Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
301 AM EDT Mon Sep 30 2019
Valid 12Z Thu Oct 03 2019 - 12Z Mon Oct 07 2019
...Heavy rain threat diminishes over the central Plains late this
week but could return by next Sunday into Monday...
...Record warmth continues for the Southeast into Thursday...
...Overview and Guidance/Uncertainty Assessment...
Relatively zonal/progressive flow is expected to be in place
across the CONUS to start the medium range period as an upper
trough initially across the Rockies lifts out into the central
U.S. The heavy rain threat should be diminishing along a wavy
surface front across the central Plains. Meanwhile, a less
vigorous upper trough is forecast to move through the Pacific
Northwest and the northern Rockies late this week before moving
into the Plains by this weekend and into next Monday. There are
some indications for heavy rain to develop over the central Plains
these couple of days as a low pressure system could form.
Global models show fairly good agreement on the synoptic pattern
evolution across the U.S. through Day 5 (Sat). There is a trend
toward a more robust development of a frontal wave over the
Northeast on Thursday and Friday, especially the GFS. By Sunday
and Monday, potential exists for another frontal wave to develop
in the Midwest. Therefore, more of the ensemble means are used to
handle the uncertainty for this system. The WPC medium range
forecast was a general consensus of the 12Z ECMWF and the 18Z GFS
together with their ensemble means. Only a small percentage of
the 18Z GFS is used for days 6 and 7 since the frontal wave
appears to be too strong.
...Weather Highlights/Threats...
The heavy rain threat near a frontal boundary across the central
Plains should begin to diminish on Thursday as the main dynamics
of the system shifts further northeast into New England ahead of a
developing frontal wave. Localized heavy rain is possible across
portions of New England on Thursday into early on Friday as the
frontal wave could strengthen before it moves offshore.
Meanwhile, a vigorous upper trough is expected to bring scattered
mixed precipitation across the northern Rockies on Friday. By the
weekend, the upper trough should begin to inject moisture from the
Gulf and increase the threat of heavy over the central Plains
ahead of a frontal system.
Record warmth over the Southeast is expected to continue into
Thursday before a gradual cooling trend sets in. Overall,
temperatures will become less extreme across the country as we
head toward the weekend.
Meanwhile, deep-layer easterly flow will bring an influx of
tropical moisture across southern Florida and into the Gulf of
Mexico this week north of a tropical low.
Kong
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