AP-LH--DTX-MI Lake Huron Area Forecast Discussion, LH

000

FXUS63 KDTX 151103

AFDDTX

AREA FORECAST DISCUSSION

NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI

703 AM EDT WED JUL 15 2015

.AVIATION...

ALREADY WELL MIXED NE FLOW WILL GUST NEAR 20 KNOTS DURING THE

MORNING AS SURFACE HEATING RAMPS UP. THE HEATING WILL WORK ON JUST

ENOUGH BOUNDARY LAYER MOISTURE LEFT OVER FOR SOME SCATTERED

STRATOCU. THE CLOUD MOISTURE WILL MIX OUT QUICKLY BY AFTERNOON AND

THE WIND WILL SETTLE TO 15 KNOTS OR LESS AS HIGH PRESSURE BUILDS

INTO THE REGION. THAT WILL LEAD TO CLEAR AND CALM CONDITIONS TONIGHT

INTO THURSDAY MORNING AT ALL TERMINALS.

//DTW THRESHOLD PROBABILITIES...

* NONE.

&&

.PREV DISCUSSION...ISSUED 347 AM EDT WED JUL 15 2015

SHORT TERM... TODAY AND TONIGHT

HIGH PRESSURE WILL CONTINUE INBOUND FROM NORTHERN ONTARIO TODAY AND

BRING CONSIDERABLY COOLER AND LESS HUMID AIR INTO SE MICHIGAN

COMPARED TO MID JULY STANDARDS. SUBSIDENCE AND COOL NW FLOW BETWEEN

A BROAD UPPER LEVEL RIDGE OVER THE CENTRAL U.S. AND A DEEP LOW OVER

QUEBEC WILL SUPPORT THE SURFACE HIGH AS IT BUILDS INTO THE REGION.

THIS SYSTEM WILL ENSURE DRY CONDITIONS AND PLENTIFUL SUNSHINE THAT

WILL BE NEEDED TO HELP BOOST TEMPERATURES INTO THE LOWER AND MID

70S...STILL ABOUT 10 DEGREES BELOW NORMAL. READINGS ALONG THE LAKE

HURON SHORELINE WILL LIKELY BE LIMITED TO THE UPPER 60S BY

DIMINISHING BUT STILL STEADY NORTHEAST WIND THROUGH THE DAY.

THE SURFACE HIGH WILL SETTLE OVERHEAD TONIGHT RESULTING IN IDEAL

RADIATIONAL COOLING UNDER CLEAR SKY AND CALM WIND. UPSTREAM

OBSERVATIONS OVER THE NORTHERN GREAT LAKES EARLY TODAY INDICATE

SURFACE DEWPOINT IN THE LOWER TO MID 40S THAT WILL MODIFY VERY

LITTLE AS THE AIR MASS MOVES INTO OUR AREA. THIS WILL SET THE STAGE

FOR OVERNIGHT LOWS IN THE MID TO UPPER 40S OUTSIDE OF METRO AREAS

AND EVEN LOWER 40S IN THE TYPICALLY COOL AREAS OF THE INTERIOR

THUMB. RECORD LOWS FOR JULY 16: DTW 49/1945, FNT 45/1945, MBS

45/1946.

LONG TERM...

THURSDAY. DEEP LAYER SUBSIDENCE AND DRY AIR THROUGH THE DEPTH OF THE

COLUMN WILL BE IN PLACE THURSDAY MORNING. PROGRESSIVE UPPER AIR

EVOLUTION WILL FORCE HIGH PRESSURE TO THE EAST ALLOWING RETURN FLOW

TO ORGANIZE DURING THE DAY. VEERING OF WINDS TO THE SOUTHEAST WILL

ELIMINATE MARINE INFLUENCE INT HE THUMB AND SUPPORT HIGH

TEMPERATURES SEVERAL DEGREES WARMER THAN TODAY...MID TO UPPER 70S.

AIRMASS MODIFICATION WILL CONTRIBUTE JUST A DEGREE OR TWO OVER

TODAY'S HIGHS ELSEWHERE. INCREASE IN MID/HIGH CLOUDS BY AFTERNOON

AND EVENING AS RIDGE FLATTENS AND ZONAL FLOW ADVECTS IN UPSTREAM

CLOUDS AND CONVECTIVE DEBRIS.

THURSDAY NIGHT INTO FRIDAY MORNING. CONVECTIVE EPISODE OVER THE

CENTRAL PLAINS TODAY WILL GIVE RISE TO A CONVECTIVELY ENHANCED

SHORTWAVE THAT WILL SWEEP NORTHEAST WITHIN PREVAILING SW FLOW

THURSDAY NIGHT INTO FRIDAY MORNING. STRONG CONSENSUS AND RUN-TO-RUN

CONTINUITY INCREASES CONFIDENCE IN THE WAVE TRACKING ACROSS

WISCONSIN AND THE UPPER PENINSULA. VAST MAJORITY OF PRECIP WILL

REMAIN TIED TO DYNAMIC SHORTWAVE FORCING AND DEFORMATION AREA WHICH

WILL REMAIN WELL NORTH AND WEST OF THE CWA. HOWEVER, STRONG 50KT LLJ

WILL WORK THROUGH SOUTHEAST MICHIGAN WELL AFTER MIDNIGHT, PERHAPS

INTO EARLY FRIDAY MORNING. INSTABILITY WILL BE MARGINAL AT BEST

GIVEN UNFAVORABLE NOCTURNAL TIMING AND PALTRY MID-LEVEL LAPSE RATES.

HOWEVER, VERY STRONG MOISTURE ADVECTION INTO THE CONVERGENT LEAD

EDGE OF THE LLJ SHOULD BE SUFFICIENT TO SUPPORT AT LEAST A BAND OF

SHOWERS/EMBEDDED THUNDER. OVERALL A LOW IMPACT TIME FRAME WITH

EXPECTATIONS AT THIS POINT LEANING TOWARD A BRIEF DURATION OF

SHOWERS.

FRIDAY. ATTENTION THEN TURNS TO SEVERE CONVECTIVE POTENTIAL ON

FRIDAY AS THE SURFACE COLD FRONT ALIGNS WITH INCREASINGLY ZONAL MID-

LEVEL FLOW. MODEL CONSENSUS SUGGESTS DEWPOINTS OF 70+ DURING PEAK

HEATING, WHICH IS NOT UNREASONABLE GIVEN UPSTREAM OBS OVER THE LAST

FEW DAYS AND THE STRENGTH OF WSW FLOW/MOIST ADVECTION THAT WILL BE

TAKING PLACE DURING THE PRIOR 12 HOURS. THE KINK IN THE FORECAST FOR

SUCH SCENARIOS IS USUALLY THE EVOLUTION OF UPSTREAM CONVECTION AND

THE SUBSEQUENT IMPACT ON LAPSE RATES/CAPPING OVER SOUTHEAST

MICHIGAN. HOWEVER, POTENTIAL FOR UPSTREAM CONVECTION TO PLAY A

DETRIMENTAL ROLE SEEMS MINIMAL AT THIS POINT, SO STEEP LAPSE RATES

SEEM A GOOD BET. RATHER, CAPPING RESULTING FROM ONGOING WARM

ADVECTION IN THE 900-800MB LAYER WILL NEED TO BE OVERCOME, AND LACK

OF A WELL-DEFINED TRIGGER CASTS CONSIDERABLE DOUBT ON POTENTIAL.

ACCORDINGLY, THE 00Z SUITE OF GUIDANCE INDICATES 0-1KM MLCAPE

RANGING FROM 2000 TO 4000 J/KG WITH A TELLING LACK OF QPF AND A WARM

LAYER EVIDENT IN AREA SOUNDINGS. FRIDAY, AT LEAST MOST OF IT, WILL

BE CHARACTERIZED BY CONSIDERABLE MUGGINESS AND TEMPERATURES REACHING

THE UPPER 80S, PERHAPS TOUCHING 90.

MARINE...

SMALL CRAFT ADVISORIES REMAIN IN EFFECT TODAY FOR SAGINAW BAY AND

SOUTHERN LAKE HURON DUE TO STRONG ONSHORE WIND AND HIGH WAVES. THE

WIND WILL STEADILY DIMINISH TODAY AS LOW PRESSURE EXITS TO THE

ATLANTIC COAST IN FAVOR OF HIGH PRESSURE FROM NORTHERN ONTARIO.

SUSTAINED WIND IN THE 20 TO 25 KNOT RANGE WITH GUSTS AROUND 30 KNOTS

PRODUCED 4 TO 7 FOOT WAVES AT THE SOUTH LAKE HURON BUOYS DURING THE

NIGHT. THE WIND AND WAVE ACTION WILL DIMINISH DURING THE AFTERNOON

ON SAGINAW BAY BUT TAKE UNTIL EVENING TO DO SO OVER THE SOUTH THIRD

OF LAKE HURON.

HIGH PRESSURE WILL SETTLE OVER LAKE HURON AND LOWER MICHIGAN TONIGHT

AND BRING QUIET MARINE CONDITIONS BACK TO THE AREA THROUGH THURSDAY.

THE NEXT LOW PRESSURE SYSTEM IS SET TO ENTER THE GREAT LAKES

THURSDAY NIGHT INTO FRIDAY WITH THE MAIN CONCERN BEING A RETURN OF

SHOWERS AND THUNDERSTORMS. WIND AND WAVE CONDITIONS WILL REMAIN

GENERALLY FAVORABLE INTO THE WEEKEND.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...BEACH HAZARDS STATEMENT THROUGH THIS EVENING FOR MIZ048-049-055-063.

LAKE HURON...SMALL CRAFT ADVISORY UNTIL 10 PM EDT THIS EVENING FOR LHZ441>443.

SMALL CRAFT ADVISORY UNTIL 5 PM EDT THIS AFTERNOON FOR LHZ421-422.

LAKE ST CLAIR...NONE.

MICHIGAN WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....BT

SHORT TERM...BT

LONG TERM....JVC

MARINE.......BT

YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE

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

Delivered by Weather Underground Inc. Wed Jul 15 2015 7:03AM EDT