The City of Ann Arbor outdoor warning siren system test will be conducted today, Tuesday June 11, at 1 pm.
The city has 22 siren locations, which are tested every second Tuesday of the month, March through November, with one-minute of steady wailing.
Washtenaw County’s outdoor warning sirens are usually tested at noon the first Saturday of each month March through September. Due to a continuing threat of severe weather, today’s test has been cancelled.
Washtenaw County Emergency Operations Center: “SIREN TEST CANCELLED. SEVERE STORMS WITH 60 MPH WINDS, ISOLATED TORNADOES AND URBAN FLOODING ARE POSSIBLE TODAY/TONIGHT.”
Per NWS Detroit’s latest hazardous WX outlook:
Expect storms to develop and move through SE MI at 30 mph throughout the evening and into tonight. The risk of strong storms continues overnight.
There is a slight chance of any storms that develop being severe; a 15% chance of damaging wind or large hail; and a small chance of isolated tornadoes.
Storms have developed over the western third of southern lower MI and are slowly moving west; additional development could occur in other areas of southern MI with little warning. Storms in northern Indiana tracking west-northwest are strong and at times severe; these might hit A2 or pass south of us.
Ann Arbor is included in MD 903, which stretches from Nashville approximately up to Port Huron.
Within this area, thunderstorm activity is expected to increase throughout the afternoon, with organized clusters or lines of strong-to-severe storm are expected to form. These storms would bring strong winds and possibly damaging hail, along with the lightning and heavy rain that is expected with any strong storm system. We might (40% probability) see a severe thunderstorm watch for the area issued shortly.
MESOSCALE DISCUSSION 0903
NWS STORM PREDICTION CENTER NORMAN OK
1233 PM CDT FRI MAY 31 2013
AREAS AFFECTED...FAR SE MI...WRN OH...FAR SE IND...CNTRL/ERN KY...N
CNTRL TN
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 311733Z - 311900Z
CORRECTED FOR AFFECTED AREA
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...THUNDERSTORM COVERAGE WILL INCREASE THROUGH THE AFTERNOON.
LOOSELY ORGANIZED STRONG TO SEVERE STORM CLUSTERS WILL BE CAPABLE OF
PRODUCING STRONG WINDS AND MARGINALLY SEVERE HAIL.
DISCUSSION...SCATTERED THUNDERSTORMS WERE DEVELOPING IN AREA OF
INCREASING ASCENT AHEAD OF UPPER SHORTWAVE IMPULSE MOVING ACROSS THE
MID-MS VALLEY EARLY THIS AFTERNOON. POCKETS OF STRONGER HEATING
ACROSS SE MI/WRN OHIO INTO PARTS OF CNTRL AND ERN KY HAS ALLOWED FOR
WEAK DESTABILIZATION WITH SBCAPE VALUES AROUND 1000 J/KG. BULK SHEAR
VALUES AROUND 20-40 KTS SHOULD LEAD TO AT LEAST SOME ORGANIZED
CLUSTERS/LINE SEGMENTS. THE BEST LOCATIONS FOR THIS TO OCCUR WOULD
BE ACROSS FAR SW MI /WHERE STORMS ARE CURRENTLY ONGOING/ INTO PARTS
OF IND AND OHIO WHERE DEEP LAYER SHEAR IS A BIT STRONGER THAN
FURTHER SOUTH INTO KY/TN. HOWEVER...A REMNANT MCV EVIDENT IN
SATELLITE IMAGERY MOVING ACROSS THE LOWER OHIO VALLEY MAY SERVE TO
FOCUS STRONGER THUNDERSTORM DEVELOPMENT THIS AFTERNOON ACROSS KY
DESPITE WEAKER DEEP LAYER SHEAR. STRONG WINDS AND MARGINALLY SEVERE
HAIL WILL BE THE MAIN THREATS WITH ANY ORGANIZED STORMS THAT CAN
DEVELOP TODAY. TRENDS WILL BE MONITORED FOR POSSIBLE WW ISSUANCE.
..LEITMAN/HART.. 05/31/2013
ATTN...WFO...RLX...CLE...MRX...JKL...ILN...DTX...LMK...IWX...
GRR...OHX...IND...PAH...
LAT...LON 35778565 35868653 36028704 36568743 37298738 37958704
40308554 42028418 43628266 43478203 42768135 41478167
39918246 37318371 36258449 35798517 35778565Expect thunderstorms across the area this afternoon and evening; warm, moist, unstable air across SE MI will contribute to storms developing quickly and without much warning. (We’ve seen this already today with this line of storms.) The principal risks with these storms are probable damaging wind gusts and large hail, with a slight risk of isolated tornadoes. Also expect locally heavy rainfall. We have a slight risk of some of these storms becoming severe, particularly in the late afternoon.
Washtenaw County emergency operations center: “SEVERE STORMS WITH 65 MPH WINDS, ONE INCH HAIL, ISOLATED TORNADOES AND URBAN FLOODING ARE POSSIBLE TODAY AND TONIGHT.”
NWS Detroit:
THERE IS A CHANCE OF THUNDERSTORMS OVER ALL OF SOUTHEAST MICHIGAN TODAY WITH THUNDERSTORMS LIKELY TONIGHT. THERE IS A SLIGHT RISK OF SEVERE WEATHER BOTH TODAY AND TONIGHT...BUT WITH THE BEST CHANCE BEING DURING THE WARMEST PART OF THE LATE AFTERNOON INTO EARLY EVENING. THE PRIMARY HAZARD WILL BE HEAVY DOWNPOURS AND DAMAGING WIND GUSTS NEAR 60 MPH...BUT HAIL UP TO 1 INCH IS ALSO POSSIBLE AS STORMS MOVE FROM SOUTHWEST TO NORTHEAST AT 30 MPH. WARM AND HUMID AIR WILL REMAIN IN PLACE OVER LOWER MICHIGAN TODAY THROUGH TONIGHT. THE POTENTIAL FOR SEVERE WEATHER WILL BE TIED TO AFTERNOON TEMPERATURE TRENDS AFTER SHOWERS AND THUNDERSTORMS DURING THE MORNING EITHER DISSIPATE OR EXIT THE AREA. THIS IS EXPECTED TO RESULT IN JUST SCATTERED COVERAGE UNTIL LATER TONIGHT WHEN CLUSTERS OF ACTIVITY WILL MOVE IN FROM THE MIDWEST AND OHIO VALLEY. COVERAGE WILL BE GREATER BY THEN BUT INTENSITY WILL BE DECREASING DURING THE OVERNIGHT HOURS.
NWS Detroit notes that the episodic nature of these thunderstorms creates forecasting challenges in regards to exact timing. Additional reading: NWS Detroit briefing slides for today.
Today’s severe weather outlook shows us at slight risk for severe thunderstorms:
We’ve already seen one severe storm in the area, and as more storms continue to develop over the next 10 hours, some will be severe.
Our outlook today shows us at slight risk for severe convective weather; a 15% chance of large hail; a 15% chance of damaging wind; and a 2% chance of tornadoes.
Looking forward, the SPC’s thunderstorm outlook for 4-8pm shows us around a 40% risk for thunderstorms; I believe this is conservative given what we’ve already seen today. From 8pm-midnight, they show us just outside a 40% risk area, and again from midnight-8am; again, I expect thunderstorms in are area at least through midnight.
