Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks 
NWS Climate Prediction Center College Park, MD 
300 PM EDT Fri May 10 2024 
 
6-10 DAY OUTLOOK FOR MAY 16 - 20 2024 
 
Models are in poor agreement today, and are not in good agreement with their  
own solutions from yesterday. As a result, the official forecast is made with  
considerable uncertainty, which is not too uncommon during spring. Today, the  
ECMWF and Canadian ensemble means resemble the GEFS mean from yesterday, with  
relatively low 500-hPa heights across the northern tier of the CONUS, and in  
most of the eastern CONUS. The main differences between these two models are  
found along the southern and eastern tiers of the CONUS, where the Canadian  
shows lower 500-hPa heights. Meanwhile, the GEFS mean is now much more  
amplified, with a strong mid-level ridge in the western CONUS and a downstream  
trough digging into the East. At this time, the Canadian ensemble mean is  
favored slightly more than the others for two reasons: First, its solution has  
the lowest amplitude, which is more consistent with both its own solution and  
the favored circulation pattern from yesterday; second, its mid-level pattern  
across the western half of the Northern Hemisphere agrees slightly better with  
historic teleconnections than the other two ensemble means. But the solutions  
of the other ensemble means are not discounted, particularly since the GEFS  
mean for 0z, 6z, and 12z have maintained the alternative, highly-amplified  
solution. Other features in the manual 500-hPa height blend are a strong  
anomalous mid-level ridge south of eastern Siberia with positive 500-hPa  
heights extending eastward into the Pacific Northwest, and another mid-level  
ridge over north-central Canada. Meanwhile, near- to slightly below-normal  
500-hPa heights extend from Mainland Alaska southeast into central North  
America. In the Tropical Pacific, Below-normal 500-hPa heights cover Hawaii,  
with a weak mid-level trough to the west of the state. 
 
While the uncertainties in the mid-level pattern generally result in a  
low-confidence forecast, there are some areas where tools derived from the  
ensembles agree on sensible weather. The raw, bias-corrected, and reforecast  
temperature output from the GEFS, the European ensemble, and the Canadian  
ensemble all show enhanced odds for above-normal temperatures in the Great  
Basin, central Far West, southern Texas, the Florida Peninsula, and the  
Northeast. Odds for unusual warmth during the 6- to 10-day period range from 50  
to 60 percent in these areas. Raw and calibrated temperature tools are in much  
poorer agreement in the rest of the CONUS, Alaska, and Hawaii. Across a large  
region encompassing central and western sections of the northern tier of the  
CONUS and a large part of the central and southeastern CONUS have no tilt of  
the odds toward unusually high or low temperatures due to significantly  
conflicting signals in these regions. The preponderance of tools show enhanced  
odds for colder than average weather maximized in southwestern Mainland Alaska  
while enhanced odds for warmth are encroaching into the northeastern Mainland,  
and southerly surface flow across Hawaii should favor above-normal temperatures  
there.  
 
The precipitation pattern is a compromise of the tools, leaning toward those  
from the Canadian ensemble and, due to the uncertainty, adjusted toward some  
consistency with the forecast from yesterday. An enhanced, cyclonically-curved  
mid-level jet along with anomalously moist surface flow from the south is  
expected over portions of the central Gulf Coast region and adjacent Southeast,  
resulting in a 50 to 60 percent chance for above-normal precipitation there.  
Most other areas in the CONUS have marginally increased odds for surplus  
precipitation. Across the CONUS, dryness is favored slightly only in the Big  
Bend and much of the Pacific Northwest, where positive 500-hPa height anomalies  
and anticyclonic mid-level flow are anticipated. Under a 500-hPa trough, odds  
marginally favor above-normal precipitation across Alaska. Farther south,  
Hawaii should be experiencing moist southerly surface flow downstream from a  
mid-level trough, enhancing odds for surplus precipitation there, especially in  
western parts of the state. 
 
 
The official 6-10 day 500-hPa height blend consists of 18% of Today's 0z GFS  
Ensemble Mean centered on Day 8, 32% of Today's 0z European Ensemble Mean  
centered on Day 8, and 50% of Today's 0z Canadian Ensemble Mean centered on Day  
8  
  
 
FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: Below average, 2 out of 5, due to  
poor model agreement and inconsistency among the derived tools in most  
locations. 
 
8-14 DAY OUTLOOK FOR MAY 18 - 24 2024  
 
The models remain in poor agreement during week-2, with their mean patterns  
being reasonable extrapolations of their respective 6-10 day means. The GEFS  
mean remains highly amplified, with a strong anomalous mid-level ridge  
extending from the western CONUS northward into Mainland Alaska, with a strong  
downstream mid-level trough in the eastern CONUS. The deepest 500-hPa height  
anomaly was -120 dm, centered over the Great Lakes. The Canadian ensemble mean  
has a similar configuration but is far less amplified. Slight positive 500-hPa  
height anomalies cover the southern Plains and western North America while a  
weak mid-level downstream trough is found over the eastern CONUS. The Canadian  
ensemble mean also centers the negative 500-hPa height anomaly over the Great  
Lakes, but the maximum anomaly reaches only -40 dm. The ECMWF ensemble mean has  
mid-level height anomalies similar in magnitude to the Canadian ensemble mean,  
but with a different configuration: Positive 500-hPa anomalies extend into  
Alaska from the south, and unusually low mid-level heights are in an east-west  
orientation covering the northern and central tiers of the CONUS, with 500-hPa  
heights closer to normal farther south. Similar to the 6-10 day period, the  
Canadian ensemble mean pattern is slightly favored for its consistency with  
yesterday and its lower amplitude, but other solutions can’t be ruled out given  
model inconsistency. 
 
Not unexpectedly, the disparate model solutions result in broadly inconsistent  
guidance among the derived tools. The official forecast used a consensus of the  
various derived tools, leaning toward Canadian raw and European reforecast  
output, and consistency with yesterday. The best agreement in the temperature  
tools is in south Texas and the southern Florida Peninsula, where odds for  
unusual warmth top 60 percent. Odds for extreme temperatures are much lower  
elsewhere, with enhanced odds for warmth limited to New England and the  
southern tier of the CONUS from the Four Corners eastward. In the CONUS, only  
the Pacific Northwest and adjacent Intermountain West have marginally-enhanced  
odds for cooler than normal weather, consistent with raw Canadian and  
reforecast ECMWF ensemble outputs. A preponderance of the array of solutions  
led to somewhat enhanced odds for subnormal temperatures in southwestern  
Mainland Alaska, and a marginally-increased likelihood for warmer than normal  
weather in northeastern Mainland Alaska, and the central and western sections  
of Hawaii. 
 
Precipitation tools based on the ECMWF and Canadian ensembles and the GEFS were  
in poor agreement, and the official forecast is based on a blend of these tools  
shaded toward the Canadian ensemble mean and consistency with yesterday. This  
results in a 40 to 50 percent chance for surplus precipitation in most of the  
Southeast and adjacent parts of the Lower Mississippi and Lower Ohio Valleys.  
Marginally-increased chances for above-normal precipitation are identified in  
the Northeast, eastern Great Lakes, Middle Mississippi Valley, parts of the  
central Plains and adjacent Rockies, Alaska outside the southern tier, and  
western Hawaii. Meanwhile, odds lean toward dryness in portions of the southern  
Plains and on the Big Island of Hawaii. 
 
 
The official 8-14 day 500-hPa height blend consists of: 20% of Today's 6z GFS  
Ensemble Mean centered on Day 11, 20% of Today's 0z European Ensemble Mean  
centered on Day 11, and 60% of Today's 0z Canadian Ensemble Mean centered on  
Day 11  
 
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Much below average, 1 out of 5,  
due to model disagreement, conflicting tool signals, and a lack of significant  
indications to favor any specific set of guidance. 
 
FORECASTER: Rich Tinker 
 
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 May  
16. 
 
 
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:  
19750427 - 19980508 - 19760425 - 19850514 - 19710505 
 
 
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:  
19750428 - 19980507 - 19520518 - 19850514 - 19760424 
 
 
6-10 DAY OUTLOOK TABLE 
Outlook for May 16 - 20 2024 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  N    B     OREGON      A    B     NRN CALIF   A    A      
SRN CALIF   A    A     IDAHO       A    N     NEVADA      A    N      
W MONTANA   A    N     E MONTANA   N    A     WYOMING     A    N      
UTAH        A    N     ARIZONA     A    A     COLORADO    A    A      
NEW MEXICO  A    N     N DAKOTA    N    A     S DAKOTA    N    A      
NEBRASKA    N    A     KANSAS      N    A     OKLAHOMA    N    A      
N TEXAS     N    A     S TEXAS     A    A     W TEXAS     N    N      
MINNESOTA   N    A     IOWA        N    A     MISSOURI    N    A      
ARKANSAS    N    A     LOUISIANA   A    A     WISCONSIN   A    A      
ILLINOIS    A    A     MISSISSIPPI N    A     MICHIGAN    A    A      
INDIANA     A    A     OHIO        A    A     KENTUCKY    A    A      
TENNESSEE   A    A     ALABAMA     N    A     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    A      
MARYLAND    A    A     DELAWARE    A    A     VIRGINIA    A    A      
N CAROLINA  A    A     S CAROLINA  A    A     GEORGIA     N    A      
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  A    A      
AK ALEUTIAN B    N     AK WESTERN  B    A     AK INT BSN  N    A      
AK S INT    B    A     AK SO COAST B    A     AK PNHDL    N    N      
  
                            
 
8-14 DAY OUTLOOK TABLE 
Outlook for May 18 - 24 2024 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  B    N     OREGON      B    N     NRN CALIF   N    N      
SRN CALIF   N    N     IDAHO       N    N     NEVADA      N    N      
W MONTANA   B    N     E MONTANA   N    N     WYOMING     N    N      
UTAH        N    N     ARIZONA     N    N     COLORADO    A    N      
NEW MEXICO  A    N     N DAKOTA    N    N     S DAKOTA    N    N      
NEBRASKA    N    A     KANSAS      N    N     OKLAHOMA    A    N      
N TEXAS     A    N     S TEXAS     A    B     W TEXAS     A    B      
MINNESOTA   N    N     IOWA        N    N     MISSOURI    N    A      
ARKANSAS    A    A     LOUISIANA   A    A     WISCONSIN   N    N      
ILLINOIS    N    A     MISSISSIPPI A    A     MICHIGAN    N    A      
INDIANA     N    A     OHIO        N    A     KENTUCKY    N    A      
TENNESSEE   N    A     ALABAMA     A    A     NEW YORK    N    A      
VERMONT     A    A     NEW HAMP    A    A     MAINE       A    A      
MASS        A    A     CONN        N    A     RHODE IS    A    A      
PENN        N    A     NEW JERSEY  N    A     W VIRGINIA  N    A      
MARYLAND    N    A     DELAWARE    N    A     VIRGINIA    N    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  B    A     AK INT BSN  N    A      
AK S INT    N    N     AK SO COAST N    N     AK PNHDL    N    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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