021
FXUS63 KDTX 220359
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1159 PM EDT MON APR 21 2025
KEY MESSAGES
- COOLER TUESDAY, BUT TEMPS BACK UP INTO THE 70S WEDNESDAY-FRIDAY.
- WIDESPREAD RAIN EXPECTED TO RETURN FOR FRIDAY.
AVIATION
A LOW PRESSURE SYSTEM EXITS CENTRAL ONTARIO INTO WESTERN QUEBEC
TONIGHT WHICH USHERS IN A COOLER AIRMASS FOR THE TERMINALS INTO
TUESDAY. THE COLDEST AIR WILL GENERALLY REMAIN OVER NORTHERN
MICHIGAN, BUT SUFFICIENT COOLING HAS SUPPORTED THE DEVELOPMENT OF A
STRATOCUMULUS DECK THIS EVENING. EXPECTATION IS THAT CLOUD BASES
STILL HOLD IN THE LOW-END VFR RANGE A BIT LONGER BEFORE SCATTERING
OUT EARLY TUESDAY MORNING. THE SURFACE PRESSURE GRADIENT FURTHER
RELAXES WITH TIME TONIGHT AS THE RATE OF IMPROVEMENT IS DICTATED BY
THE DEPARTURE SPEED OF THE SURFACE LOW. SURFACE HIGH PRESSURE BUILDS
INTO THE OHIO VALLEY FROM THE MISSISSIPPI VALLEY ON TUESDAY
PROMOTING A DRIER COLUMN LOCALLY WITH WEAKER WEST-SOUTHWEST WINDS.
MID-LEVEL MOISTURE AND RESULTING CLOUDS SPILL DOWNSTREAM INTO LOWER
MICHIGAN FROM THE PLAINS TUESDAY EVENING AS SURFACE FLOW BACKS
SOUTHERLY, DUE TO THE EASTWARD TRANSLATION OF OHIO VALLEY RIDGING.
DTW THRESHOLD PROBABILITIES
* HIGH FOR CEILING AT OR BELOW 5000 FEET UNTIL APPROXIMATELY 08Z
TONIGHT, THEN LOW FOR THE REST OF THE MORNING HOURS.
PREV DISCUSSION
ISSUED AT 315 PM EDT MON APR 21 2025
DISCUSSION...
MATURE LOW PRESSURE (~1000 MB) SYSTEM EXITING NORTHEAST OF THE
NORTHERN GREAT LAKES THIS EVENING. SOUTHWEST WIND GUSTS BEHIND THE
FROPA DID PEAK OUT IN THE 40-50 MPH RANGE ACROSS SOUTHEAST MICHIGAN,
ESPECIALLY AND INCLUDING SOUTH OF M-59, AS MAX TEMPERATURES REACHED
INTO UPPER 60S TO MID 70S. STILL 45-50 KNOTS OF FLOW AT THE 850 MB
LEVEL ACROSS THE NORTHERN HALF OF THE CWA, AND WILL THUS MAINTAIN THE
WIND ADVISORY FOR NOW, ALTHOUGH GUSTS TO 45 MPH WILL LIKELY BE
SPORADIC. THE NORTHERN TIP OF THE THUMB REGION FINALLY LOOKS TO GET
INTO THE ACTION AND SEE THE MORE FREQUENT/PEAK WINDS AS WINDS VEER
AROUND TO THE WEST. WINDS TO DIMINISH THIS EVENING AND TONIGHT, BUT
WINDS STILL HOLDING AROUND 10 MPH TOWARD SUNRISE TUESDAY. THUS, EVEN
WITH CLOUDS SLOWLY DISSIPATING, SHOULD NOT HAVE TO WORRY ABOUT FROST
AS TEMPS DIP INTO THE UPPER 30S TO AROUND 40 DEGREES.
MORE DISORGANIZED, BUT ABUNDANT UPPER LEVEL PV/ENERGY BACK ACROSS
THE NORTHERN ROCKIES, WHICH WILL SPIN UP A WEAK LOW/REFLECTION IN
THE UPPER MISSISSIPPI RIVER VALLEY/MIDWEST COME TUESDAY. SURFACE
FRONTAL BOUNDARY/INCREASING MOISTURE LOOKS TO REACH THE SOUTHERN
MICHIGAN BORDER TOWARD 00Z WEDNESDAY, AND THERE MAY BE ENOUGH MID
LEVEL INSTABILITY TO ALLOW FOR SHOWERS AND EVEN AN ISOLATED
THUNDERSTORM SURVIVE THE TRIP INTO SOUTHEAST MICHIGAN BY TUESDAY
EVENING. MID LEVEL LAPSE RATES ARE STEEP, GREATER THAN 7 C/KM.
HOWEVER, THE LOW INSTABILITY (MUCAPES ~1000 J/KG) RESERVOIR SHOULD
MOSTLY HOLD OVER THE WESTERN GREAT LAKES THROUGH TUESDAY NIGHT. STILL,
12Z HRRR SUGGESTS WEST TO EAST TRAINING OF CONVECTIVE ACTIVITY IS
POSSIBLE WITH THE MODEST WESTERLY LOW LEVEL JET.
MODEST SFC-850 MB BASED INSTABILITY/CAPE DEVELOPING DURING WEDNESDAY
SOUTH OF I-69 MAY TOUCH OFF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
WITH WEAK LOW LEVEL CONVERGENCE, LEFTOVER FRONTAL BOUNDARY. HOWEVER,
MODEST HEIGHT RISES (500 MB HEIGHTS OF 573+ DAM) AND SOME SEMBLANCE
OF 500 MB RIDGE AXIS BUILDING OVER THE CENTRAL GREAT LAKES,
PROMOTING GENERAL SUBSIDENCE, LEADS TO LOW CONFIDENCE. NBM POPS LOOK
OK WITH MOSTLY SLIGHT CHANCE (15-25).
FURTHER HEIGHT RISES FOR THURSDAY, BUT POTENTIAL SHORTWAVE COMING
OUT OF THE MIDWEST TO END THE WORK WEEK, MERGING WITH A NORTHERN
STREAM TROUGH TRACKING OUT OF SOUTH CENTRAL CANADA. CYCLOGENSIS
TAKING PLACE OVER THE WESTERN OHIO VALLEY BY FRIDAY SHOULD SUPPORT
WIDESPREAD RAIN OVERSPREADING SOUTHEAST MICHIGAN, WITH THE LOW ON
PACE TO EXIT EAST ON SATURDAY. ANY RESIDUAL LIGHT RAIN ENDING EARLY
IN THE MORNING, WITH DRY CONDITIONS THEN IN PLACE FOR THE REST OF
THE WEEKEND, PER 12Z EURO.
MARINE...
SHALLOW MIXING DEPTHS IN THE WAKE OF A COLD FRONT WILL CONTINUE TO
INTERACT WITH A SHALLOW YET STRONG WIND FIELD ALOFT, BRINGING GUSTS
TO GALES FOR THE MAJORITY OF THE NEARSHORE ZONES OUTSIDE OF WESTERN
LAKE ERIE. SOME SPORADIC GUSTS TO GALES REMAIN POSSIBLE FOR WESTERN
LAKE ERIE, BUT LATEST OBSERVATIONS PRECLUDE THE ISSUANCE OF ANY
SHORT-FUSED WARNING PRODUCT, WITH EXPECTATION THAT GALES FOR ALL
NEARSHORE ZONES DIMINISH BY LATE THIS EVENING. FOR LAKE HURON,
PASSAGE OF A LOW PRESSURE SYSTEM WILL VEER WIND DIRECTION FROM THE
WEST WITH COOLER AIR FILTERING IN ALOFT, WHICH WILL THEN PIVOT THE
GALE THREAT TO THE NORTHERN THIRD OF LAKE HURON OVERNIGHT. A RIDGE
OF HIGH PRESSURE WILL BUILD IN THROUGH TUESDAY AFTERNOON,
DIMINISHING WIND SPEEDS THROUGH THE DAY TOMORROW. LIGHT WINDS THEN
CONTINUE THROUGH THE MIDWEEK PERIOD AS THE PRESSURE GRADIENT REMAINS
WEAK.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...GALE WARNING UNTIL 10 AM EDT TUESDAY FOR LHZ361-362.
SMALL CRAFT ADVISORY UNTIL 10 AM EDT TUESDAY FOR LHZ421-422-441>443.
LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 4 AM EDT TUESDAY FOR
LCZ460.
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 4 AM EDT TUESDAY FOR LEZ444.
AVIATION.....KGK
DISCUSSION...SF
MARINE.......AM
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