Thursday's meeting at Fontwell is in serious doubt with several areas of the track waterlogged and more rain forecast.
Officials at the West Sussex track have called an 8am inspection on Wednesday and fear the worst.
"We have still got three or four areas that are waterlogged. We have seen some improvement in other areas of the course, but those areas have got worse if anything and it's been dry since Monday lunchtime," said clerk of the course Edward Arkell.
"If we are not going to be fit to race tomorrow there is more rain forecast from Wednesday afternoon onwards, so it is better we let everybody know and they can make alternative running plans. It's going to be a struggle."
Meanwhile officials at Musselburgh have called a precautionary inspection for 8am on Wednesday ahead of the meeting that afternoon. Ground conditions are described as good, but with a "tricky forecast".
Clerk of the course Harriet Graham tweeted: "Precautionary Inspection 8am due to forecast snow starting between 7-9am changing to sleet/rain later +3 Tricky forecast."
An 8am precautionary inspection has also been called for Wednesday's meeting at Thurles due to the uncertainty of the weather forecast.
A provisional all-chase card has been programmed by the British Horseracing Authority for Sandown on Friday in an attempt to safeguard the fixture. This will consist of the three chases originally scheduled plus three additional chase opportunities.
All additional races will be free to enter and a final decision on whether the existing hurdle races will be abandoned and the provisional chases activated will be made at 8am on Thursday.
Clerk of the course Andrew Cooper said: "Parts of the hurdle course are saturated. We are expecting further rain on Thursday, with some forecasts suggesting as much as 10mm. To give ourselves the best chance of staging a day's racing we have asked BHA to provisionally schedule an all-chase card ."
23 October 2014Johnson Houghton fined
Duke lords it at Carlisle
Southwell first for O'Brien
Fenton fined over steroids
Buywise on the money at Ludlow
Fenton guilty of drugs possession
Lockinge the big plan for Toormore
Williams hoping for Max power
Stone ruled out of Old Roan
Harty biding his time with Lane
Clonmel aim for Baily
Wetherby likely for First run
Elm tops Trophy octet
Jezki possible for Morgiana bow
Harrington expects Naylor to shine
Gosden a Fan of Newmarket scorer
Northern aces face off in Cumbria
Murphy plagued by shoulder injury
Dynaste charts direct Haydock route
O'Brien outlines Breeders' plans
Wetherby-bound Taquin to duck Power
High hopes for Adelaide run
Gilgamboa waits on ground
Dandino misses Cup date
22 October 2014December date for Balding memorial
Deputy outgunned at Fontwell
Whisky chasing Power spoils
Burke maps out Odeliz targets
Present sights set on Power prize
New category for all-weather champs
Moviesta has sales date
National aim for O'Neill star
Cheltenham on Ginge agenda
Lewis eyeing Dubai success
Henderson handed Ascot role
Panther given Breeders' go-ahead
Plain sailing for perfect Storm
Big Easy sets sail for Open fixture
Hall monitored for Giant Bolster
Stomachion in November frame
Hughes revels in 'sweet' success
BHA moves to address small fields
Connell turns to Heskin
Integral to race on next year
21 October 2014Storm breezes to Exeter victory
Moore concedes title to Hughes
Meade maps out gameplan for stars
Pele poised to tackle Hennessy
O'Neill sure of Taquin redemption
Heron seeking Great prize
Court to go on Trial
Saviour blow for Skelton
Dan makes chase debut
Moore waits on Grugy decision
O'Neill outlines That choices
Conn possible for Auction bid
Power team weigh up options
Bangor cancel schooling card
No rushing back for Long Run
Dynaste leads Old Roan contenders
Grands Crus retired
Exciting Berlais heads to Chepstow
Force handed Hong Kong mission
Park favourite for Trophy hunt
Al Kazeem team eye Hong Kong trip
Commemorative bound for Breeders'
Slade eyeing victorious swansong
20 October 2014Chelmsford City handed 58 fixtures
Alderwood to take two-mile test
Dynaste leads Old Roan contenders
Hennessy aim for Clouds
Fiesolana on Breeders' trail
High-class possibilities for Trophy
Chelmsford City handed 57 fixtures
French option for Maarek
Billy back for chasing bow
Judge to bid for Breeders' glory
Pipe mulls Moon target
High hopes for Holywell
Judge in Breeders' frame