The NWS has issued Severe Thunderstorm Watch 406, which includes Ann Arbor and extreme southeastern Michigan. (Washtenaw County is on the inner edge of the watch area, illustrated above as a blue line.) We will likely see thunderstorms this afternoon across southeastern MI as a cold front moves south from northern MI. Storm development will be fueled by the warm, very moist air that we’ve all been complaining about as the front moves through.
With any storms that develop in the area today, we can expect brief heavy rain, gusting winds, and small hail. Some storms in the area this afternoon will likely be severe. With the most severe storms expected this afternoon, we could see large hail, damaging winds, and heavy downpours. It is impossible to predict whether or when severe storms will hit downtown Ann Arbor specifically. Storm motion will be west to east.
The SPC puts us just inside the 15% risk areas for damaging winds and large hail; tornado threat today is minimal:
Our thunderstorm risk drops dramatically after 8pm today, when the front will have moved through.
Washtenaw County’s Emergency Operations Center:
THUNDERSTORMS WITH 50 MPH WINDS, HALF INCH HAIL AND URBAN FLOODING ARE POSSIBLE UNTIL 8 PM.
Severe thunderstorm watch 406 watch county notification via NWS Detroit:
WWUS63 KDTX 101631 WCNDTX WATCH COUNTY NOTIFICATION FOR WATCH 406 NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 1231 PM EDT WED JUL 10 2013 MIC091-099-115-125-147-161-163-110000- /O.NEW.KDTX.SV.A.0406.130710T1631Z-130711T0000Z/ THE NATIONAL WEATHER SERVICE HAS ISSUED SEVERE THUNDERSTORM WATCH 406 IN EFFECT UNTIL 8 PM EDT THIS EVENING FOR THE FOLLOWING AREAS IN MICHIGAN THIS WATCH INCLUDES 7 COUNTIES IN SOUTHEAST MICHIGAN LENAWEE MACOMB MONROE OAKLAND ST. CLAIR WASHTENAW WAYNE THIS INCLUDES THE CITIES OF...ANN ARBOR...CANTON...CLINTON... DEARBORN...FERNDALE...LAMBERTVILLE...LINCOLN PARK...LIVONIA... MARYSVILLE...MONROE...NOVI...PONTIAC...PORT HURON...REDFORD... ROYAL OAK...SOUTHFIELD...ST. CLAIR SHORES...STERLING HEIGHTS... TAYLOR...TEMPERANCE...TROY...WARREN...WATERFORD AND WESTLAND. $$ LCZ422-423-460-LEZ444-110000- /O.NEW.KDTX.SV.A.0406.130710T1631Z-130711T0000Z/ THE NATIONAL WEATHER SERVICE HAS ISSUED SEVERE THUNDERSTORM WATCH 406 IN EFFECT UNTIL 8 PM EDT THIS EVENING FOR THE FOLLOWING AREAS THIS WATCH INCLUDES THE FOLLOWING ADJACENT COASTAL WATERS ST. CLAIR RIVER DETROIT RIVER LAKE ST. CLAIR MICHIGAN WATERS OF LAKE ERIE FROM DETROIT RIVER TO NORTH CAPE MI $$ KURIMSKI ---- GROUPJUL132013 WASHTENAWMI
And the full text of this watch from the SPC:
SEL6 URGENT - IMMEDIATE BROADCAST REQUESTED SEVERE THUNDERSTORM WATCH NUMBER 406 NWS STORM PREDICTION CENTER NORMAN OK 1235 PM EDT WED JUL 10 2013 THE NWS STORM PREDICTION CENTER HAS ISSUED A * SEVERE THUNDERSTORM WATCH FOR PORTIONS OF EASTERN INDIANA FAR NORTHERN KENTUCKY SOUTHEAST LOWER MICHIGAN MUCH OF OHIO WESTERN PENNSYLVANIA PARTS OF THE NORTHERN WEST VIRGINIA PANHANDLE LAKE ERIE * EFFECTIVE THIS WEDNESDAY AFTERNOON AND EVENING FROM 1235 PM UNTIL 800 PM EDT. * PRIMARY THREATS INCLUDE... NUMEROUS DAMAGING WIND GUSTS LIKELY WITH A FEW SIGNIFICANT GUSTS TO 75 MPH POSSIBLE SEVERAL LARGE HAIL EVENTS WITH A FEW VERY LARGE HAIL EVENTS TO 2 INCHES IN DIAMETER POSSIBLE A FEW TORNADOES POSSIBLE THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 105 STATUTE MILES NORTH AND SOUTH OF A LINE FROM 35 MILES WEST SOUTHWEST OF MUNCIE INDIANA TO 30 MILES EAST OF ERIE PENNSYLVANIA. FOR A COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU6). PRECAUTIONARY/PREPAREDNESS ACTIONS... REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY DO PRODUCE TORNADOES. && DISCUSSION...THUNDERSTORMS ARE EXPECTED TO CONTINUE TO INTENSIFY AND BECOME MORE NUMEROUS OVER PARTS OF LOWER MI AND IND THIS AFTERNOON...SPREADING EASTWARD ACROSS OH AND INTO PA BY EARLY EVENING. VERY UNSTABLE CONDITIONS COMBINED WITH FAVORABLE WINDS ALOFT WILL PROMOTE A RISK OF DAMAGING WINDS IN THE STRONGEST STORMS. AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT TO 2 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 65 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 550. MEAN STORM MOTION VECTOR 27035. ...HART
THUNDERSTORMS ARE POSSIBLE TODAY WITH THE STRONGEST STORMS APPROACHING SEVERE LIMITS. THE PRIMARY HAZARD WILL BE DAMAGING WIND GUSTS NEAR 50 MPH...BUT HALF INCH HAIL AND HEAVY RAINFALL ARE ALSO POSSIBLE. STORM MOTION WILL BE WEST TO EAST AT 40 MPH. THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE AT ANY TIME OF THE MORNING THROUGH THE AFTERNOON...BUT WITH GREATER CHANCES TOWARD THE OHIO BORDER BY EARLY AFTERNOON. A COLD FRONT WILL MOVE SOUTHWARD FROM NORTHERN LOWER MICHIGAN DURING THE MORNING TO SOUTH OF THE OHIO BORDER BY LATE AFTERNOON AND BRING AND END TO THE STORM POTENTIAL.