530
FXUS06 KWBC 081903
PMDMRD
Prognostic Discussion for 6 to 10 and 8 to 14 day outlooks
NWS Climate Prediction Center College Park, MD
300 PM EDT Wed May 08 2024

6-10 DAY OUTLOOK FOR MAY 14 - 18 2024

Today`s dynamical model solutions are in fairly good agreement on the predicted
500-hPa circulation pattern across North America and surrounding regions during
the 6-10 day period. The manual 500-hPa height blend is based on nearly-equal
weighting of the 0z GFS, ECMWF, and Canadian ensemble means due to comparable
model skill over the past two months. The resultant manual blend features
moderate-to-strong anomalous ridges over the western Pacific, the eastern
Pacific, and the central Atlantic. A moderately amplified mid-level trough and
below-normal heights are predicted over Alaska, with the mean trough axis near
the west coast of Alaska. A significant difference is apparent between todays
and yesterdays height blends over central portions of North America.
Yesterday, shortwave energy associated with the mid-level trough over Alaska
was located over western Canada, which allowed a narrow channel/corridor of
slightly positive height anomalies to develop ahead of it across the
north-central and northeastern contiguous U.S. (CONUS). Today, this shortwave
energy is forecast to shift from western Canada into the north-central CONUS,
effectively severing the connection between the positive height anomalies
across the West (associated with the anomalous ridge over the eastern Pacific)
and the corridor of slightly positive height anomalies over the Northeast.
Mid-level troughing is now expected to overspread the East with time, as was
predicted by models several days ago. Over the east-central Pacific, weak
troughing and near-normal 500-hPa heights are favored for the Hawaiian Islands.

GEFS and European ensemble mean (ECENS) reforecast temperatures favor
above-normal temperatures for most of the CONUS, the exception being the
Southeast where the GEFS reforecast favors near-normal temperatures. This is
generally consistent with a pattern dominated by near- to above-normal 500-hPa
heights. The highest probabilities favoring above-normal temperatures exceed
70% over southern Florida and at least 60% over the vicinity of the Central
Great Basin and much of northern and central California, and northern portions
of New York and New England. A small sliver of below-normal temperatures is
favored across northwestern Washington associated with a weak trough forecast
to slide southward over the area. In Alaska, mid-level troughing and
below-normal 500-hPa heights favor below-normal temperatures across much of the
state. In Hawaii, near-normal temperatures are forecast, representing a
compromise between auto-temperatures and the consolidation of tools.

Below-normal precipitation is favored from most of the northern half of the
Pacific coast eastward across Idaho and southwestern Montana, associated with
mid-level ridging and near- to above-normal 500-hPa heights. This is supported
by GEFS reforecast precipitation, and to a much lower extent, ECENS reforecast
precipitation. For most of the remainder of the CONUS, these two reforecasts
depict increased odds of above-normal precipitation, which is consistent with
broad, low-amplitude cyclonic flow. The highest probabilities for above-normal
precipitation, in excess of 60%, are indicated  over the eastern Gulf Coast
region and Southeast. This is associated with surface high pressure off the
East Coast leading to increased onshore flow across the Gulf Coast states, a
nearby warm front, and mid-level troughing. Weak residual troughing across the
Southwest slightly elevates the probability of above-normal precipitation for
much of that region, supported by GEFS and ECMWF ensemble mean reforecast
precipitation guidance. In Alaska, above-normal precipitation is forecast over
most of the state associated with broad onshore flow and mid-level troughing.
In Hawaii, mostly above-normal precipitation is favored due to the proximity of
a weak 500-hPa trough.

The official 6-10 day 500-hPa height blend consists of 33% of Today`s 0z GFS
Ensemble Mean centered on Day 8, 34% of Today`s 0z European Ensemble Mean
centered on Day 8, and 33% 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
good agreement among model solutions and forecast temperature and precipitation
tools.

8-14 DAY OUTLOOK FOR MAY 16 - 22 2024

The two anomalous ridges predicted over the western and eastern Pacific during
the earlier 6-10 day period are forecast to consolidate into one broad
anomalous ridge, with maximum positive height anomalies of about +180 meters
forecast south of the Aleutians. This pattern evolution suggests the eastern
portion of this broad Pacific ridge is weakening, with the consolidation of
maximum height anomalies farther west. The northern portion of this ridge is
predicted to extend northward across the Alaska Peninsula and into southwestern
Alaska. The trough over Alaska is forecast to weaken during week-2. A weak
trough-ridge-trough pattern is indicated over the CONUS with heights predicted
to be near- to slightly below-normal over the north-central states, and near-
to slightly above-normal elsewhere. A weak trough and near-normal 500-hPa
heights continues to be predicted in the vicinity of Hawaii.

Above-normal temperatures are favored over most of the CONUS, consistent with
todays reforecast temperatures from the GEFS and ECENS. Odds favoring
above-normal temperatures surpass 50% for most of the Four Corners region and
Texas, and the Florida Peninsula. Predicted weak 500-hPa height anomalies and
cooler raw surface temperature tools support near to slightly above-normal
temperatures over much of the East. The presence of weak troughs in the Pacific
Northwest, the northern Rockies, and the north-central states favor near- to
below-normal temperatures across that region. In Alaska, below-normal
temperatures continue to be favored by many of the tools south of the Brooks
Range, even though the trough impacting the state is expected to weaken during
week-2. In Hawaii, near-normal temperatures are favored, representing a
compromise between the ERF consolidation tool, the auto temperature forecast,
and predicted near-normal 500-hPa heights.

Below-normal precipitation is slightly favored across sections of Washington
and Oregon, due to residual mid-level ridging anticipated over the region.
There is a slight tilt in the odds towards drier-than-normal conditions for
southern portions of the Four Corners region, and western and southern parts of
Texas. This is supported by the GEFS and especially the ECENS reforecast
precipitation tools, and is consistent with observed 30-day and 90-day
percent-of-normal rainfall and relatively dry soils. There is a slight tilt
towards above-normal precipitation from southwestern California across southern
Nevada, in advance of expected weak troughing near the California coast. Near-
to above-normal precipitation is forecast over the remainder of the CONUS due
to southerly return flow associated with mean surface high pressure over the
Southeast and a broad mid-level trough expected to progress across the East.
This is supported by most precipitation guidance, though raw precipitation
guidance from the ECENS predicts widespread below-normal precipitation from the
Desert Southwest eastward across the Southern Rockies, Southern Plains, and
southern half of the Mississippi Valley. In Alaska, above-normal precipitation
is slightly favored across the state with unsettled weather beneath a mid-level
trough continuing. Meanwhile, near- to mostly above-normal precipitation is
slightly favored for Hawaii consistent with the consolidation of tools and
auto-precipitation forecast.

The official 8-14 day 500-hPa height blend consists of: 35% of Today`s 0z GFS
Ensemble Mean centered on Day 11, 35% 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: Near average, 3 out of 5, with
good agreement in the overall circulation pattern for the period, offset by
weaker signals and some disagreement among precipitation and temperature tools.

FORECASTER: Anthony A

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 - 19750502 - 19640501 - 19980513 - 19850512


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:
19750427 - 19750502 - 19760423 - 19990509 - 19850422


6-10 DAY OUTLOOK TABLE
Outlook for May 14 - 18 2024

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  A    B     OREGON      A    B     NRN CALIF   A    B
SRN CALIF   A    N     IDAHO       A    B     NEVADA      A    B
W MONTANA   A    N     E MONTANA   A    A     WYOMING     A    N
UTAH        A    N     ARIZONA     A    N     COLORADO    A    A
NEW MEXICO  A    N     N DAKOTA    A    A     S DAKOTA    A    A
NEBRASKA    A    A     KANSAS      A    A     OKLAHOMA    N    A
N TEXAS     A    A     S TEXAS     A    A     W TEXAS     A    N
MINNESOTA   A    A     IOWA        A    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   N    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     A    A
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  N    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



8-14 DAY OUTLOOK TABLE
Outlook for May 16 - 22 2024

STATE      TEMP PCPN   STATE      TEMP PCPN   STATE      TEMP PCPN
WASHINGTON  B    N     OREGON      N    N     NRN CALIF   A    N
SRN CALIF   A    A     IDAHO       A    N     NEVADA      A    N
W MONTANA   N    N     E MONTANA   N    N     WYOMING     A    N
UTAH        A    N     ARIZONA     A    N     COLORADO    A    N
NEW MEXICO  A    N     N DAKOTA    N    A     S DAKOTA    N    A
NEBRASKA    A    A     KANSAS      A    A     OKLAHOMA    A    A
N TEXAS     A    N     S TEXAS     A    N     W TEXAS     A    N
MINNESOTA   N    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   N    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     A    A
FL PNHDL    A    A     FL PENIN    A    A     AK N SLOPE  N    A
AK ALEUTIAN B    N     AK WESTERN  B    A     AK INT BSN  B    A
AK S INT    B    N     AK SO COAST B    N     AK PNHDL    B    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.

$$