875
FXUS63 KLOT 200931
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
331 AM CST THU FEB 20 2020
SHORT TERM
325 AM CST
THROUGH FRIDAY...
A FINAL REINFORCING PUSH OF ARCTIC AIR IS SETTLING IN ACROSS THE
REGION EARLY THIS MORNING IN THE WAKE OF A SCOURING TROUGH AXIS
CLEARLY EVIDENT IN SIMPLE RGB WATER VAPOR IMAGERY. A GLANCE AT
LOW-LEVEL WATER VAPOR (CHANNEL 10) LOOPS SHOW THE GOES-16 ABI
PICKING UP SURFACE FEATURES ACROSS MUCH OF THE UPPER MIDWEST AND
NORTHERN GREAT PLAINS--A SURE SIGN OF THE BONE-DRY NATURE OF THIS
INCOMING AIRMASS. INDEED, WE'VE BEEN ABLE TO FIND A FEW RAOBS FROM
THIS EVENING SAMPLING 0.03 TO 0.04 INCH PWATS AT BISMARCK,
ABERDEEN, AND MINNEAPOLIS. THIS DRY AIRMASS WILL CONTINUE TO
OVERSPREAD OUR AREA TODAY, AND DEWPOINTS ARE CREEPING DOWN BELOW 0
AT THIS TIME. BEHIND THIS LAST REINFORCING FRONTAL PUSH,
TEMPERATURES TODAY WILL BE SOME 5 TO 10 DEGREES COOLER THAN THEY
WERE ON WEDNESDAY, AND A PERSISTENT 10-15 MPH WIND WILL MAKE IT
FEEL LIKE IT'S IN THE TEENS AND SINGLE DIGITS.
THE INCOMING COLDER AIRMASS IS STARTING TO SATURATE UP DOWNWIND OF
THE THE LAKE ACROSS PARTS OF WEST-CENTRAL MICHIGAN, AND THERE DOES
APPEAR TO BE SOME LAND-BREEZE/CONVERGENT ZONE SETTING UP FROM
MUSKEGON TO HOLLAND BASED ON SURFACE OBSERVATIONS AND STREAMLINE
ANALYSIS. HI-RES GUIDANCE IS IN GENERALLY GOOD AGREEMENT KEEPING
THIS MAIN CONVERGENT ZONE WELL TO OUR NORTHEAST, BUT THINGS DO
LOOK TO BRIEFLY SATURATE UP A BIT MORE ACROSS PARTS OF PORTER
COUNTY THIS MORNING. WHILE LAKE-INDUCED ELS ARE FORECAST TO BUILD
UP TO AROUND 6 KFT, THE SATURATED DEPTH WILL BE EXTREMELY THIN
(PROBABLY ABOUT 1 KFT OR LESS) CAPPED OFF BY THE AFOREMENTIONED
VERY DRY AIRMASS ALOFT LEADING TO SOME LIKELY NOTABLE DRY AIR
ENTRAINMENT OF ANY SHOWERS THAT ATTEMPT TO DEVELOP. THIS,
COMBINED WITH DEWPOINT DEPRESSIONS IN EXCESS OF 10-15 F DON'T SEEM
TO SUPPORT MUCH IN THE WAY OF LAKE EFFECT SNOW SHOWERS TODAY, AND
HAVE REMOVED THE LOW MEASURABLE PRECIPITATION CHANCES AS A RESULT
AND REPLACED WITH FLURRIES FOR THIS MORNING THROUGH THE MID-
AFTERNOON.
THE CORE OF THIS SPRAWLING SURFACE HIGH WILL BEGIN TO BUILD
OFF TO OUR SOUTHWEST LATER THIS EVENING AND OVERNIGHT, AND WINDS
WILL RESPOND BY SLOWLY BACKING AROUND TO THE SOUTHWEST. THERE
LOOKS TO BE A PERIOD LATER THIS EVENING WHEN WINDS MAY BRIEFLY GO
LIGHT AND VARIABLE, ALLOWING SOME OF TYPICAL COLD SPOTS TO DROP
QUICKLY INTO THE SINGLE DIGITS. SURFACE FLOW DOES LOOK TO
GRADUALLY TICK UPWARDS OVERNIGHT AS THE PRESSURE GRADIENT
TIGHTENS, HOWEVER, AND THIS MAY END UP KEEPING TEMPERATURES FROM
REALLY BOTTOMING OUT.
FOR FRIDAY, WE'LL BEGIN TO PICK UP SOME ADDITIONAL FLOW OFF THE
SURFACE AND BUFKIT SOUNDINGS LOOK SUPPORTIVE OF MIXING OF SOME 30
MPH GUSTS TO THE SURFACE THROUGH THE LATE-MORNING AND AFTERNOON
HOURS, ESPECIALLY NORTH OF I-80. WHILE WE'LL LIKELY BE STARTING
OFF FROM A FAIRLY COOL POINT IN THE MORNING, THE BREEZY SOUTHWEST
WINDS AND LIKELIHOOD OF MAXIMIZED MIXING SUPPORTS GOING ABOVE
BLENDED GUIDANCE FOR HIGHS, MORE TOWARDS STATISTICAL OUTPUT, WITH
SOME UPPER 30 TO 40 DEGREE READINGS NOT OUT OF THE QUESTION.
CARLAW
LONG TERM
325 AM CST
FRIDAY NIGHT THROUGH WEDNESDAY...
THE LONG TERM PORTION OF THE FORECAST APPEARS SOMEWHAT MORE
UNSETTLED AS BROAD CYCLONIC MID-LEVEL FLOW BECOMES MORE
ESTABLISHED ACROSS THE CENTRAL AND EASTERN CONUS, ALTHOUGH THE
QUIESCENT AND DRY STRETCH DOES LOOK TO CONTINUE THROUGH THE
WEEKEND.
SATURDAY--AND ALSO LIKELY MUCH IF NOT ALL OF SUNDAY--ARE SHAPING
UP TO BE PRETTY STELLAR DAYS ACROSS THE AREA AS LOW-LEVEL WEST TO
SOUTHWEST FLOW CONTINUES TO NUDGE A WARMER AIRMASS OVERHEAD. ASIDE
FROM SOME OCCASIONAL TUFTS OF HIGH CIRRUS, SATURDAY IS LOOKING
ESSENTIALLY CLOUDLESS WITH A STRONG MIXING POTENTIAL. LOCAL 925
MB TEMPERATURE CLIMATOLOGY INCORPORATING NO SNOWPACK UPSTREAM
CONSERVATIVELY SUPPORTS HIGHS ON SATURDAY IN THE MID 40S, WITH A
SMATTERING OF 50 DEGREE READINGS WITHIN THE REALM OF
POSSIBILITIES. SUNDAY HAS THE POTENTIAL TO BE EVEN WARMER,
ALTHOUGH THERE ARE STILL SOME LINGERING QUESTIONS ABOUT HOW MUCH
HIGH CLOUD COVER WILL GET TOSSED OVERHEAD THROUGH THE AFTERNOON
AHEAD OF OUR NEXT WEATHER DISTURBANCE. THE LATEST ECMWF ENSEMBLE
SUPPORTS WIDESPREAD LOWER 50 DEGREE HIGHS ACROSS MUCH OF THE AREA,
WHICH IS MORE OR LESS IN LINE WITH THE AFOREMENTIONED LOCAL 925
MB CLIMATOLOGY RESEARCH. HAVEN'T QUITE BIT OFF ON THIS YET, BUT
CONTINUE TO TREND THE FORECAST HIGHS INTO THE 75TH TO 85TH
PERCENTILE OF AVAILABLE BLENDED GUIDANCE FOR BOTH SATURDAY AND
SUNDAY.
THE CURRENT MULTI-MODEL CONSENSUS SUPPORTS PRECIPITATION-FREE
CONDITIONS PREVAILING THROUGH THE DAYTIME ON SUNDAY AND
POTENTIALLY EVEN THROUGH THE EVENING HOURS. AS SEEMS TO BE TYPICAL
WITH CLOSED, SOUTHERN-STREAM WAVES, GUIDANCE CONTINUES TO SLOW THE
OVERALL PROGRESSION WITH EACH RUN, AND HAVE ADJUSTED POPS UNDER
THE NATIONAL BLEND INTO SUNDAY NIGHT AS A RESULT. WITH NOTABLE
POSITIVE 500 MB HEIGHT DPROG/DT TENDENCIES NOTED DOWNSTREAM OF OUR
NEXT INCOMING WAVE, WOULDN'T BE SURPRISED IF THIS SLOWER TREND
CONTINUED. WHILE THE DETERMINISTIC AND ENSEMBLE GLOBAL GUIDANCE
REMAINS IN DECENT AGREEMENT REGARDING THE LARGE-SCALE EVOLUTION OF
THINGS INTO MONDAY AND TUESDAY, SUBTLE WOBBLES IN THE PLACEMENT OF
THE MAIN VORT MAX (WHICH IS CURRENTLY CHURNING AWAY A FEW HUNDRED
MILES OFF THE NORTHERN CALIFORNIA COAST) HAVE LED TO FLUCTUATIONS
IN THE NORTHERN-MOST EXTENT OF THE MAIN REGION OF UPPER DIVERGENCE
WHICH COULD SET UP SHOP SOMEWHERE IN OR NEAR OUR CWA. AS A
RESULT, OUTSIDE OF DELAYING THE ONSET OF HIGHER POPS, DIDN'T MAKE
ANY SWEEPING CHANGES TO THE BLENDED POPS INTO MONDAY AND BEYOND.
THIS SYSTEM LOOKS RELATIVELY WARM, AND HAVE DEPICTED MOSTLY RAIN
WITH SOME RAIN/SNOW POTENTIAL ON MONDAY AND TUESDAY MORNINGS.
BEYOND THIS, GUIDANCE INDICATES THE POTENTIAL FOR ANOTHER
SHORTWAVE/PV ANOMALY TO DROP DOWN THROUGH THE GREAT BASIN AT THE
EDGE OF THE FASTER MID-LEVEL FLOW WHICH LOOKS TO KEEP THINGS
UNSETTLED INTO THE MIDDLE AND POSSIBLY END OF NEXT WEEK.
CARLAW
AVIATION
FOR THE 06Z TAFS...
THERE ARE NO SIGNIFICANT WEATHER CONCERNS THROUGH THE PERIOD.
NORTHERLY WINDS AND VFR CONDITIONS ARE EXPECTED TO CONTINUE
THROUGH THE DAY THURSDAY AS A STRONG ARCTIC SURFACE HIGH
GRADUALLY SAGS SOUTHWARD OVER EASTERN IA TOMORROW AFTERNOON. THE
WINDS WILL THEN VEER WESTERLY THURSDAY EVENING.
KJB
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...IN NEARSHORE WATERS UNTIL 3 PM THURSDAY.
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