US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
353 PM EDT Wed Apr 24 2019
 
Valid Saturday April 27 2019 - Wednesday May 01 2019
 
Hazards:
- Heavy snow across portions of the Great Lakes and the Upper Mississippi Valley, Sat-Sun, Apr 
27-Apr 28.
- Heavy precipitation across portions of the Great Lakes and the Upper Mississippi Valley, Sat-Sun, 
Apr 27-Apr 28.
- Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, and the Southern 
Plains, Mon-Tue, Apr 29-Apr 30.
- Heavy rain across portions of the Central Plains, the Middle Mississippi Valley, the Lower 
Mississippi Valley, and the Southern Plains, Wed, May 1.
- Heavy rain across portions of the Great Lakes and the Upper Mississippi Valley, Sat-Sun, Apr 
27-Apr 28.
- Heavy snow across portions of the Central Rockies, the Central Plains, the Northern Plains, and 
the Northern Rockies, Sat-Wed, Apr 27-May 1.
- Heavy snow across portions of the Northern Plains, Sun-Wed, Apr 28-May 1.
- Flooding possible across portions of the Great Lakes and the Southern Plains.
- Flooding occurring or imminent across portions of the Lower Mississippi Valley, the Northern 
Plains, the Tennessee Valley, the Great Lakes, the Northern Rockies, the Middle Mississippi Valley, 
the Northeast, the Northern Great Basin, the Upper Mississippi Valley, the Southern Plains, and the 
Ohio Valley.
- Flooding likely across portions of the Northern Great Basin.
- High winds across portions of the Aleutians, Mon, Apr 29.
 
Detailed Summary:

The medium range period will begin with a front moving off the East Coast on Saturday as a low 
pressure system is forecast to develop and move quickly eastward across the northern Plains. The 
ECMWF has come into better agreement with the GFS in depicting a more compact and well-defined 
structure associated with this system. It appears that temperatures will be cold enough to support 
wintry precipitation for the northern portion of the system. The relatively quick motion of this 
low means that the transition from rain to snow should be relatively sharp. On the other hand, the 
rapid forward motion and a compact storm size also mean a lower predictability. Indeed, models 
continue to show noticeable run-to-run variability regarding this system. A relatively narrow strip 
of heavy snow and heavy precipitation is indicated on the WPC hazards chart across the upper 
Midwest into lower Michigan for the weekend (Apr 27-28), with an area of heavy rain to the south.

As the aforementioned low pressure system moves off the New England coast Sunday night, the next 
upper-level trough is forecast to move across the northwestern U.S. Colder air filtering in behind 
this system should increase the chance of snow across the northern Rockies by early next week. Some 
of the snow could also spread eastward into the northern Plains. Uncertainty noticeably increases 
toward the middle of next week as model solutions begin to diverge. The GFS, in particular, 
continues to show a low pressure wave intensifying along a stationary front across the central 
Plains by Tuesday into Wednesday. This would strengthen the upslope flow toward the central Rockies 
and would result in a snowfall event from Colorado into the central High Plains. However, this 
scenario is not supported by the ECMWF. The latest WPC hazards chart shows a heavy snow area along 
the eastern slopes of the northern Rockies as well as the Bighorn Mountains of Wyoming where wintry 
precipitation is most probable as indicated on the WPC Winter Weather Forecast charts.

Farther to the south, the interaction of the western U.S. upper trough with the stationary front 
across the central Plains should bring an increased chance of heavy rain across the central Plains 
into the Midwest on Monday and Tuesday (Apr 29-30). The heavy rain may shift farther southward into 
the southern Plains by Wednesday as a low pressure wave could develop along the stationary front.

Over Alaska, a strong low pressure system is forecast to edge toward the western portion of the 
Aleutians islands on or around Monday (Apr 29) bringing increasing southerly winds to the region.

Kong