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Red line is temperature. Green line is dew point. The solid black line that rises to the top right indicates the freezing level from the ground upward. Precipitation falls when the temperature and dew point line are touching at the bottom of the chart (the ground). Snow falls when the temperature and dew point lines stay to the left of the solid black freezing line. When you see the temperature line make a triangular shape bulge to the right of the freezing line, this indicates melting in that layer. If the raindrop continues to fall and the temperature line moves back to the left of the freezing line, the raindrop will refreeze. If the warm layer is high enough above the ground, the precipitation will be sleet, but if the triangular bulge happens near the ground, then rain will re-freeze as freezing rain.

No need for your BF to DoorDash a yardstick

This is it exactly... 2" per hour at 15:1 adds up real quick...

I’m comparing the ICON to the ICON. Its algorithms didn’t change from 18z to 0z.

17.1 with DP of 2. WC of 6 Brrrrr

Banter

24 here but dropping fast

So you've seen them?

here you go nw baltimore! you can learn with me! •1y ago A skew-T log-P diagram (commonly referred to as a skew-T chart) is a thermodynamic diagram used in meteorology to plot vertical profiles of temperature, dew point, and wind data in the atmosphere. It is a crucial tool for analyzing atmospheric stability and predicting weather phenomena like thunderstorms, cloud formation, and severe weather events. Key Components of a Skew-T Chart: Pressure Levels (y-axis, logarithmic scale): The vertical axis represents pressure in millibars (mb), decreasing upward (standard surface pressure is around 1000 mb, and it decreases to about 100 mb at the tropopause). These pressure levels correspond to different altitudes, with higher pressure representing lower altitudes. 2. Temperature (skewed x-axis): The horizontal axis is skewed at a roughly 45° angle to the right, representing temperature in degrees Celsius. Lines running diagonally from the lower left to the upper right are isotherms (constant temperature lines). Temperatures generally range from around -80°C to +40°C, depending on the altitude and the time of year. 3. Dry Adiabats (diagonal lines curving upward to the right): These lines represent the rate at which dry air cools as it rises. Dry air cools at approximately 10°C per kilometer as it rises in the atmosphere. If a parcel of air ascends with no condensation occurring, it will follow these lines. 4. Moist Adiabats (curved lines curving upward to the left): These lines show the cooling rate of saturated air (air with 100% humidity), which cools more slowly due to the release of latent heat when water vapor condenses. These lines start at similar angles to the dry adiabats but curve more sharply to the left with increasing altitude. 5. Mixing Ratio Lines (sloped lines nearly parallel to the isotherms, but slightly curved): These lines show the mixing ratio, or the amount of water vapor in grams per kilogram of dry air. They are important for determining relative humidity. They typically slope from the bottom left to the top right and can help identify the dew point at different altitudes. 6. Isobars (horizontal lines): These are lines of constant pressure, running horizontally across the chart. They help in reading the corresponding pressure levels for any given altitude. 7. Wind Barbs: Plotted on the side of the chart (often to the right), wind barbs show wind speed and direction at various altitudes. Each barb represents a different wind speed, with longer flags indicating higher wind speeds. 8. Parcel Path (convective parcel ascent): A key application of the skew-T is following the path of a rising air parcel. You can assess whether it is stable or unstable by comparing the air temperature profile to the parcel’s temperature. If the parcel's temperature remains warmer than the surrounding air, it is unstable and will continue to rise, indicating potential convective activity (like thunderstorms). 9. Lapse Rates: Environmental Lapse Rate (ELR) is the actual rate at which temperature decreases with altitude. This is shown by the temperature profile. Dry Adiabatic Lapse Rate (DALR) and Moist Adiabatic Lapse Rate (MALR) can be inferred by following the dry and moist adiabat lines, respectively. 10. Dew Point Curve: The dew point curve, which represents the temperature at which the air becomes saturated, is plotted alongside the temperature profile but typically lies to the left of it. The gap between the temperature and dew point curves indicates humidity; a smaller gap means higher humidity, while a larger gap means drier air. Interpretation of Stability: Stable Atmosphere: If the temperature profile decreases slowly with height or increases (inversion), a rising air parcel will cool faster than the surrounding environment, causing it to sink back down. This inhibits convection. Unstable Atmosphere: If the environmental temperature decreases more rapidly than the dry or moist adiabatic lapse rate, a rising air parcel will remain warmer than the surrounding air, causing it to continue rising, which is conducive to storm development. Conditionally Unstable Atmosphere: The atmosphere is stable for dry parcels but unstable for saturated parcels. If a parcel rises and becomes saturated, it could trigger convection. Common Applications: Cloud Formation: Where the parcel's temperature path crosses the dew point, clouds are likely to form at that level (this is known as the Lifting Condensation Level (LCL)). CAPE and CIN: CAPE (Convective Available Potential Energy) represents the area between the parcel's ascent curve and the environmental temperature curve where the parcel is warmer than the environment, indicating instability. CIN (Convective Inhibition) is the opposite, representing stable areas where rising air is cooler than the surrounding environment. Wind Shear: By observing the change in wind barbs with altitude, you can assess vertical wind shear, which is crucial in severe weather development. By understanding these components, you can analyze a skew-T chart to assess atmospheric stability, identify potential weather hazards, and interpret vertical wind patterns.

14F and dropping, It’s brutal outside.

Anyone seeing RGEM anywhere? Doesn’t seem to be running on pivotal.

Definitely; the thump will be fun regardless. Would need 5 hours of 2”/hr to hit 10, the low max of NWS forecast. Definitely seems aggressive to me, not judging - I certainly wouldn’t want to be the one making any calls for NJ / LI / NYC, just noting.

They change anything?

Another thing is usually if you are near the sleet/snow line the reality is there will be flips back and forth between snow and sleet and some mixing at the same time rather than simply hours of only sleet on one side of the line and only snow on the other. The models don't really capture this nuance I don't think.

ICON looks good!

Down to 24.1/5.9

26.2 F IMBY on the river

Cold as a witches titty out

oh shit thanks for the reminder!

16. Overperformer.

Down to 18

16

Yeah it was a touch better for us. At this point, I don’t think we’re going to see huge changes but 25-50 miles or 1-2 extra hours before sleet can mean 2-4” more of snow.

I know that a difference of a tenth of an inch could make things worse or better, but we are really splitting hairs at this point. There will be power outages, treacherous roads, and super cold temperatures, especially early in the week. Folks should prepare for the high-end amounts (which I believe they have) and just hope it underperforms.

I think part of it is that the front end thump should have some high ratios and people in here assume that since sleet shows up that the whole storm is warm now. The onset is going to be high ratio snow and could pile up more quickly than people think. .