Climate Prediction Center - 6-10 and 8-14 Day Prognostic Discussions

Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks 
NWS Climate Prediction Center College Park, MD 
300 PM EDT Thu May 16 2024 
 
6-10 DAY OUTLOOK FOR MAY 22 - 26 2024 
 
Today’s model solutions are very similar to yesterday’s and the GEFS, ECMWF  
ensemble mean (ECENS), and Canadian ensemble mean (CMCE) all depict a similar  
synoptic picture over the forecast domain during the 6-10 day forecast period.  
As is typically the case, there are relatively minor differences among today’s  
models in the predicted amplitude and phase of some longwave features. Today’s  
manual blend features negative 500-hPa height anomalies over much of the  
western and north-central contiguous U.S. (CONUS) with the largest negative  
departures around -75 meters over the Northern Rockies. Positive height  
anomalies are forecast over the southern tier of the CONUS, with 30-60 meter  
departures centered over the western Gulf region. These positive height  
anomalies are associated with a subtropical ridge. Heights over the Northeast  
and Mid-Atlantic region are forecast to be near-average. Over the Alaska  
domain, a weak trough is depicted over the Bering Sea and southwestern  
Mainland, with mid-level ridging elsewhere. This mid-level ridging represents  
the northeastern extent of a broad, zonally elongated anomalous ridge that is  
predicted over much of the North Pacific. Maximum positive height anomalies  
associated with this ridge exceed +150 meters south of the Aleutians. A weak  
mid-level trough is anticipated northwest of the Hawaiian Islands. 
 
Below normal temperature chances are increased over southwestern Mainland  
Alaska and the adjacent Alaska Peninsula, consistent with most temperature  
guidance and the forecast of a weak trough in that region. Mid-level ridging  
and positive height anomalies favor above normal temperature chances over the  
remainder of the Mainland. For the Panhandle, most of the raw and  
bias-corrected temperatures support below normal temperatures, whereas the  
various reforecast temperature fields favor above normal temperatures. The  
manual blend indicates a mean ridge axis and northerly anomalous flow, with  
warm advection approaching from the southwest. The temperature outlook is very  
dependent upon an expected cool-to-warm transition, and near normal appears to  
be the most likely category.  From the northwestern and north-central CONUS  
eastward into the Great Lakes region, below normal temperatures are favored,  
supported by most tools and mid-level troughing. Disparate temperature guidance  
over the Southwest shows any of the three categories are possible, though near  
to below normal temperatures are the most prevalent. Subtropical ridging favors  
above normal temperatures for much of the southern CONUS, with a northward  
extension of this anomalous warmth expected across the eastern third of the  
CONUS in advance of mid-level troughing. Probabilities favoring above normal  
temperatures exceed 80% for portions of South Texas. In Hawaii, a compromise  
between the auto and ERF consolidation tools favors a slight tilt towards above  
normal temperatures for Kauai and Oahu, and near normal temperatures for Maui  
and the Big Island. 
 
At the start of the 6-10 day period, a storm system is forecasted to lift  
northward across the Great Lakes region into southern Canada, with a cold front  
extending southwestward from the surface low. This cold front is expected to  
stall as it approaches the Gulf Coast, and serve to focus above normal  
precipitation across the Southeast. By the middle of the period, lee  
cyclogenesis is anticipated over eastern Colorado, with the surface low  
tracking northeastward towards the Great Lakes. This low pressure system is  
expected to bring widespread above normal precipitation to much of the Central  
and Eastern CONUS. Above normal precipitation is also anticipated across the  
northwestern quarter of the CONUS, in advance of a predicted mid-level trough  
and negative height anomalies. All these areas of favored above normal  
precipitation are well supported by most of the forecast tools. The subtropical  
ridge favors below normal precipitation for New Mexico, southern Colorado,  
western and far southern parts of Texas, and central and southern Florida.  
Above normal precipitation chances are elevated over most of Alaska in advance  
of a mid-level trough and widespread onshore flow. The exception is over the  
Panhandle, where near to below normal precipitation is favored under a  
mid-level ridge and positive height anomalies. A compromise between the  
Hawaiian auto and consolidation tools favors anomalously wet conditions  
statewide in advance of a 500-hPa trough. 
 
The official 6-10 day 500-hPa height blend consists of 33% of Today's 0z GFS  
Ensemble Mean centered on Day 8, 34% of Today's 0z European Ensemble Mean  
centered on Day 8, and 33% 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, with  
good run-to-run continuity among forecast models, offset by differences between  
models regarding strength and position of various synoptic features. 
 
8-14 DAY OUTLOOK FOR MAY 24 - 30 2024  
 
During week-2, positive 500-hPa height anomalies persist over the North Pacific  
and over much of the southern tier of the CONUS. Near to slightly below normal  
500-hPa heights are predicted over much of the western CONUS, and extending  
eastward across the northern tier to the Great Lakes region. The full height  
field depicted by the manual blend over the CONUS features a low amplitude   trough-ridge-trough pattern. For Alaska, a very weak trough is indicated in the  
full height field along the western coast, with mid-level ridging and positive  
height anomalies dominating the remainder of the state. A weak trough continues  
to be forecast northwest of Hawaii. 
 
Above normal temperatures are favored for the southern CONUS east of the  
Rockies, with a northward extension across the Ohio Valley and most of the  
Northeast and Mid-Atlantic region. This is supported by the reforecast  
temperature tools, and aligns well with the overall synoptic pattern. A  
low-amplitude trough near the West Coast tilts the odds towards below normal  
temperatures for the West Coast states, the Northern Rockies, Northern Plains,  
and Upper Mississippi Valley. In Alaska, below normal temperature chances are  
increased over approximately the southwestern quarter of the state, with above  
normal temperature chances enhanced over the North Slope, eastern parts of the  
Mainland, and the Panhandle. This pattern is consistent with the manual height  
blend features, and many of the temperature forecast tools, especially raw and  
bias-corrected temperatures from the various ensemble means. In Hawaii, the  
pattern forecasted for the 6-10 day period is expected to persist through  
week-2, with above normal temperatures favored for Kauai and Oahu, and near  
normal temperatures favored for Maui and the Big Island. 
 
Above normal precipitation is favored near the Canadian border and extending  
southward across most of the central and eastern CONUS, consistent with the  
consolidation and auto precipitation tools. Below normal precipitation is  
favored from Nevada southeastward across portions of the Four Corners region to  
far southwestern Texas, and also over far southern Texas, also supported by the  
Consolidation and auto precipitation tools. For Hawaii and Alaska,  
predominantly wet conditions are favored relative to normal with the same  
general synoptic features in place as was the case with the 6-10 day outlook. 
 
The official 8-14 day 500-hPa height blend consists of: 35% of Today's 0z GFS  
Ensemble Mean centered on Day 11, 35% 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: Above average, 4 out of 5, with  
good run-to-run continuity among forecast models, offset by differences between  
models regarding strength and position of various synoptic features. 
 
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  
June 20. 
 
 
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:  
19660519 - 19990529 - 19920508 - 19890515 - 19980505 
 
 
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:  
19990528 - 19660520 - 20010522 - 19640425 - 19660515 
 
 
6-10 DAY OUTLOOK TABLE 
Outlook for May 22 - 26 2024 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  B    A     OREGON      B    A     NRN CALIF   B    N      
SRN CALIF   B    N     IDAHO       B    A     NEVADA      B    N      
W MONTANA   B    A     E MONTANA   B    A     WYOMING     B    A      
UTAH        B    N     ARIZONA     N    N     COLORADO    N    N      
NEW MEXICO  N    B     N DAKOTA    B    A     S DAKOTA    B    A      
NEBRASKA    N    A     KANSAS      N    A     OKLAHOMA    A    A      
N TEXAS     A    A     S TEXAS     A    N     W TEXAS     A    B      
MINNESOTA   B    A     IOWA        N    A     MISSOURI    N    A      
ARKANSAS    A    A     LOUISIANA   A    A     WISCONSIN   N    A      
ILLINOIS    A    A     MISSISSIPPI A    A     MICHIGAN    A    A      
INDIANA     A    A     OHIO        A    A     KENTUCKY    A    A      
TENNESSEE   A    A     ALABAMA     A    A     NEW YORK    A    A      
VERMONT     A    A     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    A     VIRGINIA    A    A      
N CAROLINA  A    A     S CAROLINA  A    A     GEORGIA     A    A      
FL PNHDL    A    A     FL PENIN    A    B     AK N SLOPE  A    A      
AK ALEUTIAN B    N     AK WESTERN  B    A     AK INT BSN  A    A      
AK S INT    B    A     AK SO COAST B    A     AK PNHDL    N    N      
  
                            
 
8-14 DAY OUTLOOK TABLE 
Outlook for May 24 - 30 2024 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  B    N     OREGON      B    N     NRN CALIF   B    N      
SRN CALIF   B    N     IDAHO       B    N     NEVADA      N    B      
W MONTANA   B    N     E MONTANA   B    A     WYOMING     B    N      
UTAH        N    B     ARIZONA     N    N     COLORADO    N    N      
NEW MEXICO  A    B     N DAKOTA    B    A     S DAKOTA    B    A      
NEBRASKA    N    A     KANSAS      A    A     OKLAHOMA    A    A      
N TEXAS     A    A     S TEXAS     A    N     W TEXAS     A    A      
MINNESOTA   B    A     IOWA        N    A     MISSOURI    A    A      
ARKANSAS    A    A     LOUISIANA   A    A     WISCONSIN   B    A      
ILLINOIS    N    A     MISSISSIPPI A    A     MICHIGAN    N    A      
INDIANA     N    A     OHIO        A    A     KENTUCKY    A    A      
TENNESSEE   A    A     ALABAMA     A    A     NEW YORK    A    N      
VERMONT     A    N     NEW HAMP    A    N     MAINE       A    N      
MASS        N    N     CONN        N    N     RHODE IS    N    N      
PENN        A    A     NEW JERSEY  N    N     W VIRGINIA  A    A      
MARYLAND    N    A     DELAWARE    N    A     VIRGINIA    A    A      
N CAROLINA  A    A     S CAROLINA  A    A     GEORGIA     A    A      
FL PNHDL    A    A     FL PENIN    A    N     AK N SLOPE  A    A      
AK ALEUTIAN B    A     AK WESTERN  B    A     AK INT BSN  A    A      
AK S INT    B    A     AK SO COAST B    N     AK PNHDL    A    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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