1035 AM CST
BAND OF RAIN CONTINUES TO LIFT NORTHEASTWARD ACROSS THE EASTERN
CWA LATE THIS MORNING AND WILL LIFT BEYOND THE LAND PORTION OF THE
CWA BY AROUND 18Z. FRONTAL BOUNDARY/INVERTED TROUGH CURRENTLY
EXTENDS FROM NEAR BENTON HARBOR MI SOUTHWEST TO JUST NORTH OF
PEORIA. THE BOUNDARY SHOULD TIGHTEN UP THIS AFTERNOON BUT REALLY
MOVE LITTLE FROM ITS CURRENT POSITION AS LOW PRESSURE ORGANIZES
ACROSS EASTERN OKLAHOMA. 12Z MODEL GUIDANCE CONTINUES TO SHIFT THE
LOW TRACK EASTWARD SIMILAR TO WHAT THEY HAD SHOWN OVER THE WEEKEND
WHICH TAKES THE CENTER OF THE LOW RIGHT OVER CHICAGO WEDNESDAY
MORNING. GIVEN THE CURRENT POSITION OF THE FRONT AND THE TRACK OF
THE LOW LITTLE MOVEMENT OF THE BOUNDARY IS EXPECTED EVEN THROUGH
THE EVENING. HAVE ADJUSTED TEMPS TO LOWER AFTERNOON HIGHS IN THE
NORTHWEST WITH LITTLE WARMING EXPECTED THERE UNTIL POSSIBLY
TONIGHT AS MID LEVEL WARM ADVECTION TAKES OVER. LOWERED POPS TO
LIKELY FOR MUCH OF THE AFTERNOON BEHIND THE CURRENT BAND OF RAIN
GIVEN THAT THE NEXT SURGE OF ENERGY WILL NOT ARRIVE UNTIL LATE
AFTERNOON/EARLY EVENING. THAT SAID...SHOWER ACTIVITY WILL CONTINUE
AND HAVE GONE WITH LIGHT RAIN AND DRIZZLE WORDING FOR MUCH OF THE
AFTERNOON....ALSO REMOVED THUNDER MENTION UNTIL AFTER 21Z.
UPDATED GRIDS SENT AND UPDATED TEXT PRODUCTS TO FOLLOW SHORTLY.
MDB
//PREV DISCUSSION...
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 18Z...
* BREAK IN RAINFALL BUT CONTINUED IFR CIGS...WITH OCCASIONAL MVFR.
* VSBYS 2-4 MILES TO START...BUT IMPROVEMENT EXPECTED SOON.
* WIDELY VARIABLE WINDS ALONG THE FRONT...GUSTS UNCERTAIN.
* ADDITIONAL RAIN AND LOWER CIGS/VSBYS OVERNIGHT/TOMORROW.
LENNING
//DISCUSSION...UPDATED 18Z...
A BIG MESS FOR AVIATION CONTINUES INTO THE AFTERNOON. CURRENT
OBSERVATIONS AROUND THE NEIGHBORHOOD VARY FROM VFR TO LIFR. IN
TERMS OF FLIGHT CATEGORIES FOR ORD/MDW TODAY...IFR WOULD APPEAR TO
BE THE MOST LIKELY TREND...THOUGH NOT SURE IF THIS WILL BE DUE
TO CIGS OR VSBYS OR BOTH. PERIODS OF MVFR ARE ALSO LIKELY.
THE HEAVIER RAIN WILL BE TAPERING OFF EARLY THIS AFTERNOON BEFORE
PICKING BACK UP SOMETIME THIS EVENING ALONG THE FRONTAL ZONE THAT
REMAINS DRAPED OVER THE AREA. THE MAIN AREA OF LOW PRESSURE IS
APPROACHING FROM NORTHEAST OKLAHOMA...MOVING ALONG THIS
FRONT...AND WILL CROSS DIRECTLY OVERHEAD AROUND SUNRISE TOMORROW
MORNING. AFTER THE LOW PASSES...RAINS AGAIN TAPER OFF BUT GUSTY
WEST WINDS WILL DEVELOP TOMORROW AFTERNOON.
LENNING
//ORD AND MDW CONFIDENCE...UPDATED 18Z...
* LOW CONFIDENCE ON EXACT CEILING TRENDS...BUT CONTINUE TO FAVOR
IFR.
* LOW CONFIDENCE ON VSBY TRENDS. VFR MAYBE TOO OPTIMISTIC.
* NO CONFIDENCE ON WIND DIRECTION ALONG THE FRONT TODAY...BUT
EXPECT LIGHTEST WINDS WHERE DIRECTION IS MOST VARIABLE.
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.
&&
$$
