Saturday's Weather brought to you by CYC's Chris Bedford

Sailing Weather Forecast
2019 Verve Cup
Chicago Yacht Club
Issued 0520 CDT 10 AUGUST 2019

NOTICE: There are no warnings or advisories posted for the sailing area. Monitor latest official NOAA forecasts and warnings for update information.

SYNOPSIS: After a light morning, today is shaping up to produce a light-moderate lake breeze for much of the afternoon. This transitions into a little bit of gradient breeze later, which helps maintain the wind through the afternoon and into the evening. Hopefully making the most of today’s sailing breeze, as tomorrow looks to get more complicated. Although winds will be OK tomorrow, a higher chance of showers and thunderstorms may make conditions more challenging.

This morning’s weather map shows that the center of high pressure has moved from west of Chicago last night to northern/central Indiana this morning. The gradient is nearly slack, but showing a SW drift in the circulation around the western side of the high. Low pressure is over the upper plains and moving slowly east. This low will be significant in tomorrows forecast. For today its main impact will be to increase cloud cover somewhat which may have the feedback of shading and slightly tamping down the thermal component.

Light SW winds this morning are forecast to diminish to light and variable. A wait while the lake breeze get going in the late morning or mid-day. Once established, the lake breeze should be light-moderate for the afternoon.

SW 5-10 at first this morning. Becoming light and variable or calm late morning. Then a patchy onshore wind from the E will develop mid- day, backing ENE and building to around 10 knots in the afternoon.

SEAS: Less than 1 ft. Chop up to 1 ft this afternoon, possible 1-2 ft later afternoon/evening.

WEATHER: Area of middle and high clouds will be overspreading Chicago from the northwest this morning. Some breaks of sun are expected later morning into the afternoon, but some broken cloud cover is expected all day. Cumulus will develop onshore on the lake breeze convergence front late morning, pushing inland during the afternoon.

TEMPERATURES: Upper-60sF this morning, warming to upper-70sF late this morning, then slight cooling on the lake breeze.


HEDGE: 1) Forecast Confidence: AVERAGE.
Models are in good agreement today and I used a model consensus to develop the forecast table above.

2) The SW wind this morning is not expected to hold. Today’s sailing breeze will be lake breeze from the E/ENE.

3) Incoming middle and high clouds may cause some problems for this forecast. It is important to get a bit of heating inland this morning/early afternoon to initiate and build thermal component. However the cloud may cause shading that will limit the thermal and could tamp down or at least slow down the sea breeze.

4) Generally speaking, the thicker and more persistent cloud cover is this morning, the slower the transition to lake breeze will be AND the lighter that breeze will be in the afternoon.

5) If we get the lake breeze turn as forecast, then watch for left- trending breeze on the initial build/fill. Oscillating direct most of the afternoon, but a right rend may initiate in the later afternoon as some gradient starts to get in the mix.

Tomorrow is going to be a tricky day. Low pressure will be west of Chicago, generating clouds, showers, and thunderstorms. This weather is expected to move across the area in a couple “waves” through the day. Moderate to possibly fresh SE/S gradient is forecast ahead of the low. Incoming showers and thunderstorms will cause variable winds, possible wind gusts and abrupt shifts.
AM: SSE/SE 13-17 chance of gusting 20.
MID_DAY: Becoming unstable around possible showers/thunderstorms mid- day.
PM: SE/SSE 13-17. Variable again later afternoon around more possible showers and thunderstorms.

SEAS: Rougher. 1-3 ft.

WEATHER: More clouds than sun. Chance of showers and thunderstorms in the morning through mid-day. A break early afternoon, then more showers and thunderstorms possible again mid-/late-afternoon.

TEMPERATURES: Humid. Upper-60sF warming to Low-80sF