Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 271702
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1202 PM EST FRI FEB 27 2015


.AVIATION...

VERY DRY AIRMASS IN PLACE...BUT DEVELOPING LIGHT LOW LEVEL SOUTHWEST
FLOW IS ALLOWING LAKE INDUCED CLOUDS FROM LAKE MICHIGAN TO ADVECT
EASTWARD...AND IT APPEARS MBS WILL HAVE TO DEAL WITH THE LOW
VFR/BORDERLINE MVFR CEILINGS THIS AFTERNOON INTO THIS EVENING...WITH
DIMINISHING CHANCES FARTHER SOUTH...AS STRONG SURFACE HIGH ACROSS
THE NORTHERN OHIO VALLEY SHOULD ASSURE CLEAR SKIES TONIGHT ACROSS
THE DETROIT TAFS WITH NEARLY CALM WINDS. MOSTLY CLEAR SKIES WILL
PERSIST INTO TOMORROW...WITH JUST INCREASING MID/HIGH CLOUDS LATE
IN THE DAY.

//DTW THRESHOLD PROBABILITIES...

* LOW CONFIDENCE IN CEILING BELOW 5000 FT THIS AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 846 AM EST FRI FEB 27 2015

UPDATE...

ANOTHER RECORD SETTING COLD MORNING AS ALL THREE CLIMATE SITES
BROKE OR TIED THEIR RESPECTIVE DAILY RECORDS.

FNT LOW WAS AT LEAST -17 F (UNABLE TO DIAL IN TO GET FINAL VALUE).
SAGINAW LOW WAS -9 AT 707 AM.
DETROIT TIED RECORD LOW...WITH -4 F AT 717 AM.

12Z DTX SOUNDING INDICATED A 925 MB TEMP OF -19 C...AND WITH THE
COLD START AND SOME LAKE CLOUDS EXPECTED TO PUSH EAST THIS
AFTERNOON (SEE RUC13 925 MB RH) UNDER LIGHT WESTERLY
FLOW...ESPECIALLY NORTHERN AREAS...MAXES WILL PROBABLY ONLY TOP
OUT IN THE MID TEENS...ON THE LOWER END OF THE GOING FORECAST.

PREV DISCUSSION...ISSUED 358 AM EST FRI FEB 27 2015

SHORT TERM...TODAY AND TONIGHT

RECORD LOWS FOR FEB 27
DETROIT AREA: -4  (1934)
FLINT AREA:   -14 (1994)
SAGINAW:      -8  (1934)

ANOTHER COLD MORNING ACROSS SOUTHEASTERN MICHIGAN WITH AN ARCTIC
SURFACE RIDGE LOCKED IN OVERHEAD. NIL WIND AND CLEAR SKIES HAS LED
TO FAVORABLE RADIATIVE COOLING CONDITIONS. SURFACE TEMPERATURES
CURRENTLY RANGE FROM 0 TO 10 DEGREES BELOW ZERO AS OF 3AM. WITH A
LACK OF LOW CLOUD DISCERNIBLE IN IR IMAGERY...EXPECTATIONS ARE FOR
SURFACE TEMPERATURES TO CONTINUE TO BOTTOM OUT BEFORE SUNRISE WITH
MANY RURAL LOCATIONS REACHING 10 TO 20 DEGREES BELOW ZERO. WITH A
DECOUPLED SURFACE LAYER...WILL HONOR THE DECISION OF PRIOR SHIFTS
AND NOT ISSUE A WIND CHILL ADVISORY.

COLDEST MIDLEVEL TEMPERATURES PUSHING OUT OF THE STATE TODAY IN
COMBINATION WITH AN SURFACE ANTICYCLONE PUSHING INTO PORTIONS OF
OHIO WILL ALLOW WIND DIRECTIONS OVER SOUTHEASTERN MICHIGAN TO MAKE A
CONCERTED MOVE TO SOUTHWESTERLY. ENHANCED MOISTURE AND LAKE MICHIGAN
CLOUD DEBRIS IS PROGGED TO STREAM EASTWARD WITH TIME...SHOWN TO
SLIDE THROUGH PORTIONS OF THE CWA BY THIS AFTERNOON AND INTO THE
EARLY EVENING. RAP SOUNDINGS SUGGEST THERE WILL BE A CONSIDERABLE
DIURNAL COMPONENT TO ANY SKY COVER. WIND TRAJECTORIES POINT TO THE
NORTHERN CWA/SAGAINAW VALLEY AS THE MORE FAVORABLE LOCATION FOR
CLOUDS. WITH SUN...SHADED A DEGREE OR TWO HIGHER THAN MOS GUIDANCE
FOR HIGHS.

SURFACE HIGH PRESSURE PUSHING THROUGH INDIANA AND OHIO WILL SET
ANOTHER NIGHT UP FOR CALM WINDS ACROSS THE SOUTHERN HALF OF THE CWA.
LOWERED MINS FOR AREAS SOUTH OF DETROIT. OTHERWISE...A PRESSURE
GRADIENT IN PLACE OVER THE TRI CITIES/NORTHERN THUMB AND SOME
POTENTIAL FOR LINGERING CLOUDS LIMITS THE TEMPERATURE FALL POTENTIAL
FOR TONIGHT.

LONG TERM...

COLD AIRMASS WILL REMAIN IN PLACE INTO EARLY THIS WEEKEND ALTHOUGH
TEMPERATURES WILL MODERATE EVER SO SLIGHTLY AS THE LATEST ARCTIC
HIGH PRESSURE SHIFTS TO THE EAST OF THE AREA SATURDAY NIGHT. HIGHS
ON SATURDAY WILL CLIMB TO AROUND 20F WITH LOWS THAT NIGHT HOLDING
INTO THE SINGLE DIGITS TO NEAR 10F AS BOTH THE COLDEST AIR SHIFTS
EAST AND EXPANDING CLOUD COVER WORKS INTO THE AREA WITH THE APPROACH
OF A LOW PRESSURE SYSTEM.

00Z MODEL RUNS...SAVE THE NAM12...BASICALLY SUPPORT THE PREVIOUS
FORECAST AS ROUGHLY 1 TO 2 INCHES OF SNOW FALL FROM THE I-69
CORRIDOR NORTH LATE SATURDAY NIGHT INTO EARLY SUNDAY EVENING WITH 2
TO 3 INCHES SOUTH OF THAT INTO METRO DETROIT AS H7 SPECIFIC HUMIDITY
CLIMBS TO AROUND 2 G/KG ALONG THE M-59 CORRIDOR. GIVEN THE
RELATIVELY HIGH SNOW TO LIQUID RATIOS EXPECTED WITH THE COLD AIRMASS
IN PLACE...15:1 OR A BIT MORE...WOULD NOT BE SURPRISED TO SEE UP TO
4 INCHES FROM THE I-94 CORRIDOR SOUTHWARD.

TEMPERATURES WILL EDGE BACK DOWN EARLY NEXT WEEK...BUT TO MUCH MORE
REASONABLE LEVELS THAN THE PAST SEVERAL WEEKS AS HIGHS MONDAY REACH
THE MID/UPPER 20S AND LOWS HOLD IN THE TEENS SUNDAY AND MONDAY NIGHT.

THE NEXT LOW PRESSURE SYSTEM APPEARS TO BE SHAPING UP TO BE A
STRONGER SYSTEM THAN THE WEEKEND EVENT...WITH A TRACK THAT WOULD
SUPPORT A WIDE VARIETY OF PRECIPITATION ACROSS THE CWA ON TUESDAY
WITH PRIMARILY SNOW OVER THE NORTHERN CWA AND SNOW CHANGING TO A MIX
AND THEN EVENTUALLY RAIN FURTHER SOUTH. WITH THE EVENTUAL TRACK AND
STRENGTH OF THIS SYSTEM STILL IN DOUBT...WILL FORGO ANY SIGNIFICANT
DETAILS AT THIS TIME...OTHER THAN TO INCLUDE SOME MENTION OF
SLEET...FREEZING RAIN AND RAIN AS 00Z RUNS OF THE GFS...CMC AND
ECMWF DO NOT SUPPORT AN ALL SNOW EVENT FOR THE ENTIRE CWA.

MARINE...

HIGH PRESSURE WILL BE BUILD FROM THE MID MISSISSIPPI VALLEY TODAY
THROUGH THE OHIO VALLEY ON SATURDAY. MODEST SOUTHWEST RETURN FLOW
WILL DEVELOP AROUND THIS HIGH OVER THE CENTRAL GREAT LAKES. CENTRAL
SECTIONS OF LAKE HURON WILL MOST LIKELY SEE WINDS INCREASE INTO THE
15 TO 20 KNOT RANGE. OTHERWISE...WINDS WILL REMAIN ON THE LIGHT SIDE
AS THIS SOUTHWEST PRESSURE GRADIENT WEAKENS LATE IN THE WEEKEND AS A
WEAK LOW PRESSURE SYSTEM LIFTS INTO THE REGION. EVEN THE RETURN OF
COLD NORTHWEST FLOW IN THE WAKE OF THE ATTENDING COLD FRONT WILL BE
LIMITED TO 25 KNOT GUSTS OR LESS OVER MUCH OF LAKE HURON.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....SF
UPDATE.......SF
SHORT TERM...CB
LONG TERM....DG
MARINE.......DG


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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