Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
410 AM EDT Tue May 21 2013

Valid 12Z Tue May 21 2013 - 12Z Thu May 23 2013

...Widespread severe weather and heavy rainfall threat are expected along
a slow-moving cold front migrating through the Nation's mid-section...

...Windy...cool and wet conditions are in the forecast for the pacific
Northwest and northern Rockies... and

...Scattered showers and thunderstorms will continue over Florida and up
into the Mid-Atlantic region...

A cold front edging eastward through the Nation's mid-section will
continue to be a big weather maker during the short range period. 
Anomalous amounts of moisture surging northward out of the Gulf...combined
with strong dynamics aloft...should produce organized convection along and
ahead of the slow-moving frontal boundary. Heavy rainfall may accompany
the more intense showers and thunderstorms with severe weather expected
from the Southern Plains to Upper Midwest/Upper Great Lakes. A moderate
risk of severe storms will be located today and tonight for northeast
Texas into the Ark-La-Tex and southern Ozarks. Please refer to the Storm
Prediction Center for the latest information and updates for severe
weather. Farther north...moisture wrapping around a slow-moving
upper-level low anchored in the upper Mississippi Valley and a stationary
front draped to the east of this low will be the focus for light to
moderate rainfall and embedded thunderstorms from the northern Plains to
the Great Lakes and into southern New England during the next few days. 

A vigorous upper vortex settling in over the Pacific Northwest will slowly
push a cold front inland through the West and northern Rockies. Moderate 
moisture...instability and cold air aloft will produce scattered showers
and a few thunderstorms. Windy conditions along the front should enhance
precipitation amounts along the windward slopes of the higher terrain.
With conditions noticeably cooler behind the front...temperatures could
briefly fall below freezing at elevation with the possibility of snow
showers in the Washington and Oregon Cascades.

Across the East and southeast...weak energy aloft and warm advection
should keep conditions ripe for scattered showers and thunderstorms over
Florida and northward into the Mid-Atlantic states.

Gerhardt/Vojtesak

Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php