My National Weather Service-Chicago colleagues have issued A FIRE WEATHER WATCH for the GREATER CHICAGO AREA in effect from 11am to 7pm Wednesday.

The combination of STRONG WINDS, UNSEASONABLE WARMTH, SUNSHINE AND LOW RELATIVE HUMIDITIES (as low as 20-25%)–all of which are to be present under sunny skies Wednesday–will create a situation in which any fire outdoors can spread quickly.

Care in the disposal of smoking materials and holding off on outdoor burning reduced the threat of fire going out of control.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

A Fire Weather Watch means that critical fire weather conditions

are forecast to occur. Listen for later forecasts and possible

Red Flag Warnings.

7TH RAIN-FREE DAY IN CHICAGO—SUMMER LEVEL WARMTH ARRIVES AND IS TO HOLD INTO SATURDAY—WARMEST WEDNESDAY & THURSDAY

TEMPS SUBDUED SEVERAL DEGREES BY INCREASED CLOUD COVER FRIDAY AND SATURDAY—CHANGE TO COLDER WEATHER SUNDAY & MONDAY–COULD EVEN INCLUDE A FEW SNOWFLAKES SUN NIGHT/MONDAY–WARMING RESUMES LATER NEXT WEEK

Chicagoans are able to throw open the windows with the arrival of the warmest weather here in the near 7-months since last September. Temps have warmed steadily–from 49 Friday to 62 Saturday, 68 Sunday, 71 Monday and prospects for a 78-deg high Tuesday.

April 13th has been the average date for the first 80-deg high temp in Chicago. That’s Thursday’s date this week and means the predicted 80-deg highs Wed and Thu are occurring about on time based on recent climatology. Not since Sept have back to back 80-deg temps occurred in the city.

CLICK TO VIEW SLIDESHOW OF WEDNESDAY’S CONDITIONS:

  • WEDNESDAY’S PREDICTED HIGH TEMPS
  • PREDICTED WEDNESDAY HIGH TEMP DEPARTURES FROM NORMAL showing Chicago highs will come in MORE THAN 20-deg ABOVE NORMAL
  • The Wednesday afternoon predicted surface weather map projects A TIGHT PRESSURE GRADIENT–the source of powerful wind gusts topping 30 mph—Wednesday afternoon. The tightly spaces isobars (i.e. line of equal barometric pressure) indicate an atmosphere primed to produce strong winds. This forecast map is to verify at 4pm CDT Wednesday.
  • Here’s a forecast of potential peak wind gusts the next two days indicate some gusts could top 40 mph in the warmer hours of the day.
  • RELATIVE HUMIDITIES predicted at 2 p.m. CDT Wednesday

CLICK TO VIEW SLIDESHOW OF THE DEVELOPING PATTERNS:

  • Tuesday satellite image courtesy of CIRA/RAMBB shows clouds well south and north of Chicago.
  • Tuesday afternoon temps
  • 24 hour temp change through 3pm Tuesday indicating the broad area over which temps have increased compared to afternoon readings Monday.
  • The GUSTY “SW” WINDS indicated here are overcoming ANY lake cooling.
  • The Tuesday afternoon surface weather map.
  • The closely spaced isobars indicate a TIGHT PRESSURE GRADIENT which is driving the gusty “SW” winds which have topped 30 mph Tuesday afternoon
  • PROJECTED PEAK WIND GUSTS the next two days indicated some 40 mph wind gusts are a good bet from the southwest–on Wednesday in particular.
  • UPPER AIR ANALYSIS at the 500 mb./18,000 ft. level showing the DOME OF WARM AIR developing over the Lower 48 which has forced the storm-carrying jet stream well to the north of the Midwest.
  • Closer view of the developing warm air dome beneath which temps have surged to July levels in Chicago
  • PREDICTED TEMP DEPARTURES over the coming 5 days illustrating the extent of ABOVE NORMAL TEMPS
  • COOLER WEATHER TAKES HOLD SUNDAY and MONDAY–and this projection of the average temp departures for Days 5 to 10 which looks at the temp trend heading into next week.
  • Projected TEMP DEPARTURES from Days 1 to 5 per the National Weather Service GFS ENSEMBLE MODEL
  • Projected TEMP DEPARTURES from Days 1 to 5 per the National Weather Service GFS ENSEMBLE MODEL
  • FORECAST TEMP DEPARTURES for DAYS 6 to 10
  • TEMP DEPARTURES FOR DAYS 11 to 15
  • PRECIP PROBABILITIES SATURDAY
  • PRECIP PROBS Saturday night
  • PRECIP PROBS Sunday
  • Here’s the SEASONAL PER CENT OF NORMAL SNOWFALL
  • AVERAGE DATES OF THE LAST 32-DEG TEMPS courtesy of the NOAA Midwestern Regional Climate Center
  • HERE’S SNOW ON THE GROUND as of 7am CDT Tuesday morning. The melting of a snow pack measured as deep at 2 ft. across the Upper Midwest is producing river rises and some flooding in the region’s NORTH WOODS
Cloud coverage Wednesday and Thursday will be quite limited allowing maximum sunshine and warming. Only 3 to 7% of the sky may see clouds Wednesday and 2 to 9% Thursday.  By contrast, cloud coverage will increase to 53 to 56% of the sky Friday and closer to 70% Saturday when the Chicago area is to see its next chance of rain.

Interestingly, 2023 ranks as the wettest year to date in 151 years of weather records–yet prospects for unseasonable warmth, low relative humidites, gusty SW winds and abundant sunshine raise the fire danger Wednesday. My NWS Chicago colleagues are issuing a FIRE WEATHER WATCH as a precautionary measure from 11am to 7pm CDT Wednesday. ANY FIRES THAT GET GOING in such a weather regime can spread quickly so avoiding outdoor burning would be a prudent move Wednesday.

All available evidence points toward a week likely to finish nearly 16-deg above normal–easily the warmest of the year thus far. And a well developed southwest wind regime is to overcome lake cooling and push warmth into area beaches. Yet, despite the warm air, water temps in southern Lake Michigan come in at 43.6-deg. That makes any move into the water for any period of time hazardous, inviting as the air temps may make that seem. Hypothermia can set in quickly and lead to real trouble for any swimmers.

CHANGE TO MUCH COOLER WEATHER DUE BY SUNDAY AND MONDAY

Models cool the atmosphere dramatically later this weekend with temp profiles which might include some flakes of snow mixed with spotty instability rain showers in the Sunday night/Monday time frame. Weather records show measurable snow (that’s 0.1″ or more) have occurred infrequently beyond this date–but it has happened. 14 of the past 81 years have seen snow fall measurably here.

HINTS WARMING–MAY RESUME AS NEXT WEEK PROCEEDS

Even though next week appears on track to produce a weekly average temp 15-deg lower than this week, there are still hints warming may occur next week with temps back to 60 from Tuesday next week forward.

Chicago’s Warmest 2023 Temperatures Yet!

Tuesday’s unseasonable warmth—including 79 in Chicago—warmest since last October 2

The warmth holds through the work week and into Saturday—with back to back 80-degree highs expected Wednesday and Thursday—first time that’s happened in the near 7 months since last September.  Normal high this time of the year is 57 degrees—so we’re in magnificent meteorological territory!

The warming is to take place with a gusty, lake-breeze-defeating “SW” wind in coming days. But strong winds, with 30+ mph wind gusts Wednesday combined with low humidities raise the potential that any fires which occur outdoors may spread. Thus a National Weather Service FIRE WEATHER WATCH goes into effect 11am Wed through 7pm Wed evening. 

Often chilly March temps may have obscured just how mild temps have been this year. 67% of days since January have produced an ABOVE NORMAL DAILY AVERAGE TEMP versus only 28% of days below normal. 
Note: Hypothermia occurs when body temperature sinks below 96°F. Hypothermia can occur in temperatures as warm as 60°F, particularly in water or if you are outside a long time and not dressed for the weather!
MUCH COOLER WEATHER is to arrive on powerful winds Sunday into Monday. Wind gusts each day may top 40 mph at time and the arrival of a chilly pool of air aloft raises the potential of some post cold frontal instability showers which could include some flakes of snow Sunday night or Monday.  While snows are hardly frequent from mid April forward, 14 of 81 years have hosted snowflakes. But temps appears poised to stage a rebound after the Sunday/Monday chill—although a rebound nearly as energetic as the current warm spell. Still, 60-deg daytime high temps become possible from Tuesday forward next week. 

RAPID WARMING IS MELTING SNOW IN THE UPPER MIDWEST PRODUCING FLOODING

It’s been a banner snow season across the North Woods region of the Midwest. But the onset of warm air is producing a rapid snowmelt raising the specter of flooding.
The National Weather Service Forecast in Duluth is warning, “Above normal temps will be releasing a near record amount of water stored in the snow pack.”
And the National Weather Service’s National Water Center says:
“Warming temperatures will continue to produce significant snowmelt through mid-week where well above normal snowpack is in place resulting in areas of minor to isolated major river flooding.
• The areal coverage of river flooding is expected to increase through the week. Locally considerable river flooding impacts may be possible.”