Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Thu Sep 19 2019
Valid 12Z Sun Sep 22 2019 - 12Z Thu Sep 26 2019
...Imelda moisture to fuel Mid-MS Valley/Midwest to Northeast
Heavy Rains Sun/Mon...
...Overview and Guidance Evaluation/Preferences...
Models and ensembles continue to mainly offer a reasonably similar
medium range flow evolution in a pattern with above average
forecast confidence. The WPC medium range product suite was
primarily derived from a composite blend of fairly well clustered
guidance from the GFS/ECMWF/UKMET/Canadian, GEFS/ECMWF ensemble
means and the National Blend of Models into early next week.
Adjusted the blend to a combination of the better clustered
solutions of the ECMWF and GEFS/ECMWF ensembles by next midweek.
...Weather Highlights/Threats...
Deep tropical moisture with the remains of Imelda will fuel a
threat of locally excessive rainfall. Entrainment into
mid-latitude flow ahead of an approaching upper trough and surface
frontal system will focus moisture/heavy convective storm
potential with cell training/heavy downpours from the Mid-MS
Valley to the Great Lakes/Northeast. This occurs as the amplified
upper trough ejects northeastward over the Plains this weekend,
then eastward over the Midwest/Great Lakes/Northeast early next
week.
Upstream, upper low/trough energies and precipitation potential
will reload back into an unsettling West Coast Sun/Mon. The risk
then shifts to the Southwest where moisture from Lorena is drawn
into AZ/NM as the low cuts off near CA. The combination of
monsoonal/tropical moisture will lead to a heavy rain threat
through midweek.
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
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