Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 310 AM EST Tue Dec 14 2021 Valid 12Z Tue Dec 14 2021 - 12Z Thu Dec 16 2021 ...There is a Slight Risk of excessive rainfall over parts of Southern California through Wednesday morning... ...Heavy snow over the Sierra Nevada Mountains and snow over the Cascades and Northern Rockies... ...Critical Fire Weather risk for parts of the Southern High Plains... On Tuesday, a plume of moisture will stream moisture into Southern California and then move into Mexico overnight Tuesday into Wednesday. The moisture will produce coastal rain and higher elevation snow over California. The snow lingers over the Northern Rockies and Great Basin through Wednesday. The rain and snow will end over Southern California by Wednesday morning. The rain will be heavy at times. Therefore, the WPC has issued a Slight Risk of excessive rainfall over parts of Southern California through Wednesday morning. The associated heavy rain will create mainly localized areas of flash flooding, with urban areas, roads, and small streams the most vulnerable. The heavy snow will end over the Pacific Northwest overnight Tuesday. The snow will result in reduced visibility and hazardous driving conditions. A front will move onshore over the Northwest overnight Wednesday, bringing a new round of rain and higher elevation snow to the Pacific Northwest and Northern California on Wednesday. Snow will expand into parts of the Northern Rockies and Great Basin overnight Wednesday into Thursday. Meanwhile, a developing area of low pressure over the Northern High Plains, move eastward to the Middle Mississippi Valley by Wednesday evening, then move into Central Ontario by Thursday. Ahead of the front, temperatures will be 20 to 30 degrees above average over parts of the Plains into the Mississippi Valley. In addition, many record-high temperatures are forecast over parts of the Southern Plains into the Upper Midwest. The high temperatures over the Southern/Central High Plains and gusty wind will produce conditions favorable to fire weather. Therefore, the SPC has issued a Critical Risk Fire Weather threat across much of the Texas panhandle Tuesday into Wednesday due to warm temperatures, low humidity, and increased wind (15-20mph). With warmer temperatures, moisture will start to stream northward over the Southern Plains/Lower Mississippi Valley extending as far north as the Great Lakes overnight Tuesday. As a result, showers and thunderstorms will develop over parts of the Southern Plains and Lower Mississippi Valley by Tuesday. In addition, overnight Tuesday rain will begin to develop over parts of the Great Lakes and Western Ohio Valley. Rain will expand into parts of the Northeast by Wednesday evening, with snow developing over the higher elevations of Northern New England. As the rain moves eastward into Maine, cold air trapped in valleys will lead to pockets of freezing rain by Thursday morning. Also, as the system moves into the Upper Midwest, thunderstorms and snow will develop over parts of the Northern Central Plains by Wednesday evening. Overnight Wednesday, the showers and thunderstorms will increase in intensity. Therefore, the SPC has issued a Slight Risk of severe thunderstorms over parts of the Upper/Middle Mississippi Valley Wednesday into Thursday morning. The hazards associated with these thunderstorms are frequent lightning, severe thunderstorm wind gusts, hail, and a few tornadoes. Ziegenfelder Graphics are available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php