Presentation on theme: "National Weather Service Spring 2014 Flood Update March 28, 2014 Craig Schmidt, Service Hydrologist."— Presentation transcript:
National Weather Service Spring 2014 Flood Update March 28, 2014 Craig Schmidt, Service Hydrologist
Winter Sixth coldest in Minnesota history – five consecutive months below normal 50 days below zero at MSP; 77 days below zero at DLH 100+ inches of snow at DLH; most of the state 1-2 feet above normal; even more in northern WI IN SHORT… we havent dealt with a winter like this in over 30 years.
Flood Outlook Summary Overall, the spring flood threat over Minnesota remains near historical average…with a catch Mississippi slightly above average St. Croix above average Minnesota R average to below average In the Wisconsin basins (Eau Claire and Chippewa), the threat is rising to above average as we hold onto snow and move further into spring. MOST IMPORTANT POINT: the true threat lies in how April temperatures and rainfall hit us. Were holding onto a lot of water in some basins later into the spring than we normally do. This makes us more susceptible to snowmelt combining with warm spring rain as we move later into the spring.
Background: Snowfall Good portion of MN above normal this season, well above normal north and into WI Water Year to date (inches) Percent of normal
Background: Snowfall Snow Depth Snow mostly gone southwest of I-94; still plenty to melt further north and east.
Background: Precipitation Snow Depth change in last week Snow depth decreased over southern and central parts of area; actually increased far north March 19 March 27
Background: Snowfall Modeled Snow Water Equivalent (SWE) Mostly gone over southwest half…still 1-2 inches around the Twin Cities; 3-5 inches in northern WI and MN.
Soil Moisture (0-72 inch layer) Near to above average over much of the state, except Minnesota River basin and parts of the far north. Once thaw occurs, there is some room for soil to absorb water
Frost Depth: Generally 20 to 40 inches over the area, except 10 to 20 inches around the Twin Cities. Much deeper still under pavement and roads. River Ice: Thick layers of ice on most rivers; breakup jams will be a concern Other Factors
Flood outlooks posted in the coming slides include known conditions up to that point, and use climatology as the forecast weather conditions. Significant deviations in our weather pattern from climatology would result in different results. Thus, it will pay to watch our weather patterns closely through April… Flood Outlook Climatologically based
For St. Cloud…a 30% chance of minor flooding, just above historical average. Near average chance of moderate flooding (12%). Flood Outlook – Mississippi at St. Cloud
For St. Paul…historically average chance of minor flooding, about 30 percent. Flood Outlook – Mississippi at St. Paul
Less than 5 percent chance of flooding, well below average Flood Outlook – Minnesota at Mankato
For Stillwater… about a 60 percent chance of reaching flood stage, well above the 25 percent average. About a 40 percent chance of reaching moderate flood level, 20 percent chance of hitting major flood level. Flood Outlook – St. Croix at Stillwater
For the Eau Claire… about a 45 percent chance of reaching flood stage, above the 25 percent average. About a 20 percent chance of reaching moderate flood level, just above average. Flood Outlook – Eau Claire River at Fall Creek
For the Chippewa (WI)… about a 75 percent chance of reaching flood stage, above the 45 percent average. About a 30 percent chance of reaching moderate flood level, above the 15 percent historical normal. Flood Outlook – Chippewa River at Durand WI
Threat Factors Main things to watch for that would increase flood threat… Extended period of well above normal temperatures (60s, for instance), staying above freezing at night Moist air melts snow much faster than dry air, so look for dewpoints well above freezing when the air is warm Any major rain or snow event that adds a significant amount of water to wet snow (2 inches of water or more) Things to watch for that keep the flood threat manageable… Temps in the 30s and 40s, dropping below freezing at night Below to average precipitation – light to moderate snow or light rain is fine Dry air – dewpoints in the teens and 20s. So, with that said…whats the forecast?
Weather Outlook Short term forecast – through the next week Melting over the weekend, then cooler again. Another storm on the horizon early next week. Potential significant snow north of the Twin Cities
Weather Outlook Seven Day Precipitation forecast One to two inches of liquid possible over much of the area by the end of the week; snowpack will increase again over northern/central MN and northern WI
Weather Outlook 8–14 Days – April 4 through 10 Temperatures: below normal trend continues through at least early April
Weather Outlook 8–14 Days – April 4 through 10 Precipitation: equal chances of above, below, or normal
Temps: Cool trend expected to continue thru April Precipitation (not shown): no clear indication Weather Outlook 30 days – April
Temps: Cool trend expected to continue thru April, then moderate Precipitation (not shown): no clear indication Weather Outlook 90 days – April through June
Weather forecast effect on flood threat Next weeks storm could be crucial…pay close attention to forecasts on precipitation amounts next week. Likely to add to the snowpack to the northern MN and WI basins, further priming the threat for later in the spring. It could enhance short term runoff around the Twin Cities and in central WI. After that…temperatures remain cool, melting slows again. This could be a beneficial trend to reduce flood threat. Our flood threat is becoming more susceptible to late spring rains, as peak runoff will be later than normal. Stay tuned… NOTE: RFC daily forecasts will start in early April; some maybe by this weekend if forecasts show significant rises.
Yeah, we can dream… For the Dreamers… 10 month forecast – Dec/Jan/Feb next winter
*Webpages Weather info: River infohttp://water.weather.gov/ahps2/index.php?wfo=mpx River info: Text version of this outlook: by=MSP More Info? How to reach us…
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