Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks 
NWS Climate Prediction Center College Park, MD 
300 PM EDT Tue May 20 2025 
 
6-10 DAY OUTLOOK FOR MAY 26 - 30 2025 
 
Today's model solutions start off in good agreement but begin to diverge late  
in the period. A fairly amplified 500-hPa pattern should be in place at the  
start of the period which will slowly deamplify as the period progresses,  
although this process is a bit slower today than yesterday. The manual 500-hPa  
height blend emphasizes the operational European and the Canadian ensembles,  
but includes other models as well. The operational ECMWF and GFS were included  
to add more amplitude to the pattern which may be getting erroneously flattened  
by outlier members in the ensembles. Compared to yesterday, the 5-day mean  
manual height blend is deeper with the mid-level trough centered south of  
Alaska (peak anomaly -18 dm), about the same with the ridge centered in central  
Canada (+12 dm), and weaker with the mid-level trough in the eastern Contiguous  
United States (-3 dm). In addition, the extension of the mid-level ridge from  
central Canada is stronger over the western CONUS than yesterday, with  
anomalies above +9 dm covering areas from the Great Basin to the northern  
Rockies. Near-normal 500-hPa heights are predicted across Hawaii by most tools,  
with heights increasing from weak mid-level trough to the northwest and a weak  
ridge to the southeast. 
 
Mean surface high pressure is expected to stretch farther south than forecast  
yesterday, with the mean system centered around the Great Lakes or Middle  
Mississippi Valley and extending southward into the Lower Mississippi Valley  
and central Gulf Coast States, west to southwest of  the weakening mean  
mid-level trough. This should hold below-normal temperatures over most of the  
central and eastern CONUS outside the northern and southern fringes of this  
region. The tools are in fair to good agreement placing the best chances for  
sub-normal temperatures (over 60%) from the central Great Plains through the  
Lower Ohio Valley and central Appalachians. This represents an increase in odds  
from yesterday, and a farther west extension, consistent with stronger surface  
high pressure in or near the Mississippi Valley. Meanwhile, above-normal  
temperatures are anticipated for most of the western CONUS under mid-level  
ridging, which models show as somewhat stronger and more resilient than  
yesterday. Western Washington is an exception, upstream from the mid-level  
ridge and closer to the strong mid-level trough centered over the Gulf of  
Alaska. Warmer than normal conditions are favored across Hawaii, consistent  
with the consolidation and gradually rising 500-hPa heights. Farther north,  
there remains some uncertainty across Alaska. Raw ensemble mean outputs show  
greatly enhanced odds for sub-normal temperatures across the southern Mainland  
and southeastern sections, but the bias-corrected versions reduce the anomalies  
somewhat. The reforecast tools are milder still, and the Canadian ensemble  
reforecast actually favors above-normal temperatures across southeastern  
Alaska. The Alaska temperature forecast is a compromise of the tools, favoring  
cooler than normal conditions in south-central and southeastern Alaska, but  
with somewhat lower chances than depicted by the consolidation and the auto  
blend. 
 
Above-normal precipitation is favored over much of the south-central and  
southeastern CONUS, with slightly less-enhanced odds stretching northward along  
much of the East Coast. Ensemble mean surface pressure forecasts all show a  
decent inflow of moisture from the Gulf into the south-central and southeastern  
CONUS while surface high pressure to the north extends through the Ohio Valley.  
Where these circulation features converge, a quasi-stationary front will become  
established over the Southeast, which should serve as a focus for enhanced  
rainfall. Chances for surplus precipitation exceed 50% in these areas. In  
addition, some tools suggest a surface low pressure wave may form along this  
front, which would further enhance the odds for a wet period. Meanwhile,  
above-normal precipitation is also favored in most of Alaska and the Pacific  
Northwest near or upstream from the Alaskan mid-level trough. The best odds for  
surplus precipitation (over 50%) stretch from southeastern Alaska into western  
Washington under cyclonic flow between the strong mid-level trough and the  
ridge axis over the Interior West. In the CONUS, increased odds for drier than  
normal conditions stretch from the central West Coast northeastward through the  
northern Rockies, then eastward along the northern fringe of the CONUS, as far  
east as northern Maine. These areas are under the mid-level ridge in the West  
or upstream from the decaying mid-level trough along or near the East Coast.  
Consistent with the consolidation, odds lean toward wet weather across Hawaii. 
 
The official 6-10 day 500-hPa height blend consists of 17% of Today's 6z GFS  
Ensemble Mean centered on Day 8, 10% of Today's operational 6z GFS centered on  
Day 8, 18% of Today's 0z European Ensemble Mean centered on Day 8, 30% of  
Today's operational 0z ECMWF 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: About average, 3 out of 5. Good  
agreement on the height pattern among the ensemble means early in the period is  
offset by increasingly divergent solutions toward the end of the period, along  
with some areas of inconsistency among the dynamical and statistical  
temperature and precipitation tools, and the uncertainty inherent in a  
shifting, deamplifying pattern that has been handled inconsistently by the  
models in recent days. 
 
8-14 DAY OUTLOOK FOR MAY 28 - JUN 03, 2025  
 
Ensemble mean solutions for the 8-14 day period depict a slowly progressive and  
deamplifying 500-hPa circulation pattern, and dynamical model solutions are  
increasingly divergent by the end of week-2. There are significant  
uncertainties regarding which mid-level features deamplify more quickly than  
others and how progressive the pattern becomes, resulting in discrepancies in  
model solutions of the timing, placement, and magnitude of individual features.  
There is general agreement that the mid-level trough near Alaska will slowly  
fill and perhaps drift east toward the CONUS West Coast, leading into a broad  
downstream ridge with an axis somewhere from the Intermountain West to the  
central CONUS. The positive 500-hPa height anomaly maximum over central Canada  
will also weaken, but as is the case farther south and west, models are not in  
good agreement on how this evolves with time. Solutions range from keeping weak  
positive height anomalies in the neighborhood to completely quashing the ridge  
to the south, enhancing above-normal heights over the central and/or western  
CONUS. With a lack of guidance favoring one solution over another, the manual  
blend is an equal mix of the European, 6z GEFS, and Canadian ensemble means. A  
further complicating factor is the potential for a tropical or subtropical low  
pressure center to move toward the Florida Peninsula near the end of week-2, as  
shown by the GEFS. The Canadian ensemble mean is considerably weaker and drier  
with this potential system, and the European ensemble mean has little if any  
reflection of surface low pressure development. 
 
Above-normal temperatures continue to be favored across most of western North  
America under predominantly above-normal 500-hPa heights, stretching eastward  
across the northern tier of the CONUS behind the meandering, weakening eastern  
CONUS mid-level trough. Enhanced odds for above-normal temperatures reach as  
far east as the Upper Mississippi Valley, much of the Great Lakes Region, and  
most of New England. Farther south and east, surface high pressure should keep  
cool air stubbornly locked into much of the east-central states and southern  
Great Plains, with some moderation forecast closer to the East Coast. Most  
tools look significantly cooler in the southern Plains and adjacent locations  
due to the placement of the mean high pressure center farther south in the  
east-central CONUS than anticipated yesterday. Warmer than normal conditions  
are favored across much of Florida (consistent with most raw and  
statistically-adjusted model output) and over a large part of the West (under  
generally above-normal 500-hPa heights). Portions of the Pacific Northwest  
remain an exception, with lower heights drifting in from the northwest favoring  
temperatures closer to or slightly below normal. Below-normal temperatures are  
favored for much of Mainland and southeastern Alaska a little more robustly  
than yesterday with sub-normal 500-hPa heights and mid-level troughing looking  
a little more resilient than it did yesterday.  Above-normal temperatures are  
favored to persist across Hawaii during week-2 by dynamical models. 
 
With deamplifying mid-level height anomalies, the precipitation anomaly pattern  
is uncertain over much of North America. The forecast is essentially a  
compromise of the available tools. In most areas where above- or below-normal  
precipitation is favored, chances generally remain below 40%. Exceptions on the  
wet side include portions of the south-central and southeastern CONUS (where a  
lingering quasi-stationary front could serve as a focus for increased  
rainfall), the southern High Plains and adjacent Rockies (where moisture may be  
funneled in from the tropics by a surface heat-induced low pressure in the  
Southwest), and westernmost Washington (upstream from a mid-level trough). The  
latter feature also enhances the odds for surplus precipitation in southeast  
Alaska to over 40 percent, with wetness only nominally favored over the rest of  
the state. Meanwhile, below-normal precipitation is weakly favored across a  
broad area from the central West Coast through the Great Basin, northern  
Intermountain West, roughly the northern halves of the Rockies and Plains,  
parts of the Middle and Upper Mississippi Valley, and western Great Lakes  
Region. However, chances for abnormal dryness exceed 40% only in a band from  
the northern Great Basin into the northwestern Rockies. Wet weather is weakly  
favored for Hawaii, consistent with the consolidation and with its placement  
downstream from a weak mid-level trough and upstream from a weak ridge. 
 
The official 8-14 day 500-hPa height blend consists of: 33% of Today's 6z GFS  
Ensemble Mean centered on Day 11, 34% of Today's 0z European Ensemble Mean  
centered on Day 11, and 33% of Today's 0z Canadian Ensemble Mean centered on  
Day 11  
 
 
FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: Below average, 2 out of 5. Fair  
agreement on the mean pattern is offset by areas of disagreement in the raw and  
derived temperature and precipitation tools, divergent dynamical solutions  
toward the end of the period, plus the uncertainties inherent to an evolving,  
deamplifying pattern. 
 
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  
June 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:  
20040529 - 20010602 - 19640508 - 19890516 - 19860514 
 
 
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:  
20010601 - 20040529 - 19640509 - 19890516 - 19860512 
 
 
6-10 DAY OUTLOOK TABLE 
Outlook for May 26 - 30 2025 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    A     OREGON      A    A     NRN CALIF   A    B      
SRN CALIF   A    B     IDAHO       A    B     NEVADA      A    B      
W MONTANA   A    B     E MONTANA   A    B     WYOMING     A    B      
UTAH        A    N     ARIZONA     A    A     COLORADO    A    A      
NEW MEXICO  B    A     N DAKOTA    A    B     S DAKOTA    N    B      
NEBRASKA    B    B     KANSAS      B    N     OKLAHOMA    B    A      
N TEXAS     B    A     S TEXAS     B    A     W TEXAS     B    A      
MINNESOTA   A    B     IOWA        B    B     MISSOURI    B    N      
ARKANSAS    B    A     LOUISIANA   B    A     WISCONSIN   N    B      
ILLINOIS    B    N     MISSISSIPPI B    A     MICHIGAN    B    B      
INDIANA     B    N     OHIO        B    N     KENTUCKY    B    A      
TENNESSEE   B    A     ALABAMA     B    A     NEW YORK    B    A      
VERMONT     N    N     NEW HAMP    N    A     MAINE       A    N      
MASS        N    A     CONN        B    A     RHODE IS    B    A      
PENN        B    A     NEW JERSEY  B    A     W VIRGINIA  B    A      
MARYLAND    B    A     DELAWARE    B    A     VIRGINIA    B    A      
N CAROLINA  B    A     S CAROLINA  B    A     GEORGIA     B    A      
FL PNHDL    N    A     FL PENIN    A    A     AK N SLOPE  B    A      
AK ALEUTIAN B    N     AK WESTERN  N    A     AK INT BSN  B    A      
AK S INT    B    A     AK SO COAST B    A     AK PNHDL    B    A      
  
                            
 
8-14 DAY OUTLOOK TABLE 
Outlook for May 28 - Jun 03, 2025 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    A     OREGON      A    N     NRN CALIF   A    B      
SRN CALIF   A    N     IDAHO       A    B     NEVADA      A    B      
W MONTANA   A    B     E MONTANA   A    B     WYOMING     A    B      
UTAH        A    N     ARIZONA     A    A     COLORADO    A    A      
NEW MEXICO  A    A     N DAKOTA    A    B     S DAKOTA    A    B      
NEBRASKA    A    B     KANSAS      A    N     OKLAHOMA    B    A      
N TEXAS     B    A     S TEXAS     B    A     W TEXAS     B    A      
MINNESOTA   A    B     IOWA        N    B     MISSOURI    B    N      
ARKANSAS    B    N     LOUISIANA   B    A     WISCONSIN   A    B      
ILLINOIS    B    N     MISSISSIPPI B    A     MICHIGAN    N    B      
INDIANA     B    N     OHIO        B    N     KENTUCKY    B    N      
TENNESSEE   B    N     ALABAMA     B    A     NEW YORK    N    A      
VERMONT     A    A     NEW HAMP    A    A     MAINE       A    A      
MASS        A    A     CONN        N    A     RHODE IS    N    A      
PENN        N    A     NEW JERSEY  N    A     W VIRGINIA  B    N      
MARYLAND    N    A     DELAWARE    N    A     VIRGINIA    N    A      
N CAROLINA  N    A     S CAROLINA  B    A     GEORGIA     B    A      
FL PNHDL    N    A     FL PENIN    A    A     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    B    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. 
 
$$