819
FXUS06 KWBC 101936
PMDMRD
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 cant 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.

$$