753
FXUS61 KILN 200527
AFDILN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
127 AM EDT WED OCT 20 2021
SYNOPSIS
HIGH PRESSURE WILL PROVIDE MOSTLY SUNNY AND WARM CONDITIONS
THROUGH WEDNESDAY. DEVELOPING LOW PRESSURE AND AN ASSOCIATED
COLD FRONT WILL INCREASE PRECIPITATION CHANCES FROM WEDNESDAY
NIGHT THROUGH THURSDAY BEFORE COOLER CONDITIONS RETURN FOR LATE
WEEK.
NEAR TERM /UNTIL 6 AM THIS MORNING/
SURFACE HIGH PRESSURE CENTERED OVER THE SOUTHEAST UNITED STATES
WILL CONTINUE TO PROVIDE FAIR CONDITIONS THIS EVENING THROUGH
TONIGHT. OUTSIDE OF A FEW THIN CIRRUS CLOUDS THROUGH LATE
EVENING, CLEAR SKIES WILL ONCE AGAIN ALLOW EFFICIENT RADIATIONAL
COOLING. WITH THIS IN MIND, LOW TEMPERATURES SHOULD ONCE AGAIN
DIP INTO THE MID-40S.
SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/
HIGH PRESSURE SHIFTS OFF THE CAROLINA COAST WEDNESDAY AS
DEVELOPING LOW PRESSURE MOVES EAST INTO IOWA. OUTSIDE OF A FEW
MID AND HIGH CLOUDS, MOST OF THE SIGNS OF APPROACHING LOW
PRESSURE WILL HOLD OFF UNTIL AFTER SUNSET WEDNESDAY. WITH STEADY
SOUTHWESTERLY FLOW, TEMPERATURES WILL PEAK IN THE LOW 70S.
MOISTURE INCREASES OVER THE OHIO VALLEY WEDNESDAY NIGHT AS THE
SURFACE LOW SLIDES INTO THE GREAT LAKES. LATEST GUIDANCE BRINGS
BEST CHANCE OF SHOWERS LATE IN THE PERIOD TO THE NORTHERN HALF
OF THE CWA CLOSEST TO THE MID-LEVEL SHORTWAVE. UNDER INCREASING
CLOUD COVER AND SOUTHWEST FLOW AHEAD OF THE COLD FRONT, LOW
TEMPERATURES WILL STAY UP IN THE MID TO UPPER 50S.
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
THE PERIOD BEGINS WITH A HIGH CONFIDENCE FRONTAL PASSAGE ON THURSDAY
MORNING INTO EARLY AFTERNOON ACROSS THE ILN FORECAST AREA,
ACCOMPANIED BY A THREAT OF SHOWERS AND A FEW STORMS PERHAPS IN THE
SCIOTO VALLEY WITH AUTUMNAL COOLING TO FOLLOW, AND ENDS IN AN
EXTREMELY LOW CONFIDENCE PATTERN WHICH MAY SPELL CONSIDERABLE
WARMING.
IN THE DETAILS, AT 12Z ON THURSDAY, A STRONG SHORTWAVE TROUGH WILL
BE LOCATED OVER LAKE MICHIGAN WITH A COLD FRONT ARCING SOUTH THROUGH
INDIANA. OUT AHEAD OF THE FRONT, AN ELEVATED BAND OF SHOWERS MAY BE
MOVING THROUGH THE WESTERN ILN CWA ON THURSDAY MORNING IN STRONG
THETA-E ADVECTION ABOVE THE BOUNDARY LAYER. AS THE DAY PROGRESSES,
THERE IS SOME POTENTIAL FOR THESE SHOWERS TO BECOME SURFACE BASED TO
SOME DEGREE BY EARLY-MID AFTERNOON OVER THE SCIOTO VALLEY, OR
PERHAPS SURFACE-BASED SHOWER DEVELOPMENT TO OCCUR ALONG THE FRONT
ITSELF BEFORE EXITING THE FORECAST AREA. THERE IS A NARROW WINDOW
AMONG THE VARIOUS DETERMINISTIC RUNS OF ENOUGH SURFACE BASED
INSTABILITY TO DEVELOP IN PORTIONS OF THE LOWER SCIOTO VALLEY TO
ALLOW DEEP ENOUGH UPDRAFTS FOR THUNDER MENTION. THIS MAY NEED TO BE
EXPANDED NORTHWARD A LITTLE IN FUTURE FORECASTS. GIVEN STRONG FLOW
FIELDS WHICH WILL BE UNIDIRECTIONAL /SOUTHWESTERLY/ IN NATURE, IT IS
NOT OUT OF THE REALM OF POSSIBILITY THAT SOME STRONG/GUSTY STORMS
COULD OCCUR IN OUR SOUTHEAST/EASTERN COUNTIES BEFORE THE FRONT
EXITS, ESPECIALLY IF THE BOUNDARY ENDS UP PASSING THROUGH AN HOUR OR
TWO SLOWER THAN EXPECTED.
THERE WILL ALSO BE GUSTY WINDS IN THE WAKE OF THE FRONT ON THURSDAY
AFTERNOON PARTICULARLY OVER WESTERN OHIO AND EASTERN INDIANA. HAVE
MOVED WINDS AND ESPECIALLY WIND GUSTS HIGHER FOR THURSDAY AFTERNOON,
BUT POTENTIALLY NOT HIGH ENOUGH AS WE MAY SEE SOME 30KT GUSTS AT
PEAK HEATING OVER THE HIGHER TERRAIN AREAS /E.G., BELLEFONTAINE
RIDGE./
STRONG COLD ADVECTION IN THE WAKE OF THE FRONT ON THURSDAY NIGHT,
AND A REINFORCING SECONDARY COLD FRONT ON FRIDAY, GUARANTEE THE
EVENTUAL DEVELOPMENT OF PLENTY OF STRATOCUMULUS AND LIGHT SHOWER
THREAT ESPECIALLY FOR FRIDAY, WHERE HIGHS WILL ONLY MAKE THE 50S TO
AROUND 60.
UNCERTAINLY BEGINS TO RAPIDLY INCREASE OVER THE WEEKEND AND INTO
EARLY NEXT WEEK AS THERE IS NOT GOOD AGREEMENT ON THE PATH/STRENGTH
OF ENERGY ATTEMPTING TO UNDERCUT HIGH LATITUDE BLOCKING / LONGWAVE
RIDGE MOVING EAST TOWARD THE GREAT LAKES. FOR RIGHT NOW AM RUNNING
A DRY/COOL SATURDAY WITH SOME MODEST INCREASES IN RAIN CHANCES ON
SUNDAY AS A WARM FRONTAL ZONE BEGINS TO SET UP OVER THE OHIO VALLEY
AND ATTEMPT TO PUSH NORTH. HOWEVER, IF ENERGY RUNS ALONG THIS
BOUNDARY PRECIPITATION CHANCES WILL NEED TO GREATLY INCREASE AND
TEMPS MAY BE TOO OPTIMISTIC. ALSO AM EXTENDING RAIN CHANCES INTO
MONDAY TO ACCOUNT FOR THE VARIED SPEED/LATITUDE OF THE POTENTIAL
ENERGY PASSING THROUGH THE GREAT LAKES. THIS BEGINS A PERIOD OF
HIGH VARIABILITY IN THE DETERMINISTIC AND ENSEMBLE MEMBERS, WITH
NOTABLE SPREAD ON 2M TEMP PLUMES SUNDAY->TUESDAY. THIS COMES TO A
HEAD ON MONDAY/TUESDAY, WITH NBM TEMPERATURE STANDARD DEVIATIONS
MAXIMIZED OVER THE OHIO VALLEY INDICATING A GREAT AMOUNT OF
UNCERTAINTY ON WARM FRONTAL LOCATION AS THE LONGWAVE UPPER RIDGE
MOVES IN AND WEAKENING/UNDERCUTTING ENERGY MOVING OUT. WHILE THE
NBM 50%ILE AND MEAN TEMPS HAVE RISEN CONSIDERABLY FOR MON/TUE, IT
SHOULD BE NOTED THERE ARE STILL A NUMBER OF DATA WHICH SUGGESTS
ROBUST WARMING WILL NOT OCCUR TO THE LEVEL DETERMINISTIC RUNS (E.G.,
THE 10.19.12Z GFS FOR EXAMPLE), THUS CONSIDERABLE ATTENTION
NEEDS TO BE PAID TO THIS PORTION OF THE FORECAST FOR FUTURE
ADJUSTMENTS.
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
VFR WILL CONTINUE UNDER HIGH PRESSURE, EXCEPT AT LUK WHERE BR
AND FG ARE REDUCING VISIBILITY THIS MORNING. SKIES ARE SKC FOR
THE FIRST PART OF THE FORECAST, WITH CIRRUS MOVING IN LATER WELL
AHEAD OF LOW PRESSURE. WINDS FROM THE SOUTH TO SOUTHWEST WILL
RISE TO AROUND 10 KNOTS THIS AFTERNOON.
OUTLOOK...MVFR CEILINGS AND VISIBILITIES POSSIBLE THURSDAY. MVFR
CEILINGS POSSIBLE FRIDAY AND FRIDAY NIGHT.
ILN WATCHES/WARNINGS/ADVISORIES
OH...NONE.
KY...NONE.
IN...NONE.
SYNOPSIS...HOGUE
NEAR TERM...HOGUE
SHORT TERM...HOGUE
LONG TERM...BINAU
AVIATION...CONIGLIO
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