316 PM CST
THE NEXT WEATHER MAKER FOR THE AREA IS BEGINNING TO TAKE SHAPE THIS
AFTERNOON. WATER VAPOR IMAGERY SHOWS UPPER RIDGING HOLDING IN PLACE
OVER THE SOUTHEAST AND MID-ATLANTIC STATES WITH WITH AN UPPER LOW
LIFTING NORTHEAST ACROSS NORTHERN QUEBEC ALONG THE WESTERN PERIPHERY
OF THE RIDGE. THE MAIN FEATURE OF CONCERN IS AN UPPER TROUGH
SPINNING OVER THE FOUR CORNERS AND BEGINNING TO TURN NORTHEASTWARD.
AT THE SURFACE...A STATIONARY FRONTAL BOUNDARY...WHICH DRIFTED INTO
THE AREA OVERNIGHT...EXTENDS FROM NORTHWEST INDIANA BACK TOWARDS ST.
LOUIS AND ON TOWARDS THE DEVELOPING LOW PRESSURE OVER THE TEXAS
PANHANDLE. DEEPER MOISTURE CONTINUES TO STREAM NORTHEASTWARD IN THE
FAST SOUTHWESTERLY FLOW THAT HAS DEVELOPED AHEAD OF THE TROUGH. IN
ADDITION A SERIES OF VORT MAXES/LOW AMPLITUDE SHORTWAVES ARE MOVING
NORTHEASTWARD AS WELL. AS A RESULT...BANDS OF RAIN CONTINUE TO
STREAM NORTHEASTWARD IN CONJUNCTION WITH THE TRANSPORT OF MOISTURE
AND THE LOCATION OF THE SURFACE BOUNDARY WITH ONE NOW SHIFTING OFF
TO THE EAST AND ANOTHER TAKING SHAPE ACROSS MISSOURI AND POINTS
SOUTHWEST.
TONIGHT THROUGH TUESDAY MORNING...THE UPPER TROUGH WILL CONTINUE TO
PUSH EASTWARD ACROSS THE ROCKIES TONIGHT WITH HEIGHT FALLS SPREADING
INTO KANSAS...OKLAHOMA...AND NORTHERN TEXAS ALLOWING FURTHER
DEVELOPMENT OF THE SURFACE LOW WHICH SHOULD CONSOLIDATE OVER THE
EASTERN KANSAS/OKLAHOMA BORDER AREA BY MIDDAY TUESDAY. AS THE LOW
DEVELOPS AN INVERTED TROUGH WILL SHARPEN ALONG THE OLD COOL FRONTAL
BOUNDARY ACROSS THE AREA. THIS WILL HELP THE BOUNDARY TO PUSH
NORTHWESTWARD AND LIKELY BISECT THE AREA FROM NORTHEAST TO SOUTHWEST
BY LATE TUESDAY. MID LEVEL FRONTOGENESIS CURRENTLY EXTENDING FROM
NORTHERN INDIANA INTO SOUTHEASTERN MISSOURI WILL PULL OFF TO THE
EAST BY EVENING WITH ANOTHER AREA EXPECTED TO DEVELOP FROM MISSOURI
INTO EASTERN IOWA AND OVER INTO NORTHWEST INDIANA IN CONJUNCTION
WITH SHARP ISENTROPIC ASCENT. THE CURRENT AREA OF RAIN OVER THE
SOUTHEASTERN CWA WILL CONTINUE TO LIFT OFF TO THE NORTHEAST AND
THERE SHOULD BE A LULL IN THE PRECIP THROUGH EARLY EVENING. ANOTHER
SHIELD OF RAIN WILL THEN SPREAD NORTHEASTWARD ACROSS MUCH OF THE
AREA LATE THIS EVENING OR EARLY TONIGHT AND CONTINUE THROUGH TUESDAY
MORNING THANKS TO THE AFOREMENTIONED FORCING.
TUESDAY AFTERNOON THROUGH THURSDAY...LATEST MODEL GUIDANCE HAS COME
INTO BETTER AGREEMENT WITH THE TRACK AND SPEED OF THE LOW...WITH THE
LATEST GUIDANCE SOLUTION BASICALLY A MIDDLE GROUND BETWEEN THE
EARLIER GFS WHICH HAD BEEN FASTER AND FARTHER EAST AND THE EARLIER
ECMWF WHICH HAD BEEN SLOWER AND FURTHER WEST. THE SURFACE LOW WILL
CONTINUE TO MARCH NORTHEASTWARD INTO WEST CENTRAL ILLINOIS TUESDAY
AFTERNOON AS THE MAIN UPPER LOW LIFTS NORTHEASTWARD FROM
CENTRAL/EASTERN KANSAS. THE INITIAL ROUND OF FORCING WILL LIFT TO
THE NORTHEAST BY EARLY TUESDAY AFTERNOON. THIS MAY RESULT IN A LULL
IN THE PRECIP ACTIVITY FOR AT LEAST SOME OF THE AFTERNOON. ANOTHER
ROUND OF FORCING THEN ARRIVES WITH THE ARRIVAL OF THE LOW AND
ASSOCIATED COLD FRONT TUESDAY EVENING INTO TUESDAY NIGHT. BEST
CHANCES FOR EMBEDDED THUNDER ARRIVE TUESDAY AND CONTINUE INTO
TUESDAY NIGHT. RIGHT NOW IT LOOKS TO REMAIN MAINLY ELEVATED THOUGH
WILL NEED TO WATCH FOR POTENTIAL FOR SOME WIND GUSTS TO MAKE IT TO
THE SURFACE. OTHER CONCERN IS HEAVY RAIN POTENTIAL INTO WEDNESDAY WITH
MUCH OF THE CENTRAL AND WESTERN PART OF THE AREA EXPECTED TO SEE 1
TO 2 INCHES WITH SOME POTENTIAL FOR UPWARDS OF 2.5 INCHES WEST OF
A LINE FROM ROUGHLY WAUKEGAN TO LASALLE.
THE LOW SHOULD PASS OVER THE ROCKFORD AREA THEN CONTINUE ACROSS
CENTRAL LAKE MICHIGAN WEDNESDAY MORNING WHICH WILL DRAG THE RATHER
STRONG COLD FRONT ACROSS THE AREA WEDNESDAY MORNING. WINDS WILL
SHIFT FROM SOUTH TO WEST WITH THE FRONTAL PASSAGE WITH A FURTHER
SHIFT TO WEST-NORTHWEST DURING THE AFTERNOON. H85 TEMPS WILL
TUMBLE FROM AROUND +10 C TO AROUND 0 C BY MIDDAY THEN TO AROUND -4
C BY WEDNESDAY EVENING. HAVE INDICATED MAX TEMPS WEDNESDAY MORNING
WIT A COOLING TREND INTO AN THROUGH THE 40S WEDNESDAY AFTERNOON AS
COLD ADVECTION TAKES OVER. STILL ANTICIPATE THAT A DRY SLOT WILL
WRAP AHEAD OF THE UPPER LOW BEHIND THE COLD FRONT SO PRECIP MAY
CUTOFF MORE QUICKLY THAN THE FORECAST CURRENTLY INDICATES.
DEFORMATION ZONE PRECIP LOOKS TO FOCUS TO THE NORTH BUT WILL CARRY
MINIMAL POPS DURING THE AFTERNOON FOR THIS. ANOTHER UPPER TROUGH
WILL CROSS THE AREA THURSDAY AND WILL NEED TO MONITOR FOR THE
POTENTIAL FOR SCATTERED SHOWER DEVELOPMENT.
MDB
FRIDAY THROUGH THE WEEKEND...
VOLATILITY IN THE FORECAST WILL BEGIN TO RAMP UP TOWARDS THE WEEKEND
AND THERE WILL LIKELY BE CHANGES TO THE WEEKEND FORECAST OVER THE
COMING SHIFTS. FORECAST GUIDANCE HAS BEEN TRYING TO FIGURE OUT WHAT
TO DO WITH A WAVE THAT SHOULD COME RIPPLING THROUGH THE
NORTHWESTERLY FLOW THROUGH THE WEEKEND. THIS ULTIMATELY HAS PROVED
TO YIELD A LOWER CONFIDENCE EXTENDED FORECAST AS FROM EACH MODEL RUN
TO MODEL RUN... THERE HAVE BEEN LARGE DIFFERENCES AND LITTLE
CONTINUITY. WHILE THE BEST CHANCES APPEAR TO BE TOWARDS SUNDAY
NIGHT...THE EC IS MUCH MORE BULLISH WITH QPF TOTALS ACROSS THE AREA
AS A SURFACE LOW TRACKS ACROSS IOWA AND INTO MINNESOTA. MEANWHILE
THE GFS IS JUST PAINTING A TRACE TO MAYBE A FEW HUNDREDTHS OF AN
INCH OF QPF AS THE SURFACE FEATURE IS GENERALLY 2-300 MILES WEST OF
WHERE THE EC PROGS ITS MOVEMENT...BUT THE GFS HAS SHIFTED THE LOW
FROM ACROSS LAKE HURON THREE RUNS AGO...TO MINNESOTA IN THE PREVIOUS
RUN...TO ACROSS NORTH DAKOTA WITH THIS RUN. OTHERWISE...SOUTHWEST
FLOW WILL RETURN TO THE AREA AND TEMPERATURES WILL BEGIN TO REBOUND
INTO THE WEEKEND FROM THEIR MIDWEEK COOL DOWN.
SHEA
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* POSSIBLE BRIEF SHOWERS THIS AFTERNOON. MORE WIDESPREAD ACTIVITY
MOVING IN OVERNIGHT.
* IFR VSBYS NOTED IN PIA/BMI/PNT AREA...NOT EXPECTED TO SLIDE
NORTHEAST ALONG THE FRONT...BUT WORTH WATCHING.
* LIGHT AND VARIABLE WINDS BECOMING NORTHEASTERLY THIS EVENING.
* LOWERING CIGS/VSBYS OVERNIGHT...EVENTUALLY DROPPING TO IFR OR
LOWER TOMORROW.
LENNING
//DISCUSSION...UPDATED 18Z...
PASSAGE OF A WEAK FRONT THIS MORNING BROUGHT THINNING OR AT LEAST
HIGHER CIGS FOR ALL BUT THE GYY AREA. VERY WEAK PRESSURE GRADIENT
IN VICINITY OF THIS FEATURE HAS ALLOWED WINDS TO GO CALM OR LIGHT
AND VARIABLE ACROSS A WIDE AREA. A LOW PRESSURE CENTER LIFTING OUT
OF THE SOUTHERN PLAINS WILL GRADUALLY INCREASE WINDS STARTING THIS
EVENING...BUT THE CONTINUED PROXIMITY OF THE FRONT WILL PROVIDE
UNCERTAINTIES IN WIND DIRECTIONS. BEST ESTIMATE IS FOR NORTHEAST
FLOW TO DEVELOP OVERNIGHT...WITH WINDS VERY GRADUALLY VEERING TO
EAST AND THEN SOUTHEAST AS THE STALLED OUT FRONT AHEAD OF THE LOW
STARTS TO MOVE BACK NORTH AGAIN. FORECAST MODELS SHOW THE LOW
CENTER CROSSING NORTHWEST ILLINOIS TOMORROW NIGHT...WITH ALL BUT
RFD IN THE WARM SECTOR WITH SOUTHERLY FLOW AFTER MIDNIGHT TUESDAY
NIGHT.
CONDITIONS DETERIORATE OVERNIGHT WITH ONSET OF PRECIPITATION. BY
TOMORROW AFTERNOON EXPECTING A PROLONGED PERIOD WITH IFR OR
POCKETS OF LIFR ACROSS MOST OF THE AREA WITH PERSISTENT RAIN.
VSBYS MAY BE A PROBLEM FROM TIME TO TIME...BUT CIGS APPEAR TO BE
THE PRIMARY CONCERN BASED ON UPSTREAM TRENDS. LIKELY WILL HAVE TO
MAKE MANY CHANGES TO SPECIFIC ELEMENTS AS THE TIME DRAWS
CLOSER...BUT GENERAL TRENDS ARE REFLECTED IN TAFS.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* MEDIUM TO HIGH CONFIDENCE THAT ANY SHOWERS TODAY WOULD BE BRIEF
AND WOULD NOT DROP CIGS/VSBYS BELOW VFR.
* MEDIUM CONFIDENCE IN WIND TRENDS TONIGHT.
* HIGH CONFIDENCE OF PROLONGED IFR OR LOWER TOMORROW...BUT MEDIUM
TO LOW CONFIDENCE IN TIMING AND SEVERITY.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z WEDNESDAY-12Z MONDAY...UPDATED 12Z...
TUE NIGHT...MVFR...PERIODS OF IFR. RA WITH A CHANCE OF TS.
WED...MVFR BECOMING VFR. CHANCE OF SHOWERS.
THU...VFR. WX NIL.
FRI...VFR. WX NIL.
SAT...VFR. WX NIL.
SUN...VFR. CHANCE SHRA.
TRS
&&
.MARINE...
323 AM CST
WINDS HAVE GRADUALLY BEEN TRENDING DOWN THROUGH THE NIGHT AND
EARLY MORNING HOURS...MORE SO OVER THE SOUTHERN HALF OF THE LAKE
WHERE HIGH PRESSURE IS BEGINNING TO ENCROACH FROM THE SOUTH.
ACROSS THE NORTH...BREEZY CONDITIONS ARE STILL BEING OBSERVED BUT
WILL CONTINUE TO TAPER AS THE LOW OVER ONTARIO CONTINUES TO LIFT
AWAY FROM THE REGION. THE NEXT WEATHER SYSTEM OF CONCERN WILL
BEGIN TO TAKE SHAPE OVER THE CENTRAL PLAINS OVERNIGHT
TONIGHT...AND QUICKLY LIFT NORTHEAST REACHING LAKE MICHIGAN LATE
TUESDAY NIGHT. MODELS CONTINUE TO SHOW MODEST DIFFERENCES BETWEEN
THE TRACK AND INTENSITY OF THIS LOW...THUS THE IS A FAIR DEGREE OF
UNCERTAINTY IN TIMING THE WIND SHIFTS AND WIND MAGNITUDES. DOES
APPEAR THAT THE FRONTAL BOUNDARY WILL STALL ACROSS SOUTHERN OR
CENTRAL PORTIONS OF THE LAKE TUESDAY WITH A BAND OF LIGHTER
WINDS...BUT WINDS SHOULD SHARPLY INCREASE TO THE SOUTH OR NORTH OF
THE FRONTAL ZONE. AS THE LOW PASSES NORTHEAST OF THE LAKE
WEDNESDAY...A TRAILING COLD FRONT WILL SWITCH WINDS AROUND TO THE
NORTHWEST...WITH WINDS FURTHER INCREASING...AND LOW END GALES
POSSIBLE. WINDS WILL TREND BACK DOWN THURSDAY AS HIGH PRESSURE
APPROACHES AND MOVES ACROSS THE LAKE ON FRIDAY. BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
