Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 423 AM EDT Tue Jul 16 2013 Valid 12Z Tue Jul 16 2013 - 12Z Thu Jul 18 2013 ...Heat wave over the East will expand into the Plains by the middle of the week... ...Cool and wet weather will continue from western Texas into New Mexico along with the potential for flash flooding... An anomalous upper level low which has been slowly tracking west across the southern Plains is forecast to continue drifting westward, reaching the southern Arizona/New Mexico border by Thursday morning. the upper low is forecast to weaken, but the disturbance will combine with deep moisture emanating from the Gulf of Mexico via low level southeasterly flow to produce locally heavy rain with the possibility of flash flooding from west Texas into Arizona and New Mexico. While not everyone will see heavy rainfall from this system, most will see at least light rain with lots of cloud cover which will help to limit high temperatures to the 70's and 80's across the region, well below mid-July averages. The other big weather story is the heat wave currently across the east. A large mid-level ridge centered over the Ohio Valley is responsible for the heat wave, and the ridge is forecast to expand westward through Wednesday. This will have the effect of increasing high temperatures past the 90 degree mark throughout most of the central and northern Plains by Wednesday. Scattered afternoon and evening thunderstorms could bring some temporary relief from the heat in and around the Great Lakes and Appalachians, but widespread heavy rain is not anticipated. Looking north, a cold front will slowly push across the north-central U.S., but with little southward progress. The front will serve as a focus for thunderstorm activity with a possibility of severe storms, according to the Storm Prediction Center, extending across a good portion of the northern U.S. near the Canadian border for Wednesday. Otto Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php