813
FXUS63 KDTX 200353
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1153 PM EDT MON MAY 19 2025
KEY MESSAGES
- SEASONABLY COOL TEMPERATURES THROUGH THE WEEK.
- NUMEROUS RAIN SHOWERS FILL IN TUESDAY AFTERNOON AND EVENING, WITH
CONTINUED CHANCES THROUGH WEDNESDAY.
- LINGERING ON AND OFF SHOWER CHANCES PERSIST THURSDAY AND FRIDAY.
AVIATION
A BLEND OF INFLUENCE FROM HUDSON BAY HIGH PRESSURE AND PLAINS LOW
PRESSURE CONTINUES ON SE MI CONDITIONS LATE TONIGHT THROUGH TUESDAY.
LOW LEVEL DRY AIR WITH NORTHERN ONTARIO ORIGINS IS REINFORCED BY NE
WIND TO MAINTAIN THE CLEARING OF LOW CLOUDS ACCOMPLISHED EARLIER
THIS EVENING ACROSS LOWER MI. THAT LEAVES VFR UNDER MIXED HIGH
CLOUDS FOR THE REST OF TONIGHT THROUGH TUESDAY AND TUESDAY EVENING.
EASTERLY WIND IS THE WEATHER HIGHLIGHT BY AFTERNOON AS THE GRADIENT
INCREASES BETWEEN PRESSURE SYSTEMS LEADING TO GUSTS NEAR 25 KNOTS
UNDER THICKENING MID AND HIGH CLOUDS INTO TUESDAY EVENING. LIGHT
RAIN MOVES IN FROM IL/IN AND MAKES IT TO ABOUT THE DTW CORRIDOR
TOWARD SUNSET.
FOR DTW/D21 CONVECTION...NO THUNDERSTORMS TONIGHT THROUGH TUESDAY.
THRESHOLD PROBABILITIES...
* NONE.
PREV DISCUSSION
ISSUED AT 343 PM EDT MON MAY 19 2025
DISCUSSION...
ANTICYLONIC FLOW TO REINFORCE NORTHERLY FLOW OVER SE MI THROUGH THE
DAY AND WITH IT, DRY AIR ADVECTION, THAT WILL WORK TO ERODE CLOUD
COVER TRAPPED UNDER A STRONG LOW-LEVEL INVERSION THROUGH THE EVENING
HOURS. THIS WILL LEAD TO CLEAR SKIES WHICH, IN CONJUNCTION WITH THE
COOLER FLOW OFF THE LAKE, WILL DROP TEMPERATURES INTO THE MID 30S
ACROSS THE CENTRAL PART OF THE THUMB AND NORTHERN TRI-CITIES, AND
UPPER 30S TO LOW 40S ELSEWHERE. FROST DEVELOPMENT MAY BE POSSIBLE
WITHIN THE INTERIOR OF THE THUMB.
THE INTRUSION OF DRY AIR WILL HALT RIGHT ACROSS SE MI AS A SERIES OF
SHORTWAVES PIVOTS AROUND A UPPER LOW SITUATED OVER THE NORTHERN
PLAINS, WHICH WILL PIVOT INTO THE MIDWEST, ALLOWING GULF MOISTURE TO
STREAM INTO SOUTHWESTERN MICHIGAN. THIS WILL ESTABLISH A NOTABLY
SHARP MOISTURE GRADIENT (FOR THE COOLER TEMPERATURES), WITH PW
VALUES RANGING FROM A PALTRY .15 INCHES ACROSS THE TIP OF THE THUMB
TO AROUND .70 INCHES ALONG THE MI/OH BORDER. THIS WILL PLAY A PIVOTAL
ROLE IN MODULATING PRECIPITATION COVERAGE BEGINNING TOMORROW LATE
AFTERNOON AND EVENING AS A SHORTWAVE PIVOTS INTO MICHIGAN WITH A
LAGGING SURFACE LOW PRESSURE FILLING IN ACROSS THE OHIO VALLEY. THE
DRIER AIR ENTRENCHED OVER THE THUMB WILL PROVE MORE RESISTANT, WITH
MODEL SOUNDING DEPICTING DEWPOINT DEPRESSIONS AS HIGH AS 64C AT
777MB. AS A RESULT, TOP DOWN SATURATION WILL SIGNIFICANTLY LAG
RELATIVE TO SOUTHERN COUNTERPARTS, THUS POPS REMAIN LIMITED AROUND
40% ACROSS THE NORTHERN THUMB WHILE VALUES CLIMB TO 85% CLOSER TO THE
OHIO BORDER CENTERED TOMORROW NIGHT THROUGH WEDNESDAY EARLY
AFTERNOON. LACK OF INSTABILITY AND POOR MID-LEVEL LAPSE RATES
PRECLUDE ANY MENTION FOR THUNDERSTORM CHANCES.
THE DRY LAYER WILL EVENTUALLY ERODE AS THE SURFACE LOW GETS HUNG UP
AROUND LAKE ERIE WITH MULTIPLE ROUND OF SHORTWAVES PIVOTING
OVERHEAD. THIS WILL BRING MULTIPLE ROUNDS OF ON AND OFF RAIN SHOWERS
THROUGH THE MID TO LATE WEEK PERIOD AS WELL AS BELOW NORMAL
TEMPERATURES GIVEN THE REINFORCEMENT OF THE THERMAL TROUGH. 850MB
TEMPERATURES WILL STRUGGLE TO GET ABOVE 10C THROUGH THE WEEK AND IN
FACT LOOK TO DIPS BELOW 0C LATE THURSDAY INTO FRIDAY. THIS SUPPORTS
HIGHS IN THE MID TO UPPER 50S AND LOWS IN THE LOW TO MID 40S THROUGH
THE MID TO LATE WEEK PERIOD.
MARINE...
SURFACE GRADIENT FLOW FLUCTUATES BETWEEN NORTHERLY AND EASTERLY
TONIGHT OVER THE CENTRAL GREAT LAKES FROM THE EXTENSION OF BROAD
SURFACE HIGH PRESSURE CENTERED OVER SOUTHERN HUDSON BAY. GUST
COMPONENT EXISTS FOR THE SOUTHERN LAKE HURON NEARSHORES AMIDST 20-30
KNOT FLOW WITHIN THE 3-5 KFT AWL MIXED-LAYER, THEREFORE SMALL CRAFT
ADVISORIES WILL REMAIN IN EFFECT, MAINLY FOR GUSTS IN EXCESS OF 25
KNOTS. WEAKER WINDS FURTHER SOUTH, FROM PORT AUSTIN TO PORT HURON,
TREND TOWARD A LESS FAVORABLE VECTOR/FETCH WHICH SHOULD SUPPORT A
RECOVERY IN WAVE HEIGHTS OVERNIGHT, FAVORING AN EARLIER END TIME TO
THE ADVISORY. A BROAD LOW PRESSURE SYSTEM TRACKS TOWARD THE WESTERN
GREAT LAKES TUESDAY INTO WEDNESDAY BRINGING RAIN AND RENEWED GUSTY
NORTHEAST WINDS. WILL LIKELY NEED TO ADD MORE NEARSHORE ZONES TO THE
EXTENDED SMALL CRAFT ADVISORY WITH SUBSEQUENT UPDATES. GUSTS SHOULD
EASILY CLIMB INTO THE UPPER 20 KNOT RANGE ALONG THE COASTAL AREAS BY
TUESDAY EVENING. MODEST PRESSURE GRADIENT MAINTAINS 15-20 KNOT
PREVAILING WINDS THROUGH WEDNESDAY AS THE CENTER OF THE SYSTEM MOVES
INTO THE EASTERN LAKES BY WEDNESDAY NIGHT.
HYDROLOGY...
AN ELEVATED FRONT WILL BRING THE WIDELY SCATTERED TO NUMEROUS RAIN
SHOWERS FROM SOUTH TO NORTH STARTING LATE TOMORROW AFTERNOON AND
EVENING. SHOWER COVERAGE WILL EXPAND NORTH THROUGH WEDNESDAY MORNING
AND AFTERNOON. TOTAL PRECIPITATION IS EXPECTED TO RANGE BETWEEN A
QUARTER INCH TO THREE QUARTER INCHES BY WEDNESDAY AFTERNOON, MAINLY
ALONG OR SOUTH OF A LINE FROM OWOSSO TO PORT HURON. NORTH OF THIS
LINE, COVERAGE IS EXPECTED TO BE LESS ROBUST, ESPECIALLY ACROSS THE
NORTHERN TRI-CITIES AND NORTHERN THUMB.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM 10 AM TUESDAY TO 10 AM EDT WEDNESDAY FOR
LHZ441>443.
SMALL CRAFT ADVISORY UNTIL 10 PM EDT WEDNESDAY FOR LHZ421-422.
LAKE ST CLAIR...SMALL CRAFT ADVISORY FROM 10 AM TUESDAY TO 10 AM EDT WEDNESDAY FOR
LCZ460.
MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 10 AM TUESDAY TO 10 AM EDT WEDNESDAY FOR
LEZ444.
AVIATION.....BT
DISCUSSION...AM
MARINE.......KGK
HYDROLOGY....AM
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