Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
300 AM EDT Thu Oct 10 2019
Valid 12Z Sun Oct 13 2019 - 12Z Thu Oct 17 2019
...Pattern Overview and Guidance/Uncertainty Assessment...
Deep upper low over the Arrowhead of Minnesota on Sunday will lift
toward James Bay by Tuesday as broad cyclonic flow remains
anchored over the eastern half of the CONUS. A front entering the
Pacific Northwest will dive through the Plains Tuesday then lift
into the Northeast next Wed/Thu. At that time, another front (or
pair of fronts) may push into Washington/Oregon.
The 12Z ECMWF offered the best clustering near the 18Z GEFS mean
and 12Z ECMWF ensemble mean, followed by the GFS/UKMET/Canadian to
varying degrees Sun-Tue. Timing differences have been the main
challenge over the past few days but ensemble spread continues to
decrease in concert with lead time. By next Wed/Thu, higher
uncertainty spreads out of the northeast Pacific,
augmented/perpetrated by the extratropical transition of current
Super Typhoon Hagibis. Ensemble blend sufficed for now given the
multiple players upstream.
...Weather Highlights/Threats...
Rainfall will focus around the front in the Southeast Sun-Tue as
it stalls and then lifts back northward. Questions remain as to
how much precipitation can be realized but precipitable water
values should rise to about 1.50" (or +1 to +1.5 sigma). Also at
question is the amount of Pacific moisture that may stream
eastward across the Mexican plateau, which usually limits its
influence. As the western front reaches the central states, added
dynamics should increase coverage/intensity from the lower
Mississippi Valley eastward Wed/Thu.
Colder than average temperatures will linger over the northern
Plains with only gradual moderation by the middle of next week.
Fresh snow cover will likely limit maximum temperatures to the
middle 30s which is about 20-25 degrees below average over the
Dakotas. The South will see above average temperatures Mon/Tue
ahead of the front but trending cooler by next Wed/Thu.
Fracasso
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