1224 PM CDT
PRELIMINARY FOR 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.
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.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 18Z...
* NO SIGNIFICANT CONCERNS THROUGH EARLY SUNDAY.
* SLIGHT CHANCE OF SHOWERS SUNDAY AFTERNOON.
RATZER
//DISCUSSION...UPDATED 18Z...
WEAK SURFACE TROUGH MOVING SLOWLY ACROSS NORTHERN IL AT
MIDDAY...AND WILL PUSH INTO THE CHICAGO TERMINALS THROUGH LATE
AFTERNOON. TROUGH IS LOSING MOMENTUM HOWEVER...SO NOT MUCH PUSH
WITH THIS BOUNDARY AND ONLY A WIND SHIFT TO THE WEST-NORTHWEST
EXPECTED WITH SPEEDS FALLING OFF TO LESS THAN 10 KTS. LIGHT
WESTERLY COMPONENT LIKELY TO BE LESS THAN 5 KTS OVERNIGHT AS WEAK
HIGH PRESSURE WEAKENS IN RESPONSE TO NEW STRONGER TROUGH OVER THE
NORTHERN PLAINS. APPROACH OF THIS FEATURE WILL CAUSE WINDS TO BACK
TO THE SOUTHWEST AGAIN SUNDAY MORNING...WITH SPEEDS PICKING UP TO
AROUND 10 KTS AGAIN BY AFTERNOON.
VFR CONDITIONS EXPECTED THROUGH THE PERIOD...WITH ONLY AN INCREASE
IN MID/HIGH CLOUDS ON SUNDAY AS UPPER DISTURBANCE ASSOCIATED WITH
SURFACE TROUGH/COLD FRONT MOVES ACROSS THE UPPER MIDWEST. SOME
POTENTIAL FOR SOME SHOWERS DOES EXIST...MAINLY AFTER 18Z...THOUGH
COMBINATION OF A RELATIVELY MOISTURE-STARVED ENVIRONMENT AND THE
FACT THAT THE STRONGER FORCING PASSES ACROSS MN/WI TO OUR NORTH
RESULTS IN RELATIVELY LOW POINT PROBABILITIES FOR PRECIP INTO THE
AFTERNOON. WILL MAINTAIN DRY TAFS...PARTICULARLY ORD 24-30 HOUR
PERIOD AT THIS TIME. LATER FORECASTS CAN DETAIL DEGREE OF PRECIP
THREAT AND TIMING.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* HIGH CONFIDENCE ALL ELEMENTS THROUGH TONIGHT.
* LOW CONFIDENCE IN PRECIP SUNDAY AFTERNOON.
RATZER
//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...
SUNDAY NIGHT...CHC OF -SHRA.
MONDAY...VFR.
TUESDAY...CHC OF SHRA/TSRA LATE.
WEDNESDAY...MVFR CIGS POSSIBLE.
THURSDAY AND FRIDAY...CHC RA/MVFR CIGS.
IZZI
&&
.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.
&&
$$
