Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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997
FXUS63 KDTX 060843
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
343 AM EST SAT FEB 6 2016

.DISCUSSION...

TEMPERATURES WILL BE A FEW DEGREES ABOVE NORMAL DURING AN OTHERWISE
TYPICAL EARLY FEBRUARY DAY AROUND SE MICHIGAN. THE LARGE SCALE
WEATHER PATTERN WILL BE GOVERNED BY THE NORTHERN STREAM OF SPLIT
FLOW ALOFT OVER THE GREAT LAKES WITH THE TROUGH AXIS DRIFTING TO OUR
EAST. SUBSIDENCE ON THE UPSTREAM SIDE OF THE TROUGH WILL BE
AUGMENTED BY RIGHT FRONT EXIT REGION FORCING OVER LOWER MICHIGAN
TODAY INTO TONIGHT. THIS WILL OCCUR OVER THE TOP OF A BROAD
SOUTHWEST FLOW IN THE LOW TO MID LEVELS BETWEEN HIGH PRESSURE OVER
THE OHIO VALLEY AND THE POLAR FRONT SETTLING INTO LAKE SUPERIOR. THE
SETUP WILL MAINTAIN DRY CONDITIONS OVER SE MICHIGAN OTHER THAN SOME
VIRGA ON RADAR AND LEAVES CLOUD AND TEMPERATURE TRENDS AS THE MAIN
FOCUS.

EARLY MORNING SATELLITE IMAGERY SHOWS A BROAD AREA OF MULTILEVEL
CLOUDS OVER THE UPPER MIDWEST EXTENDING INTO LOWER MICHIGAN. MODEL
ANALYSIS FIELDS INDICATE THE CLOUDS ARE THE RESULT OF WEAK
ISENTROPIC ASCENT EMBEDDED IN THE BROAD SOUTHWEST FLOW WHICH IS
EXPECTED TO CONTINUE THROUGH THE DAY. THE WEAK WARM ADVECTION IS
REFLECTED IN SLIGHT 1000-850 MB THICKNESS WARMING THAT WILL HELP
TEMPERATURES RETURN AT LEAST TO LEVELS REACHED YESTERDAY FOR HIGHS
IN THE MID 30S TO AROUND 40. A FEW OF THE TYPICALLY WARMER LOCATIONS
COULD REACH LOWER 40S...ESPECIALLY IN THE DETROIT AREA TO OHIO
BORDER WHERE SOME BREAKS IN THE CLOUDS WILL ALLOW EXTRA SURFACE
HEATING BEFORE READINGS DROP BACK INTO THE MID TO UPPER 20S ALL
AREAS TONIGHT.

THE TRANQUIL FIRST HALF OF THE WEEKEND WILL END UP ON A MORE ACTIVE
NOTE STARTING SUNDAY. THE STRONG LOW PRESSURE SYSTEM MOVING INLAND
OVER THE PACIFIC NW TODAY WILL REACH THE UPPER MIDWEST BY SUNDAY
MORNING AND BEGIN TO AFFECT OUR AREA BY AFTERNOON. DEVELOPMENTS IN
MODEL SOLUTIONS INDICATE A FASTER ONSET OF PRECIPITATION ON THE
FRONT FLANK WARM ADVECTION PORTION OF THE SYSTEM. THE GOOD NEWS HERE
IS THAT TEMPERATURES WILL BE PUSHING HIGHS IN THE LOWER TO MID 40S
OVER THE ENTIRE AREA ENSURING ALL RAIN TO BEGIN THE EVENT. GFS MODEL
SOUNDINGS INDICATE A COLDER PROFILE DUE TO EVAPORATIVE COOLING IN
HIGHER PRECIPITATION RATES COMPARED TO THE OTHER MODELS. THAT COULD
END UP BEING A FACTOR CONTRIBUTING TO A FASTER CHANGE OVER TO SNOW
SUNDAY EVENING BUT STRONG SOUTH WIND DURING THE DAY FAVORS THE
WARMER PROFILES DURING THE AFTERNOON. THE COLD FRONTAL PASSAGE
SUNDAY EVENING WILL PUSH THE CHANGE OVER TO SNOW BUT WILL ALSO BE
FOLLOWED BY THE MID LEVEL DRY SLOT. THE TIMING/POSITION OF THE DRY
SLOT IS A LOW PREDICTABILITY ASPECT OF THE SYSTEM GIVEN THE
ADJUSTMENTS IN MODEL SOLUTIONS THUS FAR AND WITH MORE ANTICIPATED
OVER THE NEXT COUPLE OF RUNS. THE BEST ESTIMATE WITH THE CURRENT
DATA SUPPORTS ANY DISRUPTION TO THE DGZ HOLDING OFF UNTIL AFTER
MIDNIGHT WHICH STILL ONLY ALLOWS FOR SNOW ACCUMULATION UNDER 1 INCH
MOST AREAS SUNDAY NIGHT.

THE LOW PRESSURE SYSTEM WILL CONTINUE TO DIG IN AND CLOSE OFF
OVERHEAD DURING MONDAY. ADDITIONAL SNOWFALL POTENTIAL WILL BE
STRONGLY DEPENDENT ON THE FINER DETAILS OF THIS PROCESS INCLUDING
THE POSITION AND EVOLUTION OF THE DRY SLOT AND SURFACE LOW/TROUGH
ALL OF WHICH ARE SHOWN WITH CONSIDERABLE VARIATION THROUGH THE
MODELS. THE VARIATION IS TYPICAL FOR THIS TYPE OF CLOSED SYSTEM IN
WHICH CHANCE POPS FIT THE FORECAST BEST UNTIL MORE RELIABLE
PLACEMENT OF FOCUSING MECHANISMS CAN BE RESOLVED FOR MONDAY INTO
TUESDAY. THE LARGE SCALE EVOLUTION OF THE SYSTEM IS SHOWN TO BE MORE
PROGRESSIVE BY WEDNESDAY. SHOULD THIS HOLD...THEN THE LOW WOULD BE
TO OUR EAST BY WEDNESDAY NIGHT AND LEAVE NORTHWEST FLOW OF ARCTIC
AIR OVER THE REGION FOR THE REST OF THE WEEK ONLY TO BE REINFORCED
BY ANOTHER ARCTIC FRONT BY NEXT WEEKEND.

&&

.MARINE...

SW WINDS WILL INCREASE DURING THE DAY IN ADVANCE OF THE NEXT LOW
PRESSURE. WIND GUSTS WILL APPROACH 30 KNOTS AT TIMES OVER CENTRAL
LAKE HURON. EXPANSIVE LOW PRESSURE WILL THEN SETTLE OVER THE GREAT
LAKES FOR THE FOLLOWING SEVERAL DAYS. MODERATE WINDS WILL
GRADUALLY BACK FROM SOUTHEASTERLY EARLY SUNDAY TO NORTHWESTERLY BY
TUESDAY.

&&

.AVIATION...ISSUED 1152 PM EST FRI FEB 5 2016

VFR CONDITIONS ARE EXPECTED DURING THE UPCOMING FORECAST AS WEAK
SURFACE TROUGH SWEEPS REMAIN MVFR CIGS EAST OF AREA AS THE FORECAST
BEGINS. CIGS WILL BOUNCE BETWEEN 5-10KFT OR SO INTO SATURDAY AS MID
LEVEL MOISTURE ENCROACHING ON THE WESTERN GREAT LAKES TONIGHT EDGE
INTO THE AREA AS THE NEXT TROUGH APPROACHES. AFTER A BRIEF VEERING
OF WINDS TO THE WNW IN WAKE OF AFOREMENTIONED TROUGH...EXPECT A
GENERAL SW FLOW THRU THE REST OF THE FORECAST...CLIMBING INTO THE 10
TO 15 KNOT RANGE MIDDAY SATURDAY AS PRESSURE GRADIENT TIGHTENS SOME
AND BEST DAYTIME MIXING ENSUES.

FOR DTW...VFR CONDITIONS ARE EXPECTED AND ANY CIGS AOB 5KFT WILL BE
THE EXCEPTION TO THE RULE AS A 10KFT FOOT DECK TONIGHT IS REPLACED
BY 6-9KFT SCT-BKN DECK ON SATURDAY.

//DTW THRESHOLD PROBABILITIES...

* LOW FOR CIGS AOB 5KFT THROUGH THE FORECAST.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...BT
MARINE.......JVC
AVIATION.....DG


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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