US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
325 PM EST Mon Dec 23 2019
 
Valid Thursday December 26 2019 - Monday December 30 2019
 
Hazards:
- Heavy precipitation across portions of southern California, Thu, Dec 26.
- Heavy precipitation across portions of the southern to central Rockies, and into the southern to 
northern High Plains, Fri, Dec 27.
- Heavy precipitation across portions of the higher elevations of central Arizona, Thu-Fri, Dec 
26-Dec 27.
- Heavy rain across portions of the southern to central Plains, Fri, Dec 27.
- Heavy rain across portions of the central Plains into the Midwest, Sat-Sun, Dec 28-Dec 29.
- Heavy rain across portions of the southern Appalachians, Sun, Dec 29.
- Much above normal temperatures from across the Midwest to the lower Great Lakes, Thu, Dec 26.
- Flooding possible across portions of the Southeast.
- Flooding occurring or imminent across portions of the Pacific Northwest and the Northern Plains.
- Heavy precipitation across much of the Alaska Panhandle, Thu, Dec 26 and Sat-Mon, Dec 28-Dec 30.
- Heavy precipitation across portions of the southern Alaska, Sun-Mon, Dec 29-Dec 30.
- Much below normal temperatures across portions of mainland Alaska, Fri-Mon, Dec 27-Dec 30.
 
Detailed Summary:

The main concern for significant weather impacts during the medium-range period (Dec 26-30) will be 
highly dependent on the eventual track and intensity of a low pressure system across the central 
U.S. by next weekend into Monday.  Models are in good agreement on the track and evolution of a 
cut-off low moving eastward across the Desert Southwest late this week.  As the low gets ready to 
move off the southern Rockies into the Plains, model solutions diverge greatly as the ECMWF, UKMET, 
and CMC largely keep the low separate from the northern stream near the Canadian border.  On the 
other hand, the GFS decidedly interacts and then phases the low with the northern stream, resulting 
in a major cyclone impacting the central U.S. toward the Great Lakes this weekend.  This scenario 
is considered an outlier since this is not supported by the majority of the deterministic solutions 
nor by the ensemble means.  Given the uncertainty, a conservative approach is taken in depicting 
hazards areas on the WPC hazards map.  Nonetheless, a good chance snow mountain snow appears more 
certain over the higher elevations of southern California, central Arizona and parts of the central 
and southern Rockies late this week.  Heavy rain will also be possible across the lower elevations. 
 By the weekend, heavy rain is anticipated for the central Plains to the Midwest.  It is possible 
that the northern edge of the heavy rain areas will be in the form snow or mixed precipitation.  By 
next Monday, wintry precipitation could be moving across the Northeast but the uncertainty is 
currently too high to warrant a heavy precipitation area there.  Prior to the arrival of this low 
pressure system, much above normal temperatures are expected for the Midwest into the lower Great 
Lakes on Thursday, where high temperatures are forecast to be more than 20 degrees above normal.

In Alaska, a series of deep low pressure systems is expected to deliver stormy weather through much 
of the medium-range period near the coastal areas of southern Alaska.  Heavy mountain snows are 
expected along the higher terrain of southern Alaska and the Alaskan Panhandle.  A cooling trend 
will bring much below normal temperatures across the interior sections of central and southern 
Alaska.  The Aleutians will be impacted by a large cyclone through the weekend into Monday but 
winds are forecast to be below storm force, and thus, no high wind areas are depicted for that 
region.

Kong