Area Forecast Discussion
Issued by NWS Gaylord, MI

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FXUS63 KAPX 021948
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
348 PM EDT WED SEP 2 2015

.NEAR TERM...(THIS EVENING THROUGH TONIGHT)
ISSUED AT 345 PM EDT WED SEP 2 2015

HIGH IMPACT WEATHER POTENTIAL: HEAVY RAIN CONCERNS?

PATTERN SYNOPSIS/ANTICIPATED EVOLUTION: QUITE THE INTERESTING
PATTERN OUT THERE TODAY FOR SURE. TO BEGIN WITH...JUST
UNCHARACTERISTICALLY HIGH DEW POINTS ACROSS THE NORTHERN LAKES...WITH
WIDESPREAD READINGS IN THE LOWER 70S. COMBINE THAT WITH TEMPERATURES
IN THE 80S...AND APPARENT TEMPERATURES ARE SPIKING TO AROUND 90
DEGREES. TO COMPLETE THE SUMMER FEEL...ABOVE COMBO OF HEAT/HUMIDITY
KICKING OFF WIDELY SCATTERED SHOWERS AND THUNDERSTORMS...SOME OF
WHICH ARE PRODUCING LOCALLY HEAVY RAIN. ESSENTIALLY...ABOUT YOUR
TYPICAL LATER SUMMER DAY...IN FLORIDA! SUCH AN AIRMASS TIED TO
NORTHERN EXTENT OF BROAD SUBTROPICAL RIDGING EXTENDING OVER MUCH OF
THE EASTERN TWO THIRDS OF THE NATION...ITSELF PART OF A RATHER
AMPLIFIED EARLY SEPTEMBER PATTERN. THE NEXT INTERESTING FEATURE IS
CONVECTIVELY AGITATED VORT LOBE/MID LEVEL WAVE ROTATING SLOWLY
ACROSS NORTHWEST WISCONSIN...WITH A BROAD AREA OF SHOWERS/STORMS
ACCOMPANYING IT.

PRIMARY FORECAST CONCERNS/CHALLENGES: SHOWER AND THUNDERSTORM
EVOLUTION.

DETAILS: FIRST THINGS FIRST...AND EXPECT CURRENT SHOWER AND
THUNDERSTORM ACTIVITY TO RUN ITS COURSE EARLY THIS EVENING AS
DIURNAL SUPPORT IS LOST. WEAK WIND FIELDS/LIMITED SHEAR SHOULD
PREVENT MUCH OF A SEVERE THREAT...ALTHOUGH WILL NEED TO WATCH FOR
BRIEF WET MICROBURSTS IN HEAVY RAIN CORES. FOCUS FOR THE OVERNIGHT
CENTERS ON THE AFFECTS FROM THAT SLOWLY APPROACHING WISCONSIN WAVE.
DIFFERENCES ARE MANY ON HOW GUIDANCE HANDLES THIS WAVE...WITH NAM-
WRF/GFS MODELS MORE AGGRESSIVE AT WEAKENING IT AND DRIVING BEST RAIN
CHANCES INTO OUR SOUTHWEST ZONES LATER TONIGHT. OTHER MODELS REMAIN
MUCH MORE ROBUST WITH MID LEVEL SUPPORT...HELPING DRIVE A MORE
WIDESPREAD AREA OF RAIN AND EMBEDDED STORMS INTO AT LEAST MUCH OF
NORTHERN LOWER LATER TONIGHT. SATELLITE TRENDS SUPPORT A MORE MATURE
WAVE THAN THE FORMER PROGS WOULD IMPLY...AT LEAST ADDING SOME
CREDENCE TO THE MORE AGGRESSIVE AND WETTER PROGS. WILL CAUTIOUSLY
TREND POPS A LITTLE FARTHER NORTH...BUT STILL LIMITING THEM TO
CHANCE WORDING. NO DOUBT THIS WILL REMAIN A NEAR TERM ISSUE THIS
EVENING...WITH FUTURE ADJUSTMENTS MORE THAN EXPECTED.

IF STORMS DO INDEED FIRE OVERNIGHT...ONCE AGAIN JUST NOT SEEING MUCH
IF ANY SEVERE THREAT GIVEN LIMITED SHEAR/WEAK STORM ORGANIZATION.
HEAVY RAIN...HOWEVER...DOES REMAIN A CONCERN WITH SLOW MOVING CELLS
AND MOISTURE RICH AIRMASS. WILL NO DOUBT CONTINUE TO MENTION THIS
HEAVY RAIN POTENTIAL IN OUR LATEST HAZARDOUS WEATHER PRODUCTS.

&&

.SHORT TERM...(THURSDAY THROUGH SATURDAY)
ISSUED AT 345 PM EDT WED SEP 2 2015

THURSDAY THROUGH SATURDAY...THE LARGE AREA OF HIGH PRESSURE WHICH
HAS BEEN ANCHORED OVER THE ERN TWO THIRDS OF THE COUNTRY SINCE THE
BEGINNING OF THE WORK WEEK...WILL REMAIN NEARLY STATIONARY INTO THE
UPCOMING HOLIDAY WEEKEND WHILE A STORM SYSTEM TRIES TO ORGANIZE OVER
THE ROCKIES. AT UPPER LVLS...BROAD 500MB RIDGE WHICH BUILT OVER
MUCH OF THE COUNTRY TO BEGIN THE WORK WEEK...WILL SHARPEN EAST OF
THE ROCKIES BY FRIDAY WHILE A TROUGH DEEPENS OVER THE PACIFIC
NORTHWEST. THIS PATTERN WILL GENERATE MAINLY DRY CONDS ACROSS MUCH
OF THE GREAT LAKES THROUGH THE WEEKEND. HOWEVER...A WEAK RIPPLE
DEVELOPING IN THE 500MB FLOW OVER THE WRN LAKES WILL MOVE ACROSS THE
REGION THURSDAY. MODEL SOUNDINGS AND MSTR PROGS SHOWING PLENTY OF
LOW AND MID LVL MSTR (SFC DEW PTS NEAR 65F WITH 850MB DEW PTS NEAR
17C) IN PLACE IN ADVANCE OF THE BOUNDARY TO GENERATE CONVECTION OVER
NRN MI THURSDAY AFTERNOON AND EVENING (MU CAPE ~2500 J/KG, LI ~
-4C WITH 850/500MB LAPSE RATES OF 6-7C/KM). CORRESPONDING MID LVL
QVECTORS SHOWING THE BEST CONVERGENCE ASSOCIATED WITH APPROACHING
UPPER TROUGH...EXITING EAST OF THE REGION BY 00Z FRI.

THE EXTEND PERIOD OF WELL ABOVE NORMAL TEMPERATURES WILL CONTINUE
ACROSS THE GREAT LAKES THROUGH THE FCST PD...WITH CONTINUED PRESENCE
OF SURFACE AND UPPER LVL RIDGE IN PLACE FROM THE GULF STATES THROUGH
THE OHIO VALLEY. 850MB TEMPS ASSOCIATED WITH THIS PATTERN WILL
SLOWLY WARM FROM AROUND 16C THURSDAY TO AROUND 20C OVER THE WEEKEND.
THIS PATTERN SHOULD GENERATE AFTERNOON TEMPS IN THE MID 80S ACROSS
NRN MI THURSDAY AND FRIDAY WITH HIGHS WARMING INTO THE UPPER 80S
SATURDAY.

&&

.LONG TERM...(SATURDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 345 PM EDT WED SEP 2 2015

FLATTENING OF THE H5 RIDGE THAT WAS SETUP OVER THE GREAT LAKES WILL
HELP TO USHER OUT THE WELL ABOVE NORMAL TEMPERATURES FROM EARLIER IN
THE WEEK. SUNDAY AND MONDAY WILL STILL BE WELL ABOVE NORMAL...BUT
TEMPERATURES WILL DIP BY MIDWEEK. A WEAK COLD FRONT...ATTENDANT TO
LOW PRESSURE MOVING THROUGH ONTARIO...WILL HELP TO KNOCK
TEMPERATURES DOWN SOME EARLY IN THE WEEK AND BRING THE POSSIBILITY
OF SOME WIDESPREAD SHOWERS. NOT A LOT OF AGREEMENT WITH TIMING RIGHT
NOW...BUT THIS COULD AFFECT SOME LABOR DAY ACTIVITIES. A SECOND
SYSTEM...MOVING OUT OF THE PLAINS...WILL BRING ANOTHER CHANCE OF
MORE WIDESPREAD SHOWERS FOR MIDWEEK AND HELP TO GET TEMPERATURES
BACK DOWN TO NORMAL RANGES.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 143 PM EDT WED SEP 2 2015

A RATHER LOW CONFIDENCE FORECAST. STILL WATCHING DIURNALLY DRIVEN
SHOWERS/STORMS THIS AFTERNOON AND EARLY EVENING...AFFECTING
PRIMARILY TVC AND APN. THESE WILL REMAIN SCATTERED...AND SPECIFIC
IMPACTS/IF ANY/ WILL HAVE TO WAIT UNTIL STORM ORGANIZATION AND
PROPAGATION ARE REALIZED. UNCERTAINTY INCREASES TONIGHT AS
INITIAL CONVECTION WANES...WAITING ON WHAT IMPACTS UPSTREAM WAVE
HAS ON RENEWED DEVELOPMENT OVERNIGHT. STILL BELIEVE SOME POTENTIAL
FOR SHOWERS/STORMS TO DRIFT ACROSS LAKE MICHIGAN WITH THIS
FEATURE...IMPACTING TVC AND MBL DURING THE LATE OVERNIGHT AND
EARLY MORNING. OTHER ISSUE WILL BE BR/FOG DEVELOPMENT WITH
ABUNDANT LOW LEVEL MOISTURE. GIVEN LITTLE APPRECIABLE CHANGE IN
THE OVERALL AIRMASS...WOULD EXPECT SIMILAR DEVELOPMENT AS SEEN
THE LAST FEW NIGHT.

WHAT HAPPENS TONIGHT WILL GREATLY DICTATE THURSDAY MORNING
CONDITIONS. FOR NOW WILL TREND A TOUCH OPTIMISTIC...LETTING THINGS
EVOLVE TONIGHT BEFORE HITTING WITH MUCH DETAIL IN THE FORECAST.

&&

.MARINE...
ISSUED AT 345 PM EDT WED SEP 2 2015

LIGHT SYNOPTICALLY DRIVEN WINDS IN STABLE OVER-WATER
ENVIRONMENT SET TO CONTINUE THROUGH THURSDAY. BIGGER CONCERN REMAINS
THUNDERSTORM POTENTIAL...WITH ANY CONVECTION CAPABLE OF PRODUCING
BRIEF GUSTY AND ERRATIC WINDS. MAIN THREAT FOR THIS WOULD BE ACROSS
LAKES MICHIGAN AND HURON. OTHER ISSUE WILL BE MARINE FOG/STRATUS AS
UNSEASONABLY WARM/MOIST AIR OVERSPREADS THE LAKES.

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LH...NONE.
LM...NONE.
LS...NONE.
&&

$$

NEAR TERM...MSB
SHORT TERM...SWR
LONG TERM...ALM
AVIATION...MSB
MARINE...MSB


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