alaska where near normal temperatures are  
favored. The ERF-CON and automated temperature tools support above normal  
temperatures across Hawaii, similar to the earlier 6-10 day temperature outlook. 
 
The 8-14 day precipitation outlook continues to be characterized by significant  
uncertainty, as indicated by the broad expanse of favored near normal  
precipitation across the Lower 48 states, and the relatively weak tilts toward  
above or below normal precipitation. Above normal precipitation chances are  
elevated from the Appalachians to the Atlantic coast, consistent with the  
majority of tools. Above normal precipitation is also favored from much of  
Oregon and northern California eastward across central portions of the  
Intermountain West, central and southern Rockies, and central portions of the  
Great Plains into western Missouri. This is supported by the reforecast  
precipitation tools and most of the raw precipitation tools. Below normal  
precipitation odds are favored from Washington state eastward across the  
northern tier to the Upper Great Lakes region, in proximity to a moderately  
strong anomalous ridge. Onshore flow ahead of a mid-level trough near the west  
coast of Alaska continues to favor above normal precipitation for most of the  
state during week-2. For Hawaii, the automated precipitation forecast favors  
near normal precipitation, while the ERF-CON tool favors drier-than-normal  
conditions. The near normal precipitation forecast is favored today, based on  
the significant likelihood of two tropical systems moving through the Hawaii  
region during this forecast period. There is substantial uncertainty in the  
exact tracks and intensities of these two tropical systems. 
 
The official 8-14 day 500-hPa height blend consists of: 30% of Today's 0z GFS  
Ensemble Mean centered on Day 11, 40% of Today's 0z European Ensemble Mean  
centered on Day 11, and 30% of Today's 0z Canadian Ensemble Mean centered on  
Day 11  
 
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Near average, 3, on a scale of  
1-5, due to reasonable agreement among the various height forecasts and surface  
temperature forecasts, but substantially offset by poor agreement among the  
precipitation tools. 
 
FORECASTER: Anthony A 
 
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  
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:  
19540829 - 19980818 - 20050827 - 19530825 - 19900825 
 
 
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:  
20050825 - 19530825 - 20050905 - 19980817 - 19540828 
 
 
6-10 DAY OUTLOOK TABLE 
Outlook for Aug 29 - Sep 02, 2024 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    B     OREGON      A    B     NRN CALIF   A    A      
SRN CALIF   B    N     IDAHO       A    B     NEVADA      A    A      
W MONTANA   A    B     E MONTANA   B    B     WYOMING     B    N      
UTAH        A    A     ARIZONA     A    N     COLORADO    N    A      
NEW MEXICO  A    A     N DAKOTA    B    B     S DAKOTA    B    N      
NEBRASKA    B    A     KANSAS      N    A     OKLAHOMA    A    N      
N TEXAS     A    N     S TEXAS     A    A     W TEXAS     A    A      
MINNESOTA   B    N     IOWA        N    A     MISSOURI    A    N      
ARKANSAS    A    N     LOUISIANA   A    N     WISCONSIN   N    A      
ILLINOIS    A    A     MISSISSIPPI A    N     MICHIGAN    A    A      
INDIANA     A    N     OHIO        A    N     KENTUCKY    A    N      
TENNESSEE   A    N     ALABAMA     A    N     NEW YORK    A    A      
VERMONT     A    A     NEW HAMP    A    A     MAINE       A    A      
MASS        A    A     CONN        A    A     RHODE IS    A    A      
PENN        A    A     NEW JERSEY  A    A     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    A    A     AK N SLOPE  A    A      
AK ALEUTIAN B    A     AK WESTERN  B    A     AK INT BSN  A    A      
AK S INT    N    A     AK SO COAST N    A     AK PNHDL    N    A      
  
                            
 
8-14 DAY OUTLOOK TABLE 
Outlook for Aug 31 - Sep 06, 2024 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    B     OREGON      A    A     NRN CALIF   A    A      
SRN CALIF   A    N     IDAHO       A    N     NEVADA      A    A      
W MONTANA   A    B     E MONTANA   A    B     WYOMING     N    N      
UTAH        A    A     ARIZONA     A    N     COLORADO    A    A      
NEW MEXICO  A    A     N DAKOTA    B    B     S DAKOTA    B    N      
NEBRASKA    B    A     KANSAS      B    A     OKLAHOMA    N    N      
N TEXAS     A    N     S TEXAS     A    N     W TEXAS     A    N      
MINNESOTA   B    B     IOWA        B    N     MISSOURI    B    N      
ARKANSAS    N    N     LOUISIANA   A    N     WISCONSIN   B    B      
ILLINOIS    B    N     MISSISSIPPI A    N     MICHIGAN    B    N      
INDIANA     B    N     OHIO        B    N     KENTUCKY    B    N      
TENNESSEE   N    N     ALABAMA     A    N     NEW YORK    N    A      
VERMONT     N    A     NEW HAMP    N    A     MAINE       A    A      
MASS        A    A     CONN        N    A     RHODE IS    A    A      
PENN        N    A     NEW JERSEY  A    A     W VIRGINIA  N    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  A    A      
AK ALEUTIAN B    N     AK WESTERN  A    A     AK INT BSN  A    A      
AK S INT    A    A     AK SO COAST N    A     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. 
 
$$