758 PM CDT
MADE SOME MINOR TWEAKS TO SKY...TEMPERATURE AND DEW POINT GRIDS
BASED ON EARLY EVENING TRENDS...BUT NO SIGNIFICANT CHANGES TO
FORECAST AT THIS TIME. SOME PATCHY LIGHT FROST POSSIBLE IN OUTLYING
AREAS...BUT MUCH LESS WIDESPREAD THAN LAST NIGHT/THIS MORNING.
ALLSOPP
PREVIOUS DISCUSSION...
255 PM CDT
LATE THIS AFTERNOON THROUGH MON NIGHT...
A MOISTURE STARVED SHORT WAVE WAS FROM WESTERN LAKE SUPERIOR S
ACROSS WI AND EASTERN IA TO NE MO AT MIDDAY. ONLY SOME THIN CIRRUS
WAS AHEAD OF THE SHORT WAVE TROUGH. AT THE SURFACE...A WEAK COLD
FRONT WAS ALIGNED WITH THE MID-UPPER TROUGH. AS THE SHORT WAVE
CONTINUES TO THE E TODAY THIS FRONT WILL MOVE TO FAR SE WI AND NE
TO W CENTRAL IL BY 00Z.
UPSTREAM...ANOTHER SHORT WAVE OVER THE CENTRAL PLAINS WAS PRODUCING
SHOWERS FROM SOUTHERN SD TO NORTHER KS AND E TO S CENTRAL IA. THIS
SHORT WAVE WILL CONTINUE TO THE SE TODAY AND TONIGHT...REACHING A
CENTRAL IL TO LA LINE BY 12Z SUN. THE NORTHERN PORTION WILL BE
ENCOUNTERING INCREASINGLY DRY AIR. WITH SE MOVEMENT AND THE DRY AIR
OVER THE LOCAL AREA ANY THREAT OF SHOWERS TONIGHT WILL BE FROM
NORTHERN MO AND CENTRAL IL SOUTHWARD.
MEANWHILE...ANOTHER SHORT WAVE FARTHER UPSTREAM...OVER SOUTHERN
SASKATCHEWAN AND EASTERN MT AT MIDDAY...WILL BE MOVING ESE TO NEAR
THE SOUTHERN MANITOBA-ONTARIO BORDER S ACROSS THE UPPER MS VALLEY
WITH THE WARM AIR ADVECT ON AND RESULTING UPWARD VERTICAL VELOCITY
SPREADING ACROSS THE UPPER MIDWEST OVERNIGHT. A STRONG UPPER JET MAX
WILL BE DROPPING SE ACROSS THE NORTHERN PLAINS AND THE UPPER MIDWEST
DURING THE DAY SUN...WITH THE BEST UPPER DIVERGENCE PROGGED TO
SPREAD ESE FROM THE UPPER MS VALLEY ACROSS LAKE SUPERIOR...THE U.P.
OF MI AND WI...AND AS FAR E AS LAKE MI BY 00Z MON.
WHILE MID LEVELS OVER THE LOCAL AREA ARE SHOWN BY THE MODELS TO
GRADUALLY MOISTEN WITH TIME SUN THE LOW LEVELS REMAIN FAIRLY DRY.
THEREFORE...WITH BETTER DYNAMICS TO THE N AND DRY LOW LEVELS LOCALLY
FORESEE ONLY MID LEVEL CLOUDS TO BE ON THE INCREASE WITH JUST A
SLIGHT CHANCE OF A FEW LIGHT SHOWERS AND SPRINKLES ACROSS THE LOCAL
FORECAST AREA SUN. THREAT OF LIGHT SHOWERS RISES TO CHANCE CATEGORY
AS LOWER LEVELS MOISTEN AND UPPER TROUGH MOVES ACROSS THE AREA
PUSHING ANOTHER COLD FRONT SE ACROSS THE FORECAST AREA.
WEAK COLD AIR ADVECTION ON NW FLOW PERSISTS INTO MON AFTERNOON
BEFORE MID LEVEL WARM AIR ADVECTION ARRIVES LOCALLY LATE
AFTERNOON/EARLY EVENING AS A BROAD UPPER RIDGE MOVES E FROM THE
PLAINS TO THE UPPER MIDWEST AND MID MS VALLEY BY DAYBREAK TUE
AHEAD OF A POSITIVELY TILTED UPPER TROUGH THE DEVELOPS AS A GULF
OF ALASKA UPPER LOW AND A SHORT WAVE TO ITS SW MERGE AS THE
PROGRESS EASTWARD...WITH THE TROUGH AXIS EXTENDING FROM THE
SOUTHERN CANADIAN PRAIRIE SW ACROSS THE ROCKIES AND THE NORTHERN
CA COAST. MODELS MOVE AN ASSOCIATED SURFACE LOW FROM THE CENTRAL
PLAINS E TO AROUND THE MID MO VALLEY DURING MON NIGHT.
TUE THROUGH SAT...
MODELS STILL HAVE SOME VARIATIONS IN THE TRACK OF LIFTING THE LOW
OUT OF THE PLAINS TUE AND INTO THE GREAT LAKES TUE EVENING. STRONG
CONSENSUS AMONGST MODELS THAT THE TRACK WILL BE N OF THE LOCAL
FORECAST AREA THOUGH HOW FAR N WILL HAVE AN IMPACT ON WHERE
OVERRUNNING PRECIPITATION SHIELD AND WHERE WARM SECTOR AND SHOWERS
WILL BE LOCATED...ALONG WITH BEING A BIG FACTOR FOR MAX
TEMPERATURES TUE. AT THIS POINT IT LOOKS LIKE THE LOCAL AREA WILL
BE SOLIDLY IN THE WARM SECTOR BY MIDDAY TUE THUS HAVE SPREAD MILD
TEMPS ALL THE WAY N TO THE WI BORDER AND HAVE GONE WITH SHOWERS VS
RAIN. ALSO HAVE MENTION OF CHANCE OF THUNDER THOUGH GFS AND ECMWF
THERMAL PROFILES SUGGEST THAT THE MID LEVEL MAY BE TOO WARM TO
ALLOW DEEP CONVECTION TO OCCUR.
FOR WED...WITH MINOR DISTURBANCES RIDING ENE IN THE SOUTHERN
STREAM AND SE ON THE NORTHERN STREAM CANNOT RULE OUT PRECIPITATION
TOTALLY SO HAVE SLIGHT CHANCE OF SHOWERS. DURING WED NIGHT A WAVE
IN THE SOUTHERN STREAM WILL RIDE ALONG THE BAROCLINIC ZONE SET UP
OVER SOUTHERN MO...CENTRAL IL AND NORTHERN IN WITH A CHANCE OF
SHOWERS ALONG AND N OF THE BAROCLINIC ZONE. SLIGHT CHANCE OF LIGHT
SHOWERS TO PERSIST INTO THU AS THE BAROCLINIC ZONE IS PROGGED TO
BE VERY SLOW TO SETTLE S AHEAD OF THE SHARPENING UPPER TROUGH
MOVING E FROM THE CENTRAL HIGH PLAINS AND THE SOUTHERN ROCKIES.
WHILE COOLER AIR WILL BE BROUGHT SOUTHWARD IN THE WAKE OF THE
TUE-TUE NIGHT SYSTEM REMAINS PRIMARILY OVER THE UPPER MIDWEST AND
THE GREAT LAKES THOUGH IT DOES COOL ENOUGH FOR THE POTENTIAL FOR
LAKE EFFECT SHOWERS THU THROUGH FRI NIGHT...INCLUDING IL SHORES AS
LOW LEVEL FLOW TO HAVE AN EASTERLY COMPONENT.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 06Z...
* SCT'D SHRA/TSRA SUNDAY EVENING
IZZI
//DISCUSSION...UPDATED 06Z...
LIGHT WINDS TONIGHT WILL BECOME SOUTHWEST AND PICK UP A BIT
SUNDAY. DEPENDING ON THE EXTENT OF HIGH CLOUDINESS THERE COULD BE
A FEW GUSTS AROUND 15KT DURING THE AFTERNOON SUNDAY. FRONT AND
POWERFUL UPPER LEVEL JET WILL ARRIVE SUNDAY EVENING LIKELY
BRINGING A PERIOD OF SHOWERS TO THE TERMINALS. GIVEN THE STEEP
LAPSE RATES ALOFT HAVE INTRODUCED SOME VCTS INTO THE TAFS AS WELL
TO HINT AT THE POTENTIAL FOR SOME SCATTERED THUNDERSTORMS
DEVELOPING. WINDS SHIFT TO NORTHWEST BEHIND THE FRONT OVERNIGHT
SUNDAY ENDING THE SHRA/TSRA THREAT AND ALLOWING FOR A RETURN TO
VFR CONDITIONS.
IZZI
//ORD AND MDW CONFIDENCE...UPDATED 06Z...
* HIGH CONFIDENCE IN ALL FORECAST ELEMENTS THROUGH THE DAY SUNDAY
* MEDIUM CONFIDENCE ON SHRA/TSRA TIMING/LIKELIHOOD SUNDAY EVENING
IZZI
//OUTLOOK FOR ORD/MDW FOR 12Z MONDAY-12Z SATURDAY...UPDATED 00Z...
MONDAY...VFR
TUESDAY...CHANCE OF TSRA
WEDNESDAY...MVFR CIGS POSSIBLE
THURSDAY...CHANCE SHRA/MVFR CIGS
FRIDAY...MVFR CIGS POSSIBLE
SHEA
&&
.MARINE...
245 AM CDT
WINDS WILL BECOMING SOUTH AND INCREASE SOME THIS AFTERNOON AND
EVENING AS A LOW TRACKS NORTH OF LAKE SUPERIOR. RELATIVELY WARM
AIR RUNNING INTO THE CHILLY MARINE LAYER SHOULD PREVENT FULL
FORCE OF WINDS FROM BEING FELT...ESPECIALLY OVER SOUTHERN PORTIONS
OF THE LAKE THIS AFTERNOON. FRONT SWEEPS ACROSS THE LAKE TONIGHT
AND COULD SEE A BRIEF PERIOD OF 30KT WINDS FOR A COUPLE/FEW HOURS
BEHIND THE FRONT BEFORE WINDS BEGIN TO SUBSIDE AGAIN LATE
TONIGHT.
NEXT LOW DEVELOPS OVER THE PLAINS AND TRACKS EAST INTO WISCONSIN
TUESDAY AFTERNOON. WHILE THERE ARE STILL SOME DIFFERENCES IN MODEL
SOLUTIONS FOR THIS LOW...THEY ARE SMALLER THAN THE LAST FEW DAYS.
WINDS SHOULD INCREASE TUESDAY AS THIS LOW TRACKS QUICKLY MOVES
EAST TOWARD THE REGION...THOUGH AGAIN WARM AIR WITH THE SOUTHERLY
FLOW OVER THE SOUTHERN PORTIONS OF THE LAKE SHOULD KEEP WINDS FROM
GETTING TOO OUT OF HAND. IN THE WAKE OF THE LOW STILL THINK WINDS
WILL RAMP UP QUICKLY OUT OF THE NORTH/NORTHWEST WITH A POTENTIAL
FOR AT LEAST A PERIOD OF GALES BEHIND THE LOW. ENOUGH DIFFERENCES
REMAIN TO HOLD OFF ON GOING ABOVE 30KT IN THE FORECAST JUST
YET...BUT GALES STILL LOOK POSSIBLE FOR A TIME LATE TUESDAY NIGHT
INTO WEDNESDAY AND MAY NEED TO BE ADDED AS MODELS COME AROUND TO
A MORE UNIFIED SOLUTION WITH THIS NEXT SYSTEM.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
