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 03Z...
* NO CONCERNS OVERNIGHT
* SLIGHT CHANCE OF SHOWERS SUNDAY AFTERNOON
SHEA
//DISCUSSION...UPDATED 00Z...
WEAK SURFACE TROUGH CONTINUES TO MOVE THROUGH NORTHERN ILLINOIS
THIS EVENING...BUT WILL DO LITTLE TO THE TERMINALS OVERNIGHT.
WINDS HAVE BECOME LIGHT AND VARIABLE AND WILL CONTINUE THAT WAY
THROUGH THE MORNING HOURS. WINDS WILL PICK UP INTO THE AFTERNOON
HOURS AND OCCASIONALLY GUST INTO THE MID TEENS...SIMILAR TO THIS
AFTERNOON.
HIGH LEVEL CLOUDS WILL INCREASE THROUGH THE DAY AS A WEAK
DISTURBANCE MOVES THROUGH THE AREA INTO THE LATE AFTERNOON AND EARLY
EVENING HOURS. THE SYSTEM IS QUITE MOISTURE DEPRIVED AND THE BETTER
FORCING WILL REMAIN ACROSS WISCONSIN...BUT AN OVERALL LOW
PROBABILITY REMAINS ACROSS ALL OF THE TERMINALS AT OR BEYOND 00Z.
FOR NOW WILL HAVE A MENTION OF LIGHT VFR SHOWERS AND CAN ADJUST AS
NEED BE AS THE TIME GETS CLOSER.
SHEA
//ORD AND MDW CONFIDENCE...UPDATED 03Z...
* HIGH CONFIDENCE ALL FORECAST ELEMENTS OVERNIGHT
* LOW CONFIDENCE IN PRECIP CHANCES SUNDAY AFTERNOON/EVENING
SHEA
//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...
157 PM CDT
MAIN CONCERNS WITH THE MARINE FORECAST FALL WITHIN THE TUESDAY AND
WEDNESDAY TIMEFRAME...WITH LOW PRESSURE SYSTEM EXPECTED TO MOVE
THROUGH THE GREAT LAKES REGION. WHILE VARIOUS MODEL SOLUTIONS ARE IN
GENERAL AGREEMENT WITH OCCURRENCE OF THIS FEATURE...THERE
REMAINS ENOUGH SPREAD IN THE LOW TRACK FORECASTS TO LOWER CONFIDENCE
IN DETAILS OF WIND FORECAST DURING THIS TIME. GENERAL CONSENSUS
INDICATES THE LOW WILL TRACK FROM THE IA/MN BORDER ACROSS CENTRAL OR
NORTHERN LAKE MICHIGAN...THOUGH THERE ARE A FEW OUTLIER MODEL
SOLUTIONS WHICH TAKE THE LOW BOTH FARTHER SOUTH AND NORTH OF THIS
PATH. FAVORING BLEND WHICH TAKES LOW AS STATED ABOVE AND HAVE BASED
WIND FORECAST ON THIS...THOUGH DETAILS AND TIMING OF WIND SHIFTS AND
SPEEDS WILL NEED TO CONTINUE TO BE REFINED AS MODELS COME INTO
BETTER FOCUS WITH THIS SYSTEM. COULD EVENTUALLY FORESEE A PERIOD OF
GALES FROM LATE TUESDAY INTO WEDNESDAY...THOUGH HAVE HELD OFF ANY
HEADLINE AT THIS TIME BASED ON ABOVE INDICATED CONFIDENCE FACTORS.
RATZER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
