Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
303 PM EDT Wed Aug 14 2019
Valid 12Z Sat Aug 17 2019 - 12Z Wed Aug 21 2019
...Overview and Guidance/Predictability Assessment...
Models and ensembles agree at larger scales that broad troughing
over the northern CONUS becomes more zonal late this weekend as
upper ridging rebuilds again near the New Mexico/Texas border.
Broad cyclonic flow will persist across southern Canada with an
active pattern there. Great inconsistency remains with the
development and location of troughs and lows starting Saturday
night with the 06Z/00Z GFS bring much more progressive with a
trough over the eastern Canadian Prairies that becomes a closed
low over Quebec by Monday than the 00Z ECMWF which has slowed over
recent runs and features more of a trough than closed low over
Quebec which is also seen in the 00Z UKMET/CMC. Another area of
differences between the the GFS and ECMWF/UKMET/CMC is with strong
shortwave troughs rounding a deep low over the Northwest
Territories which results in a low solution farther inland with
the GFS than the other models. Therefore lower inclusion of the
GFS was made than usual.
Heavy rain potential along a stalled front near the eastern Gulf
coast to the lower Mississippi Valley into Monday. To the north,
shortwave passages along a cold front will focus weekend
convection from the Upper Midwest/Great Lakes eastward to the Ohio
Valley and Northeast/Mid-Atlantic early-mid next week.
In this pattern of less troughing and more ridging, temperatures
will be above normal in the Southwest/Southern Plains and Midwest
to Northeast for Day 3-7 the period. Daily temperature records
look limited to the high minimums over the southeast this weekend,
expanding to the northeast early next week.
Additional 3-7 Day Hazards information can be found on the WPC
medium range hazards chart at:
- Heavy rain across portions of the Middle Mississippi Valley,
Sat, Aug 17.
- Heavy rain across portions of northern Florida, Sat-Sun, Aug
- Flooding occurring or imminent across portions of the Northern
- Excessive heat across portions of the Southwest, Tue-Wed, Aug
- Excessive heat across portions of the Lower Mississippi Valley
and the Southern Plains, Sat-Mon, Aug 17-Aug 19.
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation, winter weather outlook probabilities
and heat indices are at: