US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
322 PM EDT Tue May 07 2019
 
Valid Friday May 10 2019 - Tuesday May 14 2019
 
Hazards:
- Heavy rain across portions of the Lower Mississippi Valley, the Tennessee Valley, the 
Mid-Atlantic, the Southern Appalachians, the Southeast, and the Southern Plains, Fri-Sun, May 
10-May 12.
- Heavy rain across portions of the Lower Mississippi Valley and the Southern Plains, Tue, May 14.
- Heavy rain across portions of the Mid-Atlantic, Sat-Sun, May 11-May 12.
- Flooding possible across portions of the Central Plains, the Lower Mississippi Valley, the 
Northern Plains, the Great Lakes, the Middle Mississippi Valley, the Upper Mississippi Valley, the 
Southern Plains, and the Ohio Valley.
- Flooding occurring or imminent across portions of the Central Plains, the Lower Mississippi 
Valley, the Northern Plains, the Great Lakes, the Middle Mississippi Valley, the Upper Mississippi 
Valley, the Southern Plains, and the Ohio Valley.
- Flooding likely across portions of the Central Plains.
- Much below normal temperatures across portions of the Southern Rockies, the Central Plains, and 
the Southern Plains, Fri-Sat, May 10-May 11.
- Heavy precipitation across portions of the Alaska Panhandle and southeastern mainland Alaska, 
Fri, May 10.
 
Detailed Summary:

It'll be a fairly active pattern across the southern half of the contiguous U.S. during this 
forecast period. The equatorward progress of a strong cold front crossing the central and eastern 
states will slow significantly Friday into Sunday as a result of predominantly southwesterly flow 
at the mid and upper levels. The front is forecast to extend from the southern Mid-Atlantic states 
west-southwestward through the lower Mississippi Valley and southeastern Texas and will be the 
primary focusing mechanism for rainfall through this weekend. Periods of organized showers and 
thundershowers will develop as a result of short wave energy ejecting out of a slow-moving upper 
low in the southwestern U.S. combining with a very moist and unstable air mass. Similar to 
yesterday, the model consensus shows the highest totals (3-5 inches+) from eastern/southeastern 
Texas across central/northern Louisiana into central Mississippi Friday and Saturday where moisture 
and instability will be maximized. Organized rainfall will extend eastward along the front into the 
southern Appalachians and expand into the central mid-Atlantic states during Sunday in response to 
surface low development in advance of an amplifying northern stream short wave trough.

Behind this front, a cool Canadian air mass will sink southward through the southern Plains and 
Rockies, with temperatures (especially daytime highs under cloudy skies) upwards of 15-25 degrees 
below normal expected Friday into Saturday. Temperatures across this region will moderate by Sunday 
and Monday, but still remain below average.

Over the southwestern U.S., the aforementioned upper low will have plenty of Pacific moisture 
associated with it. A series of embedded short waves rotating through the low will support a large 
area of showers and possible thundershowers from central California eastward into New Mexico from 
Friday through Sunday. Isolated rainfall totals across this region may be in excess of .5 to 1 inch 
any of those days, but large model QPF differences made pinpointing the most favorable location(s) 
quite difficult. As a result, we opted not to include a hazard area. As this low progresses 
eastward, it will again encounter deeper Gulf moisture returning into Texas and bring the potential 
for more widespread heavy rainfall to parts of Texas and Louisiana Monday and Tuesday. Confidence 
at this time range is low, but given recent rainfall, did opt to introduce a heavy rainfall hazard 
over eastern Texas across northern Louisiana for Tuesday where some guidance indicates totals in 
excess of several inches.

In Alaska, a surface low quickly deepening in the western Gulf of Alaska Thursday will bring the 
threat for moderate-heavy precipitation along sections of the south-central mainland as it pushes 
inland Friday. Models indicate the main threat will be be focused from Seward eastward along the 
coast to near Yakutat. As was the case yesterday, this is a fairly marginal threat case, with 
liquid equivalent totals forecast by model guidance mostly in the 1-2 inch range. However, we still 
want to highlight the system as the associated strong mid-upper level dynamics could result in 
locally high precipitation rates, especially across favored orographic areas.

Klein