Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
402 PM EDT Tue Jun 04 2019
Valid 12Z Fri Jun 07 2019 - 12Z Tue Jun 11 2019
...Excessive Rain and Flash Flood/Flooding Risk to Spread from the
Mid-Lower Mississippi and Tennessee/Lower Ohio Valleys to the
south-central Appalachians/Mid-Atlantic and Southeast...
...Guidance discussion...
Guidance agrees an amplified/closed upper level features moving
through the northern and southern streams of the Westerlies. The
guidance showed good agreement with modest differences detail-wise
which could be effectively dealt with in a blend. The medium
range 500 hPa heights, pressures, and fronts were were derived
from an even split of the 00z Canadian, 00z UKMET, 06z GFS, and
00z ECMWF Friday through Sunday, with increasing amounts of 00z
NAEFS mean and 00z ECMWF ensemble mean being used Monday and
Tuesday, eventually encompassing close to half of the blend. Most
of the lower 48 grids used a more equal portion of deterministic
and ensemble mean guidance. This solution maintains reasonably
good WPC continuity.
...Southeast/Mid-South impacts...
The southern stream member lures moisture return from the Gulf of
Mexico/Atlantic, fueling a threat of heavy rain and flash
flooding/flooding. There is a strong signal for a slow spread of
activity Friday-Tuesday from the Mid-Lower Mississippi and
Tennessee/Lower Ohio Valleys to the south-central
Appalachians/Mid-Atlantic and Southeast. WPC medium range QPF
advertises 3-6" areal average amounts, with locally higher amounts
possible in areas of cell training/back building/cell mergers.
Deepest tropical moisture is linked to a southwest Gulf of Mexico
disturbance monitored by NHC whose low-level vorticity moves into
the lower 48 between Wednesday and Thursday per ECMWF ensemble
spaghetti plots.
...Northern Tier impacts...
A significant/anomalous cooling and unsettling upper trough from
northern stream flow evolves from the Northwest/West to the
north-central U.S. from late this week into early next week.
Guidance is converging on a more clustered forecast, bolstering
confidence in widespread moderate to terrain enhanced
precipitation. This includes snows for northern Rockies higher
elevations of per WPC medium range winter weather outlook
probabilities.
Roth/Schichtel
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
Hazards:
- Heavy rain across portions of the Northeast, the Mid-Atlantic,
the Central Appalachians, the Great Lakes, and the Ohio Valley,
Tue, Jun 11.
- Heavy rain across portions of the Central/Southern Plains, Tue,
Jun 11.
- Heavy rain across portions of the Central Plains, the Lower
Mississippi Valley, the Central Appalachians, the Tennessee
Valley, the Middle Mississippi Valley, the Mid-Atlantic, the
Southern Appalachians, the Southeast, and the Ohio Valley,
Fri-Tue, Jun 7-Jun 11.
- Flooding possible across portions of the Middle Mississippi
Valley, the Great Lakes, and the Ohio Valley.
- Flooding occurring or imminent across portions of the Plains,
the Mississippi Valley, the Central/Northern Great Basin, the
Great Lakes, and the Ohio Valley.
- Flooding likely across portions of the Southern Rockies, the
Central Great Basin, and the Southwest.
- Excessive heat across portions of the Southern Plains, Fri-Mon,
Jun 7-Jun 10.
- Much above normal temperatures across portions of California,
the Pacific Northwest, and the Northern Great Basin, Mon-Tue, Jun
10-Jun 11.
- Much below normal temperatures across portions of the
Northern/Central Great Basin, the Northern/Central Plains, the
Northern/Central Rockies, California, and the Pacific Northwest,
Fri-Sat, Jun 7-Jun 8.
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at:
https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml