346 PM CDT
LAST NIGHT AND EARLY TODAY AN AREA OF SHOWERS WITH A FEW
THUNDERSTORMS DEVELOPED ALONG A COLD FRONT STRETCHING BETWEEN TWO
DISTANT LOW PRESSURE CENTERS...ONE EAST OF HUDSON BAY IN QUEBEC AND
ONE OVER OKLAHOMA. MODEL AND SPC MESOANALYSIS MUCAPE FIELDS WERE
SHOWING A COUPLE HUNDRED J/KG OF MOSTLY ELEVATED INSTABILITY WITH
THIS EARLIER ACTIVITY...BUT BOTH MODEL TRENDS AND LATEST SPC
ANALYSIS HAVE THE BETTER THERMODYNAMICS AND LOW LEVEL FRONTOGENESIS
FOCUSED FARTHER TO THE SOUTHWEST THIS AFTERNOON...CLOSER TO THE
OK/TX LOW. LIGHTNING AND RADAR DATA CONTINUED TO INDICATE SOME
STRONGER CELLS NORTH OF OUR AREA FOR A WHILE...LIKELY RELATED TO
LINGERING FRONTAL STRENGTH AND WEAK INSTABILITY THAT SEEMS TO HAVE
DIMINISHED BY THIS POINT. WILL PLAN TO KEEP SHOWERS WITHOUT TSRA
OVERNIGHT AND TOMORROW...ALTHOUGH AN ISOLATED THUNDERSTORM IS NOT
TOTALLY OUT OF THE QUESTION.
THE OTHER WILDCARD FOR TONIGHT IS THE POSSIBILITY OF MIXED RAIN/SNOW
AFTER MIDNIGHT IN NW ILLINOIS. A COUPLE OF SITES IN EASTERN IOWA
ARE REPORTING SNOW THIS AFTERNOON IN A HEAVIER PRECIP BAND...PERHAPS
WHERE FROZEN PRECIP IS COPIOUS ENOUGH TO COOL THE SURROUNDING
AIRMASS...OR WHERE HYDROMETEORS ARE LARGE ENOUGH TO MAKE IT ALL THE
WAY DOWN THROUGH THE SHALLOW WARM SURFACE LAYER. ADDED MENTION OF A
MIX IN OUR FAR NW CWA IN COORDINATION WITH MKX AND DVN...BUT AM NOT
EXPECTING ANY ACCUMULATION FROM THIS ACTIVITY...SHOULD IT IN FACT
DEVELOP.
THE SURFACE AND CLOSED UPPER LOW RESPONSIBLE FOR TONIGHT'S ACTIVITY
WILL SPIN SOUTH OF THE AREA TOMORROW...LEAVING US ON THE COOL
NORTHERN FRINGE OF PRECIP. GFS/GEM SOLUTION HOLDS ON TO THE
SHOWERS THROUGH TOMORROW AFTERNOON...WHILE NAM AND ECMWF ARE MUCH
QUICKER TO DRY THINGS OUT. EITHER WAY...EXPECT MOST OF THE AREA
TO SEE RAIN THROUGH THE MORNING...WITH LIKELY POPS DOWN SOUTH
THROUGH THE AFTERNOON.
COOL NORTHEAST WINDS AHEAD OF AN UPSTREAM RIDGE WILL KEEP THE AREA
QUITE CHILLY TOMORROW COMPARED TO THE WEEK SO FAR...BUT FRIDAY AND
THE WEEKEND APPEAR TO RECOVER NICELY AS THE RIDGE MOVES EAST OF THE
AREA AND SUNSHINE WITH MILDER SOUTH TO SOUTHEAST WINDS RETURN. NOT
COMPLETELY CONFIDENT ABOUT TEMPERATURES THIS WEEKEND...BUT BUMPED
SATURDAY HIGHS A COUPLE OF DEGREES ABOVE LATEST GUIDANCE. SUNDAY
ALSO COULD BE WARMER THAN WE CURRENTLY ADVERTISE...BUT INCREASING
AFTERNOON CLOUD COVER COULD CAP THE WARMING TREND A BIT. IT APPEARS
THE VIGOROUS STORM SYSTEM LIFTING THROUGH THE NORTH CENTRAL MIDWEST
WOULD NEED TO BE ABOUT 300 MILES FARTHER SOUTHEAST TO HAVE MUCH
EFFECT ON THE LOCAL AREA...BUT IT WILL BE INTERESTING TO WATCH AND
SEE IF LATER MODEL RUNS DO SLIDE THIS FEATURE ANY CLOSER TO THIS
AREA...GIVING US A NEGATIVELY TILTED UPPER TROUGH WITH A DEEPENING
SURFACE LOW TAPPING INTO AN OPEN GULF.
THE NEXT LIKELY WEATHER SYSTEM APPROACHES THE AREA SUNDAY NIGHT INTO
EARLY NEXT WEEK. AT THIS TIME IT APPEARS ANOTHER COLD OR STATIONARY
FRONTAL ZONE WILL SET UP JUST SOUTHEAST OF THE AREA...WITH FRONTAL
CONVERGENCE AND UPPER LEVEL SHORTWAVE ENERGY SUPPORTING THE CHANCE
FOR SHOWERS OVER PART OF THE AREA. BY TUESDAY INTO WEDNESDAY THE
GFS/ECMWF BOTH HAVE A STRONGER SURFACE LOW LIFTING NORTHEAST ALONG
THIS BAROCLINIC ZONE FROM EAST TEXAS INTO ILLINOIS. AGAIN IT
APPEARS WE WILL BE MOSTLY ON THE COOL SIDE OF THIS SYSTEM...BUT A
TREND FARTHER NORTH COULD SET US UP FOR DECENT RAINFALL AND POSSIBLY
A LA NINA COOL SEASON SEVERE WEATHER EPISODE. IN REALITY...THE LOW
LEVEL BAROCLINICITY AND UPPER LEVEL TROUGH AMPLITUDE DO NOT ACTUALLY
APPEAR STRONG ENOUGH TO SUPPORT ANYTHING LIKE THIS AS EARLY AS NEXT
WEEK...BUT SOME HINTS THAT THE ATMOSPHERE MIGHT BE CAPABLE OF DOING
SO THIS FALL ARE STARTING TO APPEAR.
LENNING
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 20Z...
* WIND SHIFT TO THE N/NE LATE AFTERNOON/EARLY EVENING AS COLD
FRONT MOVES THROUGH THE AREA.
* CIGS TRENDING DOWN OVERNIGHT...TO IFR POSSIBLY LIFR.
* PRECIPITATION TIMING. BMD
//DISCUSSION...UPDATED 18Z...
A COLD FRONT IS SLOWLY PUSHING EAST ACROSS THE REGION WITH ISOLATED
TO SCATTERED SHOWERS OCCURRING ALONG THE FRONTAL BOUNDARY NEAR AND
WEST OF A LINE FROM MKE TO RFD. OUT AHEAD OF THE FRONT...SSW WINDS
HAVE BEEN DIMINISHING AS THE PRESSURE GRADIENT RELAXES. FORCING
ALONG THE FRONTAL BOUNDARY IS WEAK...AND WITH DRY LOW LEVEL AIR IN
PLACE...SHOWER ACTIVITY WILL CONTINUE TO BE SOMEWHAT ISOLATED WITH
OUTSIDE CHANCES OF IMPACTING THE TERMINALS THROUGH THIS EVENING.
MODELS IN DECENT AGREEMENT SHOWING FROPA FOR ORD/MDW AROUND 23-00Z
THIS EVENING. WINDS WILL SWITCH AROUND TO NORTH/NORTHEASTERLY...
BUT THERE MAY BE A SLIGHT DELAY IN GUSTS PICKING UP OUT OF THE
NORTH AS COLD AIR ALOFT FILTERS SOUTH. PRECIPITATION CHANCES WILL
INCREASE BEHIND THE FRONT AS BAND OF FRONTOGENESIS MOVES THROUGH
THE AREA. CIGS WILL LOWER AS THE COLUMN SATURATES...AND EXPECT
CONDITIONS TO DROP TO LOW END MVFR AND POTENTIALLY IFR OVERNIGHT.
UPSTREAM OBS ALREADY SHOWING IFR CIGS. MET GUIDANCE SEEMS TO HAVE
THE BEST LOCK ON THESE CIGS SUGGESTING IFR/LIFR CONDITIONS AFTER
MIDNIGHT ZULU THROUGH DAYBREAK THURSDAY...WHILE MAV/LAV GUIDANCE
ONLY TAKES DOWN HIGH END MVFR. CIGS SHOULD IMPROVE QUICKLY
THURSDAY AFTERNOON AS ANTICYCLONIC FLOW MOVES INTO THE AREA. BMD
//ORD AND MDW CONFIDENCE...UPDATED 20Z...
* HIGH CONFIDENCE IN WIND TIMING/DIRECTION...MEDIUM CONFIDENCE IN
WIND SPEED.
* MEDIUM-HIGH CONFIDENCE IN CIG TRENDS...WITH IFR CONDITIONS
EXPECTED...MEDIUM CONFIDENCE IN TIMING.
* LOW TO MEDIUM CONFIDENCE IN PRECIPITATION TIMING. BMD
//OUTLOOK FOR ORD/MDW FOR 00Z FRIDAY-12Z WEDNESDAY...UPDATED 12Z...
THURSDAY NIGHT...VFR.
FRIDAY...VFR.
SATURDAY...VFR.
SUNDAY...VFR.
MONDAY...CHANCE OF SHRA LATE...OTHERWISE VFR.
TUESDAY...SHRA LIKELY...OTHERWISE VFR.
RODRIGUEZ
&&
.MARINE...
159 PM CDT
DEVELOPING SURFACE LOW OVER THE SOUTHERN PLAINS WILL DEEPEN AS IT
MOVES INTO SOUTHERN ILLINOIS TOMORROW MORNING. THE MORNING MODEL
RUNS HAVE TRENDED A BIT STRONGER WITH THE WINDS OVER THE SOUTHERN
PORTIONS OF THE LAKE AND BUFKIT SOUNDINGS NOW SUPPORT A PERIOD OF
GALE FORCE NORTHEASTERLY WINDS TONIGHT INTO THURSDAY MORNING. THERE
ARE DIFFERENCES IN THE TIMING OF THE STRONGEST WINDS...BUT THERE IS
ENOUGH CONFIDENCE NOW THAT THERE WILL BE A PERIOD OF GALES DURING
THIS TIME FRAME SO HAVE OPTED TO COVER THE RANGE OF TIME
POSSIBILITIES WITH A GALE WARNING. WINDS WILL DIE OFF TOMORROW
AFTERNOON AS SURFACE LOW THEN DIVES SOUTHEAST AND HIGH PRESSURE
BUILDS IN. THE NEXT BIG WIND MAKER WILL BE OVER THE WEEKEND AS AN
INTENSE SURFACE LOW TRACKS INTO THE UPPER MIDWEST. HAVE INTRODUCED
SOUTHERLY GALES INTO THE GRIDS SAT NIGHT INTO SUNDAY...WITH
POTENTIAL FOR 40KT+ WINDS A DISTINCT POSSIBILITY SUNDAY.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...LMZ740-LMZ741-LMZ742...7 PM WEDNESDAY TO
3 AM FRIDAY.
SMALL CRAFT ADVISORY...LMZ743-LMZ744-LMZ745...10 PM WEDNESDAY TO
3 AM FRIDAY.
&&
$$
