237
FXUS63 KDTX 300740
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
340 AM EDT THU APR 30 2026
KEY MESSAGES
- CHANCE (20-30%) OF LIGHT SHOWERS BOTH TODAY AND FRIDAY.
- A STRETCH OF WELL BELOW AVERAGE TEMPERATURES WILL PERSIST INTO
THIS WEEKEND. THIS WILL BRING POTENTIAL FOR FROST/FREEZE CONDITIONS
EACH MORNING FRIDAY THROUGH SUNDAY.
DISCUSSION
CLOSED UPPER LOW OVER LAKE SUPERIOR DEEPENS AS IT MEANDERS EASTWARD
OVER THE NEXT 48 HOURS. LOWER MI REMAINS ENTRENCHED WITHIN COOL
CYCLONIC FLOW DURING THIS PERIOD, WITH 850MB TEMPS NEAR -3C THIS
MORNING TRENDING COOLER TOWARD -5 TO -7C BY FRIDAY NIGHT INTO
SATURDAY - THESE VALUES IN THE BOTTOM 10TH PERCENTILE FOR THIS TIME
OF YEAR. PERVASIVE OVERNIGHT SHOWERS AND DRIZZLE WILL DIMINISH IN
COVERAGE THIS MORNING AS PVA AND HEIGHT TENDENCY PROGS TREND
NEUTRAL. MOSTLY CLOUDY SKIES FOLLOW FOR MOST OF THE DAY WITH HIGH
TEMPS INCHING UP TO THE LOW TO MID 50S. THE COLD AIR ALOFT AND LATE
APRIL SUN ANGLE STEEPEN LOW-LEVEL LAPSE RATES THIS AFTERNOON TO
OFFER A CHANCE OF DIURNALLY DRIVEN SHOWERS INTO THIS EVENING. THERE
WILL BE POTENTIAL FOR SOME WET SNOWFLAKES OR GRAUPEL TO MIX IN GIVEN
LOW WET BULB ZERO HEIGHTS.
IT WILL BE A COMPLICATED SETUP FOR FROST DEVELOPMENT TONIGHT WITH
LOW CONFIDENCE ON THE DEGREE OF CLOUD COVER AFTER SUNSET. LOSS OF
DAYTIME HEATING WILL ALLOW ANY DIURNAL SHOWERS/CLOUDS TO DIMINISH
THIS EVENING BUT THEN THE NEXT SHORTWAVE PIVOTING AROUND THE MEAN
TROUGH WILL RENEW MID-LEVEL MOISTURE ADVECTION INTO THE AREA WHICH
COULD LIMIT RADIATIONAL COOLING. THE GRADIENT WILL BE WEAK AND SFC
DEW POINTS FALLING TO THE LOWER 30S WILL ALLOW TEMPS TO SETTLE TO
NEAR FREEZING WITHIN ANY PROLONGED CLEARING. HIGHEST CONFIDENCE FOR
FROST WILL BE IN THE TYPICAL COOLER SPOTS OF THE THUMB AND SAGINAW
VALLEY, AND LOWEST CONFIDENCE EXISTS AROUND METRO DETROIT AND SOUTH
OF I-94 WHICH MAY SEE SOME SHOWERS MOVE IN LATE, ASSOCIATED WITH THE
SHORTWAVE. WILL LET SUBSEQUENT SHIFTS EVALUATE ADDITIONAL DATA AND
THE NEED FOR ANY HEADLINES TONIGHT.
A CORRIDOR OF HEIGHT FALLS AND PVA PASS OVERHEAD ON FRIDAY, CAUSING
MID-LEVEL TEMPS TO LOWER AND INDUCE DEEPER DIURNAL MIXING. THIS
BRINGS A HIGHER COVERAGE OF CONVECTIVE SHOWERS DURING THE DAYLIGHT
HOURS. HIGHS GENERALLY A DEGREE OR TWO COOLER THAN TODAY. FRIDAY
NIGHT INTO SATURDAY MORNING WILL PRESENT ANOTHER WINDOW FOR
FROST/FREEZE POTENTIAL WITH SLIGHTLY HIGHER CONFIDENCE IN THIS
PERIOD GIVEN THE COOLER AND DRIER AMBIENT NEAR-SURFACE CONDITIONS.
LITTLE SUPPORT ALOFT FOR SHOWER GENERATION ON SATURDAY AND WITH LESS
BOUNDARY LAYER MOISTURE AVAILABLE, MAINTAINED A DRY FORECAST FOR
NOW. SIMILARLY COOL CONDITIONS CONTINUE WITH ANOTHER ROUND OF
FROST/FREEZE CONSIDERATIONS SATURDAY NIGHT INTO SUNDAY MORNING.
STALLED TROUGHING FINALLY GIVES WAY TO A SHORTWAVE RIDGE ON SUNDAY
WITH ENSUING SOUTHWEST FLOW SUPPORTING POSITIVE THICKNESS ADVECTION
AND TEMPERATURES REBOUNDING BACK TOWARD 60. A WEAK CLIPPER BRINGS A
CHANCE OF RAIN BY LATE IN THE DAY. A BROAD UPPER LOW STAYS PARKED
OVER NORTHERN ONTARIO EARLY NEXT WEEK WITH DEEPER TROUGHING SETTING
UP OVER THE UPPER MIDWEST, FAVORING DEEPER SOUTHWEST FLOW DIRECTING
INTO THE AREA. MORE SEASONABLE TEMPERATURES LOOK TO BE IN STORE NEXT
WEEK WITH POTENTIAL FOR PERIODS OF WET WEATHER.
MARINE
THE GREAT LAKES WILL REMAIN UNDER THE INFLUENCE OF A SLOW MOVING
UPPER-LEVEL LOW PRESSURE SYSTEM. THIS WILL BRING PERIODIC ISOLATED
TO SCATTERED SHOWER CHANCES THROUGH THE END OF THE WEEK, ALONG WITH
LIGHTER WINDS UNDER A MORE DIFFUSE PRESSURE GRADIENT. WIND DIRECTION
TO GENERALLY HOLD FROM THE NORTHWEST WITH STRONGER WINDS HOLDING
ACROSS NORTHERN LAKE HURON, WHERE GUSTS AROUND 20 KNOTS WILL BE
POSSIBLE.
PREV DISCUSSION
ISSUED AT 1157 PM EDT WED APR 29 2026
AVIATION...
SHOWERS INCREASING COVERAGE OVER SW LOWER MI LEADING UP TO MIDNIGHT
ARE ON THE WEST FLANK OF AN INTENSE SMALLER SCALE MID LEVEL
CIRCULATION THAT HAS SUPPORTED ACTIVITY OVER SE MI FOR MUCH OF THE
EVENING. THE UPSTREAM DEVELOPMENT MOVES EASTWARD WHILE SHRINKING IN
COVERAGE BUT STILL DEMANDS ACCOUNTING FOR ALONG THE TERMINAL
CORRIDOR FOR MUCH OF THE LATE NIGHT PERIOD. THE EXTRA BOUNDARY LAYER
MOISTURE ALSO SUSTAINS BORDERLINE MVFR/VFR CEILING IN AND NEAR THE
ASSOCIATED NW-SE SURFACE PRESSURE TROUGH AS IT GRADUALLY FILLS
TOWARD SUNRISE. A MORE NEUTRAL NW LOW LEVEL WIND THEN WORKS TO BRING
A LOW CLOUD DECREASE DOWN FROM NORTHERN LOWER MI WHILE MID CLOUDS
LINGER DURING THE MORNING. IT IS A COOLER FLOW THAT IS SUBJECT TO A
DAYTIME INSTABILITY BOOST OF CUMULUS THAT DEVELOPS INTO BROKEN
CEILING IN THE LOWER RANGE OF VFR BY AFTERNOON. A STRAY SHOWER IS
ALSO FAVORED IN THIS SETUP BUT WITH COVERAGE AND DURATION TOO LOW
FOR A TERMINAL MENTION FROM MID AFTERNOON INTO THURSDAY EVENING.
D21/DTW CONVECTION...NO THUNDERSTORMS EXPECTED THROUGH THIS TAF
PERIOD.
DTW THRESHOLD PROBABILITIES...
* HIGH FOR CEILING AT OR BELOW 5,000 FEET TONIGHT AND THURSDAY.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...TF
MARINE.......KDK
AVIATION.....BT
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