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 23 2019 
 
6-10 DAY OUTLOOK FOR MAY 29 - JUN 02, 2019 
 
Some model disagreement has emerged since yesterday regarding the placement of  
mid-level low pressure over eastern Canada. The 0z ECMWF, along with its  
ensembles, maintain continuity from yesterday with this feature centered just  
south of Hudson Bay, as does the 0z Canadian and the 0z GFS. However, today's  
6z GFS showed a noticeable shift, placing this feature farther northwest where  
it would have much less of an impact on the forecast over the northern tier of  
the CONUS. Given that all of the other model solutions continue to show this  
mid-level low pressure area centered over Ontario, the 6z GFS is not considered  
in today's manual blend, and instead the 0z run is used. The resultant manual  
blend favors negative height anomalies for the Great Lakes and the Upper  
Mississippi Valley as a result of the mid-level low over Ontario. Positive  
500-hPa height anomalies are shown for the Southeast, under zonally oriented  
flow, while troughing and near to below normal 500-hPa heights are favored for  
much of the West. The exception is the Pacific Northwest, where split flow is  
forecast as a result of ridging over the Western Canada, favoring positive  
height anomalies.  
 
Above normal temperature probabilities are favored for much of the East due to  
surface high pressure over the Western Atlantic and southwesterly flow. The  
influence of mid-level low pressure over Ontario favors increased below normal  
temperature probabilities for the Great Lakes, Upper Mississippi Valley, and  
the Northern Plains. Farther to the West, troughing is favored to be the  
dominant feature, with some weakening late. The GEFS shows a trend toward  
warmer temperatures later in the period, with the ECMWF ensembles persisting  
below normal temperatures longer. Today's forecast continues to support higher  
below normal temperature probabilities but these are reduced relative to  
yesterday. With ridging forecast over western Canada, above normal temperatures  
are favored for the Pacific Northwest. Near to above normal 500-hPa heights  
forecast over much of Alaska enhance the likelihood of above normal  
temperatures for most of the state, except for parts of the south coast of the  
mainland, where near normal temperature probabilities are favored due to the  
influence of mid-level low pressure forecast over the Gulf of Alaska. 
 
Above normal precipitation probabilities remain elevated for most of the West  
due to forecast troughing. Ridging over western Canada favors increased below  
normal precipitation probabilities for the Pacific Northwest. Surface high  
pressure off the East Coast favors increased below normal precipitation  
probabilities over the Southeast and Gulf Coast. With troughing remaining over  
the West, southerly flow over the Plains and Mississippi Valley favors enhanced  
chances of above normal precipitation. The ECMWF ensemble mean shows a  
precipitation maximum over eastern Oklahoma with over 2 inches of rain forecast  
during the period. Frontal activity may enhance precipitation across the Middle  
and Upper Mississippi Valley, into the Great Lakes and Northeast due to the  
aforementioned mid-level low pressure over Ontario. On the backside of this  
system, below normal precipitation probabilities are increased over the  
Northern High Plains. Mid level low pressure forecast south of the Alaskan  
mainland favors increased probabilities of above normal precipitation over  
mainland Alaska and the Aleutians. 
 
The official 6-10 day 500-hPa height blend consists of 25% of Today's 0z GFS  
Ensemble Mean centered on Day 8, 50% of Today's 0z European Ensemble Mean  
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: Average, 3 out of 5, due to good  
agreement between models and tools on most features, offset by uncertainty  
related to a deamplifying pattern. 
 
8-14 DAY OUTLOOK FOR MAY 31 - JUN 06, 2019  
 
All guidance significantly weakens the Eastern Canadian mid-level low relative  
to yesterday during the week-2 period. As a result, today's manual blend  
generally shows Pacific flow emerging with some lingering troughing in the  
West. Ridging over western Canada is also forecast to weaken, reducing the  
heights over the Pacific Northwest relative to the 6-10 day period. Near normal  
500-hPa heights are forecast for much of the CONUS for week-2, with some  
indication in the model guidance of a broad ridge developing late in the week-2  
period. 
 
Initially, below normal temperatures are favored for much of the West as  
troughing is forecast to have an influence. However, as troughing weakens, a  
trend toward warmer temperatures is favored throughout week-2, resulting in an  
average of near normal temperatures forecast over a large region. Above normal  
temperatures are favored for the Pacific Northwest and western California, with  
probabilities lowered compared to yesterday with aforementioned weakening of  
the ridge over western Canada. For the East, the region of above normal  
temperatures is expanded due to the absence of mid-level low pressure over  
Canada. Above normal temperatures are now favored westward to the Southern and  
Central Plains and northward through southern New England. Only the Great Lakes  
has increased chances for below normal temperatures, but with probabilities  
greatly reduced from yesterday. Due to the forecast above normal heights over  
mainland Alaska, increased above normal temperature probabilities are  
highlighted for northern mainland Alaska and the Aleutians, while below normal  
temperature probabilities are favored for the south coast of mainland Alaska  
due to the continued influence of mid-level low pressure. 
 
The precipitation probability forecast during the week-2 is more uncertain due  
to the pattern becoming more zonal. Initial troughing favors above normal  
precipitation for much of the western CONUS, with the exception of the Pacific  
Northwest, where below normal precipitation is forecast. Pacific flow favors a  
west to east storm track across the CONUS elevating chances of above normal  
precipitation over a broad area. There is a continued signal in the ECMWF  
ensembles for elevated precipitation chances for parts of the Lower Midwest  
where probabilities for above normal precipitation are higher compared to  
surrounding areas. Below normal precipitation probabilities are favored for  
parts of the Florida Peninsula. For the Gulf Coast, some individual ensemble  
members of the ECMWF and the GEFS bring up tropical moisture from the Caribbean  
in early June. Given the MJO is forecast to be in an 8-1 phase, which favors  
enhanced convection over this region,tropical activity would be supported. Near  
normal precipitation probabilities are favored due to the uncertainty related  
to this possible tropical influence. Increased above normal precipitation  
probabilities remain favored for Alaska, consistent with dynamical forecast  
tools. 
 
The official 8-14 day 500-hPa height blend consists of: 20% of Today's 0z GFS  
Ensemble Mean centered on Day 11, 60% of Today's 0z European Ensemble Mean  
centered on Day 11, and 20% 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  
forecast development of a zonal pattern and lack of amplified features. 
 
FORECASTER: Thomas Collow 
 
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  
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:  
19950511 - 19530513 - 19590519 - 20080523 - 19930603 
 
 
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:  
19950511 - 20080523 - 19530512 - 19590518 - 19930604 
 
 
6-10 DAY OUTLOOK TABLE 
Outlook for May 29 - Jun 02, 2019 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    B     OREGON      A    B     NRN CALIF   A    A      
SRN CALIF   B    A     IDAHO       N    A     NEVADA      B    A      
W MONTANA   A    N     E MONTANA   N    B     WYOMING     B    A      
UTAH        B    A     ARIZONA     B    A     COLORADO    B    A      
NEW MEXICO  B    A     N DAKOTA    B    B     S DAKOTA    B    N      
NEBRASKA    B    N     KANSAS      B    A     OKLAHOMA    N    A      
N TEXAS     A    A     S TEXAS     A    A     W TEXAS     B    A      
MINNESOTA   B    A     IOWA        B    A     MISSOURI    A    A      
ARKANSAS    A    A     LOUISIANA   A    N     WISCONSIN   B    A      
ILLINOIS    A    A     MISSISSIPPI A    B     MICHIGAN    B    A      
INDIANA     A    A     OHIO        A    A     KENTUCKY    A    A      
TENNESSEE   A    A     ALABAMA     A    B     NEW YORK    A    A      
VERMONT     A    A     NEW HAMP    A    A     MAINE       N    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    N      
N CAROLINA  A    N     S CAROLINA  A    B     GEORGIA     A    B      
FL PNHDL    A    B     FL PENIN    A    B     AK N SLOPE  A    A      
AK ALEUTIAN A    A     AK WESTERN  A    A     AK INT BSN  A    A      
AK S INT    A    A     AK SO COAST N    A     AK PNHDL    A    A      
  
                            
 
8-14 DAY OUTLOOK TABLE 
Outlook for May 31 - Jun 06, 2019 
 
STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN    
WASHINGTON  A    B     OREGON      A    B     NRN CALIF   A    B      
SRN CALIF   A    A     IDAHO       N    A     NEVADA      N    A      
W MONTANA   A    B     E MONTANA   A    N     WYOMING     N    A      
UTAH        N    A     ARIZONA     N    N     COLORADO    N    A      
NEW MEXICO  N    A     N DAKOTA    N    N     S DAKOTA    N    N      
NEBRASKA    N    N     KANSAS      N    A     OKLAHOMA    A    A      
N TEXAS     A    N     S TEXAS     A    N     W TEXAS     N    A      
MINNESOTA   N    A     IOWA        N    A     MISSOURI    A    A      
ARKANSAS    A    A     LOUISIANA   A    N     WISCONSIN   N    A      
ILLINOIS    A    A     MISSISSIPPI A    N     MICHIGAN    B    A      
INDIANA     A    A     OHIO        A    N     KENTUCKY    A    A      
TENNESSEE   A    A     ALABAMA     A    N     NEW YORK    N    N      
VERMONT     N    N     NEW HAMP    N    N     MAINE       N    N      
MASS        A    N     CONN        A    N     RHODE IS    A    N      
PENN        A    N     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    N      
FL PNHDL    A    N     FL PENIN    A    N     AK N SLOPE  A    A      
AK ALEUTIAN A    A     AK WESTERN  A    A     AK INT BSN  A    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. 
 
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