FXUS61 KILN 241145
AFDILN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE WILMINGTON OH
645 AM EST THU DEC 24 2009
.SYNOPSIS...
A DEEP SURFACE LOW WILL OCCLUDE OVER THE OZARKS TODAY...AS A
STRONG UPPER TROUGH DIGS INTO THE SOUTHERN AND CENTRAL PLAINS. THE
SURFACE LOW WILL MEANDER NORTHWARD INTO IOWA THROUGH FRIDAY
NIGHT...SENDING AN OCCLUDED FRONT INTO THE OHIO VALLEY BY EARLY
FRIDAY.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPPER RIDGE IS PUSHING OFF TO THE EAST...ALLOWING FOR A
STRENGTHENING LOW LEVEL JET TO PUSH INTO THE LOWER OHIO VALLEY
THIS MORNING. STRONGEST LOW LEVEL WINDS WILL REMAIN WEST OF THE
AREA TODAY...BUT ENOUGH FLOW WILL EXIST NORMAL TO THETA GRADIENT
TO BRING INCREASING ISENTROPIC LIFT THROUGH THE DAY. LOW LEVELS
ARE QUITE DRY...ESPECIALLY ACROSS THE EASTERN CWA. HOWEVER...MODELS
HAVE BEEN STRUGGLING WITH THE EXTENT OF LOW-LEVEL SATURATION IN THESE
STEADY ISENTROPIC LIFT SCENARIOS...AND THINK THEY ARE TOO SLOW
BRINGING PRECIP INTO THE CWA TODAY. WHILE ANY PRECIP WILL BE VERY
LIGHT...STILL THINK THERE IS ENOUGH LIFT TO WARRANT SLIGHT CHANCE
OR LOW CHANCE POPS ACROSS THE WESTERN HALF OF THE CWA THROUGH
EARLY AFTERNOON. SURFACE SHOULD WARM ABOVE FREEZING BEFORE ANY
PRECIP ARRIVES...SO THREAT FOR FREEZING RAIN IS DIMINISHING.
HOWEVER...LOW LEVEL WETBULB VALUES WILL STILL BE NEAR OR BELOW
FREEZING...SO LIGHT SLEET IS A POSSIBILITY IF ANY PRECIP MAKES IT
THIS FAR EAST THIS MORNING. NOSE OF LOW LEVEL JET WILL NUDGE INTO
THE SOUTHWEST CWA LATE THIS AFTERNOON...WITH LARGE AREA OF RAIN
APPROACHING SOUTHEAST INDIANA AND NORTHERN KENTUCKY BY EARLY
EVENING.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
SURFACE LOW TRACKS NORTH TO NEAR ST LOUIS OVERNIGHT...WITH STRONG
LOW LEVEL FIELD SPREADING NORTHWARD TO THE EAST OF THE LOW. STRONG
CONVERGENCE AND ISENTROPIC LIFT WILL ALLOW FOR A WIDESPREAD AREA
OF RAIN WHICH WILL OVERSPREAD THE ENTIRE CWA FROM SOUTHWEST TO
NORTHEAST OVERNIGHT THURSDAY AND EARLY FRIDAY. 850 HPA-WINDS WILL
BE VERY STRONG...POTENTIALLY IN EXCESS OF 75-KT...BUT LOW LEVEL
INVERSION WILL BE MUCH TOO STRONG TO ALLOW ANY SIGNIFICANT
MOMENTUM TRANSFER TO THE GROUND. STILL...WITH VERY TIGHT GRADIENT
IN PLACE AND WINDS UP TO 60-KT AT 925 HPA...EXPECT A STIFF EAST-
SOUTHEAST WIND THURSDAY NIGHT AND FRIDAY MORNING WITH GUSTS UP TO
40 MPH POSSIBLE AT TIMES.
OCCLUDED FRONT WILL LIFT NORTHEAST ACROSS THE CWA FRIDAY
MORNING...BRINGING AN END TO THE WIDESPREAD RAIN ACROSS THE
SOUTHWEST BY MID FRIDAY MORNING...AND ACROSS CENTRAL OHIO BY EARLY
AFTERNOON. WILL STILL BE PLENTY OF LOW LEVEL MOISTURE BEHIND THE
FRONT...AND WITH WEAK LOW LEVEL CONVERGENCE IN PLACE...EXPECT
SCATTERED RAIN SHOWERS TO PERSIST THROUGH FRIDAY AFTERNOON. COLD
AIR ADVECTION DOES NOT GET GOING UNTIL EARLY FRIDAY EVENING...SO
ANY CHANGE OVER TO SNOW WILL NOT OCCUR UNTIL AFTER DARK FRIDAY.
LITTLE IF ANY SNOW ACCUMULATION WILL OCCUR WITH THIS ACTIVITY.
LINGERING LOW LEVEL MOISTURE AND UPPER LOW MOVING IN FROM THE WEST
WILL MAINTAIN A CHANCE FOR SCATTERED SNOW SHOWERS SATURDAY AND
SATURDAY NIGHT...WITH ANY ACCUMULATION LIMITED TO A HALF INCH OR
LESS.
&&
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
THERE WILL BE A CHANCE OF SNOW SHOWERS SUNDAY AND MONDAY AS THE
UPPER LOW TRAVELS THROUGH THE WESTERN GREAT LAKES TO OHIO. IT
APPEARS THAT THE FETCH OFF LAKE MICHIGAN WILL BE FAVORABLE FOR
ENHANCEMENT OF THE SNOW SHOWERS ON MONDAY...ESPECIALLY OVER
NORTHERN COUNTIES. HIGH PRESSURE WILL PROVIDE DRY CONDITIONS AS IT
MOVES ACROSS THE REGION ON TUESDAY AND WEDNESDAY.
COLD WEATHER WILL PERSIST THROUGH THE PERIOD AND WE MAY NOT SEE
TEMPERATURES REACH NORMAL VALUES AT ALL. HIGHS ARE FORECAST TO BE IN
THE 20S AND 30S.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
A STRONG LOW PRESSURE SYSTEM OVER NORTHEAST TEXAS THIS MORNING
WILL LIFT NORTH ALONG THE MISSISSIPPI RIVER THROUGH FRIDAY. AS IT
DOES...A TIGHTENING PRESSURE GRADIENT WILL LEAD TO INCREASING
SOUTHERLY LOW LEVEL WINDS AS WE HEAD INTO TONIGHT. THIS WILL
RESULT IN DEVELOPING AND STRENGTHENING ISENTROPIC LIFT THIS
AFTERNOON AND TONIGHT ACROSS OUR AREA BUT THE BEST LIFT WILL
REMAIN OFF TO OUR WEST AT LEAST THROUGH THIS AFTERNOON. RIGHT
NOW...WIDESPREAD PCPN IS OCCURRING JUST TO OUR WEST ACROSS
ILLINOIS AND INDIANA. HOWEVER...DRIER SOUTHEASTERLY FLOW IS
HELPING TO KEEP PCPN FROM MAKING MUCH OF AN EASTWARD PUSH. MODELS
ARE CONSISTENT WITH HOLDING OFF PCPN ACROSS OUR AREA THROUGH THIS
AFTERNOON AND EARLY EVENING. HOWEVER...MODELS HAVE BEEN HAVING A
TOUGH TIME DEALING WITH THE PCPN ASSOCIATED WITH THE ISENTROPIC
LIFT OVER THE PAST COUPLE OF DAYS SO AM A LITTLE CONCERNED THAT
THEY MAY BE TOO SLOW BRINGING PCPN IN TONIGHT. WILL THEREFORE
SPEED UP PCPN ONSET A BIT FASTER THAN WHAT IS INDICATED BY THE 00Z
NAM/GFS/ECMWF. WILL ALLOW FOR A VCSH INTO THE WEST LATE THIS
AFTERNOON AND THEN SLOWLY SPREAD PREVAILING PCPN WEST TO EAST THIS
EVENING INTO TONIGHT. EXPECT CIGS TO REMAIN VFR INTO THIS EVENING
BEFORE CRASHING FAIRLY QUICKLY INTO AT LEAST MVFR CATEGORY WITH
ONSET OF MORE STEADY PCPN TONIGHT.
OUTLOOK...MVFR CIGS POSSIBLE ON SUNDAY.
&&
.ILN WATCHES/WARNINGS/ADVISORIES...
OH...NONE.
KY...NONE.
IN...NONE.
&&
$$
SYNOPSIS...HAWBLITZEL
NEAR TERM...HAWBLITZEL
SHORT TERM...HAWBLITZEL
LONG TERM...CONIGLIO
AVIATION...JGL
