Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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171
FXUS63 KDTX 071700
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1200 PM EST SUN FEB 7 2016

.AVIATION...

MID CLOUDS AND SOUTHERLY FLOW GUSTING TO 20 KNOTS OR BETTER THIS
AFTERNOON. THE 12Z DTX SOUNDING SHOWED A DRY SUB 700 MB
LAYER...BUT STRONG SOUTH-SOUTHWEST WINDS ADVECTING SOME MODEST
MOISTURE...AND 12Z MODELS SUGGESTING A FLARE UP OF LIGHT
RAIN/SPRINKLES AND AT LEAST MVFR CEILINGS AS SURFACE FRONT TRACKS
THROUGH DURING THE EVENING HOURS OVER SOUTHEAST MICHIGAN. IT IS A
DIFFICULT FORECAST...AS UPSTREAM OBSERVATIONS AROUND ST LOUIS
EXTENDING INTO THE WESTERN OHIO VALLEY DO NOT INDICATE THIS...BUT
THERE IS SOME VIRGA TRANSLATING THROUGH LOWER MICHIGAN AT THE
MOMENT. ALSO...SURFACE DEW PTS ARE RUNNING CLOSER TO 30
DEGREES...AND NOT SURE WE WILL RISE INTO THE UPPER 30S AS
SUGGESTED. NONE-THE-LESS...STILL ENOUGH EVIDENCE TO CARRY
BORDERLINE VFR/MVFR CEILINGS FOR THIS EVENING AND TONIGHT...WITH
JUST ENOUGH DRYING AND COLD ADVECTION MONDAY MORNING TO SCOUR OUT
THE LOW CLOUDS BEFORE RETURNING DURING THE AFTERNOON HOURS.

AT DTW... SOUTH-SOUTHWEST WINDS GUSTING TO 20 KNOTS OR BETTER THIS
AFTERNOON WILL TRANSPORT MODEST MOISTURE...EXPECTED TO GENERATE A
FEW SPRINKLES OR LIGHT RAIN SHOWERS THIS EVENING (1-4Z)...WHICH WILL
HELP DROP CEILINGS AROUND 3000 FEET...PERSISTING FOR A GOOD PORTION
OF THE NIGHT. CONFIDENCE IN CLEARING OCCURRING TOWARD SUNRISE IS
AVERAGE TO LOW...AS A BORDERLINE MVFR/IFR CEILING IS NOT OUT OF THE
QUESTION MONDAY MORNING AS ADDITIONAL MOISTURE ATTEMPTS TO MOVE UP
FROM THE SOUTH.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CIGS AOB 5KFT AFTER 00Z THROUGH 10Z...LOW DURING MONDAY
  MORNING...WITH MEDIUM CONFIDENCE DURING THE AFTERNOON.

* HIGH CONFIDENCE IN PRECIPITATION FALLING AS LIGHT RAIN DURING
  EVENING.

&&

.PREV DISCUSSION...ISSUED 345 AM EST SUN FEB 7 2016

DISCUSSION...

EARLY MORNING OBSERVATIONAL EVIDENCE SUPPORTS THE MORE SUBDUED
PRECIP FORECAST TREND THAT BEGAN IN THE PREVIOUS FORECAST CYCLE FOR
TODAY AND TONIGHT. THE MOISTURE AXIS PRECEDING THE UPPER LOW OVER
THE MIDWEST IS PRODUCING RADAR RETURNS WHILE SURFACE OBS PROVE THIS
TO BE ONLY VIRGA UNTIL FAR NORTHERN WISCONSIN AND UPPER MICHIGAN.
SURFACE OBSERVATIONS OVER THE SOUTHERN PLAINS INDICATE THE RETURN
FLOW OF GULF MODIFIED AIR HAS YET TO DEVELOP IN THE LOW LEVELS WHICH
THE LAST COUPLE OF MODEL RUNS HAVE CAPTURED AND ARE NOW FACTORING
INTO PRECIP POTENTIAL OF THE LOW AS IT MOVES INTO THE GREAT LAKES.
IT DOES LOOK LIKE A MODEST MOISTURE RECOVERY WILL OCCUR BUT IT WILL
BE LATER TONIGHT AND MOSTLY EAST OF OUR AREA AFTER PASSAGE OF THE
COLD FRONT. CHANCE POPS THEN HAVE THE POSSIBILITY WELL COVERED FOR
THE INCOMING MID LEVEL MOISTURE TO PRODUCE A FEW POCKETS OF
SATURATION IN THE DRY LOW LEVEL AIR MASS ALREADY IN RESIDENCE...
MAINLY IN THE TRI CITIES AND NORTHERN THUMB REGION.

THE LACK OF PRECIPITATION TODAY WILL OPEN THE DOOR FOR A RUN OF
TEMPERATURES FARTHER INTO THE MID 40S IN MODERATE SOUTHWEST LOW
LEVEL FLOW DURING THE AFTERNOON. MODEL SOUNDINGS INDICATE THE
BOUNDARY LAYER MIXING INTO THE 950-925 MB RANGE...GOOD ENOUGH FOR
GUSTS NEAR 20 KNOTS TO SUPPORT THE SURGE OF WARMER AIR. MILD
CONDITIONS WILL ALSO LINGER THROUGH TONIGHT EVEN BEHIND THE MODEST
COLD FRONT/OCCLUSION WITH TEMPERATURES PROJECTED TO TAKE MOST OF THE
NIGHT TO DROP BELOW FREEZING. THIS WILL MITIGATE THE IMPACT OF RAIN
SHOWERS CHANGING TO SNOW SHOWERS AS THE PROFILE COOLS ALOFT SUBJECT
TO THE MOISTURE LIMITATIONS MENTIONED ABOVE. THE SURFACE LOW IS ALSO
SHOWN IN THE MODELS TO BE FILLING AND BROADENING AS IT MOVES FROM
CENTRAL CANADA TODAY TO ABOUT THE STRAITS AREA MONDAY MORNING. THE
RESULTING WEAK LOW LEVEL FLOW WILL NOT BE FAVORABLE FOR DRIZZLE
PRODUCTION EVEN IF AN ORGANIZED MID LEVEL DRY SLOT CAN MATERIALIZE.

THE LOW PRESSURE SYSTEM WILL REMAIN ALMOST DIRECTLY OVER SE MICHIGAN
MONDAY AND TUESDAY. THE SURFACE REFLECTION WILL REMAIN BROAD WITH
THE BULK OF LOW LEVEL CONVERGENCE TO OUR EAST IN LOOSE MODEL
AGREEMENT THAT WILL BE SUBJECT TO ADJUSTMENT IN LATER FORECAST
CYCLES. THE GENERAL ENVIRONMENT IN THE LATEST MODEL DEPICTIONS
FAVORS SCATTERED COVERAGE OF SNOW SHOWERS MONDAY INTO MONDAY NIGHT
IN STEEPENING LAPSE RATES UNDER THE COLD POOL ALOFT AND WITH LITTLE
TO NO LOW LEVEL FOCUSING MECHANISM. THE LACK OF LOW LEVEL SUPPORT
WILL BE PARTIALLY COMPENSATED FOR BY IMPROVING NW FLOW AND LAKE
EFFECT CONTRIBUTIONS THAT WILL BECOME BETTER ORGANIZED FOR MORE
NUMEROUS SNOW SHOWER COVERAGE TUESDAY...AND EVEN INTO WEDNESDAY AS
THE SYSTEM BEGINS MOVING AWAY. THE LATEST GLOBAL MODELS CONTINUE TO
INDICATE THE LOW EXITING THE GREAT LAKES THURSDAY WHICH WILL ALLOW
ARCTIC AIR TO FLOOD OVER LOWER MICHIGAN AND CAUSE MAX TEMPS TO
STRUGGLE INCREASINGLY TO HOLD THE 20S WEDNESDAY THROUGH FRIDAY. THE
ECMWF THEN OFFERS A DIRECT HIT BY A REINFORCING 1045 MB ARCTIC HIGH
BY NEXT WEEKEND WHILE THE GFS SUGGESTS A SHOT GLANCING THROUGH THE
NORTHERN GREAT LAKES INTO THE NEW ENGLAND STATES. EITHER WAY...A
ROUND OF WELL BELOW NORMAL TEMPERATURES IS A GOOD BET WITH THE
DIFFERENCES BEING BETWEEN SINGLE DIGIT HIGHS OR HIGHS IN THE TEENS
NEXT WEEKEND.

MARINE...

MODERATE SSW WINDS WILL CONTINUE THROUGH THIS EVENING BEFORE
DIMINISHING CONSIDERABLY TONIGHT INTO TUESDAY AS EXPANSIVE LOW
PRESSURE SETTLES ACROSS THE GREAT LAKES. WINDS WILL BACK TO
NORTHWESTERLY BY LATE TUESDAY INTO WEDNESDAY AND INCREASE AS LOW
PRESSURE DEPARTS DURING THE MIDWEEK PERIOD. NO HEADLINES ARE
ANTICIPATED AT THIS TIME.

&&

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

$$

AVIATION.....SF
DISCUSSION...BT
MARINE.......JVC


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