Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1020 PM EST TUE NOV 25 2014

.UPDATE...

EVENING SURFACE ANALYSIS HAS A RIDGE OF HIGH PRESSURE RUNNING FROM
THE WESTERN GREAT LAKES INTO THE LOWER OHIO VALLEY AND POINTS
SOUTH. SATELLITE IMAGERY SHOWS A SOLID DECK OF STRATUS TRAPPED
ALONG AND EAST OF THE RIDGE AXIS OVER ALL OF LOWER MICHIGAN
AUGMENTED BY LIGHT BUT COLD WESTERLY FLOW OVER LAKE MICHIGAN. THE
DTX 00Z SOUNDING IS REPRESENTATIVE OF OTHERS AROUND THE REGION
THAT DEPICT A SHARP INVERSION DUCTING BOUNDARY LAYER MOISTURE WITH
ENOUGH DEPTH TO ENSURE PERSISTENCE WITH THE LOSS OF SURFACE
HEATING. SATELLITE TRENDS AND MODEL DEPICTIONS OF A SLOW EASTWARD
PACE ON THE SURFACE HIGH SUGGEST COVERAGE WILL LINGER THROUGH MUCH
OF WEDNESDAY MORNING. THE EVENING UPDATE REFLECTS THIS TREND ALONG
WITH AN UPWARD NUDGE ON MIN TEMPS THAT SHOULD SETTLE INTO THE MID
20S BY SUNRISE.

&&

.AVIATION...ISSUED 653 PM EST TUE NOV 25 2014 

//DISCUSSION...

SURFACE OBSERVATIONS FROM LATE AFTERNOON INTO EARLY EVENING INDICATE 
MVFR STRATUS LOCKED WITHIN THE RIDGE OF SURFACE HIGH PRESSURE FROM 
THE WESTERN GREAT LAKES INTO THE OHIO VALLEY. CONSIDERING THE LACK 
OF DIURNAL DISSIPATION OF THESE CLOUDS UPSTREAM OF THE LAKES... 
EXPECT A SLOWER CLEARING TREND OVER LOWER MICHIGAN DURING THE NIGHT. 
IT MAY TAKE UNTIL THE SURFACE RIDGE MOVES NORTH OF THE REGION TO 
SCOUR OUT THE LOW CLOUDS THROUGH THE TERMINAL CORRIDOR. INCREASED 
EASTERLY LOW LEVEL WIND DURING WEDNESDAY MORNING WILL MARK THE 
TRANSITION WITH A SHORT FETCH OVER LAKES HURON AND ERIE PRODUCING 
MINIMAL ADDITIONAL CLOUD MOISTURE. THE SURFACE PRESSURE PATTERN WILL 
THE REMAIN FLAT DURING WEDNESDAY...BETWEEN DEPARTING HIGH PRESSURE 
AND THE NEXT WEAK LOW PRESSURE SYSTEM ENTERING THE MIDWEST. EXPECT 
VFR CONDITIONS AND LIGHT WIND TO PERSIST INTO WEDNESDAY NIGHT. 

//DTW THRESHOLD THREATS...

* HIGH PROBABILITY THAT CEILINGS WILL REMAIN BELOW 5000 FT THROUGH 
  TONIGHT.

&&

.PREV DISCUSSION...ISSUED 344 PM EST TUE NOV 25 2014 

SHORT TERM...TONIGHT
 
SNOW SHOWERS THAT HAVE BEEN PRESENT ACROSS MUCH OF THE NORTHERN CWA 
WILL SLOWLY DIMINISH TOWARDS NIGHTFALL. STRONG SOUTHWESTERLY WINDS 
HAVE ALLOWED LAKE EFFECT BANDS OFF OF LAKE MICHIGAN TO MAKE THEIR 
WAY INTO THE SAGINAW VALLEY AND I-69 CORRIDOR FOR MUCH OF THE 
AFTERNOON. CURRENT MODEL TRENDS SHOW WEAK MID LEVEL RIDGING TO TAKE 
PLACE AFTER 00Z RESULTING IN SURFACE HIGH PRESSURE TO BUILD ACROSS 
THE GREAT LAKES REGION TONIGHT. THIS HIGH WILL ALLOW WINDS TO 
DIMINISH AND BECOME LIGHT AND VARIABLE OVERNIGHT CAUSING LAKE EFFECT 
SNOW SHOWERS TO COME TO AN END. IN ADDITION...THE SOLID STRATUS DECK 
OVER SOUTHEAST MICHIGAN WILL BECOME MORE BROKEN OVERNIGHT AS MID 
LEVEL DRY AIR FILTERS IN TO THE REGION. LIGHT WINDS AND SOME 
CLEARING WILL ALLOW TEMPERATURES TO DROP INTO THE LOW TO MID 20S 
ACROSS SOUTHEAST MICHIGAN.

LONG TERM...

UPPER TROUGH WILL ROTATE THROUGH THE GREAT LAKES ON WEDNESDAY 
THROUGH THURSDAY WITH A FAST-MOVING EDGEWAVE DIGGING INTO THE OHIO 
VALLEY EARLY ON WEDNESDAY. WITH THE BULK OF FORCING IN THE REGION 
TIED TO THIS WAVE AND THE NORTHERN BRANCH TROUGH AXIS STILL WELL 
UPSTREAM, SE MICHIGAN WILL BE LEFT IN A RATHER BENIGN ZONE ON 
WEDNESDAY CHARACTERIZED BY A NONDESCRIPT SURFACE PRESSURE PATTERN. 
LITTLE AIRMASS MODIFICATION FROM TODAY WILL PRODUCE SIMILAR HIGH 
TEMPERATURES UNDER CLOUDY CONDITIONS, THOUGH SURFACE WINDS WILL BE 5 
KNOTS OR LESS. 12Z NAM SOUNDINGS SUGGEST A SUFFICIENTLY DEEP LAYER 
OF BOUNDARY LAYER MOISTURE TO MOVE FORWARD WITH THE INHERITED MOSTLY 
CLOUDY FORECAST. A FEW FLURRIES MAY BE POSSIBLE DURING PEAK HEATING 
GIVEN MARGINALLY FAVORABLE THERMODYNAMIC PROFILE.

NORTHERN TROUGH WILL APPROACH WED NIGHT INTO THURSDAY WITH CLOUD 
COVER AND DECENTLY MIXED CONDITIONS EXPECTED TO LIMIT THURSDAY 
MORNING'S LOWS TO THE MID 20S. CROSS-SECTIONS ON THURSDAY REVEAL 
VERY HIGH STATIC STABILITY ABOVE 700MB. THIS WILL SIGNIFICANTLY 
DAMPEN OR ALTOGETHER ELIMINATE THE VERTICAL RESPONSE TO THE WAVE IN 
THE MID-LEVELS. HOWEVER, CONVERGENCE ALONG THE COLD FRONT DOES LOOK 
PRETTY SOLID. COMBINED WITH A QUICK HITTING SHOT OF SR ISENTROPIC 
ASCENT ON THE 275K SURFACE AND MODEST AUGMENTATION OF THE MOISTURE 
FIELD FROM THE LAKE AGGREGATE, COULD SEE A LINE OF SNOW SHOWERS WORK 
THROUGH DURING THE HOLIDAY BRINGING A DUSTING TO PERHAPS A HALF INCH 
OF ACCUMS. STRONG DEPENDENCE ON SUB-700MB FORCING/DYNAMICS AND SHORT-
LIVED NATURE OF FORCING REALLY SUGGEST NOTHING MORE THAN A CHANCE 
POP. ANTICYCLONIC FLOW WILL BUILD IN FOR THURSDAY NIGHT AS COLD HIGH 
PRESSURE WORKS INTO THE AREA BEHIND THE FRONT. H85 TEMPERATURES WILL 
FALL TO -13C SUPPORTING CURRENT FORECAST LOWS IN THE UPPER TEENS BY 
FRIDAY MORNING.

ON FRIDAY...SPRAWLING LOW PRESSURE OVER THE UPPER MIDWEST WILL 
BATTLE RETREATING HIGH PRESSURE OVER THE EASTERN SEABOARD. LOW 
PRESSURE WILL WIN-OUT AS IT IS ACCOMPANIED BY A LATITUDINAL FLOW 115 
KT JET. WITH THE ZONAL FLOW IN PLACE...A RECOVERY TO NEAR NORMAL 
TEMPERATURES WILL ENSUE FOR THE WEEKEND. NEXT SURFACE FEATURE /HIGH 
PRESSURE OVER NORTHERN CANADA/ WILL GET LITTLE UPPER AIR 
SUPPORT...BUT NONETHELESS LOOKS TO BRING COLD TEMPS BACK TO THE 
REGION EARLY NEXT WEEK. HAVE TRENDED THOSE GRIDS COOLER WITH 
LITTLE CONFIDENCE IN SNOW CHANCES PAST DAY 4.

MARINE...

WINDS AND WAVES ARE EASING THIS AFTERNOON ALLOWING ALL GALE WARNINGS 
TO EXPIRE. SMALL CRAFT ADVISORIES ALONG THE TIP OF THE THUMB HAVE 
BEEN EXTENDED THROUGH EARLY THIS EVENING UNTIL SIGNIFICANT WAVE 
HEIGHTS FALL BELOW THE 3 TO 5 FOOT THRESHOLD. A WEAK PRESSURE 
GRADIENT WILL RESULT IN LIGHT WINDS TONIGHT THROUGH WEDNESDAY NIGHT. 
A FAST MOVING LOW PRESSURE WILL THEN BRING A QUICK SHOT OF 
NORTHWESTERLY GALES OR NEAR-GALES ON THURSDAY AFTERNOON WHICH SHOULD 
BE NO MORE THAN 6 HOURS IN DURATION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

UPDATE.......BT
AVIATION.....BT
SHORT TERM...RK
LONG TERM....JVC/MM
MARINE.......JVC


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

National Weather Service Glossary of Abbreviations