000
FXUS63 KLOT 142020
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
320 PM CDT SUN MAR 14 2010

.DISCUSSION...
317 PM CDT

TONIGHT...THE SURFACE LOW OVER THE COAST OF VIRGINIA AND DELAWARE
WILL CONTINUE TO MOVE OFF THE COAST TONIGHT. THE CIRCULATION OF
THE UPPER AIR TROUGH MOVE EAST OF NORTHERN ILLINOIS AND NORTHWEST
INDIANA BY MONDAY AFTERNOON. WE USED THE CANADIAN MODEL FOR THE
MOVEMENT OF THIS EAST COAST STORM. WE USED THE GFS AND ECMWF FOR
LOCAL FORECAST TEMPERATURE AND CLOUD TRENDS. THIS IS AFTER LOOKING
AT THOSE MODELS FORECAST OF UPPER AIR WIND AND COMPARING THEM WITH
WATER VAPOR AND VISIBLE SATELLITE IMAGERY LOOPS.

THE VISIBLE SATELLITE IMAGERY SHOWS CLEARING OVER CENTRAL
WISCONSIN THIS AFTERNOON. WE WILL FORECAST MOSTLY CLOUDY SKY
TONIGHT BUT IT MAY GO SCATTERED. MORE FINE TUNING ON THE SKY
FORECAST CAN BE DONE THIS EVENING. BECAUSE OF THE MOISTURE ON THE
GROUND FROM THE RAIN...WE WILL FORECAST SOME PATCHY FOG AFTER 06
UTC.

MONDAY THROUGH THURSDAY...DRY WEATHER AND TEMPERATURES IN THE
LOWER TO MIDDLE 50S WILL OCCUR MONDAY THROUGH WEDNESDAY. A SMALL
500 MB RIDGE IS FORECAST OVER THE GREAT LAKES BY MONDAY EVENING.
WE USED THE ECMWF MODEL FOR OUR FORECAST. WE CHECKED THE MOVEMENT
OF THE 300 MB JET STREAM SEEN ON 300 MB SURFACE ANALYSIS AND WATER
VAPOR IMAGERY LOOPS WITH THE MODEL FORECAST. DURING TUESDAY
NIGHT...A SHORT WAVE TROUGH IS FORECAST TO MOVE THROUGH ILLINOIS
AND IOWA AND WILL BE IN ARKANSAS AND OKLAHOMA BY WEDNESDAY
AFTERNOON. WE WILL FORECAST A SLIGHT CHANCE OF SHOWERS IN OUR
FORECAST AREA OF NORTH CENTRAL ILLINOIS... NORTHEAST ILLINOIS AND
NORTHWEST INDIANA TUESDAY NIGHT AND EARLY WEDNESDAY. MOST OF THE
SHOWERS WILL BE IN OUR WESTERN PORTION OF THE CWA...OVER NORTH
CENTRAL ILLINOIS.

THURSDAY THROUGH MONDAY...DRY WEATHER IS FORECAST THURSDAY AND
FRIDAY. THEN A LONG WAVE TROUGH IS FORECAST TO MOVE INTO CENTRAL
PLAINS. THIS MAY GIVE SUPPORT FOR A STRONG SURFACE LOW TO FORM IN
OKLAHOMA AND MOVE INTO ILLINOIS BY SUNDAY. WE WILL FORECAST RAIN
AND RAIN MIXED WITH SNOW FOR SATURDAY THROUGH SUNDAY. THIS
FORECAST 500 MB LONG WAVE WILL BE WATCHED TO SEE HOW MUCH COLD AIR
BELOW 700 MB MOVES SOUTH IN THE CENTRAL PLAINS DURING THE REST OF
THIS WEEK.

&&

.AVIATION...

1800Z TAFS...MAIN CONCERN FOR THE PERIOD WILL FOCUS ON CEILINGS
THROUGH THE PERIOD AND WINDS FOR THE AFTERNOON.  THE REGION
REMAINS UNDER BROAD CYCLONIC FLOW ASSOCIATED WITH AN UPPER LOW
CENTERED OVER THE MID ATLANTIC REGION. CIGS HAVE BEEN MVFR THROUGH
THE MORNING HOURS AND ARE SHOWING INDICATIONS OF SLOW
IMPROVEMENT. LATEST VISIBLE SATELLITE IMAGERY SHOWS SOME PARTIAL
CLEARING MOVING OVER NERN IL...WHICH IS LIKELY RESPONSIBLE FOR SOME
HIGHER GUSTS MIXING DOWN TO THE SURFACE. THE SATELLITE TRENDS
INDICATE THAT THE PARTIAL CLEARING SHOULD ONLY LAST A FEW
HOURS...SO HAVE ONLY CARRIED GUSTS IN EXCESS OF 25KT UNTIL 21Z. BY
THAT POINT...CIGS SHOULD BECOME OVC AGAIN AND GUSTS WILL RETURN TO
EARLIER LEVELS...AT 20-25KT. WITH LITTLE PROGRESSION TO THE LARGE
SCALE PATTERN...WINDS WILL REMAIN GENERALLY NORTHERLY TO NNELY
THROUGH THE PERIOD

WITH SOME DIURNAL WARMING...THE TREND WILL BE FOR CIGS TO IMPROVE
TO VFR FOR A WHILE LATE THIS AFTERNOON AND EARLY THIS EVENING.
MOISTURE TIME SECTIONS DO SHOW SOME DECREASE IN LOW LEVEL
MOISTURE...SO THERE IS GOOD CONFIDENCE IN THIS IMPROVEMENT TO VFR
FOR THE EVENING RUSH HOURS...BUT THE MODEL FORECAST TREND IS FOR
INCREASING LOW LEVEL SATURATION BY LATE EVENING...SO HAVE TRENDED
BACK TO MVFR FOR THE NIGHT. FEEL THAT ONLY DPA...OR PERHAPS RFD
HAVE THE BEST POTENTIAL FOR CIGS TO DROP TO IFR. THERE IS A SMALL
CHANCE THAT CIGS AT ORD OR MDW COULD DROP BLW 1000FT...BUT NOT
CONFIDENT ENOUGH AT THIS TIME TO INTRODUCE INTO THE TAF.

KREIN

&&

.MARINE...
230 PM CDT

THE NORTH TO NORTHEAST WINDS WILL CONTINUE OVER THE LAKE FOR THE
NEXT SEVERAL DAYS. AS THE LARGE LOW PRESSURE SYSTEM OVER THE MID
ATLANTIC REGION MOVES OUT TO SEA...THE GRADIENT WILL GRADUALLY
WEAKEN FROM 10-20KT TO ARND 10-15KT BY MONDAY. WILL KEEP THE SMALL
CRAFT ADVISORY FOR NEARSHORE WATERS THROUGH THIS EVENING AS
COASTAL PLATFORMS CONTINUE TO INDICATE OCNL 25KT GUSTS AND WITH
THE EXTENDED NLY FETCH...WAVES OVER THE NEARSHORE WATERS WILL BE
SLOW TO SUBSIDE FROM 3-5FT TO 2-4 FT OVERNIGHT TONIGHT. AS THE LOW
CONTINUES TO MOVE OUT TO SEA AND HIGH PRESSURE BUILDS OVER THE
CNTRL PLAINS...THE NORTHERLY GRADIENT WILL REMAIN IN PLACE OVER
THE LAKE THROUGH WEDNESDAY MORNING. HIGH PRESSURE SHOULD BEGIN TO
BUILD OVER THE LAKE BY LATE WEDNESDAY...ALLOWING WINDS TO WEAKEN
FURTHER.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 1 AM MONDAY.

&&

$$

NWS LOT Office Area Forecast Discussion