Tracking a Significant Spring Storm Impacting the Central U.S. This Week

A significant storm will track across the central U.S. and into the Great Lakes through Thursday. Heavy snow and blowing snow is expected from the northern Plains into the Upper Midwest. Further south, severe thunderstorms are expected from the southern Plains into the Midwest as well as a multi-day excessive rain and flooding event Wednesday through Saturday from the Ozarks into the Ohio Valley. Read More >

X-Band

A frequency band of microwave radiation in which radars operate.

X-Ray Background

In solar-terrestrial terms, a daily average background X-ray flux in the 1 to 8 angstrom range. It is a midday minimum designed to reduce the effects of flares.

X-Ray Burst

In solar-terrestrial terms, a temporary enhancement of the X-ray emission of the sun. The time-intensity profile of soft X-ray bursts is similar to that of the H-alpha profile of an associated flare.

X-Ray Flare Class

In solar-terrestrial terms, rank of a flare based on its X-ray energy output. Flares are classified by the order of magnitude of the peak burst intensity (I) measured at the earth in the 1 to 8 angstrom band as follows:

Class	Intensity (in Watts/m²)
B	I < 10^-6
C	10^-6 <= I < 10^-5
M	10^-5 <= I < 10^-4
X	I >= 10^-4

X-Rays

Very energetic electromagnetic radiation with wavelengths intermediate between 0.01 and 10 nanometers (0.1-100 Angstroms) or between gamma rays and ultraviolet radiation. Essentially all X-Rays from space are absorbed in the Earth's upper atmosphere.

XBT

Expendable Bathythermograph

XCITED

Excited

XCPT

Expecting

XPC

Expect

XSEC

Cross Section

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