Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EDT Tue Mar 10 2020 Valid 00Z Wed Mar 11 2020 - 00Z Fri Mar 13 2020 ...First wave of heavy rain across the Southwest through Wednesday morning will be followed by the second wave later on Thursday... ...A developing low pressure system will bring unsettled weather across much of the Mississippi and Ohio Valley on Thursday... The weather pattern across the U.S. is getting more active as the week progresses. First of all, much needed rain is currently spreading into the southwestern U.S. ahead of an occluded cyclone approaching from the eastern Pacific. This first wave of moisture is bringing occasional heavy rain across southern California into the Desert Southwest, where the risk for flash flooding is marginal to slight through tonight. By Wednesday, the occluded system is forecast to become more diffused as it edges toward the coast. The bulk of the moisture will then move further inland across Arizona with a slightly lower chance for heavy rain on Wednesday. However, a second wave of moisture is expected to move toward the Desert Southwest from northern Mexico later on Thursday. This will once again increase the potential of flash flooding Thursday evening as the chance of heavy rain increases area-wide. Meanwhile, a cold front will bring mainly light rainfall amounts for the East Coast through tonight. Another disturbance will spread wintry precipitation across the upper Midwest into the Great Lakes through Wednesday. Farther west, a stronger upper-level trough will spread a period of mountain snow down the northern Rockies through Wednesday. This upper-level trough is forecast to interact with a nearly stationary front across the Mid-South to result in the development of a low pressure system in the Mid-Mississippi Valley on Thursday. It appears that rain and thunderstorms will expand eastward across the Deep South on Thursday as rain chances increase and expand eastward farther north toward the Ohio Valley. Meanwhile, the upper Great Lakes will be cold enough to support wintry precipitation on Thursday as the low pressure system intensifies. Kong Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php