Area Forecast Discussion
Issued by NWS Chicago, IL

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KLOT 062033
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
233 PM CST SAT FEB 6 2016

.SHORT TERM...
231 PM CST

TONIGHT THROUGH SUNDAY...

MAIN NEAR TERM CONCERNS ARE PRIMARILY CLOUDY COVER TONIGHT AND
SUNDAY...AND RELATIVELY MILD TEMPERATURES FOR THE REMAINDER OF THE
WEEKEND BEFORE WE SLIDE BACK INTO MORE TYPICAL MID-WINTER
CANDIDNESS FOR THE COMING WEEK.

LOW PRESSURE WAS PASSING NORTH OF THE GREAT LAKES REGION THIS
AFTERNOON...WITH A TRAILING COLD FRONT WHICH WILL BECOME NEARLY
STATIONARY ACROSS UPPER MICHIGAN TONIGHT. MODEST LOW LEVEL
SOUTHWEST WINDS WERE IN PLACE ACROSS THE MIDWEST...WITH
CONSIDERABLE SUNSHINE AND MILD TEMPERATURES IN THE UPPER 30S TO
MID 40S OVER THE WFO LOT FORECAST AREA. EXTENSIVE LOW CLOUD COVER
WAS IN PLACE IMMEDIATELY NORTH AND NORTHWEST OF THE CWA...THOUGH
GUIDANCE TRENDS INDICATE THAT INCREASING SOUTH-SOUTHWEST WINDS
OVERNIGHT INTO SUNDAY WILL KEEP THE BULK OF THE LOW CLOUD COVER
OUT OF THE FORECAST AREA WITH FAR NORTH CENTRAL IL MORE LIKELY TO
BE ALONG THE EDGE OF THE LOW CLOUDS. MOSTLY CLEAR OR PARTLY CLOUDY
SKIES THIS EVENING WILL ALLOW TEMPS TO FALL BACK INTO THE UPPER
20S TO AROUND 30...WINDS INCREASING TO 10-15 MPH OVERNIGHT WILL
LIKELY HOLD TEMPS STEADY AFTER MIDNIGHT OR EVEN COME UP A DEGREE
OR TWO IN SOME PLACES. PATCHY MID/HIGH CLOUD COVER IS EXPECTED TO
INCREASE LATE TONIGHT AS WELL...IN PERSISTENT WARM ADVECTION
REGIME.

STRONG MID-LEVEL SHORT WAVE TROUGH SEEN IN WATER VAPOR IMAGERY
THIS AFTERNOON OVER THE NORTHERN HIGH PLAINS AND SOUTHERN CANADIAN
PRAIRIES WILL PROPAGATE SOUTHEAST ACROSS THE UPPER MIDWEST BY
SUNDAY MORNING...WITH A DIGGING JET STREAK AMPLIFYING THE UPPER
TROUGH ACROSS THE REGION LATE IN THE DAY. DESPITE STRONG HEIGHT
FALLS DEVELOPING DURING THE DAY...FORECAST SOUNDINGS AND TIME-
SECTIONS DEPICT DRY LOW LEVELS WITH MOISTURE MAINLY CONFIDENCE TO
THE MID AND UPPER LEVELS THROUGH THE AFTERNOON. THE RESULT IS
MINIMAL/NO PRECIPITATION POTENTIAL PRIOR TO SUNDAY EVENING.
SUNDAY LOOKS TO BE THE WARMEST DAY FOR AT LEAST THE NEXT
WEEK...WITH 925 MB T FIELDS SUPPORTING HIGHS IN THE LOW-MID 40S
ACROSS THE FORECAST AREA. BLEND OF DOMESTIC GUIDANCE LOOKS PRETTY
REASONABLE. IT WILL BE BREEZY AS WELL WITH WEST-SOUTHWEST WINDS
EXPECTED TO GUST 25-30 MPH...AND POTENTIALLY HIGHER IF WE MIX
DEEPER PER GFS SOUNDINGS.

RATZER

&&

.LONG TERM...
229 PM CST

SUNDAY NIGHT THROUGH SATURDAY...

A HIGHLY AMPLIFIED UPPER LEVEL PATTERN WILL CONTINUE INTO THE LONGER
TERM FORECAST PERIOD WITH A STRONG NORTHERN STREAM SHORTWAVE
DROPPING FROM THE UPPER MISSISSIPPI VALLEY SUNDAY NIGHT ACROSS LAKE
MICHIGAN AND INTO LOWER MICHIGAN MONDAY.  AN ASSOCIATED COLD FRONT
WILL PUSH ACROSS THE REGION LATE SUNDAY NIGHT INTO MONDAY WITH
BLUSTERY CONDITIONS DEVELOPING THROUGH THE DAY WITH NWLY WINDS
GUSTING TO 25 TO 30MPH AT TIMES.  STRONG COLD ADVECTION SHOULD BEGIN
IN EARNEST MONDAY NIGHT AS THE UPPER LOW MOVES SLOWLY TOWARD THE ERN
GREAT LAKES AND UPPER RIDGING BUILDS OVER THE PAC NORTHWEST.  THE
UPPER FLOW PATTERN SHOULD CONTINUE TO INCREASE IN AMPLITUDE INTO
MIDWEEK WHILE SHOWING LITTLE PROGRESSION.  THIS WILL SET UP THE NEXT
ROUND OF COLDER CONDITIONS FOR THE REGION AS A PERSISTENT FETCH OF
COLD AIR OUT OF THE ARCTIC WILL OVERSPREAD THE REGION.  BY
TUESDAY...HIGH TEMPS SHOULD ONLY BE IN THE UPPER TEENS TO MIDDLE
20S.  OVERNIGHT LOWS WEDNESDAY AND THURSDAY MORNING SHOULD GENERALLY
BE IN THE SINGLE DIGITS ACROSS THE AREA...WITH TEMPS ARND 10-12F
OVER THE SERN PORTIONS OF THE CWA AND DOWNTOWN CHICAGO.  WIND CHILL
READINGS SHOULD BE LOWEST WEDNESDAY MORNING AS WINDS ARND 10 MPH
PERSIST OVERNIGHT...DRIVING WIND CHILLS DOWN TO -10 TO -15F.  BY
THURSDAY...THE PATTERN IS EXPECTED TO BREAK DOWN A BIT WITH THE
UPPER RIDGE OVER THE WRN CONUS FLATTENING IN RESPONSE TO A DEEP
UPPER LOW DROPPING SOUTH OF HUDSON BAY WHICH WILL ALSO HELP THE
UPPER TROUGH TO SHIFT TO THE EAST.  SO...BY LATE IN THE
PERIOD...CONDITIONS SHOULD TREND A LITTLE WARMER...BUT TEMPERATURES
SHOULD STILL BE WELL BELOW NORMAL.

THE GREATEST CHANCE FOR PCPN WILL BE SUNDAY NIGHT INTO TUESDAY AS A
SERIES OF SHORTWAVES DROP SEWD THROUGH THE FAST NWLY FLOW SETTING UP
ACROSS THE REGION.  THE MAY END UP BEING A PERIOD OF RELATIVELY HIGH
POPS AND LOW QPF AS THERE SHOULD BE LITTLE IN THE WAY OF DEEP LAYER
MOISTURE FOR THE SHORTWAVES TO WORK WITH. BY MONDAY AFTERNOON INTO
TUESDAY...PCPN MAY ALSO JUST BE SCT SNOW SHOWERS UNDER CYCLONIC FLOW
ALOFT.  THERE WILL LIKELY BE SOME ACCUMULATION FOR THE PERIOD FROM
SUNDAY NIGHT THROUGH TUESDAY WITH CURRENT INDICATORS SUGGESTING 1 TO
3 INCHES OF SNOW OVER THE 48 HOUR PERIOD.  FROM WEDNESDAY THROUGH
SATURDAY...EXPECT THAT PCPN CHANCES WILL SHUT OFF AS UPPER FLOW
TRENDS TOWARD A BROAD UPPER TROUGH OVER PORTIONS OF THE CONUS EAST
OF THE ROCKIES AND WEAK RIDGING ALONG THE ROCKIES.  SOME LAKE EFFECT
SNOW SHOWERS COULD IMPACT THE ERN SHORES OF LAKE MICHIGAN...BUT THE
LOCAL AREA SHOULD TREND DRY.

KREIN

&&

.AVIATION...
FOR THE 18Z TAFS...

MAIN AVIATION CONCERNS ARE A SHORT DURATION OF MVFR CIGS EARLY
THIS AFTERNOON...AND POTENTIAL FOR GUSTY WEST-SOUTHWEST ON SUNDAY.

WEAK SURFACE TROUGH WAS ALONG THE MISSISSIPPI RIVER AT MIDDAY.
SOUTHWEST FLOW ABOVE THE SURFACE WAS HELPING TO ADVECT AN AREA OF
LOW LEVEL MOISTURE AND MVFR CEILINGS ACROSS FAR NORTHERN IL...WITH
NORTHERN IL TERMINAL SITES GENERALLY ALONG THE SOUTHERN PERIPHERY
OF THE MORE SOLID CLOUD COVER. BASED ON VISIBLE SATELLITE TRENDS...
A BRIEF 1-3 HOUR PERIOD OF MVFR CIGS IN THE 1500-2000 FT RANGE
WILL LIKELY AFFECT ORD/DPA/MDW/RFD...WITH GYY EXPECTED TO REMAIN
SCATTERED AT BEST. RFD WILL BE CLOSER TO THE MORE WIDESPREAD CLOUD
COVER TO THE NORTH AND WEST THOUGH IT APPEARS THAT RFD WILL ALSO
SCATTER OUT. WINDS THEN LOOK TO BACK SLIGHTLY MORE SOUTH-SOUTHWEST
THIS EVENING...IN RESPONSE TO SURFACE PRESSURE FALLS ASSOCIATED
WITH LOW PRESSURE MOVING SOUTHEAST INTO THE NORTHERN PLAINS.
EXTENSIVE AREA OF IFR/LIFR OVER IA EXPECTED TO LIFT MORE NORTHEAST
THAN EAST OVERNIGHT...WITH GUIDANCE KEEPING IL/NW IN TERMINALS
VFR WHILE ERODING AND SHIFTING IFR CIGS NORTHEAST ACROSS WI.

AFOREMENTIONED LOW PRESSURE TRACKS ACROSS THE NORTHERN GREAT LAKES
REGION THROUGH SUNDAY...WITH A GRADUAL TIGHTENING OF THE GRADIENT
AND INCREASING SOUTH-SOUTHWEST WINDS OVERNIGHT. STRONG LOW LEVEL
INVERSION IS EXPECTED TO LIMIT GUSTINESS LATE TONIGHT...THOUGH
WINDS LIKELY GUSTING 20+ KTS FROM THE WEST-SOUTHWEST SUNDAY AS
PACIFIC COLD FRONT MOVES ACROSS THE REGION TRAILING THE LOW.
FORECAST SOUNDINGS FROM VARIOUS MODELS MAINTAIN CONSIDERABLE DRY
AIR IN THE LOW-MID LEVELS WITH VFR CONDITIONS EXPECTED AND MINIMAL
PRECIP THREAT.

RATZER

&&

.MARINE...
231 PM CST

MAIN MARINE FORECAST CONCERNS FOR LAKE MICHIGAN INCLUDE A PERIOD
STRONG SOUTH-SOUTHWEST WINDS TONIGHT INTO SUNDAY SUNDAY MORNING...
THEN A PROLONGED PERIOD OF STRONG NORTHERLY WINDS MONDAY NIGHT
INTO WEDNESDAY. MARGINAL NORTH GALES ARE POSSIBLE DURING THIS
PERIOD... PRIMARILY MONDAY NIGHT INTO TUESDAY.

MODEST WEST-SOUTHWEST WINDS ACROSS THE LAKE THIS AFTERNOON WILL
INCREASE TONIGHT...ESPECIALLY ACROSS NORTHERN PORTIONS...AS AN
AREA OF DEEP LOW PRESSURE MOVES SOUTHEAST FROM SASKACHEWAN.
SOUTHERLY WINDS WILL INCREASE TO 30 KT LATE TONIGHT AS THE
GRADIENT TIGHTENS AHEAD OF THE APPROACHING LOW...CONTINUING SUNDAY
BEFORE SLOWLY DIMINISHING AS THE SURFACE LOW APPROACHES NORTHERN
LAKE MICHIGAN LATE SUNDAY NIGHT. WINDS WILL SHIFT TO THE NORTH-
NORTHWEST MONDAY AS THE LOW DRIFTS OFF TO THE EAST...WITH WINDS
INCREASING ONCE AGAIN LATE MONDAY/MONDAY NIGHT AS THE GRADIENT
TIGHTENS BETWEEN THE SLOWLY DEPARTING LOW AND AN AREA OF HIGH
PRESSURE DEVELOPING SOUTHEASTWARD FROM THE CANADIAN PRAIRIES. THE
PATTERN WILL BE SLOW TO CHANGE AS ANOTHER DEEP LOW OFF THE
ATLANTIC COAST WILL KEEP THINGS BLOCKED. THIS WILL MAINTAIN FAIRLY
STRONG NORTHERLY WINDS THROUGH MID-WEEK. THE STRONGEST
WINDS...AROUND 30 KT AND POTENTIALLY A PERIOD OF MARGINAL
GALES...LOOKS TO BE MONDAY NIGHT INTO TUESDAY. COLDER AIR
SPREADING ACROSS THE REGION WILL COMBINE WITH THESE STRONG WINDS
TO PRODUCE A RISK OF MODERATE FREEZING SPRAY MONDAY NIGHT THROUGH
TUESDAY NIGHT.

RATZER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE)

FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSCHICAGO
WWW.TWITTER.COM/NWSCHICAGO
WWW.YOUTUBE.COM/NWSCHICAGO


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.