667
FXUS63 KDTX 211421 AAA
AFDDTX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1021 AM EDT THU OCT 21 2021
UPDATE
AS OF 1020 AM EDT...CURRENT FORECAST LARGELY REMAINS ON TRACK WITH
MAIN UPDATES TO ACCOUNT FOR LATEST POP TRENDS IN HI-RES GUIDANCE LATE
THIS MORNING THROUGH THE AFTERNOON HOURS. SURFACE LOW PRESSURE
CONTINUES TO LIFT NORTHEAST INTO NORTHERN LOWER LATE THIS MORNING,
WITH TRAILING COMPACT MIDLEVEL CIRCULATION NEAR SOUTHERN LAKE
MICHIGAN. SOUTHEAST MICHIGAN CURRENTLY RESIDES IN A RELATIVE DRY SLOT
BETWEEN THE DEPARTING CONVECTIVE ACTIVITY FROM THIS MORNING
ACCOMPANYING THE SURGE IN THETA-E ALONG THE INITIAL LEAD FRONTAL
BOUNDARY, AND A STRONGER COLD FRONT THAT WILL ACCOMPANY THE
AFOREMENTIONED MIDLEVEL CIRCULATION AND STRONG DCVA APPARENT VIA
WATER VAPOR IMAGERY.
BREAKS IN CLOUD COVER MOVING THROUGH LOWER MICHIGAN SHOULD ALLOW FOR
A FEW DEGREE BOOST IN HIGH TEMPERATURES TODAY, WITH MOST AREAS
SOLIDLY SEEING A SHOT AT MID 60S READINGS. THE CLEARING WILL ALSO
HELP ENHANCE ALREADY EFFICIENT INBOUND BOUNDARY LAYER MIXING
POTENTIAL WITH WESTERLY WIND GUSTS INCREASING THIS AFTERNOON TO
AROUND 25 MPH, WITH 30 MPH GUSTS NOT OUT OF THE QUESTION. AS THE
MIDLEVEL CIRCULATION SPINS ALONG THE I-96 CORRIDOR LATER THIS
AFTERNOON INTO THIS EVENING, THE ACCOMPANYING INCREASED DYNAMIC
FORCING COUPLED WITH A RUSH OF COLDER AIR ALOFT WILL ALLOW FOR
ANOTHER ROUND OF BLOSSOMING SHOWERS ESPECIALLY ACROSS NORTHERN AREAS,
BUT WOULD NOT BE SURPRISED TO SEE A FAIRLY WIDESPREAD COVERAGE OF
NUMEROUS SHOWERS IN THE 3PM-8PM TIMEFRAME. INCREASING 3-6 KM LAPSE
RATES (APPROACHING 7 C/KM) AND A FEW HUNDRED J/KG CAPE NOTED ON THE
12Z KAPX UPSTREAM SOUNDING WILL ALSO PROVIDE THE OPPORTUNITY FOR SOME
ISOLATED THUNDERSTORMS AS WELL. LOW FREEZING LEVELS (DECREASING
BELOW 8 KFT), MAY SUPPORT SOME SMALL HAIL POTENTIAL AS WELL.
PREV DISCUSSION
ISSUED AT 634 AM EDT THU OCT 21 2021
AVIATION...
DEEP MOISTURE AXIS WITH ACCOMPANYING AREA OF SHOWERS AND
THUNDERSTORMS WILL SHIFT EAST OF THE SOUTHEAST MICHIGAN AIRSPACE AT
12Z. SOME POTENTIAL REMAINS FOR PERIODIC MVFR CONDITIONS YET THIS
MORNING, BUT RECENT OBSERVATIONAL TRENDS SUGGEST PRIMARILY LOWER VFR
GOING FORWARD EARLY TODAY. MODERATELY MIXED WEST-SOUTHWEST FLOW
WILL SUPPORT GUSTY CONDITIONS INTO THE AFTERNOON - 20 TO 25 KNOTS AT
TIMES. ADDITIONAL POCKETS OF SHOWERS POSSIBLE, PARTICULARLY AS THE
TRAILING COLD FRONT SURGES SOUTHEAST THIS EVENING. IMPROVING
MOISTURE DEPTH ALONG THE FRONTAL ZONE AGAIN BRINGS SOME REDUCTION IN
CLOUD BASES EARLY TONIGHT, FAVORING MORE WIDESPREAD MVFR CONDITIONS.
WIND SHIFT TO NORTHWESTERLY EXPECTED WITH THE FRONTAL PASSAGE.
DTW THRESHOLD PROBABILITIES...
* MEDIUM IN CEILINGS AT OR BELOW 5000 FEET THROUGH TONIGHT.
PREV DISCUSSION...
ISSUED AT 410 AM EDT THU OCT 21 2021
DISCUSSION...
AN UNSETTLED DAY IS IN STORE AS LOW PRESSURE CROSSING LAKE MICHIGAN
THIS MORNING CONTINUES ITS TREK EASTWARD ACROSS THE STATE. A PLUME
OF HIGHER THETA-E IS SPREADING ACROSS SOUTHEAST MICHIGAN AT PRESS
TIME AS THE SYSTEM'S SOUTHWESTERLY LOW-LEVEL JET BECOMES DIRECTED
OVERHEAD. COINCIDENT WITH THE INCREASING MOISTURE IS THE ARRIVAL OF
STRONGER SYNOPTIC SCALE LIFT IN THE FORM OF HEIGHT FALLS WITH THE
INBOUND DYNAMIC UPPER WAVE AND ASCENT TIED TO THE LEFT EXIT REGION
OF THE UPPER JET. THIS IS COMING TOGETHER TO RESULT IN THE
CONVECTIVE SHOWERS AND STORMS NOTED IN REGIONAL RADAR MOSAIC THIS
MORNING. THIS ACTIVITY WILL TRACK ACROSS THE FORECAST AREA OVER THE
NEXT SEVERAL HOURS WITH BRIEF DOWNPOURS AND LIGHTNING THE MAIN
THREATS. THE NEAR-SURFACE LAYER REMAINS STABLE AT THIS TIME SO
STORMS WILL REMAIN MAINLY ELEVATED, BUT CAN'T RULE OUT SOME GUSTY
WINDS TO 40 MPH IN ANY STRONGER STORMS. A TRAILING COLD FRONT SWEEPS
ACROSS THE STATE FROM WEST TO EAST DURING THE LATE MORNING AND
USHERS ANY LINGERING SHOWERS/STORMS OUT.
AFTER THE MID-MORNING ROUND, MOST AREAS WILL SEE A RELATIVE LULL IN
PRECIP FOR THE LATE MORNING INTO EARLY AFTERNOON AS WE ENTER A POST-
FRONTAL PSEUDO WARM SECTOR. LOW-LEVEL LAPSE RATES STEEPEN
CONSIDERABLY WITHIN THE GROWING MIXED LAYER WITH WEST WIND BECOMING
GUSTY TO AROUND 25 MPH OR SO. HIGH TEMPERATURES DURING THIS PERIOD
ARE FORECAST TO REACH THE LOWER TO MID 60S. MEANWHILE, A STRONGER
COLD FRONT IS DRAGGED SOUTHWARD ACROSS NORTHERN LOWER MICHIGAN THIS
AFTERNOON AS THE LOW DEPARTS ACROSS LAKE HURON. ANOTHER ROUND OF
LIGHTER SHOWERS IS LIKELY TO ACCOMPANY THIS SECOND FRONT THIS
EVENING WITH ANY LINGERING SHOWERS TAPERING OFF TONIGHT AS MUCH
COOLER AIR SETTLES IN. TEMPERATURES FALL TO THE 30S ACROSS MOST OF
THE AREA BY FRIDAY MORNING WITH METRO DETROIT AND LOCATIONS ALONG
THE LAKESHORES CLINGING ON TO THE LOWER 40S.
A DRY BUT MOSTLY CLOUDY DAY IS EXPECTED FRIDAY AS COOLER AIR
CONTINUES TO SETTLE IN. 850MB TEMPS BOTTOM OUT IN THE -2 TO -5 C
RANGE WHICH POINTS TO HIGH TEMPS IN THE LOWER TO MID 50S. COLD
ADVECTION CEASES BY FRIDAY AFTERNOON BUT THE COOL AIR MASS LARGELY
STAYS PUT THIS WEEKEND AS A BROAD UPPER LOW BECOMES ESTABLISHED OVER
JAMES BAY. THERE WILL BE SEVERAL SPOKES OF SHORTWAVE ENERGY THAT
PIVOT AROUND THE CYCLONIC FLOW OVER THE COURSE OF THE WEEKEND WITH
THE MOST SUBSTANTIAL HEIGHT FALLS CURRENTLY PROGGED TO SWING THROUGH
DURING THE DAY ON SATURDAY. THIS LOOKS TO TRIGGER SOME LAKE ENHANCED
SHOWERS THAT MAINLY FOCUS OVER THE THUMB AS THE WAVE ENHANCES
NORTHWEST FLOW OVER THE LAKES.
REBOUNDING HEIGHTS IN THE WAKE OF THE WAVE WILL CUT OFF ANY SHOWERS
AND MAY ALLOW AN AREA OF WEAK HIGH PRESSURE TO DEVELOP OVER THE
REGION SATURDAY NIGHT. MODELED RH FIELDS DEPICT SOME REDUCTION IN
THE CLOUD FRACTION AS WELL, WHICH WOULD ALLOW FOR A RADIATIVE
COMPONENT TO AID IN TEMPERATURES FALLING TO THE LOWER TO MID 30S
ACROSS MUCH OF THE AREA. NOT EXPECTING A WIDESPREAD FROST AT THIS
POINT, BUT RURAL AREAS IN THE TRI-CITIES AND THUMB REGIONS WILL
STAND THE BEST CHANCE FOR SOME SUB-FREEZING READINGS SUNDAY MORNING.
THE NEXT CHANCE FOR WIDESPREAD RAIN ARRIVES LATE SUNDAY INTO MONDAY
AS A LOW PRESSURE SYSTEM TRACKS FROM THE MID-MISSISSIPPI VALLEY INTO
THE SOUTHERN GREAT LAKES.
MARINE...
A DEEPENING LOW PRESSURE SYSTEM CURRENTLY OVER THE MIDWEST WILL
TRACK EAST TODAY ALONG THE STALLED FRONT DRAPED ACROSS CENTRAL LAKE
HURON. SHOWERS WILL CONTINUE TO DEVELOP THROUGH THE DAY ALONG THIS
FRONTAL BOUNDARY WITH INCREASED COVERAGE AND THUNDERSTORM CHANCES
LATER THIS MORNING AS THE LOW SENDS A COLD FRONT EASTWARD ACROSS THE
AREA. WEST WIND WILL BECOME GUSTY ACROSS WESTERN LAKE ERIE AND LAKE
ST. CLAIR THIS AFTERNOON WHICH HAS PROMPTED SMALL CRAFT ADVISORIES
THROUGH THIS EVENING.
THE ELONGATING LOW WILL THEN EXIT TO THE EAST LATER THIS EVENING,
FORCING A STRONG COLD FRONT SOUTHWARD ACROSS THE LAKES. THIS WILL
LEAD TO STRONGER NORTH WIND GUSTING UPWARDS OF 30 KT ACROSS LAKE
HURON AND RAPIDLY BUILDING WAVE HEIGHTS ACROSS THE CENTRAL AND
SOUTHERN BASINS. SMALL CRAFT ADVISORIES HAVE BEEN ISSUED ALONG THE
NEARSHORE WATERS OF THE THUMB THIS AFTERNOON THROUGH FRIDAY MORNING.
NORTH WIND THEN TAPERS OFF ON FRIDAY AS COOLER AIR SETTLES INTO THE
REGION.
HYDROLOGY...
A LOW PRESSURE SYSTEM TRACKS ACROSS LOWER MICHIGAN TODAY, OFFERING
SEVERAL PERIODS OF RAINFALL. THE FIRST AND MAIN ROUND WILL BE THIS
MORNING AS AN AREA OF SHOWERS AND STORMS TRACK WEST TO EAST ACROSS
THE STATE AHEAD OF A COLD FRONT. SOME LOCALIZED MODERATE TO HEAVY
DOWNPOURS WILL BE POSSIBLE WITH THIS ACTIVITY. A RELATIVE LULL IS
THEN EXPECTED FOR THE LATE MORNING TO EARLY AFTERNOON HOURS BEFORE
THE NEXT COLD FRONT SWINGS THROUGH FROM NORTHWEST TO SOUTHEAST. THIS
WILL BRING ADDITIONAL LIGHTER SHOWERS DURING THE LATE AFTERNOON AND
EVENING. ADDITIONAL STORM TOTAL RAINFALL AMOUNTS WILL GENERALLY
REMAIN NEAR OR BELOW A HALF INCH, BUT LOCALIZED AREAS - PARTICULARLY
NORTH OF I-69 - MAY SEE HIGHER AMOUNTS. THE PROGRESSIVE NATURE OF
THE SYSTEM IS EXPECTED TO MINIMIZE POTENTIAL FLOODING APART FROM
LOCALIZED PONDING ON ROADS AND IN POOR DRAINAGE AREAS.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM EDT FRIDAY
FOR LHZ421-441>443.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 10 PM EDT THIS
EVENING FOR LHZ422.
LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LCZ460.
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LEZ444.
UPDATE.......IRL
AVIATION.....MR
DISCUSSION...TF
MARINE.......DRK/TF
HYDROLOGY....TF
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page