NWS Climate Prediction Center



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Latest 6 to 10 Day Temperature Outlook

Prognostic Discussions


Valid: Aug 05 - 09, 2021 (6-10 Day Outlook)
Valid: Aug 07 - 13, 2021 (8-14 Day Outlook)
Issued: Jul 30, 2021


Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks 
NWS Climate Prediction Center College Park, MD 
300 PM EDT Fri July 30 2021 
 
6-10 DAY OUTLOOK FOR AUG 05 - 09 2021 
 
Today’s numerical model solutions from the GEFS and ECMWF forecast suites are  
in decent agreement with respect to the location of major 500-hPa height  
features across the forecast domain, but disagree somewhat in their  
intensities, particularly across the CONUS. A persistent and anomalously strong  
closed 500-hPa low is predicted over the Bering Sea and shows an eastward  
progression, relative to yesterday’s 6-10 day forecast. A split-flow pattern is  
predicted downstream of the closed low over the Bering Sea, leading to weak  
ridging across southeastern Alaska and troughing forecast farther to the south  
along the coast of the Pacific Northwest. The mean trough along the Pacific  
Northwest coast is slightly more amplified compared to yesterday’s forecast,  
leading to below-normal mid-level heights across much of the region.  
Below-normal 500-hPa heights are also favored, and have increased in coverage  
since yesterday, over the east-central CONUS from the Corn Belt southward to  
the Gulf Coast, underneath a mean trough. Subtropical ridging is expected to  
erode and deamplify over the west-central CONUS, causing the mean mid-level  
height center over the Four Corners to shift farther southward into western New  
Mexico, further reducing the potential for northward monsoonal moisture  
advection. 
 
Above-normal temperatures are favored across extreme southeastern Mainland  
Alaska and the Alaska Panhandle, associated with a mean mid-level ridge and  
above-normal 500-hPa heights ahead of a closed mid-level low forecast over the  
Bering Sea. Eastward progression of the mean closed low over the Bering Sea  
into western Alaska increases odds of below-normal temperatures for the western  
Mainland and the Aleutians. Amplified mean troughing along the coast of the  
Pacific Northwest favors near-normal temperatures for much of the region.  
Subtropical ridging is expected to deamplify during the 6-10 day period over  
the west-central CONUS, due to the eastward progression and amplification of  
the upstream trough over the Pacific Northwest. Despite deamplification of the  
mean ridge, above-normal temperatures remain favored for much of the  
southwestern CONUS. Mean southerly surface flow enhances odds of above-normal  
temperatures across the Central and Northern Plains, Upper Midwest and Great  
Lakes, extending eastward to New England. Enhanced probabilities of  
below-normal temperatures are forecast for the Southern Plains, Lower  
Mississippi Valley, and much of the Southeast, associated with a negative  
mid-level height anomalies over the lower east-central CONUS. Over the southern  
Florida Peninsula, above-normal temperatures are favored ahead of a mean  
frontal boundary. 
 
Ahead of the closed mid-level low predicted over the Bering Sea, above-normal  
precipitation is favored over much of Mainland Alaska and the eastern  
Aleutians. Downstream, mean troughing to the south of the split mid-level flow  
along northern portions of the West Coast favors above-normal precipitation in  
the Pacific Northwest. A mean ridge over the west-central CONUS favors  
increased odds for below-normal precipitation across the Great Basin, Eastern  
Rockies, and Central and Northern Plains. In the Southwest, model solutions are  
in agreement regarding a southward displacement of the mean positive 500-hPa  
height anomaly center over the Four Corners, favoring suppression of northward  
monsoonal moisture surges. Farther east, surface high pressure is expected to  
dominate across much of the eastern CONUS, leading to below-normal  
precipitation probabilities across the Midwest and Ohio and Middle Mississippi  
Valleys. Odds tilt toward below-normal precipitation across northern New  
England, underneath positive mid-level height anomalies. The Atlantic  
subtropical ridge is expected to start building back its western periphery  
during the 6-10 day period, increasing odds for above-normal precipitation  
across the Southeast and Gulf Coast along a mean frontal boundary. 
 
The official 6-10 day 500-hPa height blend consists of 45% of Today's 6z GFS  
Ensemble Mean centered on Day 8, and 55% of Today's 0z European Ensemble Mean  
centered on Day 8  
  
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Average, 3 out of 5 due to better  
agreement of the model temperature and precipitation fields across much of the  
forecast domain, offset by large differences in the precipitation fields in the  
eastern CONUS. 
 
8-14 DAY OUTLOOK FOR AUG 07 - 13 2021  
 
During the Week-2 period, numerical model guidance depicts a generally similar  
500-hPa flow pattern to that predicted for the 6-10 day period in terms of  
phasing, but deamplified. A strong mid-level trough is forecast to persist and  
progress eastward over the Bering Sea and western Mainland Alaska during the  
Week-2 period, continuing an active pattern for western and interior Alaska.  
Downstream, very weak ridging is forecast to continue, but continue to  
deamplify, over southeastern Alaska, and a mean trough is forecast farther to  
the south along the coast of the Pacific Northwest. The ridge and trough  
pattern over the central and eastern CONUS, respectively, are favored to  
deamplify, leading to increased zonal mid-level flow during Week-2. 
 
Enhanced southwesterly onshore flow ahead of a mean mid-level trough over the  
eastern Bering Sea, that continues to progress eastward in today’s model  
solutions, favors increased odds for below-normal temperatures over much of  
Alaska, with enhanced odds over the Southwest Mainland. Above-normal  
temperatures are favored along the West Coast and into the Great Basin, but  
above-normal probabilities are reduced in magnitude compared to yesterday’s  
Week-2 forecast, as the mean ridge over the west-central CONUS is expected to  
deamplify. Enhanced above-normal temperature probabilities are favored from the  
Northern Plains eastward to the Great Lakes, underneath increased 500-hPa  
heights and mean southerly surface flow. From Texas eastward across the Deep  
South to the Southeast Coast, below-normal temperatures are favored early in  
the Week-2 period before moderating in the latter half of the period, tilting  
odds toward below-normal temperatures. Ahead of a mean frontal boundary over  
the Southeast, above-normal temperatures are favored for the Florida Peninsula. 
 
With the persistent mid-level low forecast over the eastern Bering Sea, an  
active, wetter-than-normal pattern is forecast to continue well into Week-2  
across Mainland Alaska into the Panhandle. Odds of above-normal precipitation  
are also increased across parts of the Pacific Northwest, ahead of a mean  
trough along the Pacific Northwest Coast and increased onshore flow.  
Below-normal precipitation is favored for much of the Great Basin, Eastern  
Rockies, and Great Plains, associated with mean subtropical ridging across the  
west-central CONUS that is expected to deamplify during the period. The  
positive mid-level height anomaly center over the Four Corners is favored to  
retain it’s southward position, which would tend to suppress any major  
northward surges of monsoonal moisture across the Southwest. However, there is  
the potential for a brief moisture surge during the Week-2 period, associated  
with the potential passage of a tropical cyclone south of the Gulf of  
California in the Eastern Pacific, increasing uncertainty. From the Tennessee  
Valley northward to the Great Lakes, there are increased odds of above-normal  
precipitation, as the mean trough over the eastern CONUS is favored to  
deamplify and lift northward into the region. 
 
The official 8-14 day 500-hPa height blend consists of: 40% of Today's 6z GFS  
Ensemble Mean centered on Day 11, and 60% of Today's 0z European Ensemble Mean  
centered on Day 11  
 
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Average, 3 out of 5, due to decent  
agreement in synoptic-scale features and patterns, offset by differences in  
magnitudes of these features and some differences among the model temperature  
and precipitation fields. 
 
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  
August 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:  
19780729 - 19850710 - 19610802 - 19710812 - 19770723 
 
 
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:  
19780728 - 19610801 - 19850709 - 19630812 - 19710714 
 
 
6-10 DAY OUTLOOK TABLE 
Outlook for Aug 05 - 09 2021 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  N    A     OREGON      N    A     NRN CALIF   A    N      
SRN CALIF   A    N     IDAHO       N    A     NEVADA      A    B      
W MONTANA   A    N     E MONTANA   A    B     WYOMING     A    B      
UTAH        A    B     ARIZONA     A    B     COLORADO    A    B      
NEW MEXICO  N    B     N DAKOTA    A    B     S DAKOTA    A    B      
NEBRASKA    A    B     KANSAS      A    B     OKLAHOMA    B    B      
N TEXAS     B    N     S TEXAS     B    A     W TEXAS     B    B      
MINNESOTA   A    B     IOWA        A    B     MISSOURI    B    B      
ARKANSAS    B    B     LOUISIANA   B    A     WISCONSIN   A    B      
ILLINOIS    N    B     MISSISSIPPI B    N     MICHIGAN    A    B      
INDIANA     N    B     OHIO        N    N     KENTUCKY    B    B      
TENNESSEE   B    B     ALABAMA     B    N     NEW YORK    A    N      
VERMONT     A    N     NEW HAMP    A    N     MAINE       A    B      
MASS        N    N     CONN        N    A     RHODE IS    N    N      
PENN        N    N     NEW JERSEY  N    A     W VIRGINIA  B    N      
MARYLAND    B    A     DELAWARE    B    A     VIRGINIA    B    A      
N CAROLINA  B    A     S CAROLINA  B    A     GEORGIA     B    A      
FL PNHDL    B    A     FL PENIN    N    N     AK N SLOPE  B    A      
AK ALEUTIAN B    A     AK WESTERN  B    A     AK INT BSN  N    A      
AK S INT    N    A     AK SO COAST N    A     AK PNHDL    A    N      
  
                            
 
8-14 DAY OUTLOOK TABLE 
Outlook for Aug 07 - 13 2021 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  N    A     OREGON      A    N     NRN CALIF   A    N      
SRN CALIF   A    N     IDAHO       N    B     NEVADA      A    B      
W MONTANA   N    N     E MONTANA   A    B     WYOMING     A    B      
UTAH        A    B     ARIZONA     N    B     COLORADO    A    B      
NEW MEXICO  N    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    B     W TEXAS     N    B      
MINNESOTA   A    B     IOWA        A    N     MISSOURI    A    N      
ARKANSAS    N    N     LOUISIANA   N    N     WISCONSIN   A    N      
ILLINOIS    A    A     MISSISSIPPI N    N     MICHIGAN    A    A      
INDIANA     A    A     OHIO        A    A     KENTUCKY    A    A      
TENNESSEE   N    A     ALABAMA     N    N     NEW YORK    A    A      
VERMONT     A    N     NEW HAMP    A    N     MAINE       A    N      
MASS        A    N     CONN        A    N     RHODE IS    A    N      
PENN        A    A     NEW JERSEY  A    N     W VIRGINIA  A    A      
MARYLAND    A    A     DELAWARE    A    N     VIRGINIA    A    N      
N CAROLINA  N    N     S CAROLINA  B    N     GEORGIA     B    N      
FL PNHDL    N    N     FL PENIN    A    N     AK N SLOPE  B    A      
AK ALEUTIAN B    N     AK WESTERN  B    A     AK INT BSN  B    A      
AK S INT    B    A     AK SO COAST B    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. 
 
$$ 
 

                   


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