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 ."
1 April 2015Moore breaks leg in Towcester spill
Envoy and Moore beaten at Dundalk
Ferguson fine after Wincanton spill
O'Neill opens Door to Aintree glory
Morris passes century mark
O'Neill readies Aintree squad
Huge entry for Scottish National
Cookie camp up for the Cup
Warrior heads Irish National field
Hills trio in Dante contention
Chrome headlines Lockinge entry
McNamara to Lord it at Aintree
O'Neill: McCoy fairytale no given
Ramone could rock up at Curragh
Coronation up Flintshire's street
Kil lacked zip in France - Longsdon
No Classic prep for Celebrity
Culloty duo on course for Aintree
Royale seal of approval for McCoy
Consort possible for Craven
Fry lines up double Fairyhouse raid
Gatsby seeking Tattersalls gold
Merry King to miss Grand National
Moore has Dundalk ride for O'Brien
Vautour still in Fairyhouse picture
Panther plans open before Gold run
Appleby outlines Charming gameplan
31 March 2015Mac magic earns Southwell shock
Reserves added to Irish National
Punchestown an option for Bolster
Euro could be saved for Ascot
Tullius to go the distance
Bass angling for Rainbow gold
Dreaper an Amigos ally
Maguire ruled out of National
Sirius camp ponder rise in trip
Solar powered up for Classic charge
Guest treads cautiously with Chrome
30 March 2015Noseda sorry for Sloane reaction
Botti aims high with Naadirr
Flemenstar pleases on comeback
Nicholls trims National team
Bolger rates Lucida highly
Angel in the Hunt for Cup honours
Mullins weighs up Aintree options
Hannon readies Classic team
McCoy rules out Punchestown
O'Brien big guns enjoy away day
Hannon aims high with Windshear
McCoy thrills on Ascot farewell
Huge shock in Park Express
Moore to step up Ballydoyle rides
Jacob ripe for Pineau ride
Varian suffers Kingston 'blow'
Aintree on God's radar
29 March 2015Hero makes his mark for O'Meara
Kristale limbers up for York return
Ferof in hunt for Aintree riches
Telescope back in focus
Clouds given National clearance
Chrome given Royal summons
Flemenstar unplaced on return
Dolniya excels in Sheema Classic
Solow gallops to Turf glory
Gabrial just divine in Lincoln
Naadirr strikes to take Trophy
Sole switches on late power
Tullius has to pull out the stops
Romsdal up and running
Panther pounces for Gold