786
FXUS63 KDTX 182040
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
340 PM EST TUE FEB 18 2025
KEY MESSAGES
- WIND CHILLS WEDNESDAY MORNING ARE FORECASTED TO RANGE IN THE
SINGLE DIGITS BELOW ZERO TO 15 DEGREES BELOW ZERO.
- LIGHT SNOWFALL CHANCES WEDNESDAY NIGHT INTO THURSDAY MORNING.
- TEMPERATURES OF 5 TO 10 DEGREES BELOW NORMAL WILL HOLD THROUGH THE
REMAINDER OF THE WEEK.
DISCUSSION
UPPER LEVEL CONFLUENCE IN LEFT ENTRANCE QUADRANT OF UPPER LEVEL JET
WILL PROVIDE BACKGROUND SUPPORT FOR SURFACE RIDGING AND A RELAXED
GRADIENT TONIGHT. WARM AIR ALOFT WILL MAINTAIN HIGH STATIC STABILITY
WHICH SHOULD LIMIT MUCH IN THE WAY OF OPAQUE UPPER CLOUD. EASED
MINIMUM TEMPERATURES DOWNWARD A TOUCH BASED ON THE LATEST NBM
GUIDANCE TO THE LOWER SINGLE DIGITS ABOVE ZERO. WITH MORE DECOUPLING
OF THE WIND TONIGHT, EXPECTING APPARENT TEMPERATURES TO RANGE IN THE
10 TO 15 DEGREE BELOW ZERO RANGE NORTH OF M 59 TO THE SINGLE DIGITS
BELOW ZERO SOUTH OF M 59. WILL NOT ISSUE A COLD WEATHER ADVISORY FOR
TONIGHT.
THERE IS A COMPLEXITY TO THE SETUP FOR THE MAIN VORTICITY FEATURES
RESPONSIBLE FOR THE WEDNESDAY NIGHT PRECIPITATION POTENTIAL. A DEEP
PLANETARY VORTICITY LOBE OF THE NORTHERN CANADA UPPER LEVEL LOW IS
FORECASTED TO PIVOT INTO THE MIDWEST WITH SUBSEQUENT SHORTWAVE
AMPLIFICATION. LOWER CONFIDENCE EXISTS AS THE OPERATIONAL ECMWF
SUGGESTS THAT A PORTION OF THE SHORTWAVE ENERGY RESPONSIBLE FOR THE
PRECIPITATION CHANCES WILL HAVE HAD SOME ORIGIN OUT THE NORTHEAST
UNITED STATES STORM FROM THIS PAST WEEKEND WITH THE GFS ALSO
SUGGESTING SOME ENERGY ORIGINATING NEAR GREENLAND. QUITE THE TENUOUS
EAST TO WEST TRAJECTORY. REGARDLESS, THERE HAS BEEN A CONSENSUS
THAT OLDER ATLANTIC MOISTURE TO THE NORTH AND EAST OF THE STATE WILL
EVENTUALLY BE DRAWN SOUTHWARD BY THE AFOREMENTIONED SHORTWAVE AND
HELP WITH FULLY SATURATING THE COLUMN HERE OVER SOUTHEAST MICHIGAN.
THE NAM HAS BEEN THE MOST AGGRESSIVE WITH SHORTWAVE AMPLIFICATION
AND SUGGESTS A VERY WELL ORGANIZED CORRIDOR OF 700-500MB MOIST
ISENTROPIC ASCENT. NBM DATA SUGGESTS PLENTY OF UNCERTAINTY WITH
EXPECTED QPF OF A COUPLE OF HUNDREDTHS, WITH 50TH PERCENTILE OF SNOW
AT NO ACCUMULATION. FOR THIS PRODUCT ISSUANCE WILL INCREASE POPS
INTO THE LIKELY RANGE WITH JUST A FEW TENTHS OF SNOW ACCUMULATION.
GEOPOTENTIAL HEIGHTS WILL RISE ALLOWING SURFACE HIGH PRESSURE TO
BUILD ACROSS THE GREAT LAKES FOR THE END OF THE WEEK AND BEGINNING
OF THE WEEKEND. DAYTIME TEMPERATURES WILL MODERATE A GOOD AMOUNT
WITH READINGS IN THE UPPER 20S FRI/SAT AND MIDDLE 30S. LOW
PREDICTABILITY BY THE END OF THE WEEKEND AS THE UPPER LEVEL FLOW
WILL WEAKEN SUBSTANTIALLY AND TURN TO THE NORTHWEST. LATEST
INDICATIONS ARE FOR MULTIPLE SHORTWAVES TO PASS THROUGH THAT WILL BE
VERY DIFFICULT TO TIME.
MARINE
FRIGID AIRMASS IN PLACE OVER THE GREAT LAKES REGION THIS AFTERNOON,
AND WINDS STILL GUSTING AROUND 30 KNOTS OVER NORTHERN LAKE HURON,
SUPPORTING HEAVY FREEZING SPRAY WITH CONTINUED LOCALIZED SNOW
SHOWERS. HAVE EXTENDED THE HEAVY FREEZE WARNING INTO THE EVENING.
WINDS FINALLY LOOK TO DECREASE SIGNIFICANTLY TONIGHT AS A RIDGE OF
HIGH PRESSURE BUILDS IN.
WEAK/ILL-DEFINED PRESSURE PATTERN FOR WEDNESDAY WILL RESULT IN
PREDOMINATELY LIGHT WINDS, AT OR BELOW 15 KNOTS.
HIGH PRESSURE TRACKING SOUTH THROUGH THE PLAINS WEDNESDAY NIGHT AND
THURSDAY, COUPLED WITH DEEPENING LOW PRESSURE OFF THE EAST COAST
WILL RESULT IN INCREASING NORTHERLY WINDS OVER THE CENTRAL GREAT
LAKES REGION FOR THE THURSDAY-THURSDAY NIGHT, BUT LIKELY ONLY
TOPPING OUT IN THE 20-25 KNOT RANGE PER LOCAL PROBABILISTIC
GUIDANCE.
RIDGE OF HIGH PRESSURE SLIDES THROUGH ON FRIDAY, ALLOWING FOR AT
LEAST MODERATE RETURN SOUTHWEST FLOW TO DEVELOP FRIDAY EVENING-
SATURDAY. AIRMASS STILL LOOKS TO BE COLD ENOUGH TO SUPPORT NEAR LAKE
SURFACE UNSTABLE PROFILES, AND GUSTS OF 25 TO 30 KNOTS SEEM DOABLE,
PARTICULARLY FOR CENTRAL SECTIONS OF LAKE HURON.
LOW PRESSURE LOOKS TO BE TRACKING THROUGH THE GREAT LAKES REGION
SUNDAY-MONDAY, BUT BIG DIFFERENCES AMONGST THE MODELS WITH RESPECT
TO STRENGTH AND LOCATION. A QUICK LOOK AT THE 12Z EURO ENSEMBLES
MEMBERS SUGGEST ABOUT A 25 PERCENT CHANCE OF GUSTS TO GALES OVER
NORTHERN LAKE HURON. OUTGOING FORECAST/NBM WIND GRIDS ARE MUCH LOWER
FOR THIS TIME PERIOD.
PREV DISCUSSION
ISSUED AT 1234 PM EST TUE FEB 18 2025
AVIATION...
HIGH PRESSURE HOLDS STEADY OVER THE PLAINS MAINTAINING WEST
NORTHWEST FLOW ACROSS THE AIRSPACE THROUGH TONIGHT. THESE WINDS
ACTIVATE LAKE MICHIGAN MOISTURE WHICH WILL GENERATE SCATTERED TO
BROKEN COVERAGE OF STRATOCUMULUS CLOUDS THIS AFTERNOON. CLOUD BASES
ARE EXPECTED TO BE BETWEEN 3.0 AND 5.0 KFT AGL WITH THE SHALLOW
MOIST LAYER POTENTIALLY SQUEEZING OUT A FEW FLURRIES AS WELL. THE
LOW CLOUDS DISSIPATES TONIGHT WHILE CIRRUS BEGINS STREAM IN AHEAD OF
THE NEXT UPPER LEVEL SYSTEM. CLOUDS CONTINUE TO THICKEN AND LOWER ON
THURSDAY AS ANOTHER SCATTERED TO BROKEN STRATOCUMULUS DECK DEVELOPS
MIDDAY.
DTW THRESHOLD PROBABILITIES...
* LOW IN CEILINGS AOB 5000 FEET THIS AFTERNOON (17Z TO 22Z).
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...HEAVY FREEZING SPRAY WARNING UNTIL MIDNIGHT EST TONIGHT FOR
LHZ361>363-462-463.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...CB
MARINE.......SF
AVIATION.....RBP
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