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 Tue April 22 2025 
 
6-10 DAY OUTLOOK FOR APR 28 - MAY 02, 2025 
 
Today's numerical models generally depict a high amplitude 500-hPa pattern  
across much of the country early in the period followed by a potential  
significant pattern change late in the period. The period begins with a strong  
ridge over the eastern Contiguous U.S. (CONUS) and an upstream trough over the  
interior West. Ridging is forecast off the West Coast of the CONUS and a trough  
is forecast over the Bering Sea. The ridge in the East is forecast to slowly  
decrease in magnitude and progress from the Great Lakes region toward the East  
Coast by Day 10. In its wake the trough over the interior West is forecast to  
progress to the Plains and eventually the Great Lakes. Residual troughing is  
also depicted over the Southwestern CONUS. This 500-hPa pattern evolution  
supports the development of a potent surface low on the lee side of the Rockies  
and a favorable setup for a potentially very active pattern across much of the  
Plains and Mississippi Valley. Farther to the north, the trough over the Bering  
Sea is forecast to progress and strengthen over the Gulf of Alaska before  
retreating to the Alaska Peninsula by the end of the period. This predicted  
trough evolution sets up a potentially active pattern for southeastern Alaska  
for much of the period. Mean troughing is also forecast across much of Hawaii,  
with below normal heights generally predicted across the state.  
 
Above normal temperatures are favored for most of the CONUS east of the  
Rockies. Probabilities of above normal temperatures exceed 80 percent across  
much of the Tennessee Valley and Lower and Middle Mississippi Valley where  
southerly flow is likely to be persistent throughout most of the period.  
Conversely, a tilt toward below normal temperatures is indicated for parts of  
the Southwest, due to troughing predicted through the middle of the period.  
Conversely, a rapid warmup is expected late in the period across the  
northwestern CONUS as a ridge quickly builds across the region by day 10.  
Therefore, enhanced above normal temperature probabilities are indicated for  
this region. Near to above normal temperatures are favored for much of the  
south coast of Alaska associated with predicted southerly or southwesterly  
onshore flow and above normal sea surface temperatures (SSTs) in adjacent  
waters. Below normal temperatures are more likely for northern and central  
Alaska as well as parts of the Aleutians due to persistent troughing and  
associated below normal heights. Above normal temperatures are likely for  
Hawaii, adjacent to above normal SSTs. 
 
An active period is anticipated across much of the center of the CONUS.  
Persistent southerly flow ahead of a predicted trough over the west should  
transport ample Gulf moisture northward. At the same time, surface low pressure  
is forecast to develop in the lee of the Rockies and move northeastward to the  
Northern Plains and Great Lakes. This surface low combined with available  
moisture from the Gulf leads to increased chances of above normal precipitation  
for most of the central CONUS. Probabilities of increased precipitation amounts  
relative to normal exceed 60 percent for parts of the Southern Plains and  
western Great Lakes. Conversely, a slight tilt toward below normal  
precipitation is indicated along coastal areas of the Carolinas and Georgia due  
to predicted anomalous ridging and associated surface high pressure. An active  
pattern is likely for southeastern Alaska as a surface low is forecast to  
strengthen over the Gulf of Alaska. Above normal precipitation probabilities  
exceed 50 percent for Southeast Alaska and adjacent areas of the Mainland. A  
tilt toward above normal precipitation is also indicated for Hawaii as a mean  
500-hPa trough and below normal heights are forecast across the area. 
 
The official 6-10 day 500-hPa height blend consists of 20% of Today's 6z GFS  
Ensemble Mean centered on Day 8, 50% of Today's 0z European Ensemble Mean  
centered on Day 8, and 30% 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, due to  
a predicted amplified 500-hPa flow pattern (particularly early in the period). 
 
8-14 DAY OUTLOOK FOR APR 30 - MAY 06, 2025  
 
The week-2 period begins with a moderately amplified pattern featuring  
anomalous ridging over the Eastern Seaboard and troughs over the Southwest and  
Northern Plains. As time progresses a significant pattern change ensues as a  
ridge quickly builds across the West and progresses to the Northern Plains.  
Conversely, the flow pattern remains more persistent across Alaska as anomalous  
troughing is forecast to slowly drift from the Gulf of Alaska to near the  
Alaska Peninsula by the end of the period. This trough evolution leads to  
predicted below normal heights across most of the state with the strongest  
negative height anomalies forecast for southwestern Alaska. Near to below  
normal heights are forecast to persist across Hawaii due to predicted troughing  
in the vicinity. 
 
With the flow pattern expected to transition to increased ridging across much  
of the CONUS, a moderating trend is likely across most areas of the Lower 48.  
Above normal temperatures are favored across the vast majority of the CONUS.  
The lone exception is for parts of the Rio Grande Valley and vicinity where  
weak troughing may persist into the week-2 period. Enhanced probabilities of  
near or below normal temperatures are indicated for this area. Near to above  
normal temperatures are favored for much of southern Alaska underneath  
predicted southerly flow combined with above normal SSTs adjacent to the South  
Coast. Below normal temperatures are more likely for northern and western  
Alaska associated with predicted mean troughing and northeasterly low-level  
flow. Above normal temperatures remain likely for Hawaii associated with above  
normal SSTs in nearby waters. 
 
An active pattern is anticipated to continue into week-2 for much of the  
Southern Plains, the lower half of the Mississippi Valley, and northeastward to  
the central and eastern Great Lakes, particularly early in the period. Enhanced  
southerly flow should continue to transport ample Gulf moisture northward into  
the Southern Plains and Lower Mississippi Valley early in week-2 while surface  
low pressure increases precipitation chances northeastward to the Great Lakes.  
Chances of above normal precipitation exceed 50 percent for the Arklatex and  
surrounding areas where Gulf moisture advection is likely to be most  
pronounced. Conversely, as ridging builds across the West and later into the  
Northern Plains, a slight tilt toward near or below normal precipitation is  
forecast along the West Coast eastward to the Northern and Central Plains and  
Upper Mississippi Valley. Conversely, enhanced moisture flow ahead of a  
predicted surface low over the Gulf of Alaska favors above normal precipitation  
for southern and eastern Alaska. Above normal precipitation probabilities  
exceed 50 percent for Southeast Alaska where onshore flow is likely to be most  
pronounced. Below normal precipitation is slightly favored for much of western  
Mainland Alaska associated with predicted offshore flow. A slight tilt toward  
above normal precipitation persists for Hawaii near a predicted trough. 
 
The official 8-14 day 500-hPa height blend consists of: 20% of Today's 6z GFS  
Ensemble Mean centered on Day 11, 50% 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: Below average, 2 out of 5, due to  
a predicted transitional pattern. 
 
FORECASTER: Scott H 
 
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  
15. 
 
 
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:  
20020420 - 20080417 - 19540420 - 20020504 - 19640421 
 
 
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:  
20020420 - 20080416 - 19540422 - 20020425 - 19810407 
 
 
6-10 DAY OUTLOOK TABLE 
Outlook for Apr 28 - May 02, 2025 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    N     OREGON      A    N     NRN CALIF   A    B      
SRN CALIF   N    N     IDAHO       A    N     NEVADA      A    N      
W MONTANA   A    N     E MONTANA   A    A     WYOMING     N    A      
UTAH        N    N     ARIZONA     N    N     COLORADO    N    A      
NEW MEXICO  N    A     N DAKOTA    A    A     S DAKOTA    A    A      
NEBRASKA    A    A     KANSAS      A    A     OKLAHOMA    A    A      
N TEXAS     A    A     S TEXAS     A    A     W TEXAS     A    A      
MINNESOTA   A    A     IOWA        A    A     MISSOURI    A    A      
ARKANSAS    A    A     LOUISIANA   A    A     WISCONSIN   A    A      
ILLINOIS    A    A     MISSISSIPPI A    A     MICHIGAN    A    A      
INDIANA     A    A     OHIO        A    A     KENTUCKY    A    A      
TENNESSEE   A    A     ALABAMA     A    N     NEW YORK    A    A      
VERMONT     A    A     NEW HAMP    A    N     MAINE       A    A      
MASS        A    N     CONN        A    N     RHODE IS    A    N      
PENN        A    A     NEW JERSEY  A    N     W VIRGINIA  A    A      
MARYLAND    A    N     DELAWARE    A    N     VIRGINIA    A    N      
N CAROLINA  A    N     S CAROLINA  A    B     GEORGIA     A    N      
FL PNHDL    A    N     FL PENIN    A    N     AK N SLOPE  B    N      
AK ALEUTIAN B    N     AK WESTERN  B    N     AK INT BSN  B    N      
AK S INT    N    A     AK SO COAST N    A     AK PNHDL    N    A      
  
                            
 
8-14 DAY OUTLOOK TABLE 
Outlook for Apr 30 - May 06, 2025 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    N     OREGON      A    N     NRN CALIF   A    B      
SRN CALIF   A    N     IDAHO       A    N     NEVADA      A    N      
W MONTANA   A    N     E MONTANA   A    B     WYOMING     A    N      
UTAH        A    N     ARIZONA     A    N     COLORADO    A    A      
NEW MEXICO  N    A     N DAKOTA    A    B     S DAKOTA    A    N      
NEBRASKA    A    N     KANSAS      A    N     OKLAHOMA    A    A      
N TEXAS     N    A     S TEXAS     N    A     W TEXAS     N    A      
MINNESOTA   A    N     IOWA        A    N     MISSOURI    A    A      
ARKANSAS    A    A     LOUISIANA   A    A     WISCONSIN   A    N      
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    A     MAINE       A    A      
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    A      
N CAROLINA  A    A     S CAROLINA  A    A     GEORGIA     A    A      
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  B    B      
AK ALEUTIAN B    N     AK WESTERN  B    N     AK INT BSN  B    N      
AK S INT    N    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. 
 
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