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Area Forecast Discussion
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000
FXUS61 KILN 020014
AFDILN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
714 PM EST SUN MAR 1 2015

.SYNOPSIS...
SNOW WILL END ACROSS THE MIDDLE OHIO VALLEY THIS EVENING...AS HIGH
PRESSURE BUILDS IN FROM THE WEST...PROVIDING DRY CONDITIONS FOR
MONDAY. A STRONG AREA OF LOW PRESSURE WILL MOVE NORTH OF THE
REGION ON TUESDAY THROUGH TUESDAY NIGHT. THIS WILL BRING A MIX OF
SNOW AND FREEZING RAIN...TURNING TO RAIN DURING THE AFTERNOON.
ADDITIONAL RAIN AND SNOW MAY PERSIST THROUGH WEDNESDAY NIGHT. DRY
HIGH PRESSURE WILL MOVE INTO THE REGION FOR THE END OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
WITH THE EASTWARD-PROGRESSING BAND OF SNOW NOW MOVING OUT OF THE
AREA...ALL HEADLINES HAVE BEEN CANCELLED. ANOTHER BATCH OF SNOW
OVER SOUTHERN INDIANA WILL LIKELY WORK ITS WAY INTO THE SOUTHERN
THIRD OF THE ILN FORECAST AREA IN THE NEXT FEW HOURS...PRODUCING
LIGHT ACCUMULATIONS AS TEMPERATURES SLOWLY BEGIN TO FALL.

PREVIOUS DISCUSSION >
SNOW IS NOT QUITE DONE ACROSS THE REGION THIS AFTERNOON...WITH
ANOTHER FAIRLY HEALTHY BAND MOVING INTO WEST CENTRAL OHIO AS OF
245 PM. ALTHOUGH THE SOUTHERN TIER OF ADVISORIES WAS SET TO EXPIRE
AT 300 PM...THIS WAS EXTENDED FOR A FEW HOURS...JUST TO KEEP IT UP
WHILE SNOW FOR THE EVENT HAS NOT YET ENDED. ADDITIONAL
ACCUMULATIONS ARE GOING TO BE UNDER AN INCH (PROBABLY WELL UNDER
AN INCH IN MOST LOCATIONS).

ONE OR TWO MORE WEAK BANDS OF SNOW MAY FORM THIS EVENING...AS
INDICATED BY HIGH-RESOLUTION MODELS (AND SEEMING TO BE RIDING ON
THE ELEVATED THETA-E GRADIENT ON THE LEADING EDGE OF THE COLDER
AIR). SOME CATEGORICAL POPS WERE MAINTAINED THROUGH 8PM...WITH A
GRADUAL NW-TO-SE TAPERING OFF OF LIGHT SNOW CHANCES AFTER THAT.

COLD ADVECTION BEHIND THE SURFACE FRONT IS ALREADY BEGINNING IN
THE NORTHWESTERN CWA...AND AS THIS FRONT SHIFTS SOUTHEAST THROUGH
THE REGION TONIGHT...SUB-FREEZING TEMPS WILL QUICKLY SPREAD ACROSS
THE ENTIRE FORECAST AREA. WITH FRESH SNOW AND SOME CLEARING
EXPECTED IN THE NORTHWEST CWA...MIN TEMPS WERE LOWERED INTO THE
MIDDLE TEENS...AND VALUES A LITTLE BELOW THESE APPEAR TO BE A
POSSIBILITY. MIN TEMPERATURES RANGE FROM THERE INTO THE UPPER 20S
FOR THE SOUTHEASTERN CORNER OF THE FORECAST AREA.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/...
RELATIVELY QUIET CONDITIONS ARE EXPECTED ON MONDAY...AS AN AREA OF
HIGH PRESSURE MOVES IN FROM THE WEST. THIS HIGH WILL NOT BE IN
PLACE FOR LONG...WITH ITS CENTER FORECAST TO BE OVER OHIO ON
MONDAY EVENING...AND CLEAR OF THE AREA QUICKLY THEREAFTER. THIS
SHOULD ALLOW FOR MORE SUN THAN CLOUDS ON MONDAY...THOUGH SOME
LOW-LEVEL CLOUDS WILL STILL BE SCOURING OUT IN THE EASTERN CWA
DURING THE MORNING...AND SOME HIGH CLOUDS IN ADVANCE OF THE NEXT
SYSTEM WILL ALREADY BE MOVING IN BY AFTERNOON. TEMPERATURES WILL
GET TO NEAR OR JUST ABOVE THE FREEZING MARK IN THE SOUTHERN THIRD
OF THE CWA...WITH COOLER VALUES FURTHER NORTH (WITH FRESH SNOW ON
THE GROUND). GFS RAW MODEL TEMPS (ESPECIALLY AT 00Z) APPEAR TO BE
SIGNIFICANTLY TOO COOL...AND WERE NOT USED.

AS HIGH PRESSURE MOVES AWAY ON MONDAY EVENING...ATTENTION WILL
TURN TO A MULTI-FACETED INCOMING WEATHER SYSTEM...WHICH WILL
AFFECT THE REGION THROUGH MUCH OF TUESDAY AND INTO WEDNESDAY. FLOW
ON THE BACK SIDE OF THE HIGH WILL SWITCH TO SOUTHEASTERLY AT THE
SURFACE...AND SOUTHWESTERLY ALOFT. WEAK RIDGING OVER THE OHIO
VALLEY AND SOUTHEASTERN STATES WILL GIVE WAY TO A DEVELOPING
TROUGH IN THE PLAINS...SETTING UP A FAVORABLE AND DEEP PATH FOR
MOISTURE TRANSPORT OUT OF THE GULF OF MEXICO. THERE IS HIGH
CONFIDENCE IN A SIGNIFICANT WARMING OCCURRING ALOFT BETWEEN 00Z
TUESDAY (MONDAY EVENING) AND 18Z TUESDAY (TUESDAY AFTERNOON).
HOWEVER...A SHALLOW LAYER OF ARCTIC AIR (INFLUENCED BY SNOW COVER)
WILL BE SLOW TO RETREAT...LEADING TO A SURFACE TEMPERATURE
FORECAST THAT INCREASES ONLY SLOWLY EARLY TUESDAY MORNING.
ISENTROPICALLY-DRIVEN PRECIPITATION WILL DEVELOP AND MOVE INTO THE
ILN CWA AS EARLY AS 06Z...THOUGH CONVERGENCE AHEAD OF THE
STRENGTHENING LOW-LEVEL JET WILL BE MAXIMIZED BETWEEN 12Z AND 21Z.

THE STRENGTH OF THE WARM LAYER WILL BE SUCH THAT...OUTSIDE OF A
VERY BRIEF PERIOD OF POSSIBLE SLEET NEAR THE ONSET OF
PRECIPITATION...FREEZING RAIN WILL BE THE FAVORED PRECIPITATION
TYPE FOR A PERIOD OF SEVERAL HOURS. AS AN EXAMPLE...A GFS BUFKIT
SOUNDING FOR KDAY AT 15Z TUESDAY HAS A SURFACE TEMPERATURE OF
-2...WITH A SATURATED WARM LAYER 5000 FEET THICK (AND MAXING OUT
AT +5). THUS...THE USE OF FREEZING RAIN IN THE WEATHER GRIDS WAS
SIGNIFICANTLY INCREASED...WITH HIGH-END POPS (70 TO 100 PERCENT)
TO MATCH THE CONFIDENCE. WHILE THIS PRECIPITATION MAY BE MORE
SHOWERY IN NATURE THAN PURELY STRATIFORM...LIQUID AMOUNTS ARE
LIKELY TO BE ONE TO TWO TENTHS OF AN INCH THROUGH 18Z. THE END
RESULT FOR AN ICE FORECAST IS THAT THE ENTIRE CWA WILL BE LIKELY
TO GET A LIGHT GLAZE OF A FEW HUNDREDTHS...WHILE THE NORTHWESTERN
HALF OF THE CWA WILL HAVE THE GREATEST POTENTIAL FOR HIGHER
ACCUMULATIONS...PERHAPS A TENTH OR SLIGHTLY HIGHER.
HOWEVER...WARNING CRITERIA ICE LOOKS VERY UNLIKELY.

FURTHER COMPLICATING MATTERS...THE FAR NORTHERN SECTIONS OF THE
CWA MAY GET INTO THE PRECIPITATION BEFORE THE WARM LAYER
ARRIVES...ALLOWING FOR A FEW HOURS OF LIGHT SNOW. ACCUMULATIONS
DO NOT APPEAR LIKELY TO EXCEED AN INCH.

THE FREEZING RAIN THREAT WILL END FROM SOUTH TO NORTH AS SURFACE
TEMPERATURES EVENTUALLY BEGIN A QUICK RISE...AS THE WARM FRONT
MOVES NORTH THROUGH THE FORECAST AREA. AS THIS OCCURS...THE AXIS
OF HEAVIEST PRECIPITATION WILL SET UP ACROSS THE CWA ON A SW-TO-NE
ORIENTATION. THIS AXIS WILL SHIFT SOUTHEAST WITH TIME...AS A COLD
FRONT ADVANCES FROM THE NORTHWEST...AND PUSHING THE HEAVIEST
PRECIPITATION SOUTHEAST OF THE CWA BY EARLY WEDNESDAY MORNING. AS
THIS OCCURS...TEMPERATURES MAY BECOME COLD ENOUGH FOR A MIX WITH
SNOW AT THE SAME TIME. HOWEVER...THERE IS A LOT MORE SPREAD IN THE
MODELS AT THE END OF THE EVOLUTION OF THIS WEATHER SYSTEM THAN AT
THE BEGINNING...SO THE TIMING OF THIS TRANSITION IS UNCLEAR.

IF THERE IS GOING TO BE ANY POTENTIAL FOR CONVECTIVE SHOWERS WITH
THIS SYSTEM...IT APPEARS TO BE IN THE SOUTHEASTERN CWA ON TUESDAY
EVENING. ELEVATED THUNDERSTORMS APPEAR TO BE A FAIRLY LOW
PROBABILITY...THOUGH NOT IMPOSSIBLE TO OCCUR. NEAR-SURFACE
THERMODYNAMICS LOOK RATHER UNFAVORABLE FOR ANY WIND POTENTIAL
DURING THE SAME TIME PERIOD...BUT A STRONGER SOUTHERLY PUSH OF
WARM AIR COULD CHANGE THAT.

SOME PERIODS OF HEAVY RAIN MAY BE POSSIBLE...AS PRECIPITABLE WATER
VALUES EASILY CLIMB OVER AN INCH. AS HAS BEEN COVERED IN PREVIOUS
DISCUSSIONS...THE COMBINATION OF WARMING TEMPERATURES / SNOW MELT
/ RAINFALL WILL LEAD TO A POTENTIAL FOR FLOODING DURING THE MIDDLE
OF THE WEEK. RAINFALL FORECAST AMOUNTS BY THEMSELVES ARE NOT
OVERLY CONCERNING RIGHT NOW (AN INCH OR TWO OVER A PERIOD OF 24
HOURS)...BUT THE SNOW COMPLICATES MATTERS IN THIS CASE. THE
HEAVIEST RAIN IS EXPECTED TO FALL OVER THE SOUTHERN AND
SOUTHEASTERN SECTIONS OF THE CWA.

TEMPS WILL HIT THEIR HIGHEST VALUES FOR THE ENTIRE WEEK ON TUESDAY
EVENING...BEFORE COLD AIR BEGINS MOVING IN AHEAD OF THE FRONT.
CONFIDENCE IN THE EXACT TEMPERATURE VALUES IS NOT VERY
HIGH...SINCE THIS IS A NON-DIURNAL SCENARIO DRIVEN BY STRONG
ADVECTION...AND A STRONG GRADIENT WILL EXIST ACROSS THE CWA.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
MODELS CONTINUE TO STRUGGLE AS TO HOW FAST PCPN WILL EXIT OUR AREA 
ON WEDNESDAY...OR WHETHER IT WILL REDEVELOP WELL NORTH OF 
SOUTHEASTWARD MOVING COLD FRONTAL BOUNDARY. THE GFS IS THE OUTLIER 
IN THAT IT PUSHES PCPN THROUGH THE REMAINDER OF THE REGION DURING 
THE MORNING. THIS SEEMS TO BE DRIVEN BY ITS SOLUTION OF PUSHING A 
BROAD MID LEVEL TROUGH THROUGH THE REGION QUICKER. THIS SOLUTION 
ALSO RESULTS IN FASTER CAA INTO THE REGION. THE OTHER OPERATIONAL 
MODELS...NAM...CMC AND ECMWF INDICATE A SLOWER MID LEVEL TROUGH 
PROPAGATION. THE NAM LOOKS STRANGE AT THE SFC...SO HAVE TAKEN A 
BLEND OF THE CMC/ECMWF SOLUTION. THIS SOLUTION ALLOWS FOR 
REDEVELOPMENT OF PCPN NORTH OF THE FRONTAL BOUNDARY INTO OUR REGION. 
THE REDEVELOPMENT SEEMS TO BE MAINLY DRIVEN BY UPPER LEVEL JET 
DYNAMICS RESULTING IN AN ANAFRONT CONFIGURATION. WILL KEEP POPS 
GOING ON WEDNESDAY WITH LIKELY OR HIGHER FCST FOR POINTS MAINLY 
SOUTH OF I-70. PCPN SHOULD TRANSITION TO SNOW THROUGH THE DAY AS CAA 
CONTINUES. HOWEVER...THERE COULD BE SOME MIXED PCPN EARLY ON IF CAA 
IS FASTER AT THE SFC THAN WARMER AIR ALOFT. 

PCPN SHOULD GRADUALLY EXIT THE REGION WEDNESDAY NIGHT AS MORE ARCTIC 
AIR FILTERS IN FROM THE NORTHWEST. 

THE REMAINDER OF THE EXTENDED SHOULD BE RELATIVELY QUIET CONSIDERING 
THE RECENT ACTIVE WEATHER. ARCTIC HIGH PRESSURE WILL BUILD INTO THE 
REGION ON THURSDAY...MOVING EAST OF THE AREA THURSDAY NIGHT. WELL 
BELOW NORMAL TEMPERATURES ARE FORECAST WITH HIGHS IN THE TEENS AND 
20S ON THURSDAY...FOLLOWED BY SINGLE DIGIT LOWS THURSDAY NIGHT. 
NORMAL HIGHS ARE IN THE MID AND UPPER 40S AND NORMAL LOWS ARE IN THE 
UPPER 20S TO THE LOWER 30S.  FOR FRIDAY INTO SUNDAY...AN UPPER LEVEL 
SPLIT FLOW PATTERN WILL DEVELOP OVER THE CONUS AND SRN CANADA WITH 
NORTHWESTERLY FLOW PERSISTING INTO THE GREAT LAKES. THE GOOD NEWS IS 
THAT ANY FRONTAL SYSTEMS WILL BE WEAK WITH A MODIFICATION OF THE 
AIRMASS EXPECTED. A WEAK FRONT IS FORECAST TO SHEAR OUT ACROSS THE 
GREAT LAKES FRIDAY NIGHT INTO SATURDAY...FOLLOWED BY MORE HIGH 
PRESSURE ON SUNDAY.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
LAST BASTION OF PCPN IS WORKING THROUGH THE TAFS WITH THE BACK
EDGE ALONG I-71. EXPECT IT TO CLEAR THE TAFS IN THE NEXT SEVERAL
HOURS.


FOCUS THEN TURNS TO WHAT THE CIGS AND VSBYS WILL DO. THERE IS AN
AREA OF MVFR CIGS ACROSS CENTRAL INDIANA INTO WEST CENTRAL
OHIO...WITH VFR FARTHER BACK OVER NRN INDIANA INTO IL. HOWEVER
MODEL CROSS SECTIONS ARE SHOWING THAT THE MVFR CIGS WILL HOLD
ACROSS THE REGION INTO THE MORNING BEFORE SCATTERING OUT IN THE
AFTERNOON. AS FOR VSBSYS...IT LOOKS LIKE THEY WILL REMAIN IFR/MVFR
FOR THE FIRST PART OF THE FORECAST THEN AS COLDER AIR WORKS IN
THEY SHOULD RISE TO VFR.

OUTLOOK...MVFR/IFR CEILINGS AND VISIBILITIES ARE POSSIBLE TUESDAY
INTO WEDNESDAY WITH RAIN AND SNOW.

&&

.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.

&&

$$
SYNOPSIS...HATZOS
NEAR TERM...HATZOS
SHORT TERM...HATZOS
LONG TERM...HICKMAN
AVIATION...SITES






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