414 AM CST
FOCUS OF FORECAST REMAINS ON PAIR OF STORM SYSTEMS TO AFFECT THE
REGION TODAY THROUGH WED NIGHT.
UPPER SYSTEM NUMBER ONE EXTENDS FROM THE CANADIAN ROCKIES SE TO
THE SOUTHERN PLAINS. A SHORT WAVE IS LIFTING NE OVER THE NORTHERN
PLAINS AND UPPER MS VALLEY EARLY THIS MORNING...WITH SATELLITE
REVEALING A TIGHT UPPER LOW OVER EASTERN SD WHILE THE MAIN UPPER
LOW IS OVER THE MT-SASKATCHEWAN BORDER. THE UPPER TROUGH WILL
CONTINUE TO ROTATE NNE AND TO SOUTHERN MANITOBA AND WESTERN
ONTARIO BY LATE AFTERNOON-EARLY THIS EVENING.
DUE TO THE LACK OF LOW LEVEL MOISTURE WITH 06/00Z UPSTREAM RAOBS
SHOWING 850HPA DEW POINT DEPRESSIONS IN THE TEENS CELSIUS. THIS
SYSTEM IS SPITTING OUT A LITTLE SHOWER ACTIVITY MAINLY ON THE
N-NW SIDES OF THE SD UPPER LOW AS WELL AS DIRECTLY UNDER THE
UPPER LOW CENTER. FURTHER E THERE IS A BAND OF RADAR ECHOES NW-SE
ACROSS MN INTO NE IA THOUGH MINIMAL REPORTS OF ANY RAIN REACHING
THE GROUND IN METARS FROM THAT AREA. GULF MOISTURE HAS BEGUN ITS
END RUN AROUND THE WESTERN EDGE OF THE LARGE SURFACE RIDGE
EXTENDING ALL THE WAY FROM THE GULF OF MAINE SW TO THE NORTHERN
GULF OF MEXICO WITH 50 DEG F DEW POINTS APPROACHING SE KS AND SW
MO EARLY THIS MORNING AND 60+ DEW POINTS FURTHER S OVER EASTERN
TX THIS MOISTURE.
THIS SYSTEM CONTINUES NE ACROSS ONTARIO TO W OF JAMES BAY BY
12Z MON WITH THE ASSOCIATED SURFACE LOW...CURRENTLY ON THE
ND-MANITOBA BORDER...WILL ALSO MOVE NE AND TO A POSITION CLOSE TO
UNDER THE UPPER BY MON MORNING. AS IT DOES...A TRAILING COLD FRONT
WILL DROP S OVER LOWER MI...NE AND W CENTRAL IL AND NORTHERN MO
AND THEN BECOME STATIONARY ACROSS NORTHER IN...CENTRAL IL AND
CENTRAL MO DURING MONDAY AS UPPER SYSTEM NUMBER TWO MOVES TO THE
FOUR CORNERS AREA.
WHILE THIS FIRST STORM SYSTEM WILL BE DEPARTING TOO QUICKLY FOR
THE GULF MOISTURE TO BE ENTRAINED INTO IT THIS MOISTURE WILL
CONTINUE TO BE ADVECTED ACROSS THE MID MS VALLEY AND THE LOCAL
AREA LATE TODAY AND TONIGHT...POOLING ALONG AND S OF THE SLOW
MOVING BOUNDARY APPROACHING FROM THE N. SW LOW LEVEL FLOW REMAINS
STRONG AS THE SURFACE RIDGE HOLDS ITS POSITION ALONG THE MID
ATLANTIC COAST...ACROSS THE DEEP S AND THE NORTHERN GULF AND THE
DEEPENING SURFACE LOW ASSOCIATED WITH UPPER SYSTEM NUMBER TWO
COMES OUT OVER THE SOUTHERN HIGH PLAINS OVERNIGHT TONIGHT. WHILE
THERE IS NO EVIDENCE OF ANY MID OR UPPER LEVEL FORCING...
OVERRUNNING OF THE SLOWING BOUNDARY BY THE GULF MOISTURE COULD
GENERATE SOME SHOWERS ACROSS THE AREA...ESPECIALLY SOUTH AND EAST
PORTIONS OVERNIGHT.
AS THE SECOND SYSTEM MOVES FROM THE ROCKIES ENE ACROSS THE
CENTRAL PLAINS MON AND TUE CHANCES FOR RAIN OVER THE LOCAL
FORECAST AREA WILL BE ON THE INCREASE AS DEEPENING GULF MOISTURE
EVENTUALLY SPREADS OVER THE REGION WITH PRECIPITABLE WATER VALES
PROGGED TO CLIMB UP TO AROUND 1.5 INCHES...ABOUT 200 PERCENT OF
NORMAL. FIRST WILL BE THE INITIAL PUSH OF WARM AIR ADVECTION AND
RESULTING UPWARD MOTION MON NIGHT...THEN DEEP LARGE SCALE UPWARD
ASCENT AHEAD OF THE APPROACHING UPPER TROUGH/UPPER LOW ARRIVES BY
TUE AFTERNOON.
MODELS HAVE SHOWN DECENT CONTINUITY AND AGREEMENT THERE STILL ARE
SOME DIFFERENCES. WITH MODEL RUNS GRADUALLY SLOWING DOWN THE
PROGRESSION OF THE SECOND SYSTEM OVER THE LAST COUPLE DAYS THE
LATEST ECMWF RUN HAS SPED IT UP WHILE THE SREF AND OPERATIONAL GFS
ONLY SHOWING A SLIGHTLY FASTER MOVEMENT COMPARED TO THEIR
RESPECTIVE PREVIOUS COUPLE OF RUNS. FEEL THAT THE GFS ENSEMBLE
MEANS ARE ABOUT THE BEST GUIDANCE AT THIS POINT WITH ONLY A SLIGHT
SLOWING FROM THE 05/00Z RUN TO THE 05/12Z AND A SLIGHT SLOWING
DEPICTED BY THE 06/00Z RUN. THERE IS GOOD AGREEMENT BETWEEN THE
ENSEMBLE MEMBERS THROUGH WED EVENING THEN SOME MINOR DIFFERENCES
DISREGARDING THE COUPLE OF OUTLIERS.
FOLLOWING THE GFS ENSEMBLE MEAN HAS THE SOUTHERN PLAINS SURFACE
LOW TRACKING NE TO THE MID MS VALLEY BY 00Z WED WITH A WARM FRONT
LIFTING N TO FAR NE IL...SOUTHERN LAKE MI AND CENTRAL LOWER MI.
THIS PUTS A LARGE PORTION OF THE FORECAST AREA IN THE WARM
SECTOR...SAVE N CENTRAL AND THE EXTREME NE CORNER OF IL SO MUCH OF
THE AREA WILL BE QUITE MILD AND THERE MAY BE A BREAK IN THE RAIN
DURING TUE MORNING INTO EARLY AFTERNOON BETWEEN THE WARM AIR
ADVECTION AND THE APPROACH OF THE UPPER TROUGH. MODELS SHOW A
STRONG DRY SLOT STREAMING NNE ACROSS THE AREA LATE TUE NIGHT AND
WED MORNING BUT ATTEMPT TO BRING SOME WRAP AROUND MOISTURE OVER
THE AREA DURING THE DAY. COMBINED WITH CYCLONIC FLOW AND SURFACE
HEATING THERE WILL BE A CHANCE OF SOME SHOWERS WED...MAINLY N AND
E SECTIONS OF THE FORECAST AREA.
AS SYSTEM NUMBER TWO MOVES OFF TO THE NE DURING WED NIGHT AND THU
STRONG DEEP COLD AIR ADVECTION TAKES OVER. WHILE THE AIR MASS THAT
WILL BE TAPPED IS NOT EXCESSIVELY COLD IT WILL BE QUITE A CONTRAST
TO ONLY REACH THE LOWER AND MID 40S THU AFTER THE 60S FORM MUCH OF
THE AREA ON TUE.
TRS
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 12Z...
* WIND SHEAR FROM THE SOUTH/SOUTHWEST AT 2KFT AGL BETWEEN 45 AND 55KT.
* INCREASING LOW LEVEL MOISTURE MAY PRODUCE LOW END VFR CIGS
POSSIBLY MVFR CIGS THIS AFTN.
* MOISTURE IN LOW/MID LEVELS MAY LIMIT MIXING HEIGHTS AND COULD
DIMINISH WIND GUSTS THIS AFTN.
BEACHLER
//DISCUSSION...UPDATED 12Z...
IR IMAGERY THIS MORNING CONTINUES TO INDICATE CIRRUS SHIELD
OVERHEAD STRETCHING FROM SOUTHWEST ONTARIO SOUTH THROUGH THE
MISSOURI VALLEY. SFC LOW PRESSURE CONTINUES TO WRAP ITSELF UP OVER
FAR EASTERN NORTH DAKOTA AND STEADILY LIFTING NORTH. AHEAD OF THIS
LOW PRESSURE SYSTEM THE PRESSURE GRADIENT HAS TIGHTENED...AND WAS
INFLUENCING AIRFIELDS ACROSS NORTHERN IL/NORTHWEST IN WITH
INCREASING WINDS AT THE SFC AND OCCASIONAL GUSTS. THE SOUNDING
FROM CENTRAL ILLINOIS INDICATES THAT WINDS AT 2KFT AGL ARE
53KT...SUPPORTING THE CURRENT FORECAST FOR LLWS. EXPECT SHORTLY
AFTER DAYBREAK THE MIXED LAYER WILL INCREASE AND BRING TO THE SFC
HIGH GUSTS INTO THE LOWER TO MIDDLE 20KT RANGE. THIS IS EXPECTED
TO PERSIST THROUGH TONIGHT. MEANWHILE...MOISTURE CONTINUES TO BE
ADVERTISED BY GUIDANCE IN THE MID LEVEL PORTIONS OF THE
ATMOSPHERE. THIS SUGGESTS THAT CIGS WILL STEADILY LOWER THROUGHOUT
THE AFTN AND MAY BE REDUCED TO LOW END VFR CONDS. FOR NOW HAVE
HELD ONTO VFR CIGS...ALTHOUGH FOR A FEW LOCATIONS MVFR CIGS ARE
POSSIBLE. THE OTHER CHALLENGE WILL BE THAT COVERAGE AND INTENSITY
OF THE CLOUD COVER MAY LIMIT WIND GUSTS THIS AFTN. CONFIDENCE ON
THIS SCENARIO IS LOW...THUS HAVE HELD ONTO THE WIND GUSTS THROUGH
THIS AFTN AND EARLY EVE.
LATE TONIGHT THE PRESSURE GRADIENT WILL STEADILY
DIMINISH...ALLOWING WINDS TO RELAX TO AROUND 10KT FROM THE
SOUTHWEST. CIGS MAY HOVER IN THE LOW END VFR CATEGORY THROUGH THE
OVERNIGHT PERIOD.
BEACHLER
//ORD AND MDW CONFIDENCE...UPDATED 12Z...
* HIGH CONFIDENCE IN LLWS.
* MEDIUM CONFIDENCE ON TIMING OF LLWS.
* HIGH CONFIDENCE IN SFC WIND DIR/SPEED.
* LOW/MEDIUM CONFIDENCE ON CIGS FORECAST THIS AFTN/EVE.
BEACHLER
//OUTLOOK FOR ORD/MDW FOR 00Z TUESDAY-12Z SUNDAY...UPDATED 12Z...
MONDAY NIGHT...VFR. CHC SHRA ISO TSRA W/PATCHY MVFR CIGS.
TUESDAY...MVFR. SHRA/ISO TSRA W/PATCHY MVFR CIGS.
WEDNESDAY...MVFR TRENDING VFR. THEN RA BECOMING MIXED WITH SN LATE.
THURSDAY...MVFR WITH WINTRY MIX EARLY THEN VFR AND DRY.
FRIDAY...VFR. SLIGHT CHC SHRA.
SATURDAY...VFR.
BEACHLER
&&
.MARINE...
417 AM CST
TROUGH OF LOW PRESSURE CENTERED OVER THE DAKOTAS THIS MORNING WILL
CONTINUE TO STRENGTHEN AS IT SLIDES NORTHEAST INTO SOUTHWEST
ONTARIO. TO THE EAST OF THIS SYSTEM THE PRESSURE GRADIENT IS
EXPECTED TO TIGHTEN CONSIDERABLY TODAY...RESULTING IN GUSTY WINDS
OVER LAKE MICHIGAN THROUGH TONIGHT. IT APPEARS LIKELY THAT GALE
CRITERIA WILL BE ACHIEVED...HOWEVER THE PRECISE VELOCITY AND TIMING
APPEAR TO BE A CHALLENGE. GUIDANCE HAS CONTINUED TO INDICATE THAT
JUST BEFORE DAYBREAK TODAY WINDS OVER THE LAKE WILL BE GUSTING TO
AROUND GALE CRITERIA. UNFORTUNATELY THIS MAY TAKE SLIGHTLY LONGER TO
MATERIALIZE UNTIL MID MORNING. THE SECOND CHALLENGE IS THE ABUNDANCE
OF CLOUD COVER OVER THE WESTERN GREAT LAKES. NONETHELESS JUST OFF OF
THE DECK ARND 2KFT AGL...WINDS TO 50KT HAVE BEEN OBSERVED BASED ON
RADAR DATA. THUS VERY WINDY CONDITIONS HAVE DEVELOPED ALREADY...THEY
JUST HAVE YET TO HAVE BEEN REALIZED OVER THE MARINE SFC. THIS MAY
LIMIT THE POTENCY OF MIXING FOR THIS AFTERNOON OVER LAKE
MICHIGAN...AND RESULT IN MUCH LOWER WIND GUSTS. WHILE SUB-GALE
CRITERIA IS POSSIBLE...CONFIDENCE IN REMOVING THE HEADLINES IS VERY
LOW. THUS WILL CONTINUE TO ADVERTISE GALES FOR TODAY.
PRESSURE GRADIENT QUICKLY SLACKENS TONIGHT AS THE LOW PRESSURE
QUICKLY LIFTS NORTHEAST TOWARDS HUDSON BAY. AS THIS OCCURS A RIDGE
OF HIGH PRESSURE IS EXPECTED TO BUILD IN FROM THE WEST ACROSS THE
WESTERN GREAT LAKES. A SLUGGISH FRONTAL BOUNDARY WILL EXIST JUST TO
THE SOUTH OF LAKE MICHIGAN MONDAY AS YET ANOTHER LOW PRESSURE SYSTEM
DEVELOPS OVER THE SOUTHERN PLAINS. THIS SECOND LOW PRESSURE SYSTEM
WILL THEN DEEPEN AND LIFT NORTHEAST TOWARDS THE GREAT LAKES REGION
TUESDAY. THE PRESSURE GRADIENT IS ONCE AGAIN EXPECTED TO
INCREASE...AND POSSIBLY PRODUCE SMALL CRAFT ADVISORY CONDITIONS FOR
THE ILLINOIS/INDIANA NEARSHORE WATERS THROUGH WEDNESDAY MORNING.
WHILE IT IS CONCEIVABLE THAT THE WARMER AIR ADVECTING OVER THE
COOLER LAKE MAY PRODUCE A STABLE ENVIRONMENT AND INHIBIT WAVE
GROWTH...AT THIS TIME CONFIDENCE IS VERY LOW THAT THIS WILL OCCUR.
BEACHLER
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 9 PM SUNDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS
UNTIL 3 AM MONDAY.
&&
$$
