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 15Z...
* NONE
RATZER
//DISCUSSION...UPDATED 15Z...
LIGHT SOUTHWEST FLOW AHEAD OF WEAKENING LOW PRESSURE TROUGH TODAY.
DEEPENING OF MIXED LAYER MAY ALLOW A FEW GUSTS INTO THE 10-15 KT
RANGE FOR A TIME LATE MORNING/EARLY AFTERNOON BEFORE GRADIENT
WEAKENS NEAR THE TROUGH AXIS. OTHERWISE...WEATHER NIL.
RATZER
//ORD AND MDW CONFIDENCE...UPDATED 15Z...
* HIGH CONFIDENCE IN ALL ELEMENTS
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...
245 AM CDT
WEAK TROUGH WILL SWEEP ACROSS THE LAKE THIS AFTERNOON BUT WITHOUT
MUCH FANFARE. SOUTHERLY WINDS WILL INCREASE SUNDAY AS THE GRADIENT
TIGHTENS IN ADVANCE OF A LOW TRACKING NORTH OF LAKE SUPERIOR.
FAIRLY WARM AIR BEING ADVECTED NORTH WILL RESULT IN SOMEWHAT
MARINE BOUNDARY LAYER...ESPECIALLY SOUTHERN PORTIONS OF THE LAKE.
STILL ANTICIPATE WINDS GUSTING WELL INTO THE 20 KT RANGE SUNDAY
AFTERNOON OVER NORTHERN PORTIONS OF THE LAKE BEFORE FRONT MOVES
THROUGH WITH A BRIEF PERIOD OF FRESH NORTHWEST WINDS MONDAY.
WINDS SUBSIDE FOR A TIME MONDAY NIGHT BEFORE THE NEXT STORM
APPROACHES THE REGION TUESDAY AND WEDNESDAY. STILL SIGNIFICANT
DIFFERENCES IN THE MODELS WITH REGARDS TO STRENGTH AND TRACK OF
THIS LOW SO HAVE LOWER THAN AVERAGE CONFIDENCE IN THE TUES/WED
FORECAST...BUT POTENTIAL DOES EXIST FOR FAIRLY STRONG WINDS JUST
THE DIRECTION IS TOUGH TO PINPOINT AT THIS POINT.
IZZI
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
