That warm and humid air has been pulled over the top of the leftover cooler air to the north of the warm front, triggering an increasing number of showers and thunderstorms (see College of DuPage north central US radar loop) from eastern Nebraska and northwestern Iowa into southwestern and central Minnesota during the early morning hours. The air in Kansas and Oklahoma has some dew points in the 50's or even the 60's (see yellow areas on the UCAR hourly dew point map). e early morning hours, began its wobble northwestward yesterday (see 24-hour loop of NWS WPC US surface maps). However, much warmer air is poised to the south of the warm front in South Dakota and Nebraska yesterday afternoon (line with red half-circles on the 4 PM Tuesday NWS WPC North America zoom-in map) is poised to be picked mopped up the remaining plow piles. Temperatures rebounded back into the 50's yesterday afternoon with at least Worthington breaking into the 60's (set time to 21Z on the NWS Aviation Weather Center METAR map). Warmth Giving Way to Early AM T-Storm "Blobs" I received about a dozen nice notes of concern, so thanks for your support. I had some major computer problems from last Friday through yesterday, so I apologize for the forecast absence. To view only the IFR products, check the Ceil&Vis box and uncheck all others.įor a current display of CWAs in effect, click here.Wednesday, Ap4 :20 AM Bob Weisman Meteorology Professor Saint Cloud State University Atmospheric and Hydrologic Sciences Department I (Don't) Love a Rainy Night (But Would You Rather Snow.Fri Nt Best Chance?) AIRMETs are issued for widespread IFR conditions, and Center Weather Advisories (CWA) are generally issued for LIFR conditions.įor a current display of AIRMETs in effect, click here. While in flight, listen for hazardous weather information that indicate poor conditions. To avoid landing in bad weather conditions, look at the current and forecasted weather conditions for the destination before departing. It is not uncommon for this type of fog to persist for most of the day, and is usually accompanied by stratus clouds and low ceilings.Ĭlick the image for a current map of ceiling and visibility conditions across the ZME airspace. Unlike radiation fog, the winds can continually replenish the moisture so that even sunshine cannot improve the conditions. Most of the time, this type of fog forms overnight, then dissipates the following morning after a couple hours of sunshine.Īdvection Fog This type tends to develop when moist air moves into an area (usually from a body of water such as the ocean, lake or river). In pure ground fog environments, it is not uncommon for the fog to be very shallow with low forward visibility and clear skies above. When this occurs, moisture condenses into tiny droplets, essentially forming a cloud right at the ground level. On a weather map, 100% RH is also indicated when the air temperature is the same as the dewpoint temperature. Radiation Fog Two ingredients are needed f or radiation fog to develop: Very light or calm winds, and a relative humidity of 100%. There are two types of fog that can form: Radiation Fog and Advection Fog In general, ceiling heights and resulting safety fall into four different categories: Many aircraft and pilots are rated for various ceiling minimums and thus use their rating and experience to determine whether or not it is safe to fly. In the Southeast US, they tend to be a greater hazard during the wintertime, when temperatures are colder and freezing levels are much lower than during the summer. Ceilings are a common problem when precipitation occurs.
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