Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 352 AM EDT Tue Apr 03 2018 Valid 12Z Tue Apr 03 2018 - 12Z Thu Apr 05 2018 ...Expect severe weather and flash flooding risks today from the Ohio Valley to the lower Mississippi Valley... ...Heavy snow expected for the Upper Midwest and Great Lakes... ...More rounds of snow and rain for the Pacific Northwest and northern Rockies... A surface low will strengthen as it lifts north and east from the central Plains to the Upper Great Lakes today. Thunderstorms firing off along the lifting warm front will move across the Ohio Valley--some of which could lead to heavy rainfall. A slight risk of flash flooding is possible with this activity. These thunderstorms will continue throughout the day from the Ohio Valley, which is expected to get the most amount of rainfall, and into the Northeast. Meanwhile, the cold front sweeping eastward with the strengthening surface low will sharpen as it moves from the Mississippi Valley into the western Tennessee and Ohio Valleys. Deep southerly flow will transport copious amounts of moisture ahead of the front as instability also increases. A line of thunderstorms will organize along and ahead of the front extending from the western portions of the Ohio Valley into Southeast Texas. Some of these storms could become severe especially from southwest Ohio to southeast Arkansas. Thus, the Storm Prediction Center has put this area under an enhanced risk. On Wednesday, the line of thunderstorms that will bring severe weather potential will continue moving eastward toward New England to the central Gulf Coast. The cold front will move quickly offshore by Wednesday afternoon. With limited instability in place, these thunderstorms are not expected to be severe. However, a marginal risk is in place from the Mid-Atlantic to parts of the Southeast. All precipitation will exit the East Coast by late Wednesday night--with showers still progressing southward over South Florida by Thursday morning. For more information regarding the severe weather aspect of this system, please see their products (www.spc.noaa.gov). As the surface low lifts northward toward the Great Lakes, Arctic air will plunge southward. Snow will sweep throughout the northern Plains. By Tuesday afternoon, heavy snowfall will move from the Upper Midwest to the Upper Great Lakes. Northern Michigan can expect upwards of a foot of snow! Winter storm warnings and winter weather advisories are in effect from the northern Plains to the Upper Great Lakes. Snow will begin to taper off across the Great lakes by Wednesday and ending by Wednesday night. However, lingering lake effect snow showers is expected on Thursday. Upper level energy will slide across the Pacific Northwest late Tuesday night into Wednesday morning as southwest flow at the surface will bring an increase in moisture throughout the region. Consequently, rain and higher elevation snow is expected all day and continuing into Thursday morning. Snow will fall along the Cascades and northern Rockies on Wednesday with snow increasing across the northern Rockies by Thursday. Reinhart Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php