346 AM CST
ATMOSPHERIC RIVER HAS ARRIVED OVERHEAD STRETCHING FROM THE STRAITS
OF MACKINAC SOUTHWEST THROUGH SOUTHERN WI/NORTHERN IL/CENTRAL MO.
ALONG THIS CHANNEL OF MOISTURE PWAT VALUES HAVE RISEN TO NEARLY 3
SIGMA OR 1.25 INCHES OF PRECIPITABLE WATER. FURTHER SOUTH ACROSS THE
SOUTHERN PLAINS/OZARKS...AND PROXIMITY TO THE SFC LOW CONSIDERABLE
MOISTURE CONVERGENCE CONTINUES. THIS HAS BEEN THE FAVORED REGION FOR
CONVECTIVE GROWTH AND SEVERE WEATHER STRETCHING INTO PORTIONS OF
TEXAS. OVER OUR AREA A QUASI-STATIONARY BOUNDARY WILL BEGIN TO LIFT
NORTH TODAY ALLOWING NORTHEAST WINDS TO VEER SOUTH AHEAD OF THE
SHORTWAVES ARRIVAL.
IR IMAGERY CONTINUES TO INDICATE A THIN CLOUD LAYER ALONG FAR
NORTHEAST IL STRETCHING SOUTH THROUGH EASTERN IL/WESTERN TENN
VALLEY. GUIDANCE HAS CONTINUED TO SUGGEST POSSIBLY A PERIOD OF DRY
WEATHER TODAY FOR A PORTION OF OUR EASTERN CWFA. CONFIDENCE IS
MARGINAL AT THIS TIME...SO HAVE HELD ONTO LIKELY POPS IN THIS AREA.
FURTHER NORTHWEST AND CONFIDENCE HAS REMAINED MUCH HIGHER AND ALMOST
A SURE THING. IN REGARDS TO THE CONVECTIVE CHANCES...THIS APPEARS TO
BE WAINING A BIT. WHILE THE ENVIRONMENT WILL BECOME MARGINALLY
UNSTABLE THROUGHOUT THE AFTN/EVE...WITH A POTENT LLVL JET AT 850MB
OF NEARLY 50KTS. IT WOULD BE DIFFICULT TO REMOVE MENTION OF
THUNDER...AND REMAINS POSSIBLE FOR AN EMBEDDED THUNDERSTORM TO
OCCUR. SO HAVE MAINTAINED MENTION OF SLIGHT CHANCE THUNDER FOR TODAY
THROUGH TONIGHT.
SHORTWAVE STEADILY LIFTS NORTHEAST AS THE 500MB TROUGH AXIS PIVOTS
EAST TOWARDS THE CENTRAL PLAINS THIS AFTN. BY SUNSET THE SFC LOW
SHOULD BE NEARING CENTRAL MISSOURI. SREF GUIDANCE CONTINUES TO
INDICATE THE ATMOSPHERIC RIVER WILL BE OVERHEAD THROUGH THIS
AFTN/EVE...WITH PWAT VALUES REMAINING AT OR ARND 1.00 INCH. WITH
CONSIDERABLE CLOUD COVER EXPECTED TODAY...ANY CHANCE OF TEMPS
WARMING WILL DEPEND PURELY ON THE WARM AIR ADVECTION. AS PREVIOUSLY
MENTIONED GUIDANCE HAS CORRECTED SLIGHTLY FURTHER EAST WITH THE PATH
OF THE SFC LOW...WHICH MAY ALLOW TEMPS OVER THE NORTHWEST CWFA TO
REMAIN ARND 50 DEG. CONFIDENCE REMAINS HIGH THAT ELSEWHERE TEMPS
WILL BE IN THE LOW/MID 60S.
FOCUS ON QPF REMAINS A CHALLENGE. SREF PLUMES DEMONSTRATE A LARGE
RANGE IN SOLUTIONS FROM 0.7 INCHES TO A MAXIMUM OF 3.2 INCHES FOR
MANY PORTIONS OF THE CWFA. THERE APPEARS TO BE SOME CLUSTERING IN
THE LOWER BOUNDS OF THE ENVELOPE OF SOLUTIONS OR NEAR 1.00 TO 2.00
INCHES. THUS HAVE HEDGED THE QPF FORECAST ON A STORM TOTAL IN THIS
ARENA. STILL COULD SEE SOME LOCALLY HIGHER QPF TOTALS WHEN IT IS ALL
SAID AND DONE...ESPECIALLY IF CONVECTION IS ABLE TO OCCUR. FROM A
PROBABILISTIC APPROACH THE LATEST SREF IS INDICATING A 70 TO 80
PERCENT CORE OF EXCEEDENCE OF 50MM OR ROUGHLY 2.00 INCHES OF QPF
ACROSS NORTHEAST MISSOURI STRETCHING NORTHEAST THROUGH
NORTH CENTRAL IL.
WEDNESDAY THROUGH THURSDAY...
GUIDANCE HAS DEMONSTRATED SOME LEVEL OF CORRECTION TO THE PRECISE
TRACK OF THE VORT MAX WED...GENERALLY LIFTING OVER NORTH CENTRAL IL
THEN QUICKLY SLIDING NORTHEAST TOWARDS NORTHERN LOWER MICHIGAN WED
AFTN/EVE. IN ADDITION THIS SYSTEM WILL STEADILY UNDERGO FURTHER
CYCLOGENESIS AS IT BECOMES MORE IN-PHASE WITH THE MID/UPR LVL TROUGH
AXIS WED. GUIDANCE CONTINUES TO INDICATE A DRY-SLOT ARRIVING WED
MORNING...WHICH SHOULD AID IN SHUTTING OF THE PRECIP FROM SOUTH TO
NORTH. EXPECT BY WED AFTN MUCH IF NOT ALL PRECIP SHOULD BE OFF TO
THE NORTHEAST OF THE CWFA.
TROUGH AXIS WILL BE SOLIDLY OVERHEAD WED EVE WITH THE 850MB THERMAL
TROUGH OF -4 TO -6 DEG ARRIVING. THIS COUPLED WITH CONSIDERABLE
SOLAR SHIELDING WED AND BEHIND THE SHARP COLD FRONT...SHOULD LIMIT
SFC HEATING. THUS EXPECT HIGH TEMPS TO POSSIBLY COME IN DURING THE
PRE-DAWN HOURS THEN REMAIN NEAR STEADY THROUGHOUT THE DAY. POSSIBLY
TEMPS WILL BEGIN TO FALL IN THE AFTN HOURS WED. AT THIS TIME HAVE
TEMPS IN THE UPR 40S ACROSS THE NORTHWEST CWFA...LOW/MID 50S
ELSEWHERE.
THEN FOR THUR THE ANOMALOUSLY STRONG THERMAL TROUGH REMAINS OVERHEAD
WITH ANTI-CYCLONIC FLOW BUILDING IN IN THE LOWER LVLS. THIS SHOULD
AID IN MINIMAL CLOUD COVER...HOWEVER SOME DIURNALLY DRIVEN STRATUS
CLOUDS WILL BE POSSIBLE OVER FAR NORTHEAST IL AND STRETCHING OVER
LAKE MICHIGAN. OTHERWISE WITH THE ROBUST THERMAL TROUGH
OVERHEAD...TEMPS WILL REMAIN RATHER COOL IN THE LOW/MID 40S. IT IS
POSSIBLE THAT A FEW SITES ACROSS FAR NORTHERN IL MAY REMAIN IN THE
UPR 30S. EARLY MORNING LOWS WILL MAINLY BE IN THE UPR 20S/LOW
30S...HOWEVER IF WINDS AND CLOUDS CAN DEPART QUICKER WED
AFTN/EVE...TEMPS MAY PUSH FURTHER INTO THE 20S IN MORE LOCATIONS.
FRIDAY THROUGH MONDAY...
MINIMAL SPREAD AMONGST ENSEMBLE MEMBERS IN THE FRI THRU MON
TIME FRAME. TROUGH AXIS OVER THE GREAT LAKES REGION WILL STEADILY
PIVOT EAST AS AN UPSTREAM RIDGE ARRIVES. TO THE WEST OF THIS RIDGE
IS AN ANOMALOUSLY STRONG...4 TO 5 SIGMA 500MB TROUGH DIGGING SOUTH
OF THE PAC-NW AND WILL PUSH ONSHORE NEAR SOUTHERN CALIFORNIA LATE
FRI. THE ROLE THAT THIS SYSTEM WILL PLAY ON THE DOWNSTREAM RIDGE IS
HOW AMPLIFIED THE WAVE WILL BECOME...THUS PERHAPS A MILD TREND OVER
THE WEEKEND WITH TEMPERATURES FOR THE GREAT LAKES/OHIO VALLEY
REGION. IT SHOULD BE NOTED THAT THE STRENGTH OF THIS WEST COAST
TROUGH HAS STRENGTHENED THUS THE INCREASE IN SIGMA.
WITH THE REGION REMAINING UNDER THE INFLUENCE OF RIDGING AND
DIFFLUENT FLOW IN THE MID-LVLS FOR THE FRI/SAT PERIODS...DRY CONDS
LOOK TO BE A GOOD BET AT THIS TIME. FOR THE SECOND HALF OF THE
WEEKEND INTO EARLY NEXT WEEK THE RIDGE REMAINS PROGRESSIVE AND
PUSHES EAST AS RETURN FLOW MOISTURE BEGINS TO PUSH INTO THE SOUTHERN
PLAINS/OZARKS AS THE ANOMALOUSLY STRONG 500MB TROUGH PUSHES EAST
ACROSS THE SOUTHERN ROCKIES. TRADITIONALLY THIS PATTERN SUGGESTS A
STRENGTHENING OF THE LLVL JET FROM SW TO NE ACROSS THE PLAINS STATES
INTO THE WESTERN GREAT LAKES. THUS IT IS CONCEIVABLE TO SEE
INCREASED PRECIP CHANCES LATE WEEKEND INTO EARLY NEXT WEEK...WITH A
GROWING POTENTIAL FOR CONVECTION.
THE CAVEAT TO THIS SCENARIO IS THAT THE 850MB THERMAL TROUGH IS
RATHER FLAT...WITH THE EXCEPTION OF A WEAK RIDGE OVER THE SOUTHERN
PLAINS SUN/MON. TEMPS WILL START COOL FRI IN THE MID/UPR 40S AND
LOWS IN THE MID 30S FRI NGT...HOWEVER A STEADY WARMING TREND WILL
CLOSE OUT THE WEEKEND AND CONTINUE INTO EARLY NEXT WEEK.
BEACHLER
&&
.AVIATION...
//ORD AND MDW CONCERNS...UPDATED 16Z...
* BREAK IN RAINFALL BUT CONTINUED IFR CIGS...WITH OCCASIONAL MVFR.
* VSBYS 2-4 MILES TO START...BUT IMPROVEMENT EXPECTED SOON.
* CONTINUED GUSTY VARIABLE WINDS.
LENNING
//DISCUSSION...UPDATED 12Z...
MAIN UPPER TROUGH STILL BACK OVER THE NORTHERN HIGH PLAINS AND
THE CENTRAL AND SOUTHERN ROCKIES WHILE MULTIPLE SHORT WAVES EJECT
FROM THE SOUTHERN PLAINS ACROSS THE MID MS VALLEY AND ON TO THE
WESTERN GREAT LAKES BEFORE MAIN SYSTEM LIFTS NE FORM THE SOUTHERN
PLAINS TONIGHT AND EARLY WED MORNING.
RAIN HAS TEMPORARILY ENDED ACROSS NE IL BUT ANOTHER NE FROM W
CENTRAL...NW AND N CENTRAL IL AHEAD OF NEXT UPSTREAM SHORT WAVE
MOVING NE OVER NE KS AND NW MO. THIS WILL BRING A PERIOD OF LIGHT
TO MODERATE RAIN BACK TO THE LOCAL AREA FROM AROUND DAWN THROUGH
MIDDAY. ANOTHER SHORT WAVE FURTHER UPSTREAM OVER OK EXPECTED TO
PRODUCE ANOTHER PERIOD OF RAIN LOCALLY LATE AFTERNOON AND EARLY
EVENING. CANNOT RULE OUT AN ISOLATED THUNDERSTORM GIVEN THE
STRONG DYNAMICS BUT PROBABILITY OF OCCURRENCE AT ANY ONE LOCATION
MINIMAL.
SURFACE WAVE IS NEAR UIN AT 12Z WITH THE SURFACE BOUNDARY
EXTENDING NE ACROSS FAR NW IND AND INTO FAE SW LOWER MI. PRESSURE
FALL CENTER HAS MOVED FROM SE IA AND W CENTRAL IL TO SW WI AND N
CENTRAL IL OVER THE LAST FEW HOURS. EXPECT THE DEEPENING WAVE TO
FOLLOW THE PRESSURE FALL CENTER AND HELP TO LIFT THE BOUNDARY A
LITTLE FURTHER N INTO NE IL. DEEPENING AND APPROACHING LOW IS
ALSO GENERATING SOME GUSTINESS AS A STRONG HIGH PRESSURE CENTER
SITS OVER MN RESULTING IN A TIGHTENING PRESSURE GRADIENT BETWEEN
THE HIGH AND THE LOW THOUGH DO NOT ANTICIPATE MORE THAN 15-21KT
GUSTS.
AS THE MAIN SURFACE LOW TRACKS TOWARDS THE MID MS VALLEY
OVERNIGHT THE BOUNDARY WILL LIFT FURTHER N AND IS EXPECTED TO
MOVE PAST ORD VERY LATE TONIGHT OR PREDAWN WED MORNING NE WINDS
VEERING TO SW.
TRS
//ORD AND MDW CONFIDENCE...UPDATED 16Z...
* LOW CONFIDENCE ON EXACT CIGS BUT FAVOR CONTINUED IFR.
* MEDIUM CONFIDENCE OF IMPROVING VSBYS AS RAIN TAPERS OFF.
* LOW CONFIDENCE ON EXACT WIND DIRECTION AND SPEEDS BUT HIGHER
CONFIDENCE OF GENERALLY NORTHEAST QUADRANT.
* LOW CONFIDENCE OF WHEN RAIN MIGHT PICK BACK UP LATER TODAY.
LENNING
//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...
WED NIGHT...VFR. WX NIL.
THU...VFR. WX NIL.
FRI...VFR. WX NIL.
SAT...VFR. WX NIL.
SUN...VFR. SLGT CHC -SHRA.
MON...VFR. CHC -SHRA.
TRS
&&
.MARINE...
320 AM CST
A BIT OF A TRICKY FORECAST TODAY...SPECIFICALLY REGARDING WINDS.
WINDS HAVE BEGUN TO PICK UP SOME THIS MORNING AS LOW PRESSURE
DEEPENS OVER THE OZARKS AND A WARM FRONT LIFTS NORTH ACROSS INDIANA
AND ILLINOIS. TO THE NORTH OF THE FRONT...EXPECT WINDS TO INCREASE
OUT OF THE NORTHEAST...INTO THE 20 TO 25 KT RANGE FOR SOUTHERN
PORTIONS OF LAKE MICHIGAN. A SMALL CRAFT ADVISORY HAS ALREADY BEEN
ISSUED FOR THE ILLINOIS NEARSHORE WATERS. TRICKY PART WILL BE WIND
TRENDS THIS AFTERNOON INTO THE EVENING AS THE FRONTAL TROUGH MOVES
NORTH OVER THE LAKE. WINDS WITHIN THIS ZONE WILL DROP OFF QUITE A
BIT...LIKELY INTO THE 10 TO 15 KT RANGE...AND WAVES WILL LIKEWISE
DROP BELOW CRITERIA FOR SMALL CRAFT ADVISORY. IT APPEARS THERE COULD
BE AROUND A SHORT WINDOW WHERE WE WILL BE BELOW CRITERIA...BUT WITH
UNCERTAINTY IN TIMING HOW MUCH WINDS WILL DIMINISH...WILL NOT MAKE
CHANGES TO HEADLINE AT THIS TIME. BY LATE TONIGHT...WINDS WILL ONCE
AGAIN INCREASE AS THE BOUNDARY LIFTS NORTH...WITH STRONG SOUTH TO
SOUTH-SOUTHWEST WINDS EXPECTED. THE LOW WILL CONTINUE TO DEEPEN AS
IT LIFTS INTO THE NORTHERN HALF OF THE LAKE BY WEDNESDAY AFTERNOON.
GALE FORCE WINDS ARE EXPECTED TO BEGIN WEDNESDAY AFTERNOON FOR THE
SOUTH HALF OF THE LAKE...AND AS A TRAILING COLD FRONT SWINGS ACROSS
THE LAKE WEDNESDAY EVENING...EXPECT GALES TO OCCUR ACROSS THE LAKE.
GALES SHOULD LET UP BY THURSDAY MORNING...BUT EXPECT BREEZY
CONDITIONS TO PERSIST ACROSS THE LAKE AS A MODEST PRESSURE GRADIENT
REMAINS IN PLACE THROUGH THE REMAINDER OF THE WEEK AND INTO THE
WEEKEND. BMD
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 10 PM WEDNESDAY.
SMALL CRAFT ADVISORY...LMZ742-LMZ743-LMZ744-LMZ745...10 PM
TUESDAY TO 10 PM WEDNESDAY.
GALE WATCH...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-
LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...8 AM WEDNESDAY TO 10
PM WEDNESDAY.
GALE WATCH...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
LMZ868...4 PM WEDNESDAY TO 4 AM THURSDAY.
&&
$$
