Very hot, humid air over southern lower MI is likely to contribute to some isolated thunderstorm development across the area this afternoon into the night. These storms will have the potential for very heavy rainfall, and they will move slowly (15-20mph southeast), which could cause localized flooding. Storms are not expected to be severe; they are expected to carry very little hail or damaging wind risk, and virtually no tornado potential.
Also keep in mind the heat advisory in effect today: drink plenty of water, do not leave children or pets in cars, and stay indoors as much as is possible. (Heat advisory text from NWS Detroit)
It is impossible to predict specifically whether any storms will hit Ann Arbor. As those at the Townie Street Party saw Monday night, it’s possible for the skies around downtown to look very ominous with isolated thunderstorms, but for us to receive only a few drops of rain, especially with storms which are nearly stationary. Storms this afternoon will be similarly very localized.
Looking forward, we can expect basically the same weather Thursday; and stronger severe storms are possible Friday and Friday night as a cold front comes south into the area, bringing slightly cooler temperatures for us, though Saturday will still be warm and storms are still possible Saturday.
Here’s today’s hazardous weather outlook:
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 408 AM EDT WED JUL 17 2013 MIZ047>049-053>055-060>063-068>070-075-076-082-083-180900- MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-SHIAWASSEE-GENESEE-LAPEER- ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-WASHTENAW-WAYNE-LENAWEE-MONROE- 408 AM EDT WED JUL 17 2013 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF SOUTHEAST MICHIGAN. .DAY ONE...TODAY AND TONIGHT A HEAT ADVISORY IS IN EFFECT TODAY AND TONIGHT AS HEAT INDEX VALUES REACH OR EXCEED 100 DEGREES DURING THE DAY AND ONLY FALL INTO THE 70S TONIGHT. PLEASE SEE THE LATEST FORECASTS AND STATEMENTS FOR DETAILS. ISOLATED THUNDERSTORMS ARE POSSIBLE TODAY. SEVERE WEATHER IS NOT ANTICIPATED BUT STORMS WILL HAVE THE POTENTIAL TO PRODUCE VERY HEAVY RAINFALL. STORMS WILL MOVE SLOWLY TO THE SOUTHEAST AT 15 TO 20 MPH. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY A HEAT ADVISORY REMAINS IN EFFECT THROUGH THURSDAY AS WARM TEMPERATURES AND HIGH HUMIDITY CONTINUE TO AFFECT THE AREA. THE ADVISORY MAY NEED TO BE EXTENDED INTO FRIDAY. THE PROLONGED PERIOD OF HOT DAYTIME TEMPERATURES AND WARM AND MUGGY NIGHTS WILL INCREASE STRESS ON THE BODY. THUNDERSTORMS WILL BE POSSIBLE THURSDAY THROUGH FRIDAY NIGHT ACROSS ALL OF SOUTHEAST MICHIGAN...AND SOUTH OF I-94 ON SATURDAY. THE GREATEST POTENTIAL FOR SEVERE WEATHER WILL BE FRIDAY AFTERNOON THROUGH LATE FRIDAY EVENING AS A STRONG COLD FRONT DROPS SOUTHWARD THROUGH THE AREA. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY AND TONIGHT. $$
And, for reference, the heat advisory text:
URGENT - WEATHER MESSAGE NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 329 AM EDT WED JUL 17 2013 ...HOT AND HUMID CONDITIONS PERSISTING THROUGH AT LEAST THURSDAY... .A STRONG HIGH PRESSURE SYSTEM IS RESULTING IN AN EXTENDED STRETCH OF HOT AND HUMID CONDITIONS. VERY HUMID CONDITIONS COMBINED WITH TEMPERATURES RISING INTO THE LOW TO MID 90S WILL RESULT IN HEAT INDICIES OF 100 TO 105 DEGREES TODAY AND AROUND 100 DEGREES ON THURSDAY. IN ADDITION...OVERNIGHT RELIEF FROM THE HEAT WILL BE MINIMAL AS HUMID CONDITIONS PERSIST AND LOWS HOLD PREDOMINATELY IN THE MID 70S. MIZ047>049-053>055-060>063-068>070-075-076-082-083-172000- /O.CON.KDTX.HT.Y.0001.000000T0000Z-130719T0400Z/ MIDLAND-BAY-HURON-SAGINAW-TUSCOLA-SANILAC-SHIAWASSEE-GENESEE- LAPEER-ST. CLAIR-LIVINGSTON-OAKLAND-MACOMB-WASHTENAW-WAYNE- LENAWEE-MONROE- INCLUDING THE CITIES OF...MIDLAND...BAY CITY...BAD AXE... SAGINAW...CARO...SANDUSKY...OWOSSO...FLINT...LAPEER... PORT HURON...HOWELL...PONTIAC...WARREN...ANN ARBOR...DETROIT... ADRIAN...MONROE 329 AM EDT WED JUL 17 2013 ...HEAT ADVISORY REMAINS IN EFFECT UNTIL MIDNIGHT EDT THURSDAY NIGHT... HAZARDOUS WEATHER... * HIGH HUMIDITY AND TEMPERATURES IN THE LOW TO MID 90S RESULTING IN AFTERNOON HEAT INDICIES OF 100 TO 105 DEGREES TODAY AND AROUND 100 DEGREES ON THURSDAY. * LITTLE OVERNIGHT RELIEF WITH HUMIDITY PERSISTING AND LOWS PREDOMINATELY IN THE MID 70S. IMPACTS... * HEAT EXHAUSTION OR HEAT STROKE IS POSSIBLE IN EXTREME CASES WHERE NO PROTECTIVE ACTION IS TAKEN. * MUSCLE CRAMPS AND SUN BURNS ARE ALSO POSSIBLE PRECAUTIONARY/PREPAREDNESS ACTIONS... * A HEAT ADVISORY MEANS THAT A PERIOD OF HOT TEMPERATURES IS EXPECTED. THE COMBINATION OF HOT TEMPERATURES AND HIGH HUMIDITY WILL COMBINE TO CREATE A SITUATION IN WHICH HEAT ILLNESSES ARE POSSIBLE. DRINK PLENTY OF FLUIDS...STAY IN AN AIR-CONDITIONED ROOM...STAY OUT OF THE SUN...AND CHECK ON RELATIVES AND NEIGHBORS. CHILDREN AND PETS SHOULD NEVER BE LEFT UNATTENDED IN VEHICLES UNDER ANY CIRCUMSTANCES. * PREPARE...PLAN...AND STAY INFORMED. VISIT HTTP://GO.USA.GOV/RR8 && $$